Search

SUMMARY: Stigma characteristics are important factors affecting the seed yield of hybrid rice per unit area. Natural variation of stigma characteristics has been reported in rice, but the genetic basis for this variation is largely unknown. We performed a genome‐wide association study on three stigma characteristics in six environments using 1.3 million single‐nucleotide polymorphism (SNPs) characterized in 353 diverse accessions of Oryza sativa. An abundance of phenotypic variation was present in the three stigma characteristics of these collections. We identified four significant SNPs associated with stigma length, 20 SNPs with style length (SYL), and 17 SNPs with the sum of stigma and style length, which were detected repeatedly in more than four environments. Of these SNPs, 28 were novel. We identified two causal gene loci for SYL, OsSYL3 and OsSYL2; OsSYL3 was co‐localized with the grain size gene GS3. The SYL of accessions carrying allele OsSYL3AA was significantly longer than that of those carrying allele OsSYL3CC. We also demonstrated that the outcrossing rate of female parents carrying allele OsSYL2AA increased by 5.71% compared with that of the isogenic line carrying allele OsSYL2CC in an F1 hybrid seed production field. The allele frequencies of OsSYL3AA and OsSYL2AA decreased gradually with an increase in latitude in the Northern Hemisphere. Our results should facilitate the improvement in stigma characteristics of parents of hybrid rice. Significance Statement: The utilization of heterosis in rice is an effective strategy to enhance the grain yield. However, this entails the production of F1 hybrid seeds every year. The yield of F1 hybrid seeds is affected by stigma characteristics. The cloning of OsSYL2AA filled a gap in the genetic study of style length and could be used for improving stigma characteristics to increase the yield of F1 seeds. [ABSTRACT FROM AUTHOR]

Abstract: In Brassica oleracea, production of F1 hybrid seeds mainly makes use of the improved Ogura cytoplasmic male sterile (CMS) line. However, reliance on one particular line is a risk, and it would be advantageous to develop other CMS lines. In this study, we transferred Diplotaxis erucoides cytoplasm to B. oleracea cultivars using an alloplasmic B. rapaCMS line as a bridge plant to avoid incompatibility between donor and recipient plants. The new B. oleraceaCMS lines, which were derived by four generations of backcrossing, had small rudimentary anthers with no pollen grain and showed complete male sterility. There was no functional defect in other floral organs, and the ability to receive normal pollen did not appear to be impaired. Moreover, the B. oleraceaCMS lines carrying D. erucoides cytoplasm had larger leaf areas and a normal plastochron. As a consequence, the B. oleraceaCMS lines carrying D. erucoides cytoplasm have the potential to be valuable alternatives for use in commercial B. oleracea hybrid seed production. [ABSTRACT FROM AUTHOR]

Copyright of Plants, People, Planet is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reproductive isolation barriers and the mating patterns among Pinus pumila, P. parviflora var. pentaphylla and their hybrids were examined by flowering phenology and genetic assays of three life stages: airborne-pollen grains, adults and seeds, in a hybrid zone on Mount Apoi, Hokkaido, Japan. Chloroplast DNA composition of the airborne-pollen was determined by single-pollen polymerase chain reaction. Mating patterns were analysed by estimating the molecular hybrid index of the seed parent, their seed embryos and pollen parents. The observation of flowering phenology showed that the flowering of P. pumila precedes that of P. parviflora var. pentaphylla by about 6 to 10 days within the same altitudinal ranges. Although this prezygotic isolation barrier is effective, the genetic assay of airborne-pollen showed that the two pine species, particularly P. pumila, still have chances to form F1 hybrid seeds. Both parental species showed a strong assortative mating pattern; F1 seeds were found in only 1.4% of seeds from P. pumila mother trees and not at all in P. parviflora var. pentaphylla. The assortative mating was concluded as the combined result of flowering time differentiation and cross-incompatibility. In contrast to the parental species, hybrids were fertilized evenly by the two parental species and themselves. The breakdown of prezygotic barriers (intermediate flowering phenology) and cross-incompatibility may account for the unselective mating. It is suggested that introgression is ongoing on Mount Apoi through backcrossing between hybrids and parental species, despite strong isolation barriers between the parental species. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the genetic relationships among four types (A, B, C and D) of Panicum coloratum L. on the basis of the crossability and the amplified fragment length polymorphism (AFLP) variations among the types, and the meiotic chromosome pairing and fertility in F1 hybrids obtained from crosses between different types. F1 hybrids were obtained from crosses between P. coloratum L. var. makarikariense cv. Burnett (A) and P. coloratum L. PI 404632 (D), and between P. coloratum L. CPI 16794 (B) and P. coloratum L. cv. Solai (C). Other crosses failed to produce F1 hybrid seeds. F1 hybrids between Burnett (A) and PI 404632 (D) had 2n = 36 chromosomes and regular meiotic chromosome pairing with 18 bivalents per cell. They produced approximately 80% stainable pollen and normally set seeds. F1 hybrids between Solai (C) and CPI 16794 (B) had 2n = 45 chromosomes and a mean chromosome pairing of 9.50 univalents, 17.67 bivalents and 0.05 trivalents. The most frequent paring behavior was nine univalents and 18 bivalents, suggesting that Solai has two genomes homologous to those of CPI 16794 and one different genome. The F1 hybrids showed approximately 80% stainable pollen and approximately 20% seed fertility. Cluster analysis of polymorphic AFLP in five plants of each of the four types yielded two major clusters. Burnett (A) and PI 404632 (D) clustered together, while Solai (C) clustered with CPI 16794 (B). The results of hybridization studies and AFLP analysis of the four types of P. coloratum, and meiotic examination of the derived F1 hybrids demonstrate that types A and D are genetically differentiated from types B and C, and are reproductively isolated from these two types. [ABSTRACT FROM AUTHOR]

Summary: Restorer‐of‐fertility (Rf) genes encode pentatricopeptide repeat (PPR) proteins that are targeted to mitochondria where they specifically bind to transcripts that induce cytoplasmic male sterility and repress their expression. In searching for a molecular signature unique to this class of proteins, we found that a majority of known Rf proteins have a distinct domain, which we called RfCTD (Restorer‐of‐fertility C‐terminal domain), and its presence correlates with the ability to induce cleavage of the mitochondrial RNA target.A screen of 219 angiosperm genomes from 123 genera using a sequence profile that can quickly and accurately identify RfCTD sequences revealed considerable variation in RFL/RfCTD gene numbers across flowering plants. We observed that plant genera with bisexual flowers have significantly higher numbers of RFL genes compared to those with unisexual flowers, consistent with a role of these proteins in restoration of male fertility.We show that removing the RfCTD from the RFL protein RNA PROCESSING FACTOR 2‐nad6 prevented cleavage of its RNA target, the nad6 transcript, in Arabidopsis thaliana mitochondria.We provide a simple way of identifying putative Rf candidates in genome sequences, new insights into the molecular mode of action of Rf proteins and the evolution of fertility restoration in flowering plants. [ABSTRACT FROM AUTHOR]

SUMMARY: Mitosis and cytokinesis are fundamental processes through which somatic cells increase their numbers and allow plant growth and development. Here, we analyzed the organization and dynamics of mitotic chromosomes, nucleoli, and microtubules in living cells of barley root primary meristems using a series of newly developed stable fluorescent protein translational fusion lines and time‐lapse confocal microscopy. The median duration of mitosis from prophase until the end of telophase was 65.2 and 78.2 min until the end of cytokinesis. We showed that barley chromosomes frequently start condensation before mitotic pre‐prophase as defined by the organization of microtubules and maintain it even after entering into the new interphase. Furthermore, we found that the process of chromosome condensation does not finish at metaphase, but gradually continues until the end of mitosis. In summary, our study features resources for in vivo analysis of barley nuclei and chromosomes and their dynamics during mitotic cell cycle. Significance Statement: We studied 3D chromosome organization and nuclear and microtubule dynamics in the live root apical meristems using a newly developed series of barley (Hordeum vulgare) translational fusion fluorescent marker lines. We measured the duration of the mitotic stages and analyzed the arrangement of specific cellular components such as chromosomes, nucleoli, and mitotic microtubules. We bring new insights into the dynamics of chromosome (de)condensation and microtubule organization during mitosis. [ABSTRACT FROM AUTHOR]

