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The review outlines past failures, present status and future prospects of hybrid wheat, and includes information on CMS/CHA/transgenic approaches for male sterility, heterotic groups and cost-effective hybrid seed production. Hybrid varieties give increased yield and improved grain quality in both cross- and self-pollinated crops. However, hybrid varieties in self-pollinated crops (particularly cereals) have not been very successful, except for hybrid rice in China. In case of hybrid wheat, despite the earlier failures, renewed efforts in recent years have been made and hybrid varieties with desirable attributes have been produced and marketed in some European countries. This review builds upon previous reviews, with a new outlook and improved knowledge base, not covered in earlier reviews. New technologies have been described, which include the Hordeum chilense-based CMS-fertility restorer system, chromosomal XYZ-4E-ms system and the following transgenic technologies: (1) conditional male sterility involving use of tapetum-specific expression of a gene that converts a pro-toxin into a phytotoxin causing male sterility; (2) barnase-barstar SeedLink system of Bayer CropScience; (3) split-barnase system that obviates the need of a barstar-based male restorer line; and (4) seed production technology of DuPont-Pioneer that makes use of transgenes in production of male-sterile lines, but gives hybrid seed with no transgenes. This review also includes a brief account of studies for discovery of heterotic QTL, genomic prediction of hybrid vigour and the development of heterotic groups/patterns and their importance in hybrid wheat production. The problem of high cost of hybrid seed due to required high seed rate in wheat relative to hybrid rice has also been addressed. The review concludes with a brief account of the current efforts and future possibilities in making hybrid wheat a commercial success.

Developing training sets for genomic prediction in hybrid crops requires producing hybrid seed for a large number of entries. In autogamous crop species (e.g., wheat, rice, rapeseed, cotton) this requires elaborate hybridization systems to prevent self-pollination and presents a significant impediment to the implementation of hybrid breeding in general and genomic selection in particular. An alternative to F1 hybrids are bulks of F2 seed from selfed F1 plants (F1:2). Seed production for F1:2 bulks requires no hybridization system because the number of F1 plants needed for producing enough F1:2 seed for multi-environment testing can be generated by hand-pollination. This study evaluated the suitability of F1:2 bulks for use in training sets for genomic prediction of F1 level general combining ability and hybrid performance, under different degrees of divergence between heterotic groups and modes of gene action, using quantitative genetic theory and simulation of a genomic prediction experiment. The simulation, backed by theory, showed that F1:2 training sets are expected to have a lower prediction accuracy relative to F1 training sets, particularly when heterotic groups have strongly diverged. The accuracy penalty, however, was only modest and mostly because of a lower heritability, rather than because of a difference in F1 and F1:2 genetic values. It is concluded that resorting to F1:2 bulks is, in theory at least, a promising approach to remove the significant complication of a hybridization system from the breeding process.

Shelf life is an important breeding trait in tomato, especially for the tomato production in subtropical and tropical regions. Previously we have isolated and characterized ethylene receptor mutants, Sletr1-1 and Sletr1-2 from mutant population based on Micro-Tom cultivar. Sletr1-1 showed insensitivity to ethylene while Sletr1-2 showed reduced sensitivity to ethylene. We also have demonstrated that the traits are useful for extending fruit shelf life of the hybrid tomato cultivars. For commercializing the hybrid cultivars, the seed quality is another important trait. In this study, we evaluated the effects of the Sletr1-1 and Sletr1-2 mutations on the seed quality characteristics of F1 hybrid lines generated by crossing Sletr1-1 and Sletr1-2 with three commercial tomato cultivars, Intan, Mutiara and Ratna. Sletr1-1 mutation conferred insensitivity to ethylene in the F1 hybrid seedlings, resulting in negative effects including reduced germination rate, vigor index and emergence speed index. Interestingly Sletr1-2 mutation had almost no effect on the seed quality characteristics of the F1 hybrid lines, suggesting that Sletr1-2 was suitable for producing high quality of hybrid seeds.

Inbred line development requires information on the nature and magnitude of genetic variability and transmissibility of desired trait in source populations. In this study, the level of genetic variability, heritability and genetic advance of thirteen agronomic and fresh yield traits among twelve shrunken-2 super-sweet corn populations were evaluated. Field experiments were conducted for two years in Ibadan, Nigeria using a randomised complete block design with three replicates. Estimates of genetic variability components, broad-sense heritability and genetic advance were computed for each trait. All the traits exhibited significant genotypic differences. Genotypic variance was significant for number of marketable cobs, yield of cobs, number of cobs, number of kernel rows, husk cover, ear height and days to anthesis, while environmental variance was significant for all the traits. Phenotypic coefficients of variation were higher than the corresponding genotypic coefficients of variation for all traits. Broad-sense heritability ranged from 22.2% for anthesis-silking interval to 85.1% for husk cover. The genetic advance was high (32.7%) for husk cover, medium (12.0%) for yield of cobs and low for other traits. Genetic variability was present among the shrunken-2 super-sweet corn populations. Opportunities abound for further improvement of the populations and extraction of lines for hybrid seed production. Key words: Broad-sense heritability, genotypic coefficient of variation, husk cover score, sweet corn, yield of marketable cobs.

Summary The development and adoption of hybrid seed technology have led to dramatic increases in agricultural productivity. However, it has been a challenge to develop a commercially viable platform for the production of hybrid wheat (Triticum aestivum) seed due to wheat's strong inbreeding habit. Recently, a novel platform for commercial hybrid seed production was described. This hybridization platform utilizes nuclear male sterility to force outcrossing and has been applied to maize and rice. With the recent molecular identification of the wheat male fertility gene Ms1, it is now possible to extend the use of this novel hybridization platform to wheat. In this report, we used the CRISPR/Cas9 system to generate heritable, targeted mutations in Ms1. The introduction of biallelic frameshift mutations into Ms1 resulted in complete male sterility in wheat cultivars Fielder and Gladius, and several of the selected male‐sterile lines were potentially non‐transgenic. Our study demonstrates the utility of the CRISPR/Cas9 system for the rapid generation of male sterility in commercial wheat cultivars. This represents an important step towards capturing heterosis to improve wheat yields, through the production and use of hybrid seed on an industrial scale.

