Search

Cytoplasmic male-sterility (CMS) is the primary source for the production of commercially viable onion F1 hybrids. The molecular interplay of the cytoplasmic-nuclear genes propels the restoration of fertility in the CMS system, making it cost-effective and stable. The use of the molecular markers that can determine the cytoplasm type and nuclear genotype reduces the amount of time and labour required. This study characterized the morphology of male sterile and fertile plants based on anther colour and pollen viability. Additionally, the molecular characterization of the organellar DNA differentiating cytoplasm and nuclear genotypes in 35 commercially grown open-pollinated varieties of Indian short-day onion was attempted. Our results revealed that morphological and microscopic observations for the identification of male sterile and fertile plants were not 100% corroborative. Markers located in the chloroplast (accD) and mitochondrial DNA (MKFR) revealed that Indian cultivars exhibited a greater frequency of N (normal) cytoplasm, lower frequency of S (sterile) cytoplasm and no occurrence of T (sterile) cytoplasm. All three markers viz., AcPMS1, AcSKP1, and jnurf13 revealed that 93 to 99% of the plants of all the varieties had homozygous recessive (msms) alleles at the Ms locus. The OPT marker classified the plants as having 38% msms, 39% Msms and 21% MsMs genotypes and needs further investigation. This underscores the pressing need for additional markers to precisely discern the Ms locus, facilitating the identification of male sterile and maintainer plants within open-pollinated populations of Indian short-day onions. Notably, male sterile cytoplasm was identified in eight commercial varieties, marking a pioneering revelation in Indian onion cultivation. [ABSTRACT FROM AUTHOR]

Hybridization and polyploidy are currently known as exponential factors for biodiversity. Some Paspalum species can hybridize and originate viable allopolyploids with possible agronomic use. We collected a frost resistance hybrid in north–western Misiones and determined its ploidy level, meiotic behavior, pollen viability, cytoembryology, and seed production in open and self-pollination. To elucidate its origin, we conducted a phenotypic and geographical analysis using herbarium specimens to establish its putative parental species. The hybrid was triploid, exhibiting irregular meiosis with the formation of non-viable pollen and undeveloped embryo sacs, resulting in very low seed production under both pollination conditions. Through morphological analysis, we identified Paspalum urvillei Steud. and the Paniculata group, i.e. Paspalum juergensii Hack., Paspalum umbrosum Trin., and Paspalum paniculatum L., as the putative parental species. Geographic distribution patterns suggested a possible hybridization event between P. urvillei and P. umbrosum, though further investigation is needed to precisely identify which species from the Paniculata group hybridized with P. urvillei. Future studies will help to unravel the complex genetic interactions underlying hybridization in Paspalum species and contribute to our understanding of biodiversity dynamics. [ABSTRACT FROM AUTHOR]

Reproductive barriers are the single largest impediment in breeding of Solanum aethiopicum (Shum and Gilo cultivars). Knowledge of these barriers is important for prudent germplasm utilization and genetic improvement of the species. This study investigated compatibility barriers between S. aethiopicum and its relatives. A randomized complete block design and a full diallel mating method were used to evaluate crossability and floral traits of six genotypes of four different species (S. aethiopicum, S. macrocarpon, S. anguivi and S. incanum) across two seasons. Parameters assessed were petal opening time, stigma receptivity, anther dehiscence, pollen quantity, pollen viability and crossing success. Most flowers for all parental genotypes were opened by 08:00 am. Mean number of open flowers was higher (12 ± 6) for S. aethiopicum Shum (N11) and lowest (n = 3 ± 1) for S. macrocarpon (E12; (p < 0.001), with other genotypes being intermediate. Stigma receptivity differed (p < 0.001) among genotypes and seasons and was highest for N11 at 3.31 ± 1.32 and lowest for S. incanum (In1) at 2.24 ± 1.27; other genotypes were intermediate. All genotypes possessed high pollen viability (µ > 80%) though species differed (p < 0.01). All genotypes exhibited self-compatibility to varying degrees with N11 showing the highest fruit success (67.9 ± 15.6%), seeds per fruit (82 ± 51), and F1 germination rate (79 ± 18%). Interspecific crosses using S. macrocarpon, S. anguivi and S. incanum as females showed poor or no fruit and seed. N11 (S. aethiopicum Shum) was the top performer as a female; crosses with S. macrocarpon (N11xE12) showed highest fruit success (65.9 ± 26.5), with S. anguivi (N11xA1) showing the highest seed set (n = 56 ± 34) and S. incanum (N11xIN1) showing the highest F1 germination (64 ± 19). The F1 intraspecific cross between S. aethiopicum Shum (N4) and S. aethiopicum Gilo (G4) did not germinate. Female parent functioning may be a key feature for the failure of interspecific crosses where S. aethiopicum is a donor as observed by the unilateral incompatibility. [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]