Plants have evolved well‐tuned surveillance systems, including complex defence mechanisms, to constrain pathogens. TFs are master regulators of host molecular responses against plant pathogens. While PepMV constitutes a major threat to the global tomato production, there is still a lack of information on the key TFs that regulate host responses to this virus.A combinatorial research approach was applied relying on tomato transcriptome analysis, RT‐qPCR validation, phylogenetic classification, comparative analysis of structural features, cis‐regulatory element mining and in silico co‐expression analysis to identify a set of 11 highly responsive TFs involved in the regulation of host responses to PepMV.An endemic PepMV isolate, generating typical mosaic symptoms, modified expression of ca. 3.3% of tomato genes, resulting in 1,120 DEGs. Functional classification of 502 upregulated DEGs revealed that photosynthesis, carbon fixation and gene silencing were widely affected, whereas 618 downregulated genes had an impact mainly on plant defence and carotenoid biosynthesis. Strikingly, all 11 highly responsive TFs carried abiotic stress response cis‐regulatory elements, whereas five of them were better aligned with rice than with Arabidopsis gene homologues, suggesting that plant responses against viruses may predate divergence into monocots and dicots. Interestingly, tomato C2H2 family TFs, ZAT1‐like and ZF2, may have distinct roles in plant defence due to opposite response patterns, similar to their Arabidopsis ZAT10 and ZAT12 homologues.These highly responsive TFs provide a basis to study in‐depth molecular responses of the tomato–PepMV pathosystem, providing a perspective to better comprehend viral infections. [ABSTRACT FROM AUTHOR]

The Triticum timopheevii Zhuk. (Tt) cytoplasm is the most exploited cytoplasmic male sterility (CMS) type used in triticale in commercial seed production of hybrid varieties. The present study established a recombinant inbred line (RIL) mapping population to identify genetic loci controlling fertility restoration in triticale with CMS Tt. The trait was evaluated via phenotyping the BC1F1 materials originating from a backcross of maternal line MS 112(15)‐2‐1 (on CMS Tt) and RILs. A genetic map spanning 2293 cM over 21 linkage groups was constructed using 1,170 single nucleotide polymorphisms and silico diversity array technology (DArT) markers generated through DArTseq genotyping. Two quantitative trait loci (QTL) controlling fertility restoration were localized at the 4RL chromosome. They were stable during two vegetative seasons and, depending on the year, explained 17.8 to 37.5 (QRft‐4R.1) and 17.8 to 27.1% (QRft‐4R.2) of phenotypic variance. Bioinformatic analysis was performed to predict genes potentially responsible for the trait. Four markers linked to the trait were successfully converted into a polymerase chain reaction‐based assay to select the pollen fertility QTLs easily. The exact position of QTLs detected previously in the rye and here in the triticale suggests that the same loci might control the trait. Core Ideas: We developed RIL mapping populations to detect QTLs controlling CMS Tt system in triticale.We constructed a high‐density genetic map using SNP and silico DArT markers.We identified SNP and silico DArT markers linked to and/or associated with the trait.We converted selected markers into PCR‐based assay for easy selection of the pollen fertility QTLs.We indicated genes potentially responsible for fertility restoration in triticale with CMS Tt. [ABSTRACT FROM AUTHOR]

Summary: The endosperm, a tissue that nourishes the embryo in the seeds of flowering plants, is often disrupted in inviable hybrid seeds of closely related species. A key question is whether parental conflict is a major driver of this common form of reproductive isolation.Here, we performed reciprocal crosses between pairs of three monkeyflower species (Mimulus caespitosa, Mimulus tilingii, and Mimulus guttatus). The severity of hybrid seed inviability varies among these crosses, which we inferred to be due to species divergence in effective ploidy. By performing a time series experiment of seed development, we discovered parent‐of‐origin phenotypes that provide strong evidence for parental conflict in shaping endosperm evolution.We found that the chalazal haustorium, a tissue within the endosperm that is found at the maternal–filial boundary, shows pronounced differences between reciprocal hybrid seeds formed from Mimulus species that differ in effective ploidy. These parent‐of‐origin effects suggest that the chalazal haustorium might act as a mediator of parental conflict, potentially by controlling sucrose movement from the maternal parent into the endosperm.Our study suggests that parental conflict in the endosperm may function as a driver of speciation by targeting regions and developmental stages critical for resource allocation and thus proper seed development. [ABSTRACT FROM AUTHOR]

Summary: MicroRNAs (miRNAs) play key regulatory roles in seed development and emerge as new key targets for engineering grain size and yield. The Zma‐miRNA169 family is highly expressed during maize seed development, but its functional roles in seed development remain elusive.Here, we generated zma‐miR169o and ZmNF‐YA13 transgenic plants. Phenotypic and genetic analyses were performed on these lines. Seed development and auxins contents were investigated.Overexpression of maize miRNA zma‐miR169o increases seed size and weight, whereas the opposite is true when its expression is suppressed. Further studies revealed that zma‐miR169 acts by negatively regulating its target gene, a transcription factor ZmNF‐YA13 that also plays a key role in determining seed size. We demonstrate that ZmNF‐YA13 regulates the expression of the auxin biosynthetic gene ZmYUC1, which modulates auxin levels in the early developing seeds and determines the number of endosperm cells, thereby governing maize seed size and ultimately yield.Overall, our present study has identified zma‐miR169o and ZmNF‐YA13 that form a functional module regulating auxin accumulation in maize seeds and playing an important role in determining maize seed size and yield, providing a set of novel molecular tools for yield improvement in molecular breeding and genetic engineering. [ABSTRACT FROM AUTHOR]

Sorghum is an important food crop in the world that exhibits a predominant role in fulfilling the nutritional requirements, particularly in low‐income group populations of marginal areas in Kenya. It is a principal source of proteins, carbohydrates, fats, and crude fibers (CFs), which are important nutrients necessary for human development and health. Reduced tannin in sorghum grains is desirable since it affects the availability of nutrients. This study aimed at assessing the nutrient content in filial generation one (F1) developed between Gadam (sorghum), which is low in tannin and hard coat tannin (sorghum) cultivars. The nutrient content analyses were carried out from samples collected in a completely randomized design experiment. Crude protein (CP) and tannin content were analyzed using the modified Kjeldahl method and vanillin‐HCl methanol method, respectively, whereas moisture, fat, CF, ash, and carbohydrate contents were determined using Association of Official Analytical Chemists methods. Data collected were subjected to analysis of variance using R statistical software. Among the F1s, Kari/Mtama‐1 x Gadam recorded the highest CP value of 10.390%. This differed significantly from Gadam x Kari/Mtama‐1 which recorded CP content of 9.770%. Kari/Mtama‐1 x Gadam recorded the highest fat and moisture contents of 2.299% and 8.600%, respectively. The highest CF content of 3.433% was recorded in Gadam x Serena. Gadam x Kari/Mtama‐1 recorded the highest ash content of 1.619%, whereas the highest carbohydrate (84.503%) and tannin content (0.771 mg/g) means were recorded in Seredo x Gadam. Results demonstrated that the choice of maternal and paternal parent influence CP, CF, and carbohydrate contents. Among the F1s, tannin content ranged from 0.106 to 0.771 mg/g compared to 0.953 to 1.763 mg/g recorded in Serena and Seredo (hard coat seeded cultivars). This is an indication that tannin can be downregulated through hybridization. [ABSTRACT FROM AUTHOR]