Seed production is critical for watermelon production, which mostly involves first-generation hybrid varieties. However, watermelon hybrid seed production currently requires complex procedures, including artificial isolation and pollination. Therefore, the development and use of a male-sterile system to generate watermelon hybrids can simplify the process. The scarcity of male-sterile watermelon germplasm resources necessitates the use of molecular breeding methods. Unfortunately, the genes responsible for male sterility in watermelon have not been cloned. Thus, the genetic basis of the male sterility remains unknown. In this study, two DNA pools derived from male-sterile and normal plants in the F2 population were used for whole-genome resequencing. The Illumina high-throughput sequencing resulted in 62.99 Gbp clean reads, with a Q30 of 80% after filtering. On the basis of the SNP index association algorithm, eight candidate regions (0.32 Mb) related to specific traits were detected on chromosome 6. Expression pattern analyses and watermelon transformation studies generated preliminary evidence that Cla006625 encodes a pollen-specific leucine-rich repeat protein (ClaPEX1) influencing the male sterility of watermelon. The identification and use of genic male sterility genes will promote watermelon male sterility research and lay the foundation for the efficient application of seed production technology.

We have developed long term stable high yielding rice lines, Hybrid Mimics, from commercial hybrids. The vigour of the Mimic and the hybrid are developmental changes. These Mimics could substitute for hybrid seed for planting. We have used two pre-existing high-yielding hybrid systems (FLY1 and DY527) to develop Hybrid Mimics. In the FLY1 hybrid system we selected, under field conditions, F6 lines which have high grain yields and biomass equivalent to the F1 hybrids, stable over subsequent F7, F8 and later generations. We have termed these lines Hybrid Mimics. The mimics are mostly homozygous as a consequence of selfing in each generation. We have repeated this selection procedure in the second independent hybrid system DY527, producing Mimics with similar characteristics to the F1 hybrid. In both hybrid systems the selection criterion, based on the phenotype of the F1 hybrid, results in the Mimics having grain yield and biomass similar to that of the F1 hybrid. In each generation of the breeding program the plant population has increased phenotypic homogeneity. The genomes of the Mimic plants do not contain any common heterozygous segments negating claims that the vigour of hybrids depends upon heterozygosity of particular loci. Both hybrids and Mimics have early germination and commence photosynthesis before the parents, providing enhanced growth which is maintained throughout the life cycle. The biochemical parameters of photosynthesis in the hybrids and Mimics do not differ from those of the parents. Grain quality and resistance to the two major diseases, bacterial blight and rice blast are similar in the Mimics and hybrids. The Mimics overcome the major disadvantage of hybrids where F2 phenotypic segregation prevents their use as a crop beyond the F1 generation.

Background Photo-thermo-sensitive genic male sterile (PTGMS) rice (Oryza sativa L.) is usually considered two-line male sterile rice because of its dual-purpose in two-line hybrid rice system: under short days and low temperatures, it is fertile and used for self-propagation, but under long days and high temperatures, it is sterile and used for hybrid seed production. Therefore, photoperiod and temperature conditions are extremely important for the fertility transition of two-line male sterile rice. In recent years, there have been frequent occurrences of abnormally low-temperature (ALT) resulting in failure of two-line hybrid rice seed production. The daily average temperature (DAT) during ALT events is sometimes higher than the critical sterility-inducing temperature (CSIT) of two-line male sterile rice, of which the night temperature is lower than the CSIT. DAT has been traditionally used as the single indicator of pollen fertility transition, but it is unknown why the fertility of two-line male sterile rice in seed production restored fertility under ALT conditions. Results For Hang93S (H93S), a newly released PTGMS line, we hypothesized fertility transition is determined mainly by the cumulative effective low temperature (ELT) and only a certain duration of low temperature is required every day during the fertility-sensitive period. This study simulated ALTs where the DAT was higher than the CSIT while some segments of night temperature were lower than the CSIT. The results showed H93S exhibited a fertility transition to varying degrees. Moreover, fertility was restored under simulated ALT conditions and pollen fertility increased with increasing cumulative ELT, indicating that the fertility transition was affected primarily by the cumulative ELT. Results also indicated that pollen fertility increased as the number of treatment days increased. Conclusions The fertility transition is caused mainly by the cumulative ELT. In two-line male sterile rice breeding, the effects of day length, ALT at night, and continuous response days should be considered together. The present study provides new insight into fertility transition so breeders can more effectively utilize the two-line male sterile rice, H93S, in breeding programs.

The quantitatively inherited trait plant height is routinely evaluated in triticale breeding programs as it substantially influences lodging and disease susceptibility, is a main contributor to biomass yield, and is required to improve hybrid seed production by fine-tuning plant height in the female and male parental pools in hybrid breeding programs. In this study, we evaluated a panel of 846 diverse Central European triticale genotypes to dissect the genetic architecture underlying plant height by genome-wide association mapping. This revealed three medium- to large-effect QTL on chromosomes 5A, 4B, and 5R. Genetic and physical fine-mapping of the putative QTL revealed that the QTL on chromosome 5R most likely corresponds to Ddw1 and that the QTL on chromosome 5A is likely to be Rht12. Furthermore, we observed a temporal trend in registered cultivars with a decreasing plant height during the past decades, accompanied by an increasing use of the height-reducing alleles at the identified QTL. In summary, our results shed new light on the genetic control of plant height in triticale and open new avenues for future improvement by breeding.

International audience; Doubled haploids (DH) have become a powerful tool to assist in different basic research studies, and also in applied research. The principal (but not the only) and routine use of DH by breeding companies is to produce pure lines for hybrid seed production in different crop species. Several decades after the discovery of haploid inducer lines in maize and of anther culture as a method to produce haploid plants from pollen precursors, the biotechnological revolution of the last decades allowed to the development of a variety of approaches to pursue the goal of doubled haploid production. Now, it is possible to produce haploids and DHs in many different species, because when a method does not work properly, there are several others to test. In this chapter, we overview the currently available approaches used to produce haploids and DHs by using methods based on in vitro culture, or involving the in vivo induction of haploid embryo development, or a combination of both.

The use of genetic resources in breeding is considered critical to ensure future selection gain, but the absence of important adaptation genes often masks the breeding value of genetic resources for grain yield. Testing genetic resources in a hybrid background has been proposed as a solution to obtain unbiased estimates of breeding values for grain yield. In our study, we evaluated the suitability of European wheat elite lines for implementing this hybrid strategy, focusing on maximizing seed yield in hybrid production and reducing masking effects due to susceptibility to lodging, yellow rust, and leaf rust of genetic resources. Over a 3-year period, 63 wheat elite female lines were crossed with eight male plant genetic resources in a multi-environment field experiment to evaluate seed yield on the female side. Then, the resulting hybrids and their parents were tested for plant height, lodging, and susceptibility to yellow rust and leaf rust in a further field experiment at multiple locations. We found that seed yield was strongly influenced by the elite wheat line choice in addition to environment and observed substantial differences among elite tester lines in their ability to reduce susceptibility to lodging, yellow rust, and leaf rust when the hybrid strategy was implemented. Consequently, breeders can significantly increase the amount of hybrid seed produced in wide crosses through appropriate tester choice and adapt genetic resources of wheat with the hybrid strategy to the modern cropping system.