While no significant differences in initial ovule number were found among oilseed rape Brassica napus genotypes, there was a large variation in effective ovule number (EON), which determines the final seeds per silique (SPS), a critical component of yield. In this study, we selected 18 oilseed rape Brassica napus genotypes with contrasting nitrogen utilization efficiency (NUtE) to unravel the main factors responsible for different EON and determine the critical period of EON formation under both a field and a pot experiments from 2016–2018. The high NUtE genotypes displayed significantly higher NUtE by 14.3%, along with greater yield per plant (29.4%) and SPS (21.1%) than the low NUtE genotypes. The greater productivity of the high NUtE genotypes was associated with 44.1% higher pollen grain number, 23.5% greater pollen viability, and 39.3% lower ovule abortion rate, compared to the low NUtE genotypes. In addition, the heart stage was the critical ovule development period for delineating the variability of EON among contrasting NUtE oilseed rape Brassica napus genotypes, when the high NUtE genotypes displayed higher silique net photosynthetic rate, surface area, biomass, and RNA expression levels. Taken together, this study indicated the pollen grain number, pollen viability and ovule abortion rate contributed to the final variation in EON and the heart stage was the critical period of determining the EON differences among contrasting NUtE genotypes. Increasing pollen grain number and pollen viability, and decreasing ovule abortion rate before heart stage should be the prerequisite for breeders to improve yield and NUtE of oilseed rape Brassica napus genotypes. [ABSTRACT FROM AUTHOR]

Passiflora F1 hybrids, with ornamental potential, were confirmed via GISH and analyzed for meiotic compatibility. This study aimed to analyze the meiotic behavior of P. gardneri Mast. and P. gibertii N.E. Brown and four interspecific hybrids resulting from this cross, with the aim of inferring genetic compatibility between parents and the implications of hybridization on the hybrids' genomes. Flower buds were collected for classical cytogenetic studies and anthesis flowers for pollen viability (PV) using (1) Alexander's solution and (2) fluorescein diacetate. Pollen grains were counted, measured and identified as viable or unviable, with the PV considered to be low. Genomic in situ hybridization (GISH) technique was used in prophase I. Analysis of meiotic behavior showed bivalent formation among the homologous in the parents and homeologous in the hybrids; some irregularities were found, such as lagging chromosomes, asynchrony, spindle fiber irregularities and chromosomal bridges. Post meiosis resulted in anomalous cells such as monads, dyads, triads and polyads. All results were subjected to analysis of variance, with significant differences for all analyses between hybrids, with the exception of monad formation. GISH confirmed the hybrid character and pairing between homeologous chromosomes. The results obtained in this study established the degree of homology between the parent species through analysis of chromosome pairing and chiasma formation, confirmed by GISH. Both parent species showed potential for use as paternal parents. [ABSTRACT FROM AUTHOR]