Summary: Maize is one of the world's most widely cultivated crops. As future demands for maize will continue to rise, fields will face ever more frequent and extreme weather patterns that directly affect crop productivity. Development of environmentally resilient crops with improved standability in the field, like wheat and rice, was enabled by shifting the architecture of plants to a short stature ideotype. However, such architectural change has not been implemented in maize due to the unique interactions between gibberellin (GA) and floral morphology which limited the use of the same type of mutations as in rice and wheat. Here, we report the development of a short stature maize ideotype in commercial hybrid germplasm, which was generated by targeted suppression of the biosynthetic pathway for GA. To accomplish this, we utilized a dominant, miRNA‐based construct expressed in a hemizygous state to selectively reduce expression of the ZmGA20ox3 and ZmGA20ox5 genes that control GA biosynthesis primarily in vegetative tissues. Suppression of both genes resulted in the reduction of GA levels leading to inhibition of cell elongation in internodal tissues, which reduced plant height. Expression of the miRNA did not alter GA levels in reproductive tissues, and thus, the reproductive potential of the plants remained unchanged. As a result, we developed a dominant, short‐stature maize ideotype that is conducive for the commercial production of hybrid maize. We expect that the new maize ideotype would enable more efficient and more sustainable maize farming for a growing world population. [ABSTRACT FROM AUTHOR]

With the rise of novel specialty markets and changes in consumers' preferences, the demand for high‐yielding, non‐genetically modified (non‐GM) soybean [Glycine max (L.) Merr.] cultivars has been steadily increasing over the last decade. Interest from growers in non‐GM soybean cultivars has also increased because they may benefit from premium prices, reduced seed costs, and flexible farming systems. To meet this growing demand, the University of Missouri–Fisher Delta Research, Extension, and Education Center soybean breeding team has developed and released 'S16‐15170C' (Reg. no. CV‐550, PI 699900), a high‐yielding conventional soybean cultivar with multiple disease resistance and broad adaptation to the Southern states. S16‐15170C has an indeterminate growth habit and white flowers, gray pubescence, and tan pod wall color. This soybean cultivar has been extensively tested across 12 states from 2017 to 2020 and has outyielded commercial checks in 48 out of 78 environments, with the average yield being 102.7% of checks overall. S16‐15170C is resistant to soybean cyst nematode, stem canker, frogeye leaf spot, sudden death syndrome, brown stem rot, and phytophthora root rot. The combination of high yielding potential, broad adaptability, and multiple disease resistance in a non‐GM genetic background makes S16‐15170C a suitable soybean cultivar choice for growers adopting an alternative farming system and maximizing potential returns during the season. Core Ideas: Conventional soybean allows the maximization of profits by adopting non‐GMO farming systems.S16‐15170C has high yield potential through multi‐environment performance and adaptability in the southern U.S.Genetic resistance permits sustaining yield performance under biotic stressors. [ABSTRACT FROM AUTHOR]

We analyzed the yield data of 2,070 rice hybrid F1 genotypes with inbred local cultivars (ILCv) evaluated over 32 yr (from 1988 to 2019) in 2,376 multi‐environment experiments executed at 102 locations in the irrigated ecosystem across India. The genetic gain or loss in yield of hybrid F1 genotypes estimated over the test duration was nonsignificant. The differences were highly significant between the means of group of F1 hybrid genotypes with yields higher than ILCvs in 985 experiments and the group of F1 hybrid genotypes with yields lower than ILCvs in 962 experiments. Hybrids produced 10% more yield (728–2,588 kg ha–1) than ILCvs in 672 experiments at several locations. Our analyses have established that grain yields of 7.0–7.9 Mg ha–1, were harvested in hybrid F1 genotypes with early‐ (110–120 d), mid‐early‐ (121–130 d), and medium‐ (131–140 d) maturity duration, and in those with medium slender grains (130±5 d) at many locations in 374 out of the 985 experiments. A higher level of rice (Oryza sativa L.) productivity per day (62–63 kg ha–1) was recorded with the early‐maturing and mid‐early‐maturing hybrid genotypes. Both the hybrid F1 genotypes and ILCvs produced grain yields (≥10 Mg ha–1) similar to values that were recorded previously with commercial inbred cultivars since 1968 at many locations. The attainable grain yield records of ILCvs were not broken by the yields of hybrid F1 genotypes. Hence the doubt arises whether there was any overestimation of hybrid genotypes or an underestimation of inbred yields. Therefore, any genetic gain or loss for grain yields in new genotypes developed in experiments can be estimated only when ILCvs produce their attainable yield recorded previously. There is scope for breeders to limit test locations to represent specific target areas to avoid data loss. Core Ideas: Yield data was analyzed in 2,070 hybrid F1 genotypes from 2,376 experiments in irrigated rice.Hybrids produced mean yields not exceeding 10 Mg ha‐1 attained by inbred cultivars since 1968.Genetic gain or loss in grain yield was nonsignificant in rice hybrid F1 genotypes.Yield differences were highly significant between hybrids with yields higher than inbred local cultivars and those with lower than inbred local cultivars.Early‐ and mid‐early‐maturing rice hybrid genotypes produced grain yields of 7.0–7.9 Mg ha‐1. [ABSTRACT FROM AUTHOR]

Because of the difficulty of producing F1 hybrid seeds by hand emasculation and pollination, wide use of heterosis in cotton production has been limited in China. The objective of this study was to evaluate the potential of F2 hybrids for yield and fibre quality. A half diallel involving eight parents and their F1 and F2 hybrids was grown in replicated studies at Linqing and Nanjing in 1999 and Nanjing in 2000. Yield and fibre quality was determined for all 64 entries. Fibre quality was also determined for parents and F1s, but only for Zhongmiansuo 28 (ZMS28), Xiangzamian 2 (XZM2) and Wanmian 13 (WM13) F2s. These three F2 hybrids are extensively planted in China and provide experimental controls with which to compare the performance of new hybrids. Average yield heterosis for F1s and F2s was 15.9 and 9.2%, respectively. Inbreeding depression for yield varied but some F2s greatly out-yielded the best variety. Average F1 heterosis was 6.7, 6.2 and 2.9%, respectively for number of bolls per unit area, boll weight, and lint percentage. The average F2 heterosis for the same traits was 4.4, 3.3 and 1.6%, respectively. F1 heterosis for fibre traits was low. In general, parental average was a good indicator of the yield and fibre quality of F1 hybrids. These encouraging results suggest there is sufficient heterosis for yield to use F2s in China. [ABSTRACT FROM AUTHOR]

Ergot or sugary disease of sorghum has become an important constraint in North and South American countries that rely on F1 hybrid seeds for high productivity. The objective of this research was to determine the vulnerability of various germplasm sources and publicly bred sorghum lines to sugary disease (Claviceps africana) in the United States. Flower characteristics associated with sugary disease resistance were also studied. A-/B-line pairs, R-lines, putative sources of resistance and their hybrid combinations with an A3 cytoplasmic male-sterile source were evaluated using a disease incidence, severity, and dual-ranking system. Trials were planted in a randomized complete block design with three replications and repeated in at least two planting dates. Planting dates and pedigrees had significant effects on overall ranking for resistance. A-lines were most susceptible to sugary disease. R-lines were more susceptible than B-lines with respect to incidence and severity of the disease. Newer releases of A- and B-lines were more susceptible to sugary disease than older releases. Sugary disease reaction of A-lines was a good indicator of disease reaction of B-lines. Tx2737, a popular R-line, was highly susceptible to sugary disease in spite of being a good pollen shedder because the stigma emerged from glumes 2–3 days before anthesis. The combination of flower characteristics associated with resistance were least exposure time of stigma to inoculum before pollination, rapid stigma drying after pollination, and small stigma. An Ethiopian male-fertile germplasm accession, IS 8525, had good levels of resistance. Its A3 male-sterile hybrid had the highest level of resistance in the male-sterile background. IS 8525 should be exploited in host-plant resistance strategies. [ABSTRACT FROM AUTHOR]

