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Rising daily temperatures and water shortage are two of the major concerns in agriculture.In this work, we analysed the tolerance traits in a tomato line carrying a small region of the Solanum pennellii wild genome (IL12‐4‐SL) when grown under prolonged conditions of single and combined high temperature and water stress.When exposed to stress, IL12‐4‐SL showed higher heat tolerance than the cultivated line M82 at morphological, physiological, and biochemical levels. Moreover, under stress IL12‐4‐SL produced more flowers than M82, also characterized by higher pollen viability. In both lines, water stress negatively affected photosynthesis more than heat alone, whereas the combined stress did not further exacerbate the negative impacts of drought on this trait. Despite an observed decrease in carbon fixation, the quantum yield of PSII linear electron transport in IL12‐4‐SL was not affected by stress, thereby indicating that photochemical processes other than CO2 fixation acted to maintain the electron chain in oxidized state and prevent photodamage. The ability of IL12‐4‐SL to tolerate abiotic stress was also related to the intrinsic ability of this line to accumulate ascorbic acid.The data collected in this study clearly indicate improved tolerance to single and combined abiotic stress for IL12‐4‐SL, making this line a promising one for cultivation in a climate scenario characterized by frequent and long‐lasting heatwaves and low rainfall. [ABSTRACT FROM AUTHOR]

Solanum melongena is susceptible to diverse diseases and parasites, in particular the wilts (bacterial, Fusarium and Verticillium), nematodes, and some insects. Solanum torvum is robust to Verticillium and some bacterial wilts and root-knot nematode. It was reported that interspecific hybrid plants originated out of the hybridization of these species were sterile. In our previous studies that have been carried out to overcome this interspecific hybridization barrier, only from Faselis F1 that was used as the female parent, many interspecific hybrid seeds were obtained and 9.07% of the seeds grew into plants in vitro. The percentage of pollen viability and germination of tetraploid interspecific hybrid (amphidiploid) genotypes that have been produced by in vitro colchicine treatment, were 6.8 and 3.4 fold of its source diploid genotype, respectively. However, the increment was not high enough to overcome the interspecific hybridization barrier between S. torvum and S. melongena. In this study, the changes in pollen fertility of diploid interspecific hybrids and tetraploid plants, which have grafted on Pala or Faselis F1, were investigated. Pollen viability and germination percentage in diploid genotypes were not affected by grafting, although they increased significantly (51.54% and 119.73%, respectively) in tetraploid genotypes by grafting. It was determined that the fertile diploid rootstock used for the tetraploid genotypes that produced by chromosome doubling from cultured eggplants could increase the number of seeds per fruit. It was concluded that some fertile diploid varieties can be used as rootstocks in order to increase pollen viability, germination rate and seed yield of tetraploid genotypes with low pollen yield obtained from cultivated eggplant by chromosome doubling. [ABSTRACT FROM AUTHOR]

Seventy four genotypes of the tomato (14 lines, four testers of ripening mutant and their 56 F1 crosses developed in line × tester mating fashion) were appraised under main (E1) and late (E2) planting season at Department of Vegetable Science, Punjab Agricultural University, Ludhiana, Punjab, India. To find out few general and specific combiners, if some, which might be utilized in furthermore breeding programmes to prolong the fruit harvesting span of tomato in the Punjab conditions. The findings hinted in general, the particular parent or hybrid could not be used to assess all examined characters with same efficiency. In main (E1) season line, FL-556 was found best general combiner for average fruit weight, locules number, pericarp thickness, P/E ratio, dry matter and lycopene content; PAU 114 for average fruit weight, lesser locules, pericarp thickness, TSS and dry matter. During late (E2) planting season line, Punjab Ratta found with good GCA values for average fruit weight, lesser locules number, pericarp thickness and TSS content; Roma for average fruit weight, locules number, pericarp thickness and P/E ratio. Similarly tester, alc-IIHR-2050 for pollen viability, minimum days from transplanting to first harvest, harvesting span, average fruit weight, pericarp thickness and P/E ratio in main (E1) season while, for pollen viability, average fruit weight, pericarp thickness and P/E ratio in late (E2) season. The received results furthermore illustrated the best combinations that possessed significant values of SCA which effectively combine to develop a cross with good performance. In main (E1) season from combinations, F1 hybrid SMZ-867 × rin-Rutgers were registered with best specific combiner for pollen viability, average fruit weight, lesser locules number, Pericarp thickness and P/E ratio; PAU 2381 × nor-RM-1 for harvesting span, average fruit weight, pericarp thickness, total fruit yield and lycopene content. Likewise, in late (E2) season cross, SMZ-867 × nor-RM-1 for pollen viability, minimum days from transplanting to first harvest, harvesting span and fruit yield; LT-44 × alc-IIHR-2050 for pollen viability, average fruit weight, lesser locules and pericarp thickness. [ABSTRACT FROM AUTHOR]

Modern agricultural biotechnologies, such as those derived from genetic modification, are solutions that can enable an increase in food production, lead to more efficient use of natural resources, and promote environmental impact reduction. Crops with altered genetic materials have been extensively subjected to safety assessments to fulfill regulatory requirements prior to commercialization. The Brazilian National Technical Biosafety Commission (CTNBio) provides provisions for commercial release of transgenic crops in Brazil, including requiring information on pollen dispersion ability as part of environmental risk assessment, which includes pollen viability and morphology studies. Here we present the pollen viability and morphology of non-transgenic conventional materials, single-event genetically modified (GM) products, and stacked GM products from soybean, maize and cotton cultivated in Brazil. Microscopical observation of stained pollen grain was conducted to determine the percentage of pollen viability as well as pollen morphology, which is assessed by measuring pollen grain diameter. The pollen viability and diameter of GM soybean, maize and cotton, evaluated across a number of GM events in each crop, were similar to the conventional non-GM counterparts. Pollen characterization data contributed to the detailed phenotypic description of GM crops, supporting the conclusion that the studied events were not fundamentally different from the conventional control. [ABSTRACT FROM AUTHOR]

A current trend in climate comprises adverse weather anomalies with more frequent and intense temperature events. Heatwaves are a serious threat to global food security because of the susceptibility of crop plants to high temperatures. Among various developmental stages of plants, even a slight rise in temperature during reproductive development proves detrimental, thus making sexual reproduction heat vulnerable. In this context, male gametophyte or pollen development stages are the most sensitive ones. High-temperature exposure induces pollen abortion, reducing pollen viability and germination rate with a concomitant effect on seed yield. This review summarizes the ultrastructural, morphological, biochemical, and molecular changes underpinning high temperature-induced aberrations in male gametophytes. Specifically, we highlight the temperature sensing cascade operating in pollen, involving reactive oxygen species (ROS), heat shock factors (HSFs), a hormones and transcriptional regulatory network. We also emphasize integrating various omics approaches to decipher the molecular events triggered by heat stress in pollen. The knowledge of genes, proteins, and metabolites conferring thermotolerance in reproductive tissues can be utilized to breed/engineer thermotolerant crops to ensure food security. [ABSTRACT FROM AUTHOR]

SUMMARY: The proper development of male and female gametophytes is critical for successful sexual reproduction and requires a carefully regulated series of events orchestrated by a suite of various proteins. RUVBL1 and RUVBL2, plant orthologues of human Pontin and Reptin, respectively, belong to the evolutionarily highly conserved AAA+ family linked to a wide range of cellular processes. Previously, we found that RUVBL1 and RUVBL2A mutations are homozygous lethal in Arabidopsis. Here, we report that RUVBL1 and RUVBL2A play roles in reproductive development. We show that mutant plants produce embryo sacs with an abnormal structure or with various numbers of nuclei. Although pollen grains of heterozygous mutant plants exhibit reduced viability and reduced pollen tube growth in vitro, some of the ruvbl pollen tubes are capable of targeting ovules in vivo. Similarly, some ruvbl ovules retain the ability to attract wild‐type pollen tubes but fail to develop further. The activity of the RUVBL1 and RUVBL2A promoters was observed in the embryo sac, pollen grains, and tapetum cells and, for RUVBL2A, also in developing ovules. In summary, we show that the RUVBL proteins are essential for the proper development of both male and particularly female gametophytes in Arabidopsis. [ABSTRACT FROM AUTHOR]

Context: Metrosideros bartlettii is one of the most threatened trees in New Zealand and with less than 14 individuals spread across three populations, the species is at high risk of extinction. Despite reproductive failure being identified as one of the factors contributing to population decline, little is known about its pollination biology. Aim: The current study aimed to gain knowledge of the reproductive biology of M. bartlettii by using trees in cultivation of which origin is known. Methods: We tested the effect of self-pollination, cross-pollination and hybridisation treatments on reproductive output. In addition, the viability of fresh pollen was determined for each tree and the impact of desiccation and storage temperature (5°C, −18°C and −196°C) on pollen viability assessed. Key results: Metrosideros bartlettii was found to be highly self-incompatible with seed formed via autonomous self-pollination having low viability. Hybridisation with Metrosideros excelsa , another native species commonly found in cultivation, produced viable seeds, but seedlings failed to survive. Pollen viability differed significantly among trees, and pollen stored at −18°C and −196°C retained viability after 6 months. Conclusion: Metrosideros bartlettii is self-incompatible and cross-pollination is required to increase seed production and supplement wild populations. Implications: Trees in cultivation provide a valuable tool for the conservation of M. bartlettii. However, cross-pollination is essential to prevent hybridisation and ensure genetically robust seed. Long-term storage of pollen at the temperatures determined here will help to overcome challenges in cross-pollination of trees that are spatially and geographically isolated. Metrosideros bartlettii is a critically endangered tree represented by less than 14 individuals in the wild. Due to its self-incompatible breeding system, pollen from an individual from a different population is required to produce viable seed. Short- and long-term pollen storage helps to overcome challenges in cross-pollination both in the wild and in ex situ collections. [ABSTRACT FROM AUTHOR]