Heat stress adversely affects tomato production worldwide. Breeding thermotolerant varieties is critical to adapt to increased heat stress but tomato has a narrow genetic base for heat tolerance. Identification of new sources of heat-tolerant germplasm is important to understand physiological and molecular mechanisms of adaptation to heat stress and to broaden the genetic base of heat tolerance in tomato. Here, we screened a germplasm collection comprised of 42 tomato entries using 19 quantitative (physiological, reproductive, and morphological) and five qualitative traits. The plants were grown under long term mild heat stress with temperatures and relative humidities ranging from 23.3 to 37 °C, and 47 to 100%, respectively. The analysis of variance revealed significant differences among the entries for all the quantitative traits. Biologically significant associations were recorded for many traits. Proportion of viable pollen was not associated with fruit set percentage. The clustering analysis groups the germplasm into five clusters with a clear distinction between Solanum lycopersicum and Solanum pimpinellifolium entries. We also observed differences between the entries based on their origins. Known thermo-tolerant entries were found in Clusters 3 (eg.: LA2662, LA3317, LA3120) and 4 (e.g.: CL5915-93D4-1-0, CLN1621L, LA2661). Lines BJ01, BJ02 from Republic of Benin, and WAC1 and ATS020 from Ghana in Cluster 3 are potential new sources of thermo-tolerance in tomato. Generation of hybrids from parents belonging to the clusters 1 to 4 identified in this study would improve heterosis for heat tolerance traits in tomato. Useful traits like high pollen viability and high inflorescence numbers per plant could be introgressed from S. pimpinellifolium entries into the cultivated tomato. Our study provides important information to improve heat tolerance in tomato. [ABSTRACT FROM AUTHOR]

Interspecific F1 hybrids were obtained from crosses between two Ogura cytoplasmic male sterility (Ogura CMS) broccoli lines (B14 and 137) and a rapeseed restorer line to introgress the Ogura CMS's fertility-restoration gene Rfo from rapeseed into broccoli. Ten Rfo-positive interspecific, triploid plant progenies, phenotypically between rapeseed and broccoli, were obtained but still contained multiple rapeseed genes, with reduced fertility and seed setting potential under natural pollination. For fertility and seed setting improvement, successive backcrosses with broccoli were carried out to yield BC2 progenies. Screening revealed six plants with Rfo among 25 BC2 progenies, which were investigated for agronomic traits, ploidy determination, pollen viability and SSR (simple sequence repeat) markers to evaluate for ideal individuals closer to broccoli. Pollen viability tests were carried out at different stages for various hybrid parents. The results were as follows: 137-F1 (68.54%) > B14-F1 (65.32%) > 137-BC1 (48.15%) > B14-BC1 (32.41%). Although there were significant differences among the BC1 and BC2 individuals, the genetic background of BC2 was closer to the parent broccoli compared with that of BC1 plants. The existence of the Rfo gene in broccoli not only facilitates broccoli germplasm innovation, combination of interspecific hybridization and backcrossing, but may also shed light on trait segregation in different generations. [ABSTRACT FROM AUTHOR]

Distant hybridization can enrich the genetic background and diversity of crops by combining different species, and integrate the favorable parental traits or create heterosis. In the present study, intergeneric hybridization was performed between radish and turnip and between radish and Chinese kale by hand emasculation followed by tissue culture of putative hybrid seeds. A total of three and one hybrids were obtained from the cross of 'Long yellow turnip' and 'Golden turnip' with radish, respectively, but no hybrids were obtained in their reverse cross, indicating that the same cross combination has a large difference in the reciprocal crosses, and that the hybrid has certain unidirectionality. The majority of the hybrids of radish and turnip showed male sterility, white petals, and intermediate performance in most morphological traits when compared to their parents. Four true hybrids were obtained by the cross 'Thin neck round radish' × 'Yellow flower kale', while no hybrids were obtained by reverse cross combination. The hybrids looked more like their Chinese kale parents in having inflated stems. All putative intergeneric hybrids were confirmed by agronomic characteristics, chromosome counting, molecular markers, and pollen viability. Three kinds of hybrids were confirmed as genuine hybrids possessing 19, 19, and 18 chromosomes in their corresponding somatic cells by cytological observation. In addition, three kinds of allotetraploids were produced with 38, 38, and 36 chromosomes when chromosome doubling was achieved. In comparison with the diploid hybrid, the pollen viabilities of allotetraploids were significantly improved and a small number of seeds were produced. The improvements of these amphihaploids as useful genetic resources and the potential of intergeneric hybridization to enlarge the gene pool for radish, turnip, and Chinese kale breeding are discussed. [ABSTRACT FROM AUTHOR]