Due to novel and more demanding consumers’ requirements, breeding of vegetable crops confronts new challenges to improve the nutritional level and overall appearance of produce. Such objectives are not easy to achieve considering the complex genetic and physiological bases. Overtime, plant breeders relied on a number of technologies and methods to achieve ever changing targets. F1 hybrid seed production allowed the exploitation of heterosis and facilitated the combination of resistance and other useful genes in a uniform outperforming variety. Mutagenesis and tissue culture techniques permitted to induce novel variation, overcome crossing barriers, and speed up the achievement of true-breeding lines. Marker-assisted selection was one of the milestones in fastening selection, starting from the early ’90s in almost all seed companies. Only recently, however, are novel omics tools and genome editing being used as cutting-edge techniques to face old and new challenges in vegetable crops, with the potential to increase the qualitative value of crop cultivation and solve malnutrition in 10 billion people over the next 30 years. In this manuscript, the evolution of breeding approaches in vegetable crops for quality is reviewed, reporting case studies in tomato (Solanum lycopersicum L.) and cauliflower (Brassica oleracea var. botrytis L.) as model systems for fleshy fruit and floral edible parts, respectively.

Maize weevil (Sitophilus zeamais Motschulsky) is a common insect pest affecting stored maize (Zea mays L.) worldwide and can be controlled by breeding for host resistance. Information on combining ability and gene effects conditioning maize weevil resistance would be required to devise breeding strategies. However, there are disagreements regarding the seed generation to subject to maize weevil resistance evaluation. This study determined the seed generation effect on the quality of genetic information obtained from a maize diallel cross. Eight weevil-resistant and two susceptible maize inbred lines from eastern and southern Africa were crossed in a 10-parent diallel scheme. The resulting F1 hybrid seed, F2 full-sib grain from controlled pollination, and F2 half-sib grain from open pollination were evaluated for maize weevil resistance and responses were determined using the number of F1 weevil emergence from the seed (FWE), median development period (MDP), Dobie’s index of susceptibility (DIS), and parental weevil mortality (PWM). General combining ability (GCA) and specific combining ability (SCA) effects were significant for the FWE, MDP, and DIS in all seed categories. Results revealed that reciprocal effects were predominant in F1 hybrid seed, GCA effects were predominant in F2 full-sib grain, while SCA effects were more important in the F2 half-sib grain. The F2 full-sib generation exhibited superiority in providing genetic information required for parental line selection when breeding for weevil resistance, compared to F1 hybrid and F2 half-sib grain. Resistant inbred lines MV170 and MV142, produced hybrids that exhibited high levels of maize weevil resistance across all the three seed categories thus, qualifying as suitable materials for breeding weevil resistant maize hybrids.

The application of heterosis is a promising approach for greatly increasing yield in soybean (Glycine max L.). Nuclear male sterility is essential for hybrid seed production and the utilization of heterosis. Here we report the cloning of the gene underlying the soybean male-sterile mutant ms-1, which has been widely used for recurrent selection in soybean breeding programs. We initially delimited the ms1 locus to a 16.15 kb region on chromosome 13, based on SLAF_BSA sequencing followed by genotyping of an F2 population segregating for the locus. Compared with the same region in fertile plants, the mutant region lacks a sequence of approximately 38.7 kb containing five protein-coding genes, including an ortholog of the kinesin-like protein gene NACK2, named GmMs1. The GmMs1 knockout plants generated via CRISPR/Cas-mediated gene editing displayed a complete male-sterile phenotype. Metabolic profiling showed that fertile anthers accumulated starch and sucrose normally, whereas sterile anthers had higher anthocyanin levels and lower flavonoid levels and lower antioxidant enzyme activities. These results provide insights into the molecular mechanisms governing male sterility and demonstrate that GmMs1 could be used to create male-sterile lines through targeted mutagenesis. These findings pave the way for designing seed production technology and an intelligent male-sterile line system to utilize heterosis in soybean.

Owing to their superior agronomic performance, the hybrids of vegetable crops are currently applied extensively. However, effective hybrid production requires a laborious manual emasculation to ensure the purity of hybrid seeds in tomato because of the lack of an effective male sterility system. Here, we created two types of tomato nuclear male-sterile lines with different screening markers in a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system. Co-knockouts of male sterile 10(35) (Ms10(35)) and glutathione S-transferase (GSTAA) created a male-sterile line marked by a green hypocotyl. The Ms10(35) biallelic mutation was introduced into the woolly tomato background, resulting in the linkage of male sterility and a non-woolly phenotype. Two types of male-sterile lines were easily selected at the seedling stage by hypocotyl color or trichome density and further showed high seed purity during hybrid seed production. Our work established the procedure for a rapid transfer of the male-sterile phenotype to the parents of hybrids without extra-modification by the CRISPR/Cas9 system that can be practically applied to hybrid seed production in tomato. This method will be the basis and example for sterile parent creation of multiple crops for hybrid production with the CRISPR/Cas9 system. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11032-021-01215-2.

Hybrid seed set on the female line depends primarily on its flowering synchronization with the restorer line (R), therefore, the sowing of male and female lines must be planned properly to achieve this. Field experiments on different sowing dates (May 1st, May 15th, and May 30th) of R lines (Giza 178R, Giza 179R, and Giza 181R) and cytoplasmic male sterile (CMS) lines (IR69625A, IR70368A, IR58025A, K17A, and G46A) were carried out at the farm of Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt during 2019 and 2020 to study the effect of sowing dates on flowering synchronization in hybrid rice. The results indicated that the synchronization of flowering between CMS lines and R lines has highly significant effects on the days to 50% heading, number of leaves, effective accumulated temperature (EAT), plant height, panicle exertion percentage, panicle length, number of fertile panicles, panicle weight, seed set percentage, harvest index and seed yield of hybrid rice. The highest seed yield (1.72 and 1.41 t ha−1, respectively in 2019 and 2020) was recorded from the sowing date May 1st and the hybrid combination of Giza 178R × IR58025A (2.06 and 2.12 t ha−1 in 2019 and 2020, respectively). The grain yield had a significant and highly significant positive correlation with the plant height (cm), panicle exertion percentage, panicle length, number of panicles plant−1, panicle weight, seed set percentage, and harvest index. In Egypt, May 1st is the best time for the synchronization of hybrid rice lines and a combination of Giza 178R × IR58025A may be recommended for better performance.