Rapeseed (Brassica napus, AACC) was formed by hybridization between progenitor species Brassica rapa (AA) and Brassica oleracea (CC). As a result of a limited number of hybridization events between specific progenitor genotypes and strong breeding selection for oil quality traits, rapeseed has limited genetic diversity. The production of resynthesized B. napus lines via interspecific hybridization of the diploid progenitor species B. rapa and B. oleracea is one possible way to increase genetic variation in rapeseed. However, most resynthesized lines produced so far have been reported to be meiotically unstable and infertile, in contrast to established B. napus cultivars. This hinders both maintenance and use of this germplasm in breeding programs. We characterized a large set of 140 resynthesized lines produced by crosses between B. rapa and B. oleracea, as well as between B. rapa and wild C genome species (B. incana, B. hilarionis, B. montana, B. Bourgeaui, B. villosa and B. cretica) for purity (homozygosity), fertility, and genome stability. Self-pollinated seed set, seeds per ten pods as well as percentage pollen viability were used to estimate fertility. SNP genotyping was performed using the Illumina Infinium Brassica 60K array for 116 genotypes, with at least three individuals per line. Most of the material which had been advanced through multiple generations was no longer pure, with heterozygosity detected corresponding to unknown parental contributions via outcrossing. Fertility and genome stability were both genotypedependent. Most lines had high numbers of copy number variants (CNVs), indicative of meiotic instability, and high numbers of CNVs were significantly associated with reduced fertility. Eight putatively stable resynthesized B. napus lines were observed. Further investigation of these lines may reveal the mechanisms underlying this effect. Our results suggest that selection of stable resynthesized lines for breeding purposes is possible. [ABSTRACT FROM AUTHOR]

• We present a new proposal, the so-called reproductive efficiency, which measures plants' efficiency in fertilizing their eggs. • We apply microsurgeries to the corolla tube to enable artificial self-fertilization. • Catharanthus roseus presents the mixed reproduction mode, namely: allogamy and autogamy, simultaneously. • We conclude that allogamy is the main pollination strategy. • Autogamy is a reproduction guarantee mechanism (back-up plan) that can be reinforced by cleistogamy. Despite the medicinal importance of Catharanthus roseus [L.] G. Don., the literature is still controversial about its mode of reproduction. The breeding of species depends on this information. The purpose of this study was to ascertain the preferential reproduction mode of C. roseus by using different genotypes of this species. We also sought to verify the relative importance of allogamy and autogamy on the species reproduction. Therefore, it was necessary to estimate the pollen:ovule ratio, the rates of open pollination and natural self-fertilization, the efficiency of allogamy and autogamy, and pollen viability and stigma receptivity. Furthermore, we applied fluorescence microscopy to analyze the emission and development of pollen tubes in vivo in floral buds and investigated the histochemistry of the pollen grains. Finally, through ISSR markers, we estimated the genetic diversity of the genotypes. In general, C. roseus has a mixed reproduction mode, with the possible simultaneous occurrence of allogamy and autogamy. However, allogamy was much more prevalent, and it was also more efficient as a reproductive strategy in the genotypes. The high magnitude of genetic diversity found corroborates allogamy as the most prevalent mode of reproduction. Nevertheless, autogamy occurred in all the genotypes, although the seed production efficiency was low. Autogamy can be understood as a supposed reproductive guarantee mechanism by C. roseus. [ABSTRACT FROM AUTHOR]

SUMMARY: Auxin Response Factor 8 plays a key role in late stamen development: its splice variants ARF8.4 and ARF8.2 control stamen elongation and anther dehiscence. Here, we characterized the role of ARF8 isoforms in pollen fertility. By phenotypic and ultrastructural analysis of arf8‐7 mutant stamens, we found defects in pollen germination and viability caused by alterations in exine structure and pollen coat deposition. Furthermore, tapetum degeneration, a prerequisite for proper pollen wall formation, is delayed in arf8‐7 anthers. In agreement, the genes encoding the transcription factors TDF1, AMS, MS188 and MS1, required for exine and pollen coat formation, and tapetum development, are downregulated in arf8‐7 stamens. Consistently, the sporopollenin content is decreased, and the expression of sporopollenin synthesis/transport and pollen coat protein biosynthetic genes, regulated by AMS and MS188, is reduced. Inducible expression of the full‐length isoform ARF8.1 in arf8‐7 inflorescences complements the pollen (and tapetum) phenotype and restores the expression of the above transcription factors. Chromatin immunoprecipitation‐quantitative polymerase chain reaction assay revealed that ARF8.1 directly targets the promoters of TDF1, AMS and MS188. In conclusion, the ARF8.1 isoform controls pollen and tapetum development acting directly on the expression of TDF1, AMS and MS188, which belong to the pollen/tapetum genetic pathway. [ABSTRACT FROM AUTHOR]

• Ex vitro clonal genotypes have lower pollen and seed viabilities than wild type. • Berry numbers and seed sets of clones decrease after micropropagation. • Embryonic and endosperm tissues in clonal genotypes are abnormal. Solanum nigrum is an underutilised vegetable that accumulates high leaf nutrient levels. Although numerous micropropagation protocols are reported for its mass production, there have been no follow-on studies detailing the pollen and seed viabilities of clones or clonal genotypes. It is important to determine these viabilities in cases where the inheritance of desired traits in the F1 progenies of micropropagated clones are required. In the present study, two high Fe-accumulating S. nigrum genotypes (G6 and G15) identified in a previous investigation were clonally propagated and acclimatised until sexual maturity using an established protocol. Following flower and fruit production, viability tests were performed on clonal pollen (Lugol's staining) and seeds (tetrazolium chloride test) in addition to determinations of berry and seed numbers, seed set, seed length, weight, germination and ultrastructure. A wild type (WT) population was used as the control. Compared to the WT population (82%, 75%, 200, 11,400, 57 and 51%), the G6 and G15 clones, respectively, resulted in significantly lower pollen (51 and 39%) and seed viabilities (4 and 17%), berry (23 and 16) and seed (162 and 116) numbers, seed sets (7 and 7) and germination (7 and 8%). Microscopic analyses revealed normal, abnormal, viable and nonviable pollen and seeds for G6, G15 and the WT in addition to abnormal or damaged embryonic and endosperm tissues for both clonal genotypes. Micropropagation of S. nigrum genotypes decreases their clonal pollen and seed viabilities, berry and seed production, and germination success of their F1 progenies. [ABSTRACT FROM AUTHOR]

We show that the knockout of a sugar transporter gene OsSWEET15 led to a significant drop in rice fertility with around half of the knockout mutant's spikelets bearing blighted or empty grains. The rest of the spikelets bore fertile grains with a slightly reduced weight. Notably, the ovaries in the blighted grains of the ossweet15 mutants expanded after flowering but terminated their development before the endosperm cellularization stage and subsequently aborted. β- glucuronidase (GUS) and Green Fluorescent Protein (GFP) reporter lines representing the OsSWEET15 expression showed that the gene was expressed in the endosperm tissues surrounding the embryo, which supposedly supplies nutrients to sustain embryo development. These results together with the protein's demonstrated sucrose transport capacity and plasma membrane localization suggest that OsSWEET15 plays a prominent role during the caryopsis formation stage, probably by releasing sucrose from the endosperm to support embryo development. By contrast, the empty grains were probably caused by the reduced pollen viability of the ossweet15 mutants. Investigation of ossweet11 mutant grains revealed similar phenotypes to those observed in the ossweet15 mutants. These results indicate that both OsSWEET15 and OsSWEET11 play important and similar roles in rice pollen development, caryopsis formation and seed-setting, in addition to their function in seed-filling that was demonstrated previously. [ABSTRACT FROM AUTHOR]