The interspecific hybridization was performed between five tulip cultivars, including 'Judith Leyster,' 'World's Favorite,' 'Heart of Poland,' 'Crispa Fabio' and 'Jumbo Pink,' and five wild species, including Tulipa thianschanica Regel, T. sinkiangensis Z. M. Mao, T. altaica Pall. ex Spreng, T. buhseana Boiss. and T. schrenkii Regel., to explore the cross-compatibility between tulip cultivars and wild species. In this experiment, pollen size and germinability, pollen storage life, stigma receptivity, fruit-setting, hybrid seed germination and bulblet formation were observed. The chromosome count and karyotype of hybrids were also examined. The results showed that T. altaica and five cultivars had closer genetic relationship than the other four wild species. Among the five wild Tulipa species T. altaica has the largest pollen and the highest germination rate (65.23%) compared with any other four species. The pollen viability of all five pollen parents decreased slowly across all stages at − 20 °C and decreased rapidly at 25 °C and 4 °C. A total of 1066 hybrids were obtained from interspecific hybridization combinations, including 'Heart of Poland' × T. thianschanica, 'Heart of Poland' × T. altaica, 'Crispa Fabio' × T. altaica, 'Jumbo Pink' × T. altaica, 'Crispa Fabio' × T. schrenkii and 'Jumbo Pink' × T. schrenkii. According to the chromosome count, approximately 20% and 12% aneuploidy hybrids were produced from 'Heart of Poland' (2n = 3x = 36) × T. thianschanica (2n = 2x = 24) and 'Heart of Poland' (2n = 3x = 36) × T. altaica (2n = 2x = 24), respectively, and the any other hybrids were diploid (2n = 24) in these two crosses. All the hybrids from crosses of diploid parents were diploid (2n = 24). Meanwhile, the karyotype characteristics of six parents and their six progenies were also elaborated, which had similar 3A and 3B karyotypes. The results of this study may facilitate tulip interspecific hybridization in the future. [ABSTRACT FROM AUTHOR]

Some species in Vicia sativa complex, also called aggregate (CVS), have economic and ecological advantages and they are frequently used for pasture, silage, and green manure. The main objective of this study was to explore the secondary gene pool for enhancement of common vetch (Vicia sativa L.) germplasm by genome introgressions via conventional crosses made between cultivated common vetch (Vicia sativa L. subspecies sativa) used as female parent with five other subspecies [amphicarpa (L.), Batt., cordata (Wulfen ex Hoppe) Asch. & Graebner, macrocarpa (Moris) Arcang., nigra (L.) Ehrh., and segetalis (Thuill.)], used as male parents. As indicated with very low seed sets, higher levels of sterility were the rule in hybrids in CVS. Hybrids were confirmed using flower petal color and anthocyanin pigmentation markers. Chromosome count studies revealed that certain crossing-experiments were successfully produced interspecific hybrids. Certain offspring progenies in further generations were also obtained. Our studies clearly indicated that complex CVS and hybrids obtained from these species consisted of 10, 11, 12, 13 and 14 pair of somatic chromosomes. Results indicated that there exist significant incompatibility alleles possibly expressing in the zygote or post-zygotic developmental stages within the CVS. In conclusion, present study revealed that sufficient amount of seeds could be obtained from the crosses in the CVS and this stimulates renewed interest in utilizing the secondary gene pool as a source of genetic variation in breeding programs of common vetch. [ABSTRACT FROM AUTHOR]

The common bean is the most important legume for human consumption and is grown in areas under conditions of varied rainfall and temperature that limit its yield. The objective of the present study was to identify genotypic differences in adaptation of 91 bean genotypes to high temperature under environmental conditions of a tropical dry forest ecosystem. We quantified differences among genotypes in terms of phenology, dry matter partitioning indices and grain yield. Common bean lines were derived from interspecific and intraspecific crosses among Phaseolus species of P. vulgaris, P. acutifolius, P. coccineus and P. dumosus. We identified three germplasm accessions of P. acutifolius (G 40001, G 40027, G 40141); two lines from the cross of P. vulgaris × P. acutifolius (INB 837, SIN 524); two lines from the cross of P. vulgaris × P. acutifolius × P. coccineus (SEF 14, SEF 42) and eight lines of P. vulgaris (BFS 10, SEN 46, SEN 48, SEN 70, SMN 99, SMC 140, SMR 139-1G, AMADEUS-EAP-9510-77) that are better adapted to higher temperature stress conditions, evidencing the significant contribution of P. acutifolius to heat tolerance derived from interspecific crosses in common beans. We also found a few Andean lines of growth habit I (SAP 1, SAP 1-15, SAP 1-16, G 122, SAB 618, DAB 525) with superior level of adaptation to heat stress. The superior performance of all these above identified genotypes under higher temperature conditions was attributed to early maturity, high pollen viability and greater ability to partition dry matter to reproductive growth together with greater grain filling. [ABSTRACT FROM AUTHOR]