SUMMARY: Food allergies are a major health issue worldwide. Modern breeding techniques such as genome editing via CRISPR/Cas9 have the potential to mitigate this by targeting allergens in plants. This study addressed the major allergen Bra j I, a seed storage protein of the 2S albumin class, in the allotetraploid brown mustard (Brassica juncea). Cotyledon explants of an Indian gene bank accession (CR2664) and the German variety Terratop were transformed using Agrobacterium tumefaciens harboring binary vectors with multiple single guide RNAs to induce either large deletions or frameshift mutations in both Bra j I homoeologs. A total of 49 T0 lines were obtained with up to 3.8% transformation efficiency. Four lines had large deletions of 566 up to 790 bp in the Bra j IB allele. Among 18 Terratop T0 lines, nine carried indels in the targeted regions. From 16 analyzed CR2664 T0 lines, 14 held indels and three had all four Bra j I alleles mutated. The majority of the CRISPR/Cas9‐induced mutations were heritable to T1 progenies. In some edited lines, seed formation and viability were reduced and seeds showed a precocious development of the embryo leading to a rupture of the testa already in the siliques. Immunoblotting using newly developed Bra j I‐specific antibodies revealed the amount of Bra j I protein to be reduced or absent in seed extracts of selected lines. Removing an allergenic determinant from mustard is an important first step towards the development of safer food crops. Significance Statement: Mustard is a significant elicitor of allergic reactions to food. The major allergen in brown mustard (Brassica juncea) is Bra j I, a 2S albumin seed storage protein. This is the first report of genome editing in B. juncea, and we mutated up to all four gene copies in this tetraploid plant resulting in plants with reduced levels or absence of Bra j I protein. [ABSTRACT FROM AUTHOR]

SUMMARY: The importance of the alternative donation of electrons to the ubiquinol pool via the electron‐transfer flavoprotein/electron‐transfer flavoprotein:ubiquinone oxidoreductase (ETF/ETFQO) complex has been demonstrated. However, the functional significance of this pathway during seed development and germination remains to be elucidated. To assess the function of this pathway, we performed a detailed metabolic and transcriptomic analysis of Arabidopsis mutants to test the molecular consequences of a dysfunctional ETF/ETFQO pathway. We demonstrate that the disruption of this pathway compromises seed germination in the absence of an external carbon source and also impacts seed size and yield. Total protein and storage protein content is reduced in dry seeds, whilst sucrose levels remain invariant. Seeds of ETFQO and related mutants were also characterized by an altered fatty acid composition. During seed development, lower levels of fatty acids and proteins accumulated in the etfqo‐1 mutant as well as in mutants in the alternative electron donors isovaleryl‐CoA dehydrogenase (ivdh‐1) and d‐2‐hydroxyglutarate dehydrogenase (d2hgdh1‐2). Furthermore, the content of several amino acids was increased in etfqo‐1 mutants during seed development, indicating that these mutants are not using such amino acids as alternative energy source for respiration. Transcriptome analysis revealed alterations in the expression levels of several genes involved in energy and hormonal metabolism. Our findings demonstrated that the alternative pathway of respiration mediated by the ETF/ETFQO complex affects seed germination and development by directly adjusting carbon storage during seed filling. These results indicate a role for the pathway in the normal plant life cycle to complement its previously defined roles in the response to abiotic stress. Significance Statement: The importance of the alternative donation of electrons to the ubiquinol pool via the electron‐transfer flavoprotein/electron‐transfer flavoprotein:ubiquinone oxidoreductase (ETF/ETFQO) complex during normal seed development and germination is presented. Our results provide compelling evidence for a pivotal role of the alternative ETF/ETFQO respiration pathway in the normal life cycle of a plant in addition to its previously defined roles in response the to abiotic stress. [ABSTRACT FROM AUTHOR]

This article presents ethnographic research with in situ seed savers and seed activists in London. Unpicking the knotty relations between kinship, place, and generation among seed savers and their seeds, this article focuses on how the intrinsic and extrinsic get woven through generations and how the situ or environment of an entity is (and is not) recognized in its identity and multispecies kin relations. I argue that thinking about seeds and the worlds in which they grow suggests that they are not only embedded in their environments, but also embody their environments. If seeds bring with them their worlds, then they are inherently malleable, so seed savers are concerned about how commercial seed breeding and ex situ conservation denatures seeds' embodied relationships with their environments and, with that, their inherent intergenerational malleability. [seed saving, multispecies kinship, generation, environment]. [ABSTRACT FROM AUTHOR]

The male sterility trait is an economically essential feature for the exploitation of hybrid vigour in onions; hence, scientists have looked into the molecular component of male sterility in onions. As a result, numerous molecular markers associated with male‐sterile (CMS‐S and CMS‐T) cytoplasms, male‐fertile normal (N) cytoplasm and nuclear‐male‐fertility restorers (Ms locus) were developed. The discovered markers have proven to be helpful in the effective selection and isolation of male‐sterile lines, their maintainer lines and restorer‐of‐fertility lines. These lines are required for breeding F1 hybrid to harness heterosis through marker‐assisted selection (MAS) of cytoplasmic genotypes with Ms or ms loci. Thus, the study came up with a compilation of molecular markers, by revealing their molecular perspective, practical utility and functional effectiveness in the MAS of male‐sterile cytoplasm types with nuclear‐fertility‐restorer locus, to speed up onion breeding, development of F1 hybrids and production of pure hybrid seeds. [ABSTRACT FROM AUTHOR]

Honeybees (Apis mellifera L.) are the most used pollinators for onion (Allium cepa L.) seed production. Two types of onion varieties are mainly grown worldwide: hybrids and open pollination (OP) cultivars. Although hybrids offer advantages to bulb growers, seed yields of hybrids are lower than OP cultivars. Since honeybees play a major role in onion pollination, understanding the contribution of the floral rewards to bee visitation is crucial to improve seed yield. The goal of this study is to establish the best moment for the introduction of honeybee hives into onion fields to increase seed yields. To reach this goal, the correlation between sugar compounds in nectar throughout the flowering period and honeybee foraging activity was determined. The sugar profile and bee visits were highly correlated, and fructose concentration was strongly linked to bee frequency of foraging on the onion umbels. The highest number of bee visits was recorded at 70% of flowering. Based on these results, beehives should be introduced once 40–50% of flowering is reached. Core Ideas: Hybrid onion seed production increases with pollinators.Information about the factors that influence bee activity on onion flowers is needed.Nectar composition, especially sugars, affects the frequency of pollinator visits.Among the sugars, fructose was the one that had more influence on the frequency of bee foraging on umbels.The highest number of bee visits was recorded at 70% of flowering. [ABSTRACT FROM AUTHOR]

The evaluation of genetic parameters in early generations select individuals in F2 and F2:3 and advancing only progenies with the potential to generate pure productive lines. The objectives of this study were to estimate genetic and phenotypic parameters in F2 and F2:3 populations derived from UFUS 7415 and TMG 7161 RR, evaluate different genotype selection strategies, and select progenies to improve agronomic traits. Populations in the F2 and F2:3 generations derived from a biparental cross between the parents UFUS 7415 and TMG 7161 RR were evaluated. The genetic parameters of 360 individuals in the F2 generation and 150 genotypes of each parent were evaluated. Heritability varied from 4.66% for the number of seeds per pod to 86.06% for plant height at flowering. The greatest selection gain was obtained for plant height at flowering (29.68%), related to grain production. In the F2:3 generation, 145 genotypes were evaluated and their parents, in a randomized block design with two replications. The correlations between characters and the genetic gains obtained by direct and indirect selection and based on the genotype–ideotype distance index and the Mulamba and Mock index of the sum of "ranks" were evaluated. With direct selection, selection gains ranged from –5.34 to 16.19%. The genotype–ideotype distance index showed a total selection gain of 40.49%, while the Mulamba and Mock index of the sum of ranks obtained a total gain of 39.35%. Twenty‐three genotypes were selected for the characters evaluated with both indexes in the F3 generation. Core Ideas: The genetics parameters they are estimated based on coefficients such as heritability.Correlation between two characters allows for measuring the extent of association between them.Selection indexes allow for the simultaneous selection of a group of characters. [ABSTRACT FROM AUTHOR]