Ardisia humilis is an excellent wild ornamental plant. For the purpose of fully utilization of this elite germplasm, the flowering biology and breeding system of this plant had been explored in this study. We conducted field investigation in the flowering phenology, flower-visiting insect and their visiting behaviors on A. humilis individuals introduced in homogeneous garden. Furthermore, pollen viability and stigma receptivity were detected by pollen germination in vitro and benzidine-hydrogen peroxide method, respectively. Combined with artificial pollination,the self-compatibility and the self-pollination of A. humilis were also analyzed in this study. The results were as follows: (1) The florescence of A. humilis was from mid-late May to early June, and the full flowering period was at the end of May. The flowering period of the population, single plant and single flower were approximately 25 d, 17-20 d and 1 d, respectively. (2) A. humilis developed protogynic bisexual flowers, the pistil ripened first with partial overlaps on mature stage of pistil and that of stamen, while stigma remained receptivity until 1 d after stamens fall. (3) With the out-crossing index (OCI) value of 4 and pollen / ovule value of 5.61×103, the breeding system of A. humilis was considered to be outcrossing with partial self-compatibility, and the pollinator insects were essential. (4) The seed set of natural pollination ranked the highest level (average 52.96%), followed by that of autogamy (52.29%) and of artificial-cross pollination (50.33%), with no significant differences among the three (P>0.05), but significantly higher than that of artificial geitonogamy (28.67%) (P<0.05). This study indicated that, beside of being excellent flowering plant, A. humilis was also a potentially important ornamental fruit plant due to the generalized pollination system and the strongly autogamy ability which enhancing the high success of fruits development from blossoms. (5) Lasioglossum sp. 1, Lasioglossum sp. 2 and Halictus sp. were the most observed floral visitors on Ardisia humilis. This study provides an important theoretical reference for the resource utilization and germplasm innovation of A. humilis. [ABSTRACT FROM AUTHOR]

The hormonal imbalances, including abscisic acid (ABA) and brassinosteroid (BR) levels, caused by salinity constitute a key factor in hindering spikelet development in rice and in reducing rice yield. However, the effects of ABA and BRs on spikelet development in plants subjected to salinity stress have been explored to only a limited extent. In this research, the effect of ABA and BRs on rice growth characteristics and the development of spikelets under different salinity levels were investigated. The rice seedlings were subjected to three different salt stress levels: 0.0875 dS m−1 (Control, CK), low salt stress (1.878 dS m−1, LS), and heavy salt stress (4.09 dS m−1, HS). Additionally, independent (ABA or BR) and combined (ABA+BR) exogenous treatments of ABA (at 0 and 25 μM concentration) and BR (at 0 and 5 μM concentration) onto the rice seedlings were performed. The results showed that the exogenous application of ABA, BRs, and ABA+BRs triggered changes in physiological and agronomic characteristics, including photosynthesis rate (Pn), SPAD value, pollen viability, 1000-grain weight (g), and rice grain yield per plant. In addition, spikelet sterility under different salt stress levels (CK, LS, and HS) was decreased significantly through the use of both the single phytohormone and the cocktail, as compared to the controls. The outcome of this study reveals new insights about rice spikelet development in plants subjected to salt stress and the effects on this of ABA and BR. Additionally, it provides information on the use of plant hormones to improve rice yield under salt stress and on the enhancement of effective utilization of salt-affected soils. [ABSTRACT FROM AUTHOR]

• The pollen viability, storage and germination results showed significant differences among the species of Casuarina and between stains (acetocarmine and aniline blue), storage duration, temperature and germination media (BA and BK medium). • The female flowers had a life span of about 10 days, and the stigma receptivity started 3 days after anthesis and peaked between the fourth and sixth days. • The receptivity period was linked to distinct morphological characteristics of the stigma, which can be used as a guide for hand pollination. • Successful storage of pollen and knowledge of the stigma receptivity time help breeders perform controlled pollination, leading to a high level of fruit and seed set. Casuarina species (Casuarinaceae) are nitrogen-fixing multipurpose trees planted extensively throughout the tropics for wood production and environmental services. Increasing productivity of plantations through breeding is underway in China, India and Thailand. The current focus of breeding is to produce interspecific hybrids possessing a combination of specifies-specific characters of forestry importance. Earlier hybridization attempts were less successful mainly due to insufficient knowledge on floral and pollen biologyand lack of efficient hand pollination techniques. The differences in the floral characters and their influence on pollen and seed output in three Casuarina species (C. equisetifolia, C. junghuhniana and C. cristata) were studied. Pollen from six clones were stored at three temperature levels and tested for viability from 3 to 45 days after storage using acetocarmine and aniline blue stains. In vitro germination of stored pollen was testedwith two germination media from 3 to 30 days. Female flowers were control pollinated from 1 to 7 days after anthesis and stigma receptivity was determined based on presence of germinating pollen. There was a significant effect of clone, stain, storage temperature and storage period on the viability of pollen. Pollen viability and in vitro germination reduced drastically when stored at room temperature for three days but was high under low temperature storage. While the viability of pollen stored at 4°C and -20 °C comparable up to 15 days of storage, freezer storage showed better viability at 45 days. In vitro germination was higher with the broad-based Brewbaker-Kwack medium than the basic sucrose-boron medium. The stigma was receptive from the third to seven days after anthesis and the peak period was on fourth and fifth days for C. equisetifolia and C. junghuhniana and fifth and sixth days for C. cristata. The receptivity level of the stigma was associated with distinct morphological features during lifespan of the female flower. Pollen stored under low temperatures can be used to cross parents with dissimilar flowering phenology within the same flowering season and conducting hand pollination during when the stigma is at its peak receptivity will increase hybridization success. [ABSTRACT FROM AUTHOR]

Pollen grains represent the male gametes of seed plants and their viability is critical for sexual reproduction in the plant life cycle. Palynology and viability studies have traditionally been used to address a range of botanical, ecological and geological questions, but recent work has revealed the importance of pollen viability in invasion biology as well. Here, we report an efficient visualmethod for assessing the viability of pollen using digital holographic microscopy (DHM). Imaging data reveal that quantitative phase information provided by the technique can be correlated with viability as indicated by the outcome of the colorimetric test.We successfully test this method on pollen grains of Lantana camara, a well-known alien invasive plant in the tropical world. Our results show that pollen viability may be assessed accurately without the usual staining procedure and suggest potential applications of the DHM methodology to a number of emerging areas in plant science. [ABSTRACT FROM AUTHOR]

Background and aims: Long-term monocultures seriously compromise crop productivity, which is known as replanting obstacle. Flowers are the most valuable tissue in annual plants and closely associated with pollen production, fertilization and seed set, however, their roles in replanting obstacle are unknown. We here explored how long-term monocropping impacts flowers, and revealed the potential acclimation mechanisms employing by flowers to monocropping. Methods: Field trial and pot experiments with peanut monocropped and rotated regimes were performed to study the response of peanut flowers to monocropping with physiological, transcriptomic and fungal community analyses. Results: Long-term monocropping reduced flower formation, pollen viability, pollen germination and tube growth, thereby reducing seed set in peanut. The transcriptome of flowers revealed that genes associated with the anther dehiscence, heat stress response, flavonoid biosynthesis, glutathione metabolism and potassium uptake were enriched by monocropping, which indicated that flowers experienced water deficit and oxidative stress. Inhibition of reactive oxygen species (ROS) synthesis or scavenging excess ROS rescued pollen activity decline under monocropping. By screening flower physiology and soil physicochemical properties, combined with drought and soil aggregate composition mimic experiments, we confirmed that flower water deficit and oxidative stress under monocropping were mediated by the soil structure alterations, especially large macro-aggregates (> 2 mm) reduction. Conclusion: Long-term monocropping alters soil structures, resulting in a water deficit and ROS accumulation in the flowers, which decreases pollen activity, and a multi-faceted actions including accelerated anther dehiscence, enhanced potassium absorption and better ROS scavenging capacity, are taken by flowers to acclimate to monocropping. [ABSTRACT FROM AUTHOR]

Etlingera is a genus of the family Zingiberaceae that is native to tropical Asia. Many species are economically important as a source of food, spices, medicines, and ornamental plants. This study aims to elucidate the floral morphology of E. elatior and understand the behavior of the set of stamen and style during floral anthesis, seeking to identify the mechanisms that promote xenogamy in the species. Flower morphology, time of anthesis and movement of the stamen and style during this period, pollen viability, nectar volume, floral visitors, and the reproductive system were evaluated. The flowers of E. elatior exhibited synchronous movement of the style and stamen, however, this movement was not considered as flexistyly, since the species does not present dichogamy. The synchronous movement of the stamen and pistil, by itself, was not enough to promote selfpollination. Fruiting depends on pollinators. The stigma fluid is an important means whereby pollen adheres to the mouthpart of the pollinator. Hummingbirds and bees were considered the most effective pollinators of E. elatior in the area studied. [ABSTRACT FROM AUTHOR]

Unlike animals that can escape threats, plants must endure and adapt to biotic and abiotic stresses in their surroundings. One such condition, cold stress, impairs the normal growth and development of plants, in which most phases of reproductive development are particularly susceptible to external low temperature. Exposed to uncomfortably low temperature at the reproductive stage, meiosis, tapetal programmed cell death (PCD), pollen viability, and fertilization are disrupted, resulting in plant sterility. Of them, cold-induced tapetal dysfunction is the main cause of pollen sterility by blocking nutrition supplements for microspore development and altering their timely PCD. Further evidence has indicated that the homeostatic imbalances of hormones, including abscisic acid (ABA) and gibberellic acid (GA), and sugars have occurred in the cold-treated anthers. Among them, cold stress gives rise to the accumulation of ABA and the decrease of active GA in anthers to affect tapetal development and represses the transport of sugar to microspores. Therefore, plants have evolved lots of mechanisms to alleviate the damage of external cold stress to reproductive development by mainly regulating phytohormone levels and sugar metabolism. Herein, we discuss the physiological and metabolic effects of low temperature on male reproductive development and the underlying mechanisms from the perspective of molecular biology. A deep understanding of cold stress response mechanisms in anther development will provide noteworthy references for cold-tolerant crop breeding and crop production under cold stress. [ABSTRACT FROM AUTHOR]