Funder: Canadian Seed Growers' Association; doi: http://dx.doi.org/10.13039/501100000071, Funder: National Research Council of Canada: Canadian Wheat Improvement program, Key message: Four QTL for ergot resistance (causal pathogen Claviceps purpurea) have been identified in the durum wheat cultivar Greenshank. Abstract: Claviceps purpurea is a pathogen of grasses that infects flowers, replacing the seed with an ergot sclerotium. Ergot presents a significant problem to rye, barley and wheat, in particular hybrid seed production systems. In addition, there is evidence that the highly toxic alkaloids that accumulate within sclerotia can cross-contaminate otherwise healthy grain. Host resistance to C. purpurea is rare, few resistance loci having been identified. In this study, four ergot resistance loci are located on chromosomes 1B, 2A, 5A and 5B in the durum wheat cv. Greenshank. Ergot resistance was assessed through analysis of phenotypes associated with C. purpurea infection, namely the number of inoculated flowers that produced sclerotia, or resulted in ovary death but no sclerotia, the levels of honeydew produced, total sclerotia weight and average sclerotia weight and size per spike. Ergot testing was undertaken in Canada and the UK. A major effect QTL, QCp.aafc.DH-2A, was detected in both the Canadian and UK experiments and had a significant effect on honeydew production levels. QCp.aafc.DH-5B had the biggest influence on total sclerotia weight per spike. QCp.aafc.DH-1B was only detected in the Canadian experiments and QCp.aafc.DH-5A in the UK experiment. An RNASeq analysis, undertaken to identify wheat differentially expressed genes associated with different combinations of the four ergot resistance QTL, revealed a disproportionate number of DEGs locating to the QCp.aafc.DH-1B, QCp.aafc.DH-2A and QCp.aafc.DH-5B QTL intervals.

Chemical defoliation of seed corn production fields accelerates seed maturation and desiccation and expedites seed harvest. Early seed harvest is important to minimize the risk of frost damage while in the field. This newly adopted seed production practice also allows seed companies to plan harvest and manage dryer space more efficiently. However, premature defoliation may interfere with the migration of oil bodies within embryo cells during desiccation and affect seed germination and vigor. The objective of this study was to investigate the effect of chemical defoliation on the migration patterns of oil bodies within embryo cells during desiccation. Chemically defoliated and non-defoliated plants from five commercial hybrid seed corn fields were sampled in 2014 and 2015. Whole ears with husks were harvested before and after defoliant application at 600 g H2O kg−1 fresh weight (fw), and weekly thereafter until seed reached approximately 300–350 g H2O kg−1 fw. Ten embryos extracted from center-row seeds were fixed to stop metabolic processes, then sliced, processed, and photographed using scanning transmission electron microscopy. The oil bodies within embryo cells followed normal migration patterns according to seed moisture content, regardless of defoliation treatment. Seed germination and vigor were verified and were not significantly affected by defoliation. Chemical defoliation is a viable production practice to accelerate seed corn desiccation and to manage harvest and seed dryer availability more efficiently without negatively affecting seed germination and vigor.

Genotype, environmental temperature, and agronomic management of parents influence seed yield in three-way cross hybrid maize seed production. The objective of this research was to generate information on the seed production of six three-way cross hybrids and their progenitors, adapted to tropical lowlands. Data on days to—and duration of—flowering, distance to spike and stigmas, and seed yield of five female single crosses and five male inbred lines were recorded for different combinations of four planting densities and four sowing dates in Mexico. The effect of planting density was not significant. The male inbred line T10 was the earliest and highest seed yield and T31 the latest, occupying second place in yield. The single crosses T32/T10 and T13/T14 were the earliest and had the highest effective seed yield. At the earliest sowing date, the females were later in their flowering, accumulated fewer growing degree days (GDD), and obtained higher yields since the grain-filling period coincided with hot days and cool nights. To achieve greater floral synchronization and therefore greater production of hybrid seed, differential planting dates for parents are recommended based on information from the accumulated GDD of each parent. The three-way cross hybrids were classified according to the expected seed yield of the females and the complexity in the synchronization of flowering of their parents.

The Polima system of cytoplasmic male sterility (Pol CMS) was widely used for hybrid seed production, but with high probability of occurrence of maternal false hybrid due to the fertility of Polima CMS (Pol CMS) line greatly affected by the ambient temperature, therefore, the detection of maternal false hybrids is the key to purity identification. In present study, the SSR markers were designed based on the flanking sequences of Pol CMS restorer gene Rfp , and application of SSR markers in hybrid seed purity test of rapeseed. The main results were as follows: the sequences of Rfp were subjected to basic local alignment search tool queries against the Brassica rapa genome to determine chromosome positions, and 32 SSR markers were developed based on the upstream and downstream sequences of Rfp . Among the 32 SSR markers, one codominant marker was polymorphic between Pol CMS sterile and restorer line, the PCR product length was 162 bp in Pol CMS sterile lines, and 184 bp in restorer lines. Based on the PCR sequence, two insert fragments (15 bp and 7 bp) were identified in Pol CMS restorer lines. The SSR marker co-segregated with plant fertility of individuals in the “fengyou737” F 2 population. The purity of “fengyou737”, “fengyou320” and “fengyou958” were identified by means of PCR-SSR markers and field-planting, and the results of two ways were highly consistent, indicated that the codominant SSR marker tightly linked to Rfp , and the marker can detect paternal and maternal false hybrids. The present findings will provide technical assistance for hybrid seed purity test and genetic diversity analysis in rapeseed.

Interest in understanding hybrid seed failure (HSF) has mushroomed, both in terms of identifying underlying molecular processes and their evolutionary drivers. We review phenotypic and molecular advances with a focus on the ‘effective ploidy’ concept, witnessing a recent revival after long obscurity. Endosperm misdevelopment has now been shown to underlie HSF in many inter-specific, homoploid crosses. The consistent asymmetries in seed size and developmental trajectories likely reflect parental divergence in key, dosage-sensitive processes. Transcriptomic and epigenomic studies reveal genome-wide, polarized expression perturbations and shifts in parental expression proportions, consistent with small-RNA imbalances between parental roles. Among-species differences in levels of parental conflict over resource allocation enjoy strong support in explaining why differences in effective ploidy may evolve., Current Opinion in Plant Biology, 61, ISSN:1369-5266, ISSN:1879-0356

Parthenogenesis is the main technique to produce doubled haploid lines in melon. Although parthenogenesis is a genotype-dependent process and melon has a huge genotypic diversity, we developed a successful protocol for haploid embryo production via pollination with irradiated pollen and a protocol for chromosome doubling of haploid plants of 'Piel de Sapo' genotypes. 'Piel de sapo' genotype has lower efficiencies during the process in comparison with other genotypes, for instance, of the agrestis subspecies. Nevertheless, the doubled haploid lines produced have a great potential as pure parentals for hybrid seed production.