Enhancing the accumulation of eicosapentaenoic acid and docosahexaenoic acid in transgenic Camelina through the CRISPR-Cas9 inactivation of the competing FAE1 pathway Keywords: metabolic engineering; Omega-3; Camelina; seed oil; gene editing; field trials EN metabolic engineering Omega-3 Camelina seed oil gene editing field trials 1444 1446 3 08/03/22 20220801 NES 220801 Omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs), eicosapentaenoic acid (EPA; 20:5 SP 5,8,11,14,17 sp ) and docosahexaenoic acid (DHA; 22:6 SP 4,7,10,13,16,19 sp ) are now accepted as being essential components of a healthy, balanced diet (Napier I et al., i 2019; West I et al., i 2021). Based on our observation that ALA is the endogenous C18 precursor for seed omega-3 LC-PUFA production (Han I et al., i 2020), we hypothesized that increasing the ALA pool can further enhance EPA/DHA accumulation in DHA1 Camelina. [Extracted from the article]

The recent invention of hybrid breeding technology for potato has led to an increased interest in hybrid potato R&D. Hybrid true potato seeds (TPS) are used to produce planting materials such as transplants and seedling tubers, but can also be used for direct seeding of seed or ware crops. Transplants and seedling tubers can be used to produce seed tubers or ware tubers. The rise in R&D in hybrid breeding creates the need for phenological scales of growth and development of plants produced by the various planting material types of hybrid‐TPS. The BBCH (Biologische Bundesanstalt, Bundessortenamt and CHemical Industry) scale is one of the phenological scales developed for the description of the growth and development stages of plants. In 1993, a BBCH scale with descriptions for potato plants was released. The original BBCH scale gave standardised descriptions for TPS‐ and tuber‐grown plants. Differences in the morphology of plants originating from the different planting materials in terms of types of branches and differences in below‐ground growth and development were not included. Moreover, for reproductive growth stages, crucial for hybrid breeding, the original scale is incomplete as it does not carefully take the complex sympodial branching into account. Methods of describing growth of tubers and berries are complex and impossible to use when final tuber mass or berry size is unknown. The current paper augments the original BBCH scale, while retaining its structure and logic. It provides alternative and comprehensive descriptions of growth stages suitable for potato plants grown from different types of planting materials, and for all end uses of these plants. The proposed scale is detailed enough for research and breeding but still general enough for agricultural use. [ABSTRACT FROM AUTHOR]

Seeds are valuable sources of carbohydrates, lipids, proteins, fibers, minerals, and vitamins. They provide energy and nutrition to germinating seedlings, food to humans, feed to livestock, and feedstocks to industry. High‐throughput analyses of gene expression in crops has identified many candidate genes associated with seed dormancy, longevity, germination, and vigor. In this review, we cover the latest research focusing on such key seed traits. Transcriptome analyses of time courses of seed filling have identified sets of genes expressed at different stages of this process. The potential role of epigenetics (including seed–endosperm imprinted genes) in regulating seed development and chemistry is highlighted herein. We also discuss how advances in genomics and seed biology are facilitating the unravelling of associations between seed traits with gene bank accessions and gene sequences, including how functional research can accelerate the discovery of allelic variants. Such knowledge of functional effects relating to gene variants is necessary for more efficient and cost‐effective management of genetic resources or for redesigning crops with specific seed characteristics. For instance, gene bank curators may assess seed viability by monitoring changes in gene expression of biomarker genes in dry seed samples to decide germplasm regeneration and assess genetic integrity of collections by monitoring changes in diversity and allele frequencies between samples of same accession stored in gene banks. We highlight that resistance to preharvest sprouting can be enhanced through genomics‐assisted breeding in otherwise nondormant rice (Oryza sativa L.) and wheat (Triticum aestivum L.) cultivars, while pimt, another valuable marker for seed longevity, may be deployed to enhance seed vigor in crops. [ABSTRACT FROM AUTHOR]

Common wheat (Triticum aestivum L., AABBDD genome) is thought to have emerged through natural hybridization between Triticum turgidum L. (AABB genome) and Aegilops tauschii Coss. (DD genome). Hybridization barriers and doubling of the trihaploid F1 hybrids' genome (ABD) via unreduced gamete fusion had key roles in the process. However, how T. turgidum, the maternal progenitor, was involved in these mechanisms remains unknown. An artificial cross‐experiment using 46 cultivated and 31 wild T. turgidum accessions and a single Ae. tauschii tester with a very short genetic distance to the common wheat D genome was conducted. Cytological and quantitative trait locus analyses of F1 hybrid genome doubling were performed. The crossability and ability to cause hybrid inviability did not greatly differ between the cultivars and wild accessions. The ability to cause hybrid genome doubling was higher in the cultivars. Three novel T. turgidum loci for hybrid genome doubling, which influenced unreduced gamete production in F1 hybrids, were identified. Cultivated T. turgidum might have increased the probability of the emergence of common wheat through its enhanced ability to cause genome doubling in F1 hybrids with Ae. tauschii. The ability enhancement might have involved alterations at a relatively small number of loci. [ABSTRACT FROM AUTHOR]

Hybrids of a single pair of parent species can be much more common in some geographical regions than in others. The reasons for this are not well understood, but could help explain processes such as species diversification or the range expansion of invasive hybrids. The widespread cattails Typha latifolia and T. angustifolia seldom hybridize in some parts of their range, but in other areas produce the dominant hybrid T. × glauca. We used a combination of field and greenhouse experiments to investigate why T. × glauca has invaded wetlands in the Laurentian Great Lakes region of southern Ontario, Canada, but is much less common in the coastal wetlands of Nova Scotia (NS) in eastern Canada. One potentially important environmental difference between these two regions is salinity. We therefore tested three hypotheses: (1) T. latifolia and T. angustifolia in NS are genetically incompatible; (2) the germination or growth of T. × glauca is reduced by salinity; and (3) T. latifolia, a main competitor of T. × glauca, is locally adapted to saline conditions in NS. Our experiments showed that NS T. latifolia and T. angustifolia are genetically compatible, and that saline conditions do not impede growth of hybrid plants. However, we also found that under conditions of high salinity, germination rates of hybrid seeds were substantially lower than those of NS T. latifolia. In addition, germination rates of NS T. latifolia were higher than those of Ontario T. latifolia, suggesting local adaptation to salinity in coastal wetlands. This study adds to the growing body of literature which identifies the important roles that local habitat and adaptation can play in the distributions and characteristics of hybrid zones. [ABSTRACT FROM AUTHOR]