Interspecific hybrids can be studied using methodologies in which the male gamete with high reproduction potential, viability, and fertility is prioritized. Passiflora species, with lush, showy, and exotic colors, have great potential for the ornamental plant market. In addition, artificial Passiflora hybrids were developed without many difficulties because of weak reproductive barriers. Thus, meiotic and post-meiotic behaviors were analyzed with 2% acetic carmine staining. Confirmation of interspecific hybridization was performed using SSR markers and GISH technique was used to detect genomic differentiation. The pollen viability of the parental and hybrids genotypes was tested using Alexander's solution, fluorescein diacetate and in vitro germination tests were performed using culture medium. The meiotic behavior was regular and displayed haploid number n = 9 with nine bivalent (II) chromosomal, and pairing in 90% of the cells in diakinesis. There was a significant difference (p < 0.05) in terminal and interstitial chiasma frequencies. Meiotic irregularities observed were as follows: early and/or delayed chromosomes, disorientation of spindle fibers, transverse spindles, tripolar spindles, and asynchrony; and consequently irregular post-meiotic products were observed: monads, dyads, triads, and polyads. GISH was used in the interspecific hybrids and pairing between homeologous chromosomes, and bivalent and tetravalent formation were observed. From this study, we could conclude that hybrid genotypes are fertile and pollen grains are viable and can be used in breeding programs. [ABSTRACT FROM AUTHOR]

Fixing the genomic composition and multiplication through true potato seed (TPS) is an important challenge in autotetraploid potato. Disrupted meiotic cDNA (DMC1) is a meiotic gene that plays a central role in DNA recombination through crossing over in meiosis. Using the Arabidopsis DMC1 (AtDMC1) gene sequence, we retrieved Solanum tuberosum DMC1(StDMC1) from the diploid potato genome, and subsequently, sense and antisense regions of the StDMC1 gene were amplified in potato cv. Kufri Jyoti. The sense and antisense fragments were confirmed by Sanger-sequencing and cloned in the pRI101 vector. Agrobacterium-mediated transformation of the RNAi construct resulted in 44% transformation efficiency, and a total of 137 mutant lines were obtained. These mutant lines were further validated through pollen viability testing, and selected lines were used for gene expression analysis. The acetocarmine-based pollen staining showed reduced pollen viability ranging from 14 to 21% in four DMC1 mutant lines (DMC4-37, DMC4-41, DMC6-20, and DMC6-21), as compared to the Kufri Jyoti control plants, which on average exhibited 78% pollen viability. The phenotypic data was supported by the reduced expression of the StDMC1 gene in these four mutant lines compared to the control Kufri Jyoti. The results confirmed the generation of StDMC1 knockdown lines. This is the first report of StDMC1 mutant line generation in tetraploid potatoes and will be a step forward in generating non-recombinant mutants through sexual reproduction in potatoes. [ABSTRACT FROM AUTHOR]

• Pollen morphology of eight coconut accessions differed in origin, stature, breeding behaviour and tolerance to abiotic stresses were characterised with scanning electron microscope. • Variations in pollen size, shape and exine ornamentation pattern was observed between the coconut genotypes. • Pollen physiological features such as pollen viability, germination and pollen tube length and pollen nutrient composition were evaluated for the eight coconut genotypes. • The results obtained revealed differences in pollen morphological features which can potentially be used for cultivar identification and the information on pollen viability, germination and pollen mineral contents amongst genotypes can support conservation and crop improvement studies of the genotypes. The micro-morphological characteristic of the pollen grain is one of the most important diagnostic traits use for identification and characterization of plants even to the accession levels. In this study, pollen grains characterization of eight different coconut (Cocos nucifera L.) accessions were carried out. Morphometric observations and structure analysis of the pollen grains were performed using light and scanning electron microscopy. The variation in length and width observed ranged from 55.06 -71.25 µm and 24.38 -36.27 µm amongst the accessions. The pollen grains exhibited an ellipsoidal to elliptical shape with the exine ornamentation ranging from granulate to reticulate. Pollen viability, germination and pollen tube length were significantly different amongst the tested accessions. While pollen viability varied from 92.35 to 96.5%, germination rate and pollen tube length (after 2 h) ranged from 16.05 - 31.59% and 234.95 μm to 414.96 μm respectively. Pollen mineral composition from different accessions also varied significantly with Malayan Orange Dwarf (MOD) recording higher phosphorus (0.93%), calcium (0.64%) and magnesium (0.38%) content while highest potassium (1.01%), sodium (0.71%), iron (149.35 ppm) zinc (119.59 ppm) and boron (45.05 ppm) content was noticed in San Ramon Tall (SNRT). This investigation highlights the fact that these pollen morphological features could be potentially used for differentiating the selected accessions thereby supporting their conservation and crop improvement studies. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles (nTiO2) are widely used as fertilizers in agricultural production because they promote photosynthesis and strong adhesion. Low pollination and fertilization due to rainy weather during the litchi plant's flowering phase result in poor fruit quality and output. nTiO2 would affect litchi during the flowering and fruiting stages. This study considers how nTiO2 affects litchi's fruit quality and pollen viability during the flowering stage. The effects of nTiO2 treatment on pollen vigor, yield, and fruit quality were investigated. nTiO2 effectively improved the pollen germination rate and pollen tube length of litchi male flowers. The germination rate reached 22.31 ± 1.70%, and the pollen tube reached 237.66 μm in the 450 mg/L reagent-treated group. Spraying with 150 mg/L of nTiO2 increased the germination rate of pollen by 2.67% and 3.67% for two types of male flowers (M1 and M2) of anthesis, respectively. After nTiO2 spraying, the fruit set rates of 'Guiwei' and 'Nomici' were 46.68% and 30.33%, respectively, higher than those of the boric acid treatment group and the control group. The edibility rate, titration calculation, and vitamin C of nTiO2 treatment were significantly higher than those of the control. The nTiO2-treated litchi fruit was more vividly colored. Meanwhile, the adhesion of nTiO2 to leaves was effectively optimized by using ATP and BCS to form nTiO2 carriers and configuring nTiO2 complex reagents. These results set the foundation for future applications of titanium dioxide nanoparticles as fertilizers for agriculture and guide their application to flowers and fruits. [ABSTRACT FROM AUTHOR]

Background: The research was conducted to screen rice cultivars with resistance ability to high-temperature conditions and analyze the relationship between pollen viability and filled grain of native Indonesia rice cultivars. Methods: The rice seeds were germinated, sown into a tray and then transplanted into pots filled with sandy loam and compost 3:1. After 20% of flowering, four pots of each cultivar were kept under ambient temperature (28-32°C) and the other four pots were transferred to high-temperature (33-38°C) conditions. Pollen stainability and pollen germination were conducted using IKI solution and by germinating them under in vitro conditions respectively before being viewed under the light microscope. Yield characters were analyzed to obtain a relationship with pollen viability. Result: Percentage of pollen germination, filled and empty grains of rice cultivars significantly differed between the two conditions by t-test. Ciherang and Sigeudop were two resistant cultivars for high-temperature treatment, with filled grain percentage more than 85%. There was a strong relationship between pollen germination and filled grains at ambient temperature (r=0.95; p<0.01) and high temperature (r=0.94; p<0.01). Rice cultivars that show high pollen germination under high-temperature conditions would produce a high percentage of filled grains. [ABSTRACT FROM AUTHOR]

• The susceptible genotypes exhibited the highest levels of lipid peroxidation and lesser magnitude of proline increase than the tolerant ones during reproductive cold stress in chickpea. • Proline and pollen load can be used as prominent phenotypic markers in screening for cold tolerance in chickpea breeding programme. • The breeding lines GL29183-P1, GL29183-P2 and GL29183-P3 and cultivar PBG5 can be extensively evaluated in cold prone areas to identify any line for release for general cultivation. Cold stress is one of the most important abiotic stresses affecting chickpea production in Northwestern India. Further, the short-duration varieties are more susceptible to cold injury as their reproductive phase coincides with the cold spell of this zone. So, enhancing the cold tolerance of the host plant is the only viable option to resolve this issue in chickpea. The present study involved a set of 13 advanced breeding lines (with differential cold sensitivity) and three reference varieties (GPF2, PBG5, and PBG7) of chickpea which were exposed to cold stress at the reproductive stage under field conditions during the winters of 2019–20 and 2020–21. Various physiological and biochemical parameters such as proline, electrolyte leakage, photosynthetic pigments, lipid peroxidation, and 2, 2-diphenyl-1- picrylhydrazyl (DPPH) activity were measured before and after exposure to cold to delineate the mechanism of tolerance in these genotypes. Significant genotypic variations were observed for the above-mentioned traits in both years. The genotypes GL27059 P2, GL 28202-P1, and GL28202-P2 exhibited the highest lipid peroxidation and lesser magnitude of proline increase during reproductive cold stress on a pooled basis. These genotypes performed poorly for yield traits like pod set percent, filled pods plant –1, total seeds/ plant, and seed yield/plant and hence were susceptible to cold stress. Further, a significant reduction in reproductive function of male gametophyte i.e. pollen viability and pollen load under cold stress was also observed in these susceptible genotypes. In contrast, tolerant line GL29183-P2 had significantly more pollen load and pollen viability contributing to better yield performance (viz., higher flowers/plant, pods/plant, and maximum pod set percent) among the studied advanced breeding lines. Based upon the pooled analysis, the reference variety PBG5 outperformed in yield attributes i.e., total flower/ plant, total filled pods/plant, and had a significantly higher yield than GL29183 under cold stress at the early reproductive stage. A significant increment in levels of proline (125–160%) on exposure to cold spell was observed in genotypes, GL29183 and PBG5, which contribute toward cold tolerance. Thus, an increase in proline along with maintenance of pollen load can be used as prominent phenotypic markers in screening for cold tolerance at the reproductive stage in chickpea. [ABSTRACT FROM AUTHOR]