Shallot is loosely used to describe some cultivated species and interspecific hybrids within the genus Allium whose storage organ consists of clustered bulb divisions attached at their true stems. The present review, however, focuses on the diploid member of the bulb onion taxon (Allium cepa L.). Some physiological and phenotypic differences, led taxonomists to assign shallot to the Aggregatum group together with other intermediate forms of vegetatively-propagated bulbous Alliums. No ancestral forms of the biennial cross-pollinated shallot are known. The bulbs, leaves and young scapes are consumed as an onion substitute in warm climates and serve as an important culinary condiment in Europe, South America, the USA and elsewhere. Global climate changes, diminished resources, and salinization of soil and water raise serious challenges to shallot growth, development, florogenesis, quality and storage, and increase vulnerability to pests and diseases. Additionally, the slow but continuous shift towards the use of true seeds poses concrete hazards of a fast erosion of the genetically precious, irreplaceable clonally propagated cultivars. To secure the supply, and care for the environment, society and economics we need to extend our knowledge on, and increase breeding efforts for tolerance to, biotic and abiotic stress, long keeping and hybrid seed propagation. The current review provides information on shallot origin, taxonomy, economics, distribution, genetics, current propagation and breeding methods. Pros and cons of clonal vs. true-shallot-seed propagation are discussed. Comparisons to bulb onion clearly show that the knowledge acquired, and modern tools developed for bulb onion can be associated with conventional shallot breeding methods for its betterment and benefit growers and consumers alike.

Homozygous parental lines are indispensable for commercial hybrid seed production in many ornamental and vegetable crops. The in vitro induction of haploids and doubled haploids (DHs) through gametic embryogenesis is an effective approach for single-step development of complete homozygous lines from heterozygous donor plants. Anther culture is one of the most popular and widely employed techniques for development of haploids. Here we describe the detailed protocol for rapid and successful induction of haploids in Tagetes spp. using in vitro androgenesis approach. In this protocol, we have provided the comprehensive details of various steps of anther culture in marigold right from the growing of donor plants, selection of buds, pretreatment, embryogenesis and regeneration to ploidy analysis, and chromosome doubling for development of DHs.

Protein-rich food legumes are usually cultivated as rain-dependent crops under subsistence agriculture. Besides this, most farmers are deprived of improved seeds due to lack of interest in both public and private seed industries. These factors lead to unacceptably poor yields at the farm level. In a number of field crops, the cultivation of hybrids has resulted in quantum jump in their productivity, but by contrast in legumes, only inbred cultivars are in cultivation with poor harvests. In the last few decades, breeders are attempting to develop hybrid breeding technology in two legumes, faba bean and pigeonpea, where natural out-crossing is sufficient to support their large-scale hybrid seed production. Besides these, attempts are also being made to develop a hybrid technology in soybean, where male sterility systems have been bred, and attempts are being made to enhance the level of cross-pollination to facilitate the production of cross-pollinated seed. Of the three crops, the success has been achieved only in pigeonpea [Cajanus cajan (L.) Millsp.] where three commercial hybrids have been bred. In farmers’ fields, these hybrids produce 30–50% more yield over the local control. This review deals with breeders’ efforts towards developing hybrid technology in the three legume crops along with the major accomplishments in hybrid pigeonpea breeding.

Eggplant is one of the five important, worldwide-distributed solanaceous crops. The use of anther culture technology to produce pure, 100% homozygous doubled haploid lines for hybrid seed production is possible since 1982, where the first protocol of wide application to different eggplant materials was published. From then on, different improvements and adaptations to different materials have been made. In parallel, protocols to implement isolated microspore culture technology in eggplant have been developed principally in the last decade, which opens the door for a more efficient DH production in this species. In this chapter, two protocols, one for anther and other for isolated microspore culture in eggplant, are described. Some steps and materials are common to both approaches. A detailed description of each step from is provided.

In okra, we follow the breeding methodologies of autogamous plants. This includes crossing or controlled hybridization of parents selected based on their better-combining abilities. This is followed by the pedigree selection of the segregating population for the traits of interest like biotic and abiotic stress tolerance and yield. The major breeding objectives are nearly the same across all the okra-growing countries: high yield, tolerance to various pests and diseases, better organoleptic qualities, appealing color and size of the harvestable fruits. Hand pollination is the most commonly used method of hybrid seed production in okra and improving yield and ensuring its sustainability under adverse conditions through resistant hybrids is the major objective of heterosis breeding. Sufficient genetic diversity has been reported among the parents and crosses for selection to be effective for okra hybrid production. Although both additive and dominant gene actions were found regulating the phenotypic expression of various characters, dominant gene action is considered more important. Through intensive research efforts, a large number of varieties and hybrids have been released around the world. Some of these varieties have already made a significant impact in revolutionizing the production of okra worldwide. This chapter summarizes the current status of okra crop production and its future improvement strategies.

Hybrid rice technology is a viable strategy to increase rice production and productivity, especially in countries with limited cultivable land for agriculture and irrigation water, along with costlier chemical inputs. The three-line hybrid rice technology adoption rate is slowing down because of restricted heterosis per se, the availability of better combining ability in cytoplasmic male sterile lines, lower hybrid seed reproducibility, and limited market acceptability of hybrids. Two-line heterosis breeding could overcome these shortcomings. However, the wide-scale adoption and use of two-line hybrid rice technology are possible through systematic research and breeding efforts to develop temperature-sensitive genetic male sterile (TGMS) lines with low (

Cytoplasmic male sterility (CMS) is an important tool for producing F1 hybrids, which can exhibit heterosis. The companion system, restorer-of-fertility (Rf), is poorly understood at the molecular level and would be valuable in producing restorer lines for hybrid seed production. The identity of the Rf gene in Capsicum (pepper) is currently unclear. In this study, using bulked segregant RNA sequencing (BSR-seq), a strong candidate Rf gene, Capana06g002866, which is annotated as a NEDD8 conjugating enzyme E2, was identified. Capana06g002866 has an ORF of 555 bp in length encoding 184 amino acids; it can be cloned from F1 plants from the hybridization of the CMS line 8A and restorer line R1 but is not found in CMS line 8A. With qRT-PCR validation, Capana06g002866 was found to be upregulated in restorer accessions compared to sterile accessions. The relative expression in flower buds increased with the developmental stage in F1 plants, while the expression was very low in all flower bud stages of the CMS lines. These results provide new insights into the Rf gene in pepper and will be useful for other crops utilizing the CMS system.