Pollen viability and stigma receptivity are prerequisites for successful pollination and seed set in flowering plants. In this study, the pollen viabilities and stigma receptivities of nine Lilium genotypes (six cultivars and three species native to China) were assayed by in vitro pollen germination and the benzidine-H2O2 method, respectively. Embryo sac development during anthesis was observed to further ensure the timing of controlled pollination. In addition, the relationship between stigma secretion and stigma receptivity was studied to estimate the pollination time based on phenotype. Anthers cracked on the day of flowering in all genotypes, but pollen germination during anthesis was not observed in Asiatic hybrids excepted for ‘Tiny pudhye’, which exhibited low pollen viability for a short period of time (from 0 to 1 day after anthesis). In the other genotypes, pollen germination rates were highest on anthesis (five of seven genotypes), 0–1 day after anthesis (L. sulphureum), or 0–2 days after anthesis (one Longiflorum hybrid), and then gradually decreased with days after anthesis. While, stigma receptivity first increased and then decreased during anthesis. For most genotypes, stigmas began to be receptive 1 day after anthesis, and all genotypes exhibited stigma receptivity at 2 days after anthesis. The durations of stigma receptivity and strongest stigma receptivity, were genotype dependent, and were 5–8 days and 1–4 days, respectively. Moreover, on the first flowering day, 6 of 7 genotypes had mature embryo sacs, and at the time at which stigmas began to be receptive, all tested genotypes had mature embryo sacs. Some Lilium genotypes showed stigma secretion, which can be a sign of stigma receptivity. Stigmas became receptive and reached highest receptivity within 1 day of the first appearance of secretion on the surface of the stigma and at peaking, respectively. The results of this study are valuable for the implementation of successful Lilium breeding programs. [ABSTRACT FROM AUTHOR]

High ambient temperature has adverse effects on plant vegetative and reproductive development and reduces crop yield. To better understand the importance of male and female fertility for tomato fruit set ability under high temperature conditions and to test whether heat tolerance levels among and between reproductive and vegetative traits of genotypes correlate with each other, 13 tomato cultivars were subjected to long-term moderate heat (LTMH) or short-term heat shock (STHS), depending on the trait that was evaluated. LTMH caused significant decrease in performance of nearly all reproductive traits, i.e. pollen viability, pollen number, female fertility, seeded-fruit set and flower number per inflorescence, but not in inflorescence number. Considerable variation was found among cultivars, both under control and LTMH conditions. The cultivars Nagcarlang, Saladette and Malintka 101 produced a higher percentage of viable pollen under LTMH. For fruit set under LTMH condition, only cultivars that had been previously reported as being heat-tolerant produced fruits with seeds. STHS negatively affected vegetative traits concerning seedling survival and membrane stability. Correlation analysis revealed relationships between various traits within the control and heat treatments, but not between the two. Under heat stress fruit set was positively correlated with pollen viability, as well as with flower number per inflorescence. However, no significant correlations were found between vegetative and reproductive traits. Our data highlight the prominent role of pollen viability for tomato fertility under LTMH growth conditions. The observed variation in thermotolerance among different cultivars offers the possibility to decipher underlying physiological and genetic mechanisms. [ABSTRACT FROM AUTHOR]

Among the abiotic stresses affecting plant reproduction, high temperature is one of the most prominent ones because it directly affects fruit set. So far, little attention has been paid to the investigation of the variation in high temperature tolerance among wild tomato (Solanum lycopersicum) germplasm. The objective of this study was to determine the tolerance of 17 different cultivated and wild tomato accessions to high temperature, using a pollen viability screening approach. Each of the 17 genotypes of tomato was analysed for their pollen quality under a 32 C (day)/ 26 C (night) regime. The total number of pollen per flower and the fraction of viable pollen were recorded. The number of pollen per flower varied between 35,547 and 109,490 whereas the fraction of viable pollen varied between 0.03 and 0.71. No correlation was found between these two traits. However, the combination of these traits could provide the best reproductive capability under high temperature. In this study, thermo-tolerant (LA2854, LA1478 and LA0417) as well as thermo-sensitive (LA1719, LA1580, and SWEET4) genotypes have been identified. Those genotypes can be used as novel genetic resources to get more insight into pollen thermotolerance mechanisms and be included in breeding programs. [ABSTRACT FROM AUTHOR]