Pollen grains, the male gametophytes for reproduction in higher plants, are vulnerable to various stresses that lead to loss of viability and eventually crop yield. A conventional method for assessing pollen viability is manual counting after staining, which is laborious and hinders high-throughput screening. We developed an automatic detection tool (PollenDetect) to distinguish viable and nonviable pollen based on the YOLOv5 neural network, which is adjusted to adapt to the small target detection task. Compared with manual work, PollenDetect significantly reduced detection time (from approximately 3 min to 1 s for each image). Meanwhile, PollenDetect can maintain high detection accuracy. When PollenDetect was tested on cotton pollen viability, 99% accuracy was achieved. Furthermore, the results obtained using PollenDetect show that high temperature weakened cotton pollen viability, which is highly similar to the pollen viability results obtained using 2,3,5-triphenyltetrazolium formazan quantification. PollenDetect is an open-source software that can be further trained to count different types of pollen for research purposes. Thus, PollenDetect is a rapid and accurate system for recognizing pollen viability status, and is important for screening stress-resistant crop varieties for the identification of pollen viability and stress resistance genes during genetic breeding research. [ABSTRACT FROM AUTHOR]

Oil tea (Camellia oleifera Abel.) is one of the most important woody edible oil tree species in China, with intraspecific polyploid. In order to study the variation in pollen size and vigor of C. oleifera at ploidy level, four ploidy covers a total of 32 types of Camellia pollens as the material for the experiment. The results showed that the pollen sizes of diploid, tetraploid, hexaploidy, and octaploid were positively correlated with the ploidy level. Pollen viability of C. oleifera was determined by fluorescein diacetate (FDA) dye solution staining and medium containing 10% sucrose, 0.01% boric acid, and 1% agar germination in vitro, which indicated that the pollen viability and germination rate of the hexaploid were relatively high among the four ploidy levels, at 79.69% and 71.78% respectively. The pollen vigor of diploid NR-3, tetraploid DP43, hexaploid CJ-12, and octoploid YNYC-1 was higher than that of other materials with the same ploidy level. Knowledge of different ploidy pollen sizes and pollen viability provides basic information for formulating pollen breeding plans and pollination methods of C. oleifera. [ABSTRACT FROM AUTHOR]

SWEET sucrose transporters play important roles in the allocation of sucrose in plants. Some SWEETs were shown to also mediate transport of the plant growth regulator gibberellin (GA). The close physiological relationship between sucrose and GA raised the questions of whether there is a functional connection and whether one or both of the substrates are physiologically relevant. To dissect these two activities, molecular dynamics were used to map the binding sites of sucrose and GA in the pore of SWEET13 and predicted binding interactions that might be selective for sucrose or GA. Transport assays confirmed these predictions. In transport assays, the N76Q mutant had 7x higher relative GA3 activity, and the S142N mutant only transported sucrose. The impaired pollen viability and germination in sweet13;14 double mutants were complemented by the sucrose-selective SWEET13S142N, but not by the SWEET13N76Q mutant, indicating that sucrose is the physiologically relevant substrate and that GA transport capacity is dispensable in the context of male fertility. Therefore, GA supplementation to counter male sterility may act indirectly via stimulating sucrose supply in male sterile mutants. These findings are also relevant in the context of the role of SWEETs in pathogen susceptibility. [ABSTRACT FROM AUTHOR]

Summary: Both sugar and the hormone gibberellin (GA) are essential for anther‐enclosed pollen development and thus for plant productivity in flowering plants. Arabidopsis (Arabidopsis thaliana) AtSWEET13 and AtSWEET14, which are expressed in anthers and associated with seed yield, transport both sucrose and GA. However, it is still unclear which substrate transported by them directly affects anther development and seed yield.Histochemical staining, cross‐sectioning and microscopy imaging techniques were used to investigate and interpret the phenotypes of the atsweet13;14 double mutant during anther development. Genetic complementation of atsweet13;14 using AtSWEET9, which transports sucrose but not GA, and the GA transporter AtNPF3.1, respectively, was conducted to test the substrate preference relevant to the biological process.The loss of both AtSWEET13 and AtSWEET14 resulted in reduced pollen viability and therefore decreased pollen germination. AtSWEET9 fully rescued the defects in pollen viability and germination of atsweet13;14, whereas AtNPF3.1 failed to do so, indicating that AtSWEET13/14‐mediated sucrose rather than GA is essential for pollen fertility.AtSWEET13 and AtSWEET14 function mainly at the anther wall during late anther development stages, and they probably are responsible for sucrose efflux into locules to support pollen development to maturation, which is vital for subsequent pollen viability and germination. [ABSTRACT FROM AUTHOR]

Key message: Priming alleviates membrane damage, chlorophyll degradation along with cryoprotectants accumulation during chilling stress that leads to improved reproductive functioning and increased seed yield. Chilling temperatures below 15 °C have severe implications on the reproductive growth and development of chickpea. The abnormal reproductive development and subsequent reproductive failure lead to substantial yield loss. We exposed five chickpea cultivars (PBG1, GPF2, PDG3, PDG4, and PBG5) to drought stress (Priming) during the vegetative stage and analyzed for chilling tolerance during the reproductive stage. These varieties were raised in the fields in two sets: one set of plants were subjected to drought stress at the vegetative stage for 30 days (priming) and the second set of plants were irrigated regularly (non-primed). The leaf samples were harvested at the flowering, podding, and seed filling stage and analyzed for membrane damage, water status, chlorophyll content, cellular respiration, and certain cryoprotective solutes. The reproductive development was analyzed by accessing pollen viability, in vivo and in vitro germination, pollen load, and in vivo pollen tube growth. Principal component analysis (PCA) revealed that priming improved membrane damage, chlorophyll b degradation, and accumulation of cryoprotectants in GPF2, PDG3, and PBG5 at the flowering stage (< 15 °C). Pearson's correlation analysis showed a negative correlation with the accumulation of proline and carbohydrates with flower, pod, and seed abortion. Only, PBG5 responded best to priming while PBG1 was worst. In PBG5, priming resulted in reduced membrane damage and lipid peroxidation, improved water content, reduced chlorophyll degradation, and enhanced cryoprotective solutes accumulation, which led to increased reproductive functioning and finally improved seed yield and harvest index. Lastly, the priming response is variable and cultivar-specific but overall improve plant tolerance. [ABSTRACT FROM AUTHOR]

• Unreleased pollen contained more glucose and fructose, whereas released pollen contained more sucrose. • Proline, kinetin and salicylic acid are essential for pollen development, maturity and viability. • Cadaverine, spermine, and spermidine were found in higher concentrations in unreleased pollen, whereas putrescine was found in higher concentrations in released pollen. • Accumulated 12-Octadecadienoic acid, together with palmitic acid and stearic acid has been identified to be crucial component for pollen. Elucidating the biochemical and metabolic adaptations of unreleased and released pollen provides more insights into pollen development, maturation, and vitality. Hence, in the present investigation, Putranjiva roxburghii Wall. was selected to critically examine the biochemical and metabolite profiling of released and unreleased pollen states. Metabolomic profiling revealed 276 metabolites from the unreleased pollen and 271 metabolites from the released pollen, falling into 12 different categories. The levels of auxin family hormones like indole-3-acetic acid and 1-naphthalene acetic acid, along with other biomolecules like glucose, fructose, proline, 12-Octadecadienoic acid (C18:2 w6c), cadaverine, spermine and spermidine were higher in the unreleased pollen suggesting their functional significance in the pollen maturation. Whereas, the levels of kinetin, gibberellic acid, salicylic acid, sucrose, lipid, 12-Octadecadienoic acid were higher in the released pollen compared to unreleased pollen. Furthermore, the metabolites like lysophosphatidylinositol, phosphatidylglycerol, lysophosphatidic acid, linoleic acid and its derivatives, phosphatidylcholine, monoacylglycerol, sphingosine-1-phosphate and oleacein were found unique in released pollen, indicating these metabolites may participate to complete the pollen development. Among the carbohydrates, sucrose accumulation was higher in released pollen, signifying it to be a potent source of energy reservoir for future tube growth and germination processes. Additionally, increased fatty acid levels in the released pollen may act as a structural component preventing pollen from adverse environmental conditions for their viability and fertility. Thus, the current study unraveled the metabolic pathways associated with released pollen revealing the metabolic activities. This is the first study done on the wind pollination pollen in Putranjiva roxburghii Wall. [ABSTRACT FROM AUTHOR]