The use of hybrid genotypes is a good alternative for increasing the flooded rice yield. However, there is a need for validation of the fertilizer management under different edaphoclimatic conditions and its greater profitability. This study aimed to evaluate the grain yield and profitability of rice hybrids in relation to N doses and fertilization with P and K. Five hybrid cultivars and the conventional IRGA 424 CL cultivar combined with four N doses (0, 100, 150 and 200 kg ha-1) were evaluated, all with fixed doses of 90 kg ha-1 of P2O5 and 150 kg ha-1 of K2O, besides an additional treatment without the addition of fertilizers. The N application increases, on average, by 10 and 35 % the flooded rice yield in years with favorable and unfavorable climatic conditions, respectively. Regardless of the year and genotype, the highest yields are obtained with doses of N between 106 and 200 kg ha-1, with the most profitable dose being the 150 kg ha-1 one (22 % higher than for the absence of N). The hybrids produce an average of 20 % more grains than the IRGA 424 CL cultivar, increasing the profitability by 18 %. In soil with adequate P and K availability, there is no increase in yield due to the application of these nutrients. However, in deficient soil, the fertilization with P and K increases the grain yield by 21 %. RESUMO O uso de genótipos híbridos é uma boa alternativa para aumentar a produtividade do arroz irrigado. Há, no entanto, a necessidade de validação do manejo da adubação em diferentes condições edafoclimáticas e de sua maior rentabilidade. Objetivou-se avaliar a produtividade de grãos e a rentabilidade de híbridos de arroz relacionadas a doses de N e à adubação com P e K. Avaliaram-se cinco cultivares híbridas e a cultivar convencional IRGA 424 CL combinadas com quatro doses de N (0; 100; 150; e 200 kg ha-1), todas com doses fixas de 90 kg ha-1 de P2O5 e 150 kg ha-1 de K2O, além de um tratamento adicional, sem o uso de fertilizantes. A aplicação de N incrementa, em média, em 10 e 35 % a produtividade do arroz irrigado em anos com condições climáticas favoráveis e desfavoráveis, respectivamente. Independentemente do ano e genótipo, as maiores produtividades são obtidas com doses de N entre 106 e 200 kg ha-1, sendo a dose de maior rentabilidade a de 150 kg ha-1 (22 % superior à ausência de aplicação de N). Os híbridos produzem 20 % a mais de grãos, em média, que a cultivar IRGA 424 CL, incrementando a rentabilidade em 18 %. Em solo com disponibilidade de P e K adequada, não há incrementos em produtividade pela aplicação desses nutrientes. Porém, em solo deficiente, a fertilização com P e K incrementa em 21 % a produtividade de grãos.

Flag leaf angle (FLA) is an important outcrossing trait affecting the hybrid seed production in rice (Oryza sativa L.). Natural variation of FLA has been reported in rice, but the molecular basis for this variation is largely unknown. Here we investigated the phenotypic values of FLA in 353 rice natural accessions in six environments, which indicated rich phenotypic variation. We performed a genome-wide association study on FLA using 1.3 million single nucleotide polymorphism (SNPs). A total of 37 SNPs were identified significantly associated with FLA, of which 27 were located in previously reported QTLs/Genes and 10 were novel. We identified two causal gene loci for FLA, OsFLA6 and OsFLA2; OsFLA6 was co-localized with the gene OsLIC. In addition, the accessions with large and small FLA values have corresponding high and low OsFLA6 expression. We also confirmed that the allele OsFLA2TT increased the FLA compared with that of the isogenic line carrying allele OsSYL2CC by transgenic complementation experiment. The allele frequencies of OsFLA6GG and OsFLA2TT decreased gradually with an increase in latitude in the Northern Hemisphere. Our results should facilitate the improvement of FLA of parents of hybrid rice.

SUNFLOWER is an important oil crop that has received great attention by the Egyptian agricultural sector in the early nineties, when a boom in oil extraction from the crop was observed. Since then and for more than two decades now, sunflower for oil purpose was neglected, hybrids are no longer on the market and confectionery sunflower became more profitable for Egyptian farmers. Recently, the registration of the single hybrid Sirena and its promotion based on contract basis with farmers, may present a new comeback to oil sunflower in Egypt. The aim of this study was to evaluate effect of sowing date (April vs. August) and preceding crop (maize vs. sunflower) in a double cropping system, under varying nitrogen fertilization levels (36, 72, 108 and 144kg N/ha), on growth and productivity of the newly introduced sunflower hybrid Sirena. Results from the two-year experiments, indicated that April sowing, at a prevailing average temperature of 20-24oC later rising to about 28oC at harvest time, was suitable to secure maximum seed yield of 4.39ton/ha. In a double cropping system, where sowing was performed in August, the hybrid yielded an average of 3.4 ton/ha, whether preceded by maize or sunflower. Seed oil percentage amounted to an average of 42.8% and was affected by the year, rather than sowing date or preceding crop. Effects of the nitrogen fertilization rates were masked by the soil available nitrogen, however, based on the regression analysis and equations for estimating the nitrogen requirements based on the hybrid seed yield, 72-108kg N/ha were necessary to achieve the maximum seed yield while sustaining an oil percentage above the 42%.

Characterization of hybrid seed failure in Prunus provides insight into conserved or lineage-specific hybrid incompatibility mechanisms in plant species. Postzygotic hybrid incompatibility resulting from a cross between different species involves complex mechanisms occurring at various developmental stages. Embryo arrest, followed by seed abortion, is the first stage of such incompatibility reactions and inhibits hybrid seed development. In Prunus, a rosaceous woody species, some interspecific crosses result in fruit drop during the early stage of fruit development, in which inferior seed development may be accounted for the observed hybrid incompatibility. In this study, we investigated ovule development and the transcriptomes of developing ovules in inter-subgeneric crosses of Prunus. We conducted a cross of Prunus mume (subgenus Prunus), pollinated by P. persica (subgenus Amygdalus), and found that ovule and seed coat degeneration occurs before fruit drop. Transcriptome analysis identified differentially expressed genes enriched in several GO pathways, including organelle development, stimulus response, and signaling. Among these pathways, the organelle-related genes were actively regulated during ovule development, as they showed higher expression in the early stage of interspecific crosses and declined in the later stage, suggesting that the differential regulation of organelle function may induce the degeneration of hybrid ovules. Additionally, genes related to ovule and seed coat development, such as genes encoding AGL-like and auxin response, were differentially regulated in Prunus interspecific crosses. Our results provide histological and molecular information on hybrid seed abortion in Prunus that could be utilized to develop new hybrid crops. Additionally, we compared and discussed transcriptome responses to hybrid seed failure in Prunus and other plant species, which provides insight into conserved or lineage-specific hybrid incompatibility mechanisms in some plant species.