One use of soybean [Glycine max (L.) Merr.] as food is as a vegetable, also known as edamame, in which the green pods with seeds fully developed are harvested, cooked briefly, and consumed. Few efforts have been devoted to developing new soybean cultivars with high agronomic performance and characteristics suitable for human consumption. In the present research, crosses between six soybean lines were performed in a diallel scheme without reciprocals to determine the combining ability and the type of gene action that controls the inheritance of development and yield component traits for edamame production. The results showed the existence of variability among the evaluated genotypes and indicated that the progenies presented superior performance in comparison to the parental lines for important traits. The cultivar BRS267 and the inbred line USP‐13‐19‐007 had consistently high estimates of general combining ability for pod and seed size, indicating their potential as parents in breeding for edamame. Most progenies had positive specific combining ability for pod and seed size, showing that generating novel genotypic combinations through new crossings is a promising strategy for improvement. Additive effects played a major role in the inheritance for maturity traits and for pod size, seed size, and yield; both additive and non‐additive effects were important. The magnitude and significance of the correlations indicated that it is possible to improve vegetable soybean traits without affecting grain yield. [ABSTRACT FROM AUTHOR]

Summary: Incorporating male sterility into hybrid seed production reduces its cost and ensures high varietal purity. Despite these advantages, male‐sterile lines have not been widely used to produce tomato (Solanum lycopersicum) hybrid seeds. We describe the development of a biotechnology‐based breeding platform that utilized genic male sterility to produce hybrid seeds. In this platform, we generated a novel male‐sterile tomato line by clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR‐associated protein 9 (Cas9)‐mediated mutagenesis of a stamen‐specific gene SlSTR1 and devised a transgenic maintainer by transforming male‐sterile plants with a fertility‐restoration gene linked to a seedling‐colour gene. Offspring of crosses between a hemizygous maintainer and the homozygous male‐sterile plant segregated into 50% non‐transgenic male‐sterile plants and 50% male‐fertile maintainer plants, which could be easily distinguished by seedling colour. This system has great practical potential for hybrid seed breeding and production as it overcomes the problems intrinsic to other male‐sterility systems and can be easily adapted for a range of tomato cultivars and diverse vegetable crops. [ABSTRACT FROM AUTHOR]

Summary: Genomic imprinting regulates parent‐specific transcript dosage during seed development and is mainly confined to the endosperm. Elucidation of the function of many imprinted genes has been hampered by the lack of corresponding mutant phenotypes, and the role of imprinting is mainly associated with genome dosage regulation or allocation of resources. Disruption of imprinted genes has also been suggested to mediate endosperm‐based post‐zygotic hybrid barriers depending on genetic variation and gene dosage. Here, we have analyzed the conservation of a clade from the MADS‐box type I class transcription factors in the closely related species Arabidopsis arenosa, A. lyrata, and A. thaliana, and show that AGL36‐like genes are imprinted and maternally expressed in seeds of Arabidopsis species and in hybrid seeds between outbreeding species. In hybridizations between outbreeding and inbreeding species the paternally silenced allele of the AGL36‐like gene is reactivated in the hybrid, demonstrating that also maternally expressed imprinted genes are perturbed during hybridization and that such effects on imprinted genes are specific to the species combination. Furthermore, we also demonstrate a quantitative effect of genetic diversity and temperature on the strength of the post‐zygotic hybridization barrier. Markedly, a small decrease in temperature during seed development increases the survival of hybrid F1 seeds, suggesting that abiotic and genetic parameters play important roles in post‐zygotic species barriers, pointing at evolutionary scenarios favoring such effects. Open Research Badges: This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://www.ncbi.nlm.nih.gov/bioproject/?term=PRJNA562212. All sequences generated in this study have been deposited in the National Center for Biotechnology Information Sequence Read Archive (https://www.ncbi.nlm.nih.gov/sra/) with project number PRJNA562212. Significance Statement: We have investigated the hypothesis that imprinted genes mediate reproductive barriers between species in the context of genetic and environmental variance, and demonstrate that perturbation of imprinted genes, genetic diversity as well as environmental factors act in concert to define the strength of endosperm‐based Arabidopsis hybridization barriers. [ABSTRACT FROM AUTHOR]

Peanut smut caused by Thecaphora frezii Carranza & Lindquist has been an issue for farmers and the peanut industry (Arachis hypogaea L.) in Argentina since the mid‐1990s. This disease causes pod malformation due to hypertrophy of seed tissues; in addition, colonized cells filled with teliospores give seeds a smutted mass appearance. Incidence may reach up to 52% in commercial plots, with up to 35% yield losses. Cultural management strategies and chemical treatment have not been effective; therefore, growing resistant varieties is likely to be the most effective control method for this disease. This study is aimed to identify sources of resistance in wild Arachis and to develop pre‐breeding materials for transferring the trait to cultivated peanut. After 3 yr of field trials using a randomized complete block design, the seven accessions of wild species assayed were resistant to smut. An amphidiploid [A. correntina (Burkart) Krapov. & W.C. Greg. × A. cardenasii Krapov. & W.C. Greg.] × A. batizocoi Krapov. & W.C. Greg.)4× was obtained and subsequently crossed with and experimental line of A. hypogaea for the development of a recombinant inbred line (RIL) population (89 lines). The RIL population showed a high phenotypic variability for resistance to peanut smut. The amphidiploid and 22 RILs were highly resistant, illustrating the effective transmission of resistance to peanut smut from the wild diploids into A. hypogaea. The development of RILs with resistance derived from wild species is a significant step towards the development of new peanut cultivars with different sources of resistance to peanut smut. [ABSTRACT FROM AUTHOR]

Abstract: Transgene introgression from transgenic rapeseed (Brassica napus) to different varieties of B. juncea was assessed in this study. Crossability between a transgenic rapeseed line Z7B10 (pollen donor) and 80 cultivars of 16 B. juncea varieties (including two wild accessions) was estimated by artificial pollination in a greenhouse. As a result, interspecific crossability between the transgenic Z7B10 line and the 80 B. juncea cultivars varied considerably, with seeds per flower from 0.00–10.67. Seed germination rates of the interspecific F1 hybrids ranged from 49.0%–89.3%. The estimated frequencies of natural gene flow from the transgenic Z7B10 line to 10 B. juncea cultivars with different uses in the experiment field varied from 0.08% to 0.93%. The natural F1 hybrids were highly sterile, with seeds per silique ranging from 0.27 to 1.03. In addition, seeds per flower of hybrid descendants varied from 0.02 to 0.22 when F1 hybrids were self‐pollinated, and those ranged from 0.03 to 0.30 when F1 hybrids were backcrossed with their corresponding B. juncea parents. Results of this study suggest a low level of transgene introgression from transgenic rapeseed to different B. juncea varieties, which provides a sound scientific basis for the safety management of coexisting transgenic B. napus and B. juncea varieties in China. [ABSTRACT FROM AUTHOR]

Summary: Although hundreds of genetic male sterility (GMS) mutants have been identified in maize, few are commercially used due to a lack of effective methods to produce large quantities of pure male‐sterile seeds. Here, we develop a multicontrol sterility (MCS) system based on the maize male sterility 7 (ms7) mutant and its wild‐type Zea mays Male sterility 7 (ZmMs7) gene via a transgenic strategy, leading to the utilization of GMS in hybrid seed production. ZmMs7 is isolated by a map‐based cloning approach and encodes a PHD‐finger transcription factor orthologous to rice PTC1 and Arabidopsis MS1. The MCS transgenic maintainer lines are developed based on the ms7‐6007 mutant transformed with MCS constructs containing the (i) ZmMs7 gene to restore fertility, (ii) α‐amylase gene ZmAA and/or (iii) DNA adenine methylase gene Dam to devitalize transgenic pollen, (iv) red fluorescence protein gene DsRed2 or mCherry to mark transgenic seeds and (v) herbicide‐resistant gene Bar for transgenic seed selection. Self‐pollination of the MCS transgenic maintainer line produces transgenic red fluorescent seeds and nontransgenic normal colour seeds at a 1:1 ratio. Among them, all the fluorescent seeds are male fertile, but the seeds with a normal colour are male sterile. Cross‐pollination of the transgenic plants to male‐sterile plants propagates male‐sterile seeds with high purity. Moreover, the transgene transmission rate through pollen of transgenic plants harbouring two pollen‐disrupted genes is lower than that containing one pollen‐disrupted gene. The MCS system has great potential to enhance the efficiency of maize male‐sterile line propagation and commercial hybrid seed production. [ABSTRACT FROM AUTHOR]