In this study, the morphology, cytology and crossability of amphidiploid hybrids (2n = 8x = 80; WWW′W′TTT′T′) between Nicotiana wuttkei × Nicotiana tabacum were studied. An R progeny of the hybrids were produced through in vitro chromosome doubling of the N. wuttkei × N. tabacum cv. Wiślica amphihaploids. The resulting amphidiploids showed enough self-fertility to be perpetuated by self-pollination. The plants preserved their phenotypes and the number of chromosomes over subsequent R-R selfed generations. During metaphase I the bivalent number increased progressively over the generations R to R and averaged 36.9, 37.4, 38.6 and 38.7, respectively. In addition, a progressive increase in pollen viability was observed: 50.8, 55.5, 62.3 and 65.7 % in generations from R to R, respectively. Genomic in situ hybridization of R plants revealed recombination between the parental species on two chromosomes. Reciprocal crosses of R generation amphidiploids to N. tabacum cv. Wiślica yielded sesquidiploid hybrids (2n = 6x = 64; WW′TTT′T′). When N. tabacum cv. Wiślica is the pollinator, the amphidiploid gave rise to a total of 25 sesquidiploid plants with the cytoplasmic genome of N. wuttkei, while the reverse mating resulted in a mixed population consisting of a single sesquidiploid plant with the cytoplasm of N. tabacum and 203 plants of supposedly maternal origin. Our amphidiploid N. wuttkei × N. tabacum cv. Wiślica can be concluded as sufficiently stable and is regarded as a new artificial hybrid species. [ABSTRACT FROM AUTHOR]

The reproductive stage of flowering plants is sensitive to high-temperature stresses. High temperature is a major factor influencing pollen grain viability in upland cotton ( Gossypium hirsutum). The objective of this study was to identify the relationship between cotton pollen germination percentage and temperature by assaying the pollen germination of four upland cotton cultivars in vitro at different temperatures during the blooming period. The results showed that in vitro pollen germination percentage was related to the culture temperature of pollen germination and the temperature of the square development process. High temperature affected pollen development and germination, and high-temperature tolerance differed among the cotton cultivars. The pollen germination percentage decreased rapidly with changes in the culture temperature from 30 to 39 °C. A culture temperature of 35 °C might be a critical temperature for the pollen viability transition and could be used to screen cotton cultivars that have pollen grains with high-temperature resistance. Before the high-temperature stage, cultivars with rates of decrease in the percentage of pollen germination of less than 41 % at 35 °C relative to the rates at 30 °C might be considered as high-temperature tolerance cultivars, and cultivars with rates of decrease in the percentage of pollen germination greater than 41 % might be considered as susceptible cultivars. The high-temperature stress for pollen grain germination in vitro was greater than 30 °C, and the high-temperature stress for square development might be greater than 33 °C. Boll retention was significant; it was positively correlated with the pollen germination percentage and negatively correlated with temperature during the high-temperature stage. This study provided a method for rapidly screening cultivars (lines) with high-temperature tolerance pollen in upland cotton breeding. [ABSTRACT FROM AUTHOR]

Understanding the relationship between floral and reproductive traits are critical to understand the evolution of plant species in brassica and need for selecting lines as parental lines in hybrid seed prodcution. The protogyny nature of Brassica species are characterized based on the variations in floral morphology, protogyny interval, stigma receptivity, pollen biology, compatibility and seeds set. The variation in stigma morphology features (stigma exsertion prior to anthesis) and protogyny interval (ranged from 8 to 10 days) formed phenotypically distinct. Studies on stigma receptivity and pollen viability revealed significant variability and found to be at its peak up to 3 days after anthesis and reduced drastically thereafter. Compatibility crosses and post pollination events such as pollen deposition on the surface of the stigma and culminating with the entry of the pollen tube into the embryo sac, was rapid and completed within 2 days after pollination, whereas in in-compatible cross not even single pollen was germinated on stigmatic surface and consequently no pollen tube growth even after sixth day of pollination. In compatible crosses average seed set ranged from 3 to 8 seeds per pod from cross pollination and no seed set in self. The investigation revealed that variation exists for protogyny interval, stigma receptivity and compatibility in the protogynous lines of Indian mustard and this can be exploited for the production of hybrids without emasculation. [ABSTRACT FROM AUTHOR]