Wheat breeding has significantly contributed to enhancing yield potential and stability. However, one of the most promising technologies for further sustainable yield increases, hybrid wheat, is still limited due to lack of well-established heterotic groups and insufficient heterosis to compensate cost of hybrid seed production. Thus, optimizing the appropriate parents and combinations of floral and flowering traits is important to enhance outcrossing ability. Phenotyping methods for floral and flowering traits were applied in this study. Wide phenotypic variation was observed for all the traits assessed. High heritability coupled with high genetic advance for anther extrusion, pollen mass, duration of floret opening, and openness of florets were observed. Ideally, visual anther extrusion and pollen shedding appear as promising traits allowing indirect selection of other associated floral traits, such as pollen mass and duration and degree of floret opening. Adopting these two traits in further selection will allow scoring of large numbers of genotypes in a very short time.

The quantitative trait locus SD1-2 for seed dormancy (SD) is identical to the semi-dawrf1 (sd1) gene prevailing in high-yield varieties of rice. However, sd1 alone appeared not sufficient to overcome the preharvest sprouting (PHS) problem in crop (or hybrid seed) production. This research aimed to address some genetic issues that may impact pyramiding of SD genes to improve semi-dwarf varieties for the PHS resistance. The isolated SD1-2, SD8, and SD10 loci were also associated with plant height (PH), awn or flowering time (FT), with the dormancy-enhancing alleles reducing stem elongation, increasing awned seeds, and promoting flowering, respectively. Allelic variants at SD1-2 and SD8 or SD10 were assembled in the same background as two digenic systems, each consisting of all the nine digenic genotypes. The two systems of plants were evaluated for the four traits and phenotypic data used to model trait correlations and the component additive, dominance, and epistatic effects of the two loci. FT was correlated with PH and germinability, but the correlations were opposite in direction between the two systems. Both additive and non-additive effects contributed to the variation for SD. All the three loci had effects on FT and PH in the digenic system(s). The SD10 alleles altered directions for effect on SD, with the late-flowering allele reducing germinability in the SD1-2 and SD10 system. This research demonstrated that genetic improvement of semi-dwarf cultivars for the PHS resistance involves proper selections for dormancy genes, recipient’s genetic backgrounds, and agronomic traits.

Species are often defined by their ability to interbreed (i.e., Biological Species Concept), but determining how and why reproductive isolation arises between new species can be challenging. In the Mimulus tilingii species complex, three species (M. caespitosa, M. minor, and M. tilingii) are largely allopatric and grow exclusively at high elevations (>2000 m). The extent to which geographic separation has shaped patterns of divergence among the species is not well understood. In this study, we determined that the three species are morphologically and genetically distinct, yet recently diverged. Additionally, we performed reciprocal crosses within and between the species and identified several strong postzygotic reproductive barriers, including hybrid seed inviability, F1 hybrid necrosis, and F1 hybrid male and female sterility. In this study, such postzygotic barriers are so strong that a cross between any species pair in the M. tilingii complex would cause nearly complete reproductive isolation. We consider how geographical and topographical patterns may have facilitated the evolution of several postzygotic barriers and contributed to speciation of closely related members within the M. tilingii species complex.

Species are often defined by their ability to interbreed (i.e., Biological Species Concept), but determining how and why reproductive isolation arises between new species can be challenging. In theMimulus tilingiispecies complex, three species (M. caespitosa,M. minor, andM. tilingii) are largely allopatric and grow exclusively at high elevations (>2000m). The extent to which geographic separation has shaped patterns of divergence among the species is not well understood. In this study, we determined that the three species are morphologically and genetically distinct, yet recently diverged (M. tilingiicomplex would cause nearly complete reproductive isolation. We consider how geographical and topographical patterns may have facilitated the evolution of several postzygotic barriers and contributed to speciation of closely related members within theM. tilingiispecies complex.

CMS lines are highly sensitive to temperature change for the sterility status. Determination of critical temperature for sterility breakdown in wild abortive cytoplasmic male sterile (WA-CMS) lines under field condition is essential for efficient seed production planning. CMS lines IR58025A and IR68897A were grown at different dates of sowing to give exposure to a series of temperature regime and day length at natural field condition. At panicle initiation stages, temperatures below 28.5 °C, the CMS lines were sterile and at temperatures below 30 °C, the lines became partially sterile. Above 30 °C, the CMS line reverted to fertile. The highest pollen sterility was recorded (98.3%) during the long day condition while the lowest was recorded (43.5%) during the short day condition indicating the effect of both temperature and day-length on break down of sterility. Differential expression of floral characters like panicle exertion and stigma was found with variation in temperature. This simple field-driven technique can be successfully employed to work out the functional temperature for fertility reversibility which is of utmost importance for planning seed production and maintenance of genetic purity of the hybrids. The technique will aid in designing seed production planning for hybrid rice locally in any rice-growing area of the world in the present scenario of restrictions in export and import of agricultural commodities.

The experiment was conducted in an Inland Valley Swamp during the dry spell of 2017 laid out in a randomized complete block design (RCBD) three replications at the Kabala Horticultural Crops Research Centre (KHCRC) cropping site, Ogoo Farm of the Sierra Leone Agricultural Research Institute (SLARI), Freetown, Sierra Leone. Raised beds measuring 5m x 1m (6 m2) with a 1m furrow between beds. Inter and intra row spacing of 75 cm by 50 cm with two rows per bed and two seeds per hills were directly sown. The treatments constituted NPK 15:15:15 at the rate of 0, 90, 120 and 150 kg/ha designated as T1, T2, T3 & T4 and Two hybrids of okra were used as experimental materials obtained from Indo-American Hybrid Seed Company, India; Okra-WASA-HyOKR-1 and Okra-WASA-HyOKR-2. Seeds were treated with Thiram Poison for longevity. Result indicates T2 (25.2; 35.1 cm) and T4 (56.9 cm) treatments recorded tallest plant heights followed by T2 (24.0, 34.4 & 50.1 cm), while T1 (18.8, 28.4 & 33.3 cm) had the shortest plant heights at 4, 8 & 10 Week After Planting respectively. Similarly, T4 & T2 (38.9, 65.5 & 44.8 cm) exhibited the largest SG and T1 (21.7, 33.0 & 52.0 cm) the least values at 4, 8 & 10 Week After Planting. While, the widest and narrowest LA at 4, 8 & 10 Week After Planting was observed in T3 (131.3, 135.0 & 158.5 cm2) and T1 (120.8, 121.8 & 128.1 cm2). With respect to yield and yield components, the longest (22.0 cm) and heaviest (112.7 g) fruit were recorded by T3 followed by T2 (19.1 cm & 101.3 g) with T1 having the shortest (11.7 cm) and lightest (52.3 g). The width of pod in T3 (31.2 cm) was greater than the rest of treatments and as usual, T1 indicated the least value (14.6 cm) respectively. The average NP produced plant-1 was shown by T2 & T3 (4.0) with the least of fruit produced by T1 (2.0). Also, 100 seed weight, T3 (106.7 g) weighted the highest followed by T2 (103.3 g), while T1 (60.3 g) accounted for the lowest seed weight. Conclusively, the two materials are adaptable to the climatic conditions of Sierra Leone (Western area). Hence further evaluation required across vegetable growing zones.