Chili (Capsicum annuum L.) is a horticultural plant susceptible to high-temperature stress. This research studied how agronomic and physiological characteristics of chili decline due to high temperature and determined the threshold value of temperature decreasing 50% of its yield. The experiment layout followed a randomized design, consisting of five temperature stress levels (in the growth chamber), namely, 31°C (daily temperature as a control), 33°C, 35°C, 37°C, and 39°C, with an exposure duration of 10 h. The temperature stress started when the plant reached the flowering phase. The plant parameters observed included agronomic and physiological characteristics. The study results showed that high-temperature decreased production significantly with the decline in all agronomic and physiological traits. The threshold temperature at 32.86°C has reduced the production of chili plants by 50% compared with the control. The study found that an increase in temperature of 2°C for 10 h in the flowering phase reduces chili production by 68.78%, and temperature stress at a maximum of 39°C for 10 h during flowering reduces chili production up to 87.52%. Hence, based on the study results, future research on chili should focus on developing varieties that are adaptive to high temperatures. [ABSTRACT FROM AUTHOR]

The banana cultivar "Pisang Rejang" (Musa AA "Pisang Rejang") is Fusarium wilt resistant and therefore important for banana breeding. Tetraploid (4x) and mixoploid (2x+4x) plants of this cultivar have been induced with oryzalin, and crosses of these two ploidy levels resulted in a triploid hybrid (3x) plant. The availability of these various ploidy levels needs to be accompanied by data on their reproductive biology for their efficient utilization for breeding. This study characterized male flowers concerning qualitative and quantitative morphology, pollen viability, pollen size, nectar volume, nectar Brix index, and acidity level of those different ploidy levels. Observations indicated no differences in qualitative morphological traits, such as, shape and color, but for quantitative morphological traits, such as, size, distinction existed among the different ploidy levels. The triploid plant has huge flower parts in all the quantitative morphological traits, except compound tepal width, followed by the tetraploid, diploid, and mixoploid. Variations also occurred in pollen viability, pollen size, and nectar characters from each level of ploidy. Pollen viability is the highest for the diploid plant, while the tetraploid plant produces bigger pollen than the diploid. The triploid plant produced a low percentage of viable pollen. The study findings indicate that ploidy level affects the flower's quantitative morphological characteristics, pollen viability, and pollen size, but not the flower's qualitative morphological characteristics. [ABSTRACT FROM AUTHOR]

Clerodendrum colebrookianum Walp. and Clerodendrum infortunatum L. are well known for their medicinal uses in treating various human ailments traditionally. Pollen biology study was done in both plant species to decipher pollen viability, in vitro pollen germination, and pollen storage in varied temperature conditions. Pollen viability tests was done by 2, 3, 5-triphenyl tetrazolium chloride (TTC test) for which pollen grains were collected at the anthesis stage that ascertained high viability, ranged between 71.97%±4.30 % in C. colebrookianum and 81.63%±3.23 in C. infortunatum. In vitro pollen germination was conducted under different hormones (IBA, IAA, GA3, and Kinetin) with concentrations of 100 mg L-1, 200 mg L-1 and 300 mg L-1. Highest germination percentage of 52.10±5.30% and 61.91±1.76% in GA3 (200 mg L-1) was the most suitable growth hormone concentration for inducing in vitro pollen germination in both Clerodendrum species. Statistically, the response of all the concentrations of treatments, sucrose, and hormones, with their time on in vitro pollen germination of C. colebrookianum and C. infortunatum was found significantly different (p<0.05). In contrast, non-significant differences were recorded for in vitro pollen germination between the medicinal plant species. Pollen storage under temperature gradient conditions exhibited a similar trend in the viability for both C. colebrookianum, and C. infortunatum, i.e., the pollen remained viable up to 28 days at -20°C and 6°C, respectively. This study will be helpful in future breeding, hybridization, and conservation efforts for both the Clerodendrum species. [ABSTRACT FROM AUTHOR]

SUMMARY: Pollen exine is composed of finely‐organized nexine, bacula and tectum, and is crucial for pollen viability and function. Pollen exine development involves a complicated molecular network that coordinates the interaction between pollen and tapetal cells, as well as the biosynthesis, transport and assembly of sporopollenin precursors; however, our understanding of this network is very limited. Here, we report the roles of PEM1, a member of methyl‐CpG‐binding domain family, in rice pollen development. PEM1 expressed constitutively and, in anthers, its expression was detectable in tapetal cells and pollen. This predicted PEM1 protein of 240 kDa had multiple epigenetic‐related domains. pem1 mutants exhibited abnormal Ubisch bodies, delayed exine occurrence and, finally, defective exine, including invisible bacula, amorphous and thickened nexine and tectum layer structures, and also had the phenotype of increased anther cuticle. The mutation in PEM1 did not affect the timely degradation of tapetum. Lipidomics revealed much higher wax and cutin contents in mutant anthers than in wild‐type. Accordingly, this mutation up‐regulated the expression of a set of genes implicated in transcriptional repression, signaling and diverse metabolic pathways. These results indicate that PEM1 mediates Ubisch body formation and pollen exine development mainly by negatively modulating the expression of genes. Thus, the PEM1‐mediated molecular network represents a route for insights into mechanisms underlying pollen development. PEM1 may be a master regulator of pollen exine development. Significance Statement: The present study reveals that PEM1, a rice member of methyl‐CpG‐binding domain family, is essential for pollen development through mediating pollen exine development and Ubisch body formation, although it does not appear to affect the timely degradation of tapetum, in contrast to known pollen exine development‐related genes that were generally implicated in the timely degradation of tapetum. PEM1 regulates pollen exine development by modulating the expression of a set of genes, and thus may be a master regulator of pollen development. [ABSTRACT FROM AUTHOR]

The purpose of this study was to select the suitable broad-spectrum stain for the determination of walnut pollen viability, determine the pollen viability of walnut, screen the suitable storage temperature for maintaining walnut pollen viability, and study the pollen morphology, which can provide a basis for walnut cross breeding and variety identification. In this study, six walnut cultivars mainly grown in Shaanxi were used as materials, the staining effect of TTC, MTT and I2-IK stains on walnut pollen was studied by single factor experimental design with medium method as control, the changes of walnut pollen viability were compared at room temperature of 20 °C, 4 °C and -20 °C, and the pollen morphological differences of 6 walnut cultivars were studied by scanning electron microscopy. The results showed that active and inactive pollen could be identified by MTT but TTC and I2-IK could not. The pollen variability determined by MTT and medium method was consistent among 6 walnut cultivars. The initial pollen viability of 6 walnut cultivars was divergent greatly, and the pollen viability of ‘Zhonglin 5’ and ‘Xiangling’ was significantly higher than that of other 4 cultivars. The pollen viability of walnut could only be maintained for 4-5 days at room temperature of 20 °C with 20% water content. The pollen life can be effectively prolonged for 5- 9 days at 4°C, and the pollen viability of most cultivars can only be maintained for 2 days at -20 °C . The pollen grains of 6 walnuts were nearly spherical, and the size of pollen grains was significantly differences among cultivars, in which the polar axis ranged from 39. 15 μm to 44. 35 μm, and the equatorial axis ranged from 33. 58 μm to 42. 86 μm. The pollen grains of ‘Qingxiang’ and ‘Shaanhe’ were relatively large. The pollen grains of walnuts had 13 to 20 round or oval germ pores with the long axis ranging from 3. 26 μm to 3. 75 μm, and the short axis ranging from 2. 75 μm to 3. 35 μm. The germ pores number differed significantly among cultivars. This study estimated that the stain MTT had low selectivity and broad spectrum in pollen staining of walnut cultivars, which can be used as the preferred dye for walnut pollen viability determination. The pollen life of 6 cultivars was short in natural circumstance, the initial pollen viability was relatively low ( less than 40%) besides there was great diversity among cultivars. The storage at 4 °C was favorable for walnut pollen storage whereas -20 °C was unfavorable. There were significant differences in pollen grain size and germ pore number among 6 walnut cultivars. [ABSTRACT FROM AUTHOR]

Premise: Living collections maintained for generations are at risk of diversity loss, inbreeding, and adaptation to cultivation. To address these concerns, the zoo community uses pedigrees to track individuals and implement crosses that maximize founder contributions and minimize inbreeding. Using a pedigree management approach, we demonstrate how conducting strategic crosses can minimize genetic issues that have arisen under current practices. Methods: We performed crosses between collections and compared progeny fitness, including plant performance and reproductive health. We genotyped the progeny and parental accessions to measure changes in diversity and relatedness within and between accessions. Results: The mean relatedness values among individuals within each accession suggest they are full siblings, demonstrating that there was high inbreeding and low diversity within accessions, although less so among accessions. Progeny from the wider crosses had increased genetic diversity and were larger and more fertile, while self‐pollinated accessions were smaller and less fertile. Discussion: Institutions that hold exceptional species should consider how diversity is maintained within their collections. Implementing a pedigree‐based approach to managing plant reproduction ex situ will slow the inevitable loss of genetic diversity and, in turn, result in healthier collections. [ABSTRACT FROM AUTHOR]