Genomic imprinting in the seed endosperm could be due to unequal parental-genome contribution effects in triploid endosperm tissue that trigger parent-of-origin specific activation and/or silencing of loci prone to genomic imprinting. To determine whether genomic imprinting is triggered by unequal parental-genome contribution effects, we generated a whole-genome transcriptome dataset of F1 hybrid triploid embryos (as mimics of F1 hybrid triploid endosperm). For the vast majority of genes, the parental contributions to their expression levels in the F1 triploid hybrid embryos follow a biallelic and linear expression pattern. While allele-specific expression ( ASE) bias was detected, such effects were predominantly parent-of-origin independent. We demonstrate that genomic imprinting is largely absent from F1 triploid embryos, strongly suggesting that neither triploidy nor unequal parental-genome contribution are key triggers of genomic imprinting in plants. However, extensive parental-genome dosage effects on gene expression were observed between the reciprocal F1 hybrid embryos, particularly for genes involved in defence response and nutrient reservoir activity, potentially leading to the seed size differences between reciprocal triploids. We further determined that unequal parental-genome contribution in F1 triploids can lead to overexpression effects that are parent-of-origin dependent, and which are not observed in diploid or tetraploid embryos in which the parental-genome dosage is balanced. Overall, our study demonstrates that neither triploidy nor unequal parental-genome contribution is sufficient to trigger imprinting in plant tissues, suggesting that genomic imprinting is an intrinsic and unique feature of the triploid seed endosperm. [ABSTRACT FROM AUTHOR]

Palmitic acid (C16:0) already makes up approximately 25% of the total fatty acids in the conventional cotton seed oil. However, further enhancements in palmitic acid content at the expense of the predominant unsaturated fatty acids would provide increased oxidative stability of cotton seed oil and also impart the high melting point required for making margarine, shortening and confectionary products free of trans fatty acids. Seed-specific RNAi-mediated down-regulation of β-ketoacyl- ACP synthase II ( KASII) catalysing the elongation of palmitoyl- ACP to stearoyl- ACP has succeeded in dramatically increasing the C16 fatty acid content of cotton seed oil to well beyond its natural limits, reaching up to 65% of total fatty acids. The elevated C16 levels were comprised of predominantly palmitic acid (C16:0, 51%) and to a lesser extent palmitoleic acid (C16:1, 11%) and hexadecadienoic acid (C16:2, 3%), and were stably inherited. Despite of the dramatic alteration of fatty acid composition and a slight yet significant reduction in oil content in these high-palmitic ( HP) lines, seed germination remained unaffected. Regiochemical analysis of triacylglycerols ( TAG) showed that the increased levels of palmitic acid mainly occurred at the outer positions, while C16:1 and C16:2 were predominantly found in the sn-2 position in both TAG and phosphatidylcholine. Crossing the HP line with previously created high-oleic ( HO) and high-stearic ( HS) genotypes demonstrated that HP and HO traits could be achieved simultaneously; however, elevation of stearic acid was hindered in the presence of high level of palmitic acid. [ABSTRACT FROM AUTHOR]

In flowering plants, F1 hybrid seed lethality is a common outcome of crosses between closely related diploid species, but the genetic basis of this early-acting and potentially widespread form of postzygotic reproductive isolation is largely unknown., We intercrossed two closely related species of monkeyflower, Mimulus guttatus and Mimulus tilingii, to characterize the mechanisms and strength of postzygotic reproductive isolation. Then, using a reciprocal backcross design, we performed high-resolution genetic mapping to determine the genetic architecture of hybrid seed lethality and directly test for loci with parent-of-origin effects., We found that F1 hybrid seed lethality is an exceptionally strong isolating barrier between Mimulus species, with reciprocal crosses producing < 1% viable seeds. This form of postzygotic reproductive isolation appears to be highly polygenic, indicating that multiple incompatibility loci have accumulated rapidly between these closely related Mimulus species. It is also primarily caused by genetic loci with parent-of-origin effects, suggesting a possible role for imprinted genes in the evolution of Mimulus hybrid seed lethality., Our findings suggest that divergence in loci with parent-of-origin effects, which is probably driven by genomic coevolution within lineages, might be an important source of hybrid incompatibilities between flowering plant species. [ABSTRACT FROM AUTHOR]

Unintended gene flow from transgenic plants via pollen, seed and vegetative propagation is a regulatory concern because of potential admixture in food and crop systems, as well as hybridization and introgression to wild and weedy relatives. Bioconfinement of transgenic pollen would help address some of these concerns and enable transgenic plant production for several crops where gene flow is an issue. Here, we demonstrate the expression of the restriction endonuclease Eco RI under the control of the tomato pollen-specific LAT52 promoter is an effective method for generating selective male sterility in Nicotiana tabacum (tobacco). Of nine transgenic events recovered, four events had very high bioconfinement with tightly controlled Eco RI expression in pollen and negligible-to-no expression other plant tissues. Transgenic plants had normal morphology wherein vegetative growth and reproductivity were similar to nontransgenic controls. In glasshouse experiments, transgenic lines were hand-crossed to both male-sterile and emasculated nontransgenic tobacco varieties. Progeny analysis of 16 000-40 000 seeds per transgenic line demonstrated five lines approached (>99.7%) or attained 100% bioconfinement for one or more generations. Bioconfinement was again demonstrated at or near 100% under field conditions where four transgenic lines were grown in close proximity to male-sterile tobacco, and 900-2100 seeds per male-sterile line were analysed for transgenes. Based upon these results, we conclude Eco RI-driven selective male sterility holds practical potential as a safe and reliable transgene bioconfinement strategy. Given the mechanism of male sterility, this method could be applicable to any plant species. [ABSTRACT FROM AUTHOR]

In plants that are able to self-fertilize, autonomous selfing has been hypothesized to function as an effective mechanism that prevents heterospecific mating. However, there have only been few studies that have assessed the relative and absolute contribution of different modes of selfing to total reproductive isolation acting between species. Because selfing can be expected to increase fitness costs when offspring are sired from more outcrossing sister taxa, it can be hypothesized that the contribution of post-zygotic barriers to total reproductive isolation becomes stronger in selfing than in more outcrossing relatives., To assess the efficiency of different modes of selfing against heterospecific mating, we conducted mixed-pollination experiments in three Centaurium species showing strong differences in mating system (i.e. delayed selfing in Centaurium erythraea, competing selfing in C. littorale and prior selfing in C. pulchellum). The contribution of selfing to total reproductive isolation was further examined by quantifying the strength of three pre-zygotic (flowering phenology, pollinator fidelity and pollen production) and four intrinsic post-zygotic (seed set and germination, survival and flowering capacity) barriers for each of the six species pair combinations., Although autonomous selfing as a reproductive barrier was unable to completely impede gene flow, its efficiency as a mechanism to prevents heterospecific pollination strongly depended on the mode of selfing, with prior selfing being by far the most efficient mechanism and delayed selfing only offering a limited protection against hybrid fertilization at the end of a flower's lifetime. Apart from the prevention effect of selfing, differences in pollinator fidelity and pollen production also contributed substantially to total reproductive isolation., Post-zygotic hybrid costs were high and most prevalent for seed production and germination success. Reductions in hybrid vigour were significantly associated with the mating system of the maternal species, with the highest reductions in the most selfing C. pulchellum and the lowest reductions in predominant outcrossing C. erythraea., Synthesis. Our findings indicate that selfing may prevent species from interspecific gene flow and hybridization. The association between the capacity to self-autonomously and hybrid vigour further suggests that selfing may foster post-zygotic costs following hybridization. [ABSTRACT FROM AUTHOR]