Parental imbalances in the endosperm leading to impaired development and eventual hybrid seed failure are common causes of postzygotic isolation in flowering plants. Endosperm sensitivity to parental dosage is reflected by canonical phenotypes of “parental excess” in reciprocal interploid crosses. Moreover, parental-excess traits are also evident in many homoploid interspecific crosses, potentially reflecting among-lineage variation in “effective ploidy” driven by endosperm properties. However, the genetic basis of effective ploidy is unknown and genome-wide expression perturbations in parental-excess endosperms from homoploid crosses have yet to be reported. The tomato clade (Solanum section Lycopersicon), encompassing closely related diploids with partial-to-complete hybrid seed failure, provides outstanding opportunities to study these issues. Here, we compared replicated endosperm transcriptomes from six crosses within and among three wild tomato lineages. Strikingly, strongly inviable hybrid crosses displayed conspicuous, asymmetric expression perturbations that mirror previously characterized parental-excess phenotypes. Solanum peruvianum, the species inferred to have evolved higher effective ploidy than the other two, drove expression landscape polarization between maternal and paternal roles. This global expression divergence was mirrored in functionally important gene families such as MADS-box transcription factors and E3 ubiquitin ligases, and revealed differences in cell cycle tuning that match phenotypic differences in developing endosperm and mature seed size between reciprocal crosses. Our work starts to uncover the complex interactions between expression divergence, parental conflict, and hybrid seed failure that likely contributed to plant diversity.

Elite wheat pollinators are critical for successful hybrid breeding. We identified Rht-B1 and Ppd-D1 loci affecting multiple pollinator traits and therefore represent major targets for improving hybrid seed production. Hybrid breeding has a great potential to significantly boost wheat yields. Ideal male pollinators would be taller in stature, contain many spikelets well-spaced along the spike and exhibit high extrusion of large anthers. Most importantly, flowering time would match with that of the female parent. Available genetic resources for developing an elite wheat pollinator are limited, and the genetic basis for many of these traits is largely unknown. Here, we report on the genetic analysis of pollinator traits using biparental mapping populations. We identified two anther extrusion QTLs of medium effect, one on chromosome 1BL and the other on 4BS coinciding with the semi-dwarfing Rht-B1 locus. The effect of Rht-B1 alleles on anther extrusion is genotype dependent, while tall plant Rht-B1a allele is consistently associated with large anthers. Multiple QTLs were identified at the Ppd-D1 locus for anther length, spikelet number and spike length, with the photoperiod-sensitive Ppd-D1b allele associated with favourable pollinator traits in the populations studied. We also demonstrated that homeoloci, Rht-D1 and Ppd-B1, influence anther length among other traits. These results suggest that combinations of Rht-B1 and Ppd-D1 alleles control multiple pollinator traits and should be major targets of hybrid wheat breeding programs.

Hybrid breeding in wheat has the potential to boost yields. An efficient hybrid seed production system requires elite pollinators; however, such germplasm is limited among modern cultivars. Piko, a winter wheat (Triticum aestivum L.) cultivar, has been identified as a superior pollinator and has been used in Europe. Piko has favourable pollinator traits for anther extrusion, anther length, pollen mass and hybrid seed set. However, the genetic factors responsible for Piko’s favourable traits are largely unknown. Here, we report on the genetic analysis of a Piko-derived F2 mapping population. We confirmed that Piko’s Rht-D1a allele for tall stature is associated with large anthers and high anther extrusion. However, Rht-D1 was not found to be associated with anther filament length, confirmed by near isogenic lines. Piko’s photoperiod sensitive Ppd-B1b allele shows an association with increased spike length, more spikelets and spike architecture traits, while the insensitive Ppd-B1a allele is linked with high anther extrusion and larger anthers. We identified an anther extrusion quantitative trait locus (QTL) on chromosome 6A that showed significantly biased transmission of the favourable Piko allele amongst F2 progenies. The Piko allele is completely absent in the distal 6AS region and the central 6A region revealed a significantly lower ratio (

Wheat (Triticum aestivum L.) is a self-pollinating crop whose hybrids offer the potential to provide a major boost in yield. Male sterility induced by the cytoplasm of Triticum timopheevii is a powerful method for hybrid seed production. Hybrids produced by this method are often partially sterile and full fertility restoration is crucial for wheat production using hybrid cultivars. To identify genetic loci controlling fertility restoration in wheat, we produced two CMS-based backcross (BC1) mapping populations. The restorer lines Gerek 79 and 71R1203 were used to pollinate the male-sterile winter wheat line CMS-Sperber. Seed set and numbers of sterile spikelets per spike were evaluated in 340 and 206 individuals of the populations derived from Gerek 79 and 71R1203, respectively. Genetic maps were constructed using 930 and 994 SNPs, spanning 2,160 and 2,328 cM over 21 linkage groups in the two populations, respectively. Twelve quantitative trait loci (QTL) controlled fertility restoration in both BC1 populations, including a novel restorer-of-fertility (Rf) locus flanked by the single nucleotide polymorphism (SNP) markers IWB72413 and IWB1550 on chromosome 6AS. The locus was mapped as a qualitative trait in the BC1 Gerek 79 population and was designated Rf9. Ninety-three putative candidate genes were predicted for the QTL region on chromosome 6AS. Among them were genes encoding tetratricopeptide and pentatricopeptide repeat-containing proteins in rice known to be associated with fertility restoration. This finding is a promising step to better understand the functions of genes for improving hybrid wheat.