Drought stress is detrimental to male reproduction in maize (Zea mays L.), largely through reducing the quantity and quality of pollen grains. However, transcriptional response of maize pollen grains to drought stress has not been well documented. We compared pollen gene expression for a maize hybrid (ZhongDan909) under well-watered and drought-stress conditions, based on RNA-Seq validated by quantitative real-time PCR analysis. Expression of 6424 genes and 1302 transcripts was altered in pollen grains of maize subjected to 7 days of drought during flowering. Gene Ontology annotations showed 308 differentially expressed genes, annotated and classified into 50 primary functional categories. Kyoto Encyclopedia of Genes and Genomes analyses revealed 44 differentially expressed genes in nine metabolic pathways. In relation to carbohydrate metabolism pathways, there was downregulation of a polygalacturonase gene, which could reduce cell wall lysis in early pollen germination, and an increase in callose synthase transcripts along with reduced cellulase transcripts. These altered gene expressions responsible for cell wall integrity may inhibit the initiation of pollen tube growth. The onset of tube growth could be further impeded by observed changes in gene expression that potentially influence hormone metabolism (including downregulation of AUXIN RESPONSE FACTOR 18 and EIN3-BINDING F-BOX), reduce mitochondrial function, and alter protein translation. Genes with potential roles in adaptation were also altered in their transcript levels. These included genes encoding the upregulated transcription factor ZmNF-YC2, and the downregulated ZmbHLH13, a negative regulator of jasmonic acid responses. The upregulated flavin enzyme gene DIHYDROLIPOYL DEHYDROGENASE 1, associated with increased levels of reactive oxygen species, is of interest in relating redox homeostasis to stress adaptation. Overall, the analyses identified a suite of genes involved in the development of pollen grains and tubes and responsive to drought stress. The findings enhance understanding of the gene networks underlying compromised pollen viability under drought stress. [ABSTRACT FROM AUTHOR]

The use of biotechnology for the genetic improvement of wheat (Triticum aestivum L.) has been hampered by its recalcitrance to standard transformation and regeneration protocols. Male gametes present a potentially useful option for introducing gene edits via clustered regularly interspaced short palindromic repeats (CRISPR). However, the utility of male gametes for introducing genetic improvements would be dependent on the retention of viability after treatment to introduce the CRISPR components. We have studied wheat pollen morphology and its viability in a range of germination media to identify conditions that optimize the viability of in vitro hydrated pollen. The size, shape, and aperture from seven different wheat genotypes were compared using scanning electron microscope (SEM). The SEM results revealed that the pollen of all of the wheat genotypes examined in this study were monoporate; however, a significant variation in the size of the mature pollen grains was observed. The hydrated pollen of the wheat genotypes remained viable for up to five hours at 20 ± 2 °C. Of all of the germination media tested, the medium containing 5% sucrose, 10% PEG4000, 100 mg/L boric acid, 200 mg/L calcium nitrate, 100 mg/L potassium nitrate, and 100 mg/L magnesium sulphate at pH 6.5 achieved the highest percentage of pollen germination after 5 h of hydration. Impedance Flow Cytometry (IFC) provided similar results to the in vitro germination study. This work elucidates important factors that can form the basis for a pollen-based non-genetically modified system for gene editing in wheat. [ABSTRACT FROM AUTHOR]

• Foldscope is an efficient, low-cost, lightweight, and portable microscope. • Foldscope is an alternative for a conventional compound microscope for monitoring of the pollination process. • Foldscope can be used for field-level real-time in vivo monitoring of the pollination process. An efficient, low-cost, lightweight, and portable paper microscope can be used to monitor real-time in vivo pollination, which is not feasible with a conventional compound microscope. The advantages of paper microscopes (foldscopes) remain unexplored for in vivo field-oriented assessment of pollination. In this study, experiments were carried out to calibrate and validate the capability of foldscopes to investigate in vitro pollen traits and to understand the feasibility of using in real-time in vivo field-level investigations. Comparison of optical images of pollen morphological traits (color, size, and shape) of diverse plant species (including crops) captured using a foldscope and a compound microscope revealed little to no differences. In addition, foldscopes were calibrated to monitor and estimate in vitro pollen viability in wheat, sorghum, sunflower, chickpea, soybean, and periwinkle and to determine in vitro pollen germination in chickpea, maize, and periwinkle. Pollen tube growth was observed by time-lapse imaging of pollen from periwinkle. The foldscope efficiently captured genotypic variation in in vitro pollen germination of twelve chickpea genotypes under drought revealing the possibility of foldscopes as a tool for field level, real-time in vivo monitoring of pollination under drought. [ABSTRACT FROM AUTHOR]

Triticum aestivum is a self-pollinated species with a high proportion of cleistogamous flowers constituting a blockade for out-crossing. Therefore, male parent characteristics are the main goal in the production of hybrid wheat seeds. In a two-year study conducted in Lublin (Poland), the features of flowering biology that can be relevant for the cross-pollination ability of the pollen donor were investigated in winter wheat genotypes. In particular, the anther extrusion capacity, pollen production at the anther and spike levels, and pollen biological value were examined. The pollen production in the anthers was established using an electronic particle counter. The pollen biological value was assessed based on viability (acetocarmine staining) and in vitro pollen germination (raffinose medium) assays. The inter-genotype effect for anther extrusion was significantly correlated to the post-anthesis filament length. The anther extrusion for the individual genotypes fluctuated significantly between the years of the study; however, the interaction with meteorological factors was not assessed. The considerable inter-genotype variability in the pollen donor capability for cross-pollination was highly significantly correlated with the proportion of extruded anthers rather than pollen production, indicating that anther extrusion plays a more important role in the contribution to the final amount of pollen available for cross pollination. The pollen viability determined by staining was high (between 97.5% and 100%), while the in vitro pollen germination varied substantially among the genotypes (between 17.3% and 87.8%). The pollen dispersal ability for cross-pollination in wheat can be improved mainly by increasing the proportion of extruded anthers; however, the pollen production and pollen germination potential cannot be ignored if complete characterization of the ideal male idiotype is to be achieved. [Display omitted] • Proportion of extruded anthers plays substantial role for cross-pollination in wheat. • Anther extrusion is mainly related to the post-anthesis filament length. • Pollen production and pollen germination are important for the ideal male idiotype. [ABSTRACT FROM AUTHOR]

The major bottleneck in interspecific hybridization is the sterility of the hybrid individuals. Different methods such as tissue culture techniques, molecular studies and grafting are used to overcome the sterility barriers as a result of hybridization between species. In the present study, the grafting method was used to overcome the low pollen fertility of hybrid plants obtained from the hybridization between Solanum melongena and Solanum torvum. Three different rootstocks with high fertility (Pala, Faselis F1, and S. torvum) were used for grafting. Three interspecific hybrids (8/I-3, 8/II-1 and 8/IV-2) were used as the scion. Pollen viability and pollen germination rates of these genotypes were determined. According to the data obtained, it was determined that the pollen viability and germination were affected significantly by the rootstock-genotype combination. The highest rate of pollen viability and pollen germination was obtained from Pala - 8/II-1 combination. The rate of pollen stained in "red + pink" of the 8/II-1 genotype grafted on Pala rootstock increased 98.00 times and the pollen ratio stained only in red increased 77.87 times, compared to the nongrafted. The Pala was determined as the most suitable rootstock for the interspecific hybrids. [ABSTRACT FROM AUTHOR]

Oilseed rape (Brassica napus) or Canola is an important oilseed crop produced and consumed globally. The predicted increase in the frequency of high‐temperature events associated with climate change poses a threat to Canola productivity. In the present work, we report the impact of short‐term heat stress on the reproductive fitness and yield components of Canola. Short heat stress episodes, especially above 36°C, resulted in diminished reproductive fitness due to reduced pollen viability and germinability. Heat stress exposure led to asynchronous male and female development and suppressed pollen development in developing buds. As the temperature increased above 32°C, the seed production decreased significantly. Temperatures beyond 38°C resulted in >50% reduction in total seed production and seed weight. Short‐term heat stress also reduced yield components, seed vigour and post‐harvest seed characteristics. Biochemical investigations of the seeds harvested from heat‐stressed (40°C for 12 hr) plants showed decreased oil content along with a variable fatty acid composition. The omega‐6/omega‐3 ratios increased in response to heat stress indicated a possible decline in oil nutritional quality. Understanding the impact of short heat stress episodes can provide efficient heat tolerance screening tools and pave the way for developing heat stress‐tolerant B. napus varieties. [ABSTRACT FROM AUTHOR]