Creeping bentgrass ( Agrostis stolonifera L. or A. palustris Huds.) is a highly outcrossing allotetraploid species. It can form hybrids with a number of other Agrostis species and Polypogon genus. However, cytology and pollen grain fertility of the creeping bentgrass interspecific and intergeneric hybrids are not well known. In this research, chromosome pairing behaviors during meiosis I in F1 and pollen viability of F1 hybrids, as well as seed set rate and seed germination rate of backcrosses were studied in hybrids between creeping bentgrass, and other bentgrass species and three species of Polypogon genus. Abnormal chromosome pairing, laggard chromosomes, and premature segregation in F1 hybrids were found. Pollen viability ranged from 1.6 to 48.5% amongst F1 hybrids, significantly lower than that of the parents (85.5–94.1%). Some hybrids produced pollens of different sizes within the same anther. Seed set following backcrosses using F1 hybrids as the male parent and creeping bentgrass as the recurrent parent was significantly lower than their parents. The study of chromosome paring behaviors and progeny fecundity are important in utilizing the alien genes to improve bio-stress and abio-stress resistance, and in assessing the potential transgene risks of creeping bentgrass. [ABSTRACT FROM AUTHOR]

The University of Minnesota Gaura breeding program is developing USDA Z3-4 winter-hardy genotypes via interspecific hybridization of G. lindheimeri (Z5-6) and G. coccinea (Z2-4). Prior to commencing interspecific hybridization, the reproductive barriers operating in both parental species need to be characterized. The objective of this research was to determine the type and stability of reproductive barriers operating in G. lindheimeri by statistical comparisons between pollen tube growth and seed set in a full-sib diallel. Slowed or aborted pollen tube growth in the style indicated the presence of a gametophytic self incompatibility (SI) system. A statistical method, female (FCC) and male (MCC) coefficients of crossability, was used to verify that a stable SI system was operating and that other reproductive barriers were present. Several genotypes also expressed stage-specific inbreeding depression and incongruity. The simple linear regression equation for FCC/MCC, using pollen tube growth, was Y = 0.0124 + 0.974X, which was much closer to the expected Y = 0.0 + 1.0X (indicating a stable SI system) than the equation for seed set, Y = 0.012 + 0.910X. Using pollen tube length, both general combining ability (GCA) and specific combining ability (SCA) values were highly significant for G. lindheimeri ( P ≤ 0.001). Histograms were used to delineate cut-offs to identify intra-incompatible/inter-compatible classes and S allele groups. Four possible classes were identified, but further research is needed to verify S allele genotypes. [ABSTRACT FROM AUTHOR]

The University of Minnesota Gaura breeding program is developing USDA Z3-4 winter-hardy genotypes via interspecific hybridization of G. lindheimeri (Z5-6) and G. coccinea (Z2-4). Prior to commencing interspecific hybridization, the reproductive barriers operating in both parental species need to be characterized. The objective of this research was to determine the type and stability of reproductive barriers operating in G. lindheimeri by statistical comparisons between pollen tube growth and seed set in a full-sib diallel. Slowed or aborted pollen tube growth in the style indicated the presence of a gametophytic self incompatibility (SI) system. A statistical method, female (FCC) and male (MCC) coefficients of crossability, was used to verify that a stable SI system was operating and that other reproductive barriers were present. Several genotypes also expressed stage-specific inbreeding depression and incongruity. The simple linear regression equation for FCC/MCC, using pollen tube growth, was Y = 0.0124 + 0.974X, which was much closer to the expected Y = 0.0 + 1.0X (indicating a stable SI system) than the equation for seed set, Y = 0.012 + 0.910X. Using pollen tube length, both general combining ability (GCA) and specific combining ability (SCA) values were highly significant for G. lindheimeri ( P ≤ 0.001). Histograms were used to delineate cut-offs to identify intra-incompatible/inter-compatible classes and S allele groups. Four possible classes were identified, but further research is needed to verify S allele genotypes. [ABSTRACT FROM AUTHOR]