We have developed a novel hybridization platform that utilizes nuclear male sterility to produce hybrids in maize and other cross-pollinating crops. A key component of this platform is a process termed Seed Production Technology (SPT). This process incorporates a transgenic SPT maintainer line capable of propagating nontransgenic nuclear male-sterile lines for use as female parents in hybrid production. The maize SPT maintainer line is a homozygous recessive male sterile transformed with a SPT construct containing (i) a complementary wild-type male fertility gene to restore fertility, (ii) an α-amylase gene to disrupt pollination and (iii) a seed colour marker gene. The sporophytic wild-type allele complements the recessive mutation, enabling the development of pollen grains, all of which carry the recessive allele but with only half carrying the SPT transgenes. Pollen grains with the SPT transgenes exhibit starch depletion resulting from expression of α-amylase and are unable to germinate. Pollen grains that do not carry the SPT transgenes are nontransgenic and are able to fertilize homozygous mutant plants, resulting in nontransgenic male-sterile progeny for use as female parents. Because transgenic SPT maintainer seeds express a red fluorescent protein, they can be detected and efficiently separated from seeds that do not contain the SPT transgenes by mechanical colour sorting. The SPT process has the potential to replace current approaches to pollen control in commercial maize hybrid seed production. It also has important applications for other cross-pollinating crops where it can unlock the potential for greater hybrid productivity through expanding the parental germplasm pool. [ABSTRACT FROM AUTHOR]

Overuse of a small number of Upland cotton cultivars has narrowed cotton's genetic base, leading to major difficulties in developing cotton cultivars with diverse genetic backgrounds that are able to adapt to adverse conditions. To effectively broaden the genetic base, chromosome introgression lines ( ILs) were developed, where TM-1, the genetic standard of Upland cotton, was used as the common recipient and its two feral landraces, TX-256 and TX-1046, were used as the donors. A total of 115 ILs, with an average segment length of 11.15 cM, were first developed via intraspecific hybridization by marker-assisted selection ( MAS) in BC3F2 generations, spanning 3887.75 cM of the cotton genome. Association analysis showed that 63 markers were found to be associated with boll weight ( BW), lint percentage ( LP) and seed index. The percent of phenotypic variance explained by 148 QTLs detected was 4.12% on average. Eleven and five new QTLs for BW and LP (one stable QTL identified for LP in all environments) were detected, respectively, which can be used for efficiently pyramiding favourable alleles into one cultivar by MAS. [ABSTRACT FROM AUTHOR]

The ability of taxa to cross/hybridize is useful information for plant systematists and breeders. Crossability reflects reproductive isolation and the biological species concept stresses the need for reproductive isolation between species to maintain morphological distincness. For plant breeders knowledge on crossing ability facilitate selection of taxa for character improvement breeding. In this study, the crossing relationships and chromosome numbers within and among Ugandan species of Solanum sect. Solanum is studied by making 800 crosses involving 246 combinations. Less than half of these combinations were successful, producing F1 offspring. All studied accessions are self-compatible and most accessions crossed readily with accessions of their own species. Interspecific crossings failed either to yield seeds, yielded F1 seeds that did not germinate, or resulted in F1s that did not have stainable pollen - implying a crossing barrier; or stainable pollen, but with chromosome numbers that indicated reproduction by apomixis. The results support the taxonomic treatment of Solanum based on classical, numerical and partly molecular evidences. The material studied represents eight Ugandan taxa: S. americanum, a diploid (2n = 2x = 24); five tetraploids (2n = 4x = 48) S. florulentum, S. memphiticum, S. tarderemotum, S. villosum ssp. villosum and S. villosum ssp. miniatum; and two hexaploids (2n = 6x = 72) S. scabrum subsp. scabrum and S. scabrum subsp. laevis. In addition to confirming the ploidy levels of the Ugandan accessions, the ploidy levels of S. florulentum, S. memphiticum and S. tarderemotum are reported for the first time. Non-Ugandan material of Solanum sarrachoides was found to be diploid. Knowledge of the crossing behaviour and ploidy levels in Solanum will facilitate breeding for character improvement in these important species that are used commonly as food and/or medicine in eastern Africa. [ABSTRACT FROM AUTHOR]

Tedera ( Bituminaria bituminosa vars. albomarginata and crassiuscula) is a perennial pasture species with agronomic characters ideally suited to Mediterranean climates. Tedera seed has a period of after-ripening or primary dormancy typically lasting three months, which delays assessment and breeding of elite hybrid varieties. Temperature, chemical and mechanical methods were investigated in conjunction with in vitro culture to circumvent this dormancy period across a range of parental and hybrid genotypes. Temperature treatment of T5 (Tedera accession 5) and T48 (Tedera accession 48) alone was not sufficient to break dormancy (24.0% and 14.7% germination); however, when combined with soaking in gibberellic acid ( GA3) and mechanical scarification resulted in 79.7% and 84.3% germination respectively. In an effort to further improve this result for valuable hybrid genotypes, we combined mechanical scarification with removal of seed coat after imbibition and in vitro culture on B5 medium until radicle emergence. This resulted in breaking dormancy from 96% to 100% of parent seeds and 100% of hybrid seeds. Hardening the germinated F1 or F2 seedlings 4 d after first transfer to in vitro culture resulted in 100% survival of plants to soil. This procedure is now used on a routine basis in the Australian tedera breeding programme. [ABSTRACT FROM AUTHOR]

Reciprocal crosses between species often display an asymmetry in the fitness of F1 hybrids. This pattern, referred to as isolation asymmetry or Darwin's corollary to Haldane's rule, is a general feature of reproductive isolation in plants, yet factors determining its magnitude and direction remain unclear. We evaluated reciprocal species crosses between two naturally hybridizing diploid species of Arabidopsis to assess the degree of isolation asymmetry at different postmating life stages. We found that pollen from Arabidopsis arenosa will usually fertilize ovules from Arabidopsis lyrata; the reverse receptivity being less complete. Maternal A. lyrata parents set more F1 hybrid seed, but germinate at lower frequency, reversing the asymmetry. As predicted by theory, A. lyrata (the maternal parent with lower seed viability in crosses) exhibited accelerated chloroplast evolution, indicating that cytonuclear incompatibilities may play a role in reproductive isolation. However, this direction of asymmetrical reproductive isolation is not replicated in natural suture zones, where delayed hybrid breakdown of fertility at later developmental stages, or later-acting selection against A. arenosa maternal hybrids (unrelated to hybrid fertility, e.g., substrate adaptation) may be responsible for an excess of A. lyrata maternal hybrids. Exogenous selection rather than cytonuclear incompatibilities thus shapes the asymmetrical postmating isolation in nature. [ABSTRACT FROM AUTHOR]

Introgression of unadapted genes from the wild Cicer species could contribute to the widening of genetic base of important traits such as yield, yield attributes and resistance to major biotic and abiotic stresses. An attempt was made successfully to intercross two wild annual Cicer species with three cultivated chickpea cultivars. Four interspecific cross-combinations were made, and their true hybridity was ascertained through morphological and molecular markers. These cross-combinations were also studied for some important quantitative traits under real field conditions. The range, mean and coefficient of variation of agro-morphological traits were assessed in the parental lines, their F1 and F2 generations to determine the extent of variability generated in cultivated chickpea varieties. A high level of heterosis was recorded for number of pods/plant and seed yield/plant in F1 generation. Three cross-combinations of 'Pusa 1103' × ILWC 46, 'Pusa 256' × ILWC 46 and 'Pusa 256' × ILWC 239 exhibited substantially higher variability for important yield-related traits. The present research findings indicate that these wild annual Cicer species can be easily exploited to broaden the genetic base of cultivated gene pool for improving seed yield as well as adaptation. [ABSTRACT FROM AUTHOR]