The development of varieties with strong tolerance is one of the important strategies to diminish the negative impact of chilling stress during heading on the spikelet fertility and yield formation of late-season rice. However, whether such genetic improvement has been made in inbred late rice lines in China is not clear. In the present study, three late-season inbred rice varieties, Xiangwanxian2 (XWX2, released in 1988), Xiangwanxian8 (XWX8, released in 1998) and Xiangwanxian17 (XWX17, released in 2008) were subjected to moderate (20 °C) and extreme (17 °C) chilling stress during heading, and the grain yield components and flowering-related traits of the three varieties in response to different temperature were investigated. The results showed that the newly released inbred late rice variety XWX17, demonstrated better chilling tolerance during heading than the early released varieties with respect to higher grain filling percentage. The improved grain filling percentage in XWX17 might be the results of increased spikelet fertility, which was attributed to the increase in pollen viability, anther dehiscence length and anther volume. In addition, the SPAD value and the chlorophyll a content of the flag leaf can be used as indicators to predict the rice spikelet fertility when suffering from chilling stress during heading. The present study provides evidence that the genetic approach has been made to improve the chilling tolerance of inbred late rice lines during heading; however, further research is needed to explore the physiological and molecular mechanism underlying the relationship between leaf characteristics and function with rice spikelet fertility. [ABSTRACT FROM AUTHOR]

Efficient assimilate partitioning between the source and sink organs to achieve increased grain weight is coordinated by the sugar signaling mechanism. The expression of the genes involved in sugar signaling mainly hexokinases 2 (OsHXK2), Sucrose-nonfermentation1-related protein kinase1 (OsSnRK1), trehalose-6-phosphate synthase 1 (OsTPS1) and target of rapamycin (OsTOR) under high temperature stress was examined in tolerant (NL-44) and susceptible (Vandana) varieties of rice. The photosynthetic rate, stomatal conductance, water-use efficiency, photochemical efficiency (Fv/Fm), quantum yield (ϕPSII), pollen viability, spikelet fertility and 1000 grain weight were significantly higher in NL-44 compared to Vandana under stress. The difference in the gene expression levels in the vegetative and grain-filling phases as well as between the tolerant and susceptible varieties, revealed unique pathways of sugar signaling under heat stress. In the vegetative phase, the expression of OsTOR seems to be the difference between NL-44 and Vandana for their differed heat stress tolerance whereas, in the grain-filling phase, the difference between the varieties lay in the regulation of OsHXK2. The comparative changes in the expression levels between the genes under the varying conditions indicate the sugar status in the source and sink organs that are available for translocation or remobilization. [ABSTRACT FROM AUTHOR]

Pollen fertility plays an important role in the application of heterosis in wheat (Triticum aestivum L.). However, the key genes and mechanisms underlying pollen abortion in K-type male sterility remain unclear. TAA1a is an essential gene for pollen development in wheat. Here, we explored the mechanism involved in its transcriptional regulation during pollen development, focusing on a 1315-bp promoter region. Several cis-acting elements were identified in the TAA1a promoter, including binding motifs for Arabidopsis thaliana AtAMS and AtMYB103 (CANNTG and CCAACC, respectively). Evolutionary analysis indicated that TaTDRL and TaMYB103 were the T. aestivum homologs of AtAMS and AtMYB103, respectively, and encoded nucleus-localized transcription factors containing 557 and 352 amino acids, respectively. TaTDRL and TaMYB103 were specifically expressed in wheat anthers, and their expression levels were highest in the early uninucleate stage; this expression pattern was consistent with that of TAA1a. Meanwhile, we found that TaTDRL and TaMYB03 directly interacted, as evidenced by yeast two-hybrid and bimolecular fluorescence complementation assays, while yeast one-hybrid and dual-luciferase assays revealed that both TaTDRL and TaMYB103 could bind the TAA1a promoter and synergistically increase its transcriptional activity. Furthermore, TaTDRL-EAR and TaMYB103-EAR transgenic Arabidopsis plants displayed abnormal microspore morphology, reduced pollen viability, and lowered seed setting rates. Additionally, the expression of AtMS2, a TAA1a homolog, was significantly lower in the two repressor lines than in the corresponding overexpression lines or WT plants. In summary, we identified a potential transcriptional regulatory mechanism associated with wheat pollen development. [ABSTRACT FROM AUTHOR]

Pollen grains are male gametophytes, an ephemeral haploid generation of plants, that commonly engage in competition for a limited supply of ovules. Since variation in reproductive capabilities among male gametophytes may influence the direction and pace of evolution in populations, we must be able to quantify the relative fitness of gametophytes from different sires. To explore this, we estimated the relative fitness of groups of male gametophytes in a dioecious, wind-pollinated model system, Cannabis sativa, by characterizing the non-abortion rate (measured via chemical staining) and viability (measured via in vitro germination) of pollen from multiple sires. Pollen viability quickly declined within two weeks of anther dehiscence, and pollen stored under freezer conditions did not germinate regardless of storage time. In contrast, pollen non-abortion rates declined slowly and persisted longer than the lifetime of a sporophyte plant under both room temperature and freezer conditions. Pollen samples that underwent both viability and non-abortion rate analysis displayed no significant correlation, implying that researchers cannot predict pollen viability from non-abortion rates, nor infer male gametophytic fitness from a single measure. Our work demonstrates two independent, differential approaches to measure proxies of male fitness in C. sativa. [ABSTRACT FROM AUTHOR]

• Hemerocallis are plants found all over the world. • Pollen viability allows success in breeding programs. • The suitable culture medium allows greater germination percentage of the pollen grain. • There is diversity in pollen germination among Hemerocallis genotypes. • The maximum percentage of pollen germination depends on the time after incubation. Hemerocallis is a floriferous species, which presents numerous genotypes that are constantly crossed, generating new cultivars. The germination and viability of pollen are influenced both by factors that are intrinsic and extrinsic to the pollen. In view of the above, the purpose of this study was to establish a growth medium for the germination of pollen grains. Cultivar Morgana was used in the experiments performed to establish the growth medium, in which four pH ranges were tested alongside four agar concentrations. For the next test, five sucrose concentrations were tested. Afterwards, four boric acid concentrations were added to the medium, finally followed by four calcium nitrate concentrations. After the definition of the growth medium, the incubation time for pollen grains germination of the species was evaluated. The results were then applied to four cultivars in order to verify the respective germination percentages. It was noted that the highest percentage of in vitro germination occurred with the concentrations of 4 g L−1 agar, 74.6 g L−1 sucrose, 800 mg L−1 boric acid and 590 mg L−1 calcium nitrate, with a pH of 5.74 and ideal incubation time of 3 h. Regina being to cultivar with the highest germination percentage. [ABSTRACT FROM AUTHOR]

High temperature during reproductive stage of winter crops causes sterility of pollen grains and reduced yield. It is essential to find the genotypes with higher pollen viability, as it is most sensitive to temperature extremes. A field study was conducted with wheat (Triticum aestivum L.) genotypes to understand the effect of high temperature on pollen viability and grain yield for 2 years under timely (TS) and late sown (LS) conditions. A strong correlation was observed between higher pollen viability and higher grain yield under heat stress condition. Genotypes like K7903, HD2932, WH730 and RAJ3765 showed higher pollen viability, whereas DBW17, HUW468, RAJ4014 and UP2425 had lower pollen viability under LS condition. Further, the quantification of antioxidant enzymes activity mainly, Super oxide dismutase (SOD), Catalase (CAT), Peroxidase (POD) and Glutathione peroxidase (GPX) has showed significant variation among study genotypes. Thus, the identified high pollen viability genotypes can serve as a potential source for trait based breeding under heat stress in wheat. The present study is a first of its kind to assess more number of wheat genotypes for pollen viability and antioxidants activity under field condition. It also confirms that pollen viability can be used as a potential trait to screen genotypes for heat stress tolerance in wheat. [ABSTRACT FROM AUTHOR]

Plant High-affinity K+ transporters/K+ uptake permeases/K+ transporters (HAK/KUP/KT) transporters have been predicted as membrane H+-K+ symporters in facilitating K+ uptake and distribution, while their role in seed production remains to be elucidated. In this study, we report that OsHAK26 is preferentially expressed in anthers and seed husks and located in the Golgi apparatus. Knockout of either OsHAK26 or plasma membrane located H+-K+ symporter gene OsHAK1 or OsHAK5 in both Nipponbare and Dongjin cultivars caused distorted anthers, reduced number and germination rate of pollen grains. Seed-setting rate assay by reciprocal cross-pollination between the mutants of oshak26 , oshak1 , oshak5 and their wild types confirmed that each HAK transporter is foremost for pollen viability, seed-setting and grain yield. Intriguingly, the pollens of oshak26 showed much thinner wall and were more vulnerable to desiccation than those of oshak1 or oshak5. In vitro assay revealed that the pollen germination rate of oshak5 was dramatically affected by external K+ concentration. The results suggest that the role of OsHAK26 in maintaining pollen development and fertility may relate to its proper cargo sorting for construction of pollen walls, while the role of OsHAK1 and OsHAK5 in maintaining seed production likely relates to their transcellular K+ transport activity. [ABSTRACT FROM AUTHOR]