In connection with crop improvement strategies for marginal regions it has been proposed to increase the outcrossing rate in barley which would presuppose high and persistent pollen viability to ensure successful cross fertilisation. The present study was designed to investigate the viability of mature pollen from extruded and non-extruded anthers of cultivated and wild barley ( Hordeum vulgare ssp vulgare and ssp spontaneum, respectively) in comparison with the closely related but obligatory outcrossing species H. bulbosum. Pollen viability (PV) was assessed employing the p-phenylenediamine-peroxidase-test on pollen derived from spikes or anthers immediately after collection and after treatment at 20, 30 and 40 ∘C for 1, 2, 4, 8 and 16 h. The latter treatment was interposed after 8 h by a 10 h period of darkness at 12 ∘C and thus called 26 h treatment, consecutively. Initial PV was high with 98% across all genotypes and even at 40 ∘C did not fall below 80% after 8 h. After the 26 h treatment, PV of two H. vulgare genotypes originating from semi-arid regions and of H. bulbosum fell below 60% while the other genotypes retained a PV of > 80%. Viability of pollen of extruded anthers in H. vulgare ssp. spontaneum was on average slightly but significantly lower than PV of non-extruded anthers but still remained above 90%, even after the 26 h treatment at 40 ∘C. Pollen viability of the outcrossing species H. bulbosum ranged on a very similar level as PV of H. vulgare. Results indicate that pollen of H. vulgare retains a sufficiently high level of viability to ensure successful cross-fertilisation over a period of at least 26 h even at high temperatures of up to 40 ∘C. [ABSTRACT FROM AUTHOR]

An in vitro method for the germination of common buckwheat pollen was developed. Pollen grains were successfully germinated in an artificial medium consisting of 0.2 g each of MnSO4, Ca(NO3)2.4H2O and KNO3, 0.04 g H3BO3, 15 g sucrose and 30 g polyethylene glycol (molecular weight approximately 20,000) dissolved in 100 ml of double distilled water. The viability of pollen was assessed by in vivo and in vitro germination tests at 20 °C and 25 °C over a 38 h time period. Pollen grains were collected and germinated at 4 h intervals from freshly harvested flowers grown under 16 h day length and a constant temperature. Maximum pollen viability was found 2 h and 6 h after first light when plants were maintained at 25 °C and 20 °C, respectively. Viability, as measured by germination percentage, was similar at both temperature regimes. Some pollen remained viable for approximately 34 to 38 h in intact flowers, but all pollen lost viability in less than an hour when stored at room temperature without humidity control. [ABSTRACT FROM AUTHOR]

Red clover (Trifolium pratense L.) is a major forage legume crop with diploid and tetraploid cultivars. Seed yield is an important trait in red clover, but the underlying reasons for low seed yield in individual genotypes are not well known. Here we investigated direct associations between seed yield and ovule abortion, male meiotic abnormalities, and pollen quality in well-characterized, diploid and tetraploid red clover genotypes with contrasting seed yields. Ovule development was studied after manual pollinations: in most genotypes, high rates of embryo abortion occurred between 7 and 14 days after pollination. However, the frequencies of developing, underdeveloped and shrivelled ovules were similar in diploid and tetraploid genotypes and were not associated with seed yield. Surprisingly, self-pollination only took place in tetraploid genotypes with high seed yield (83% self-pollination on average). The frequencies of meiotic abnormalities during microsporogenesis were investigated, in addition to pollen viability and pollen germination capacity. Tetraploid genotypes displayed more meiotic abnormalities (17.3% and 7.0% respectively) and lower pollen germination (39% and 63% respectively) than diploids. A negative trend was present between meiotic abnormalities and seed yield. In conclusion, our study reveals that high seed yield was associated with a low degree of abnormalities in male meiosis in diploid and tetraploid genotypes, and with the ability to self-pollinate in the tetraploid genotypes investigated. In certain genotypes, defective male meiosis may be a primary cause of low pollen quality and low seed yield. [ABSTRACT FROM AUTHOR]