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ABSTRACT Hybrid wheat could deliver the grain yield (GY) and stability levels to confront climate change while crossing genetically divergent pools should maximize heterosis. We crossed 22 breeding lines from Nebraska (USA) with two German cultivars to produce 44 hybrids. Hybrids, parents and 12 checks were reciprocally tested across their contrasting target environments for GY, plant height and flowering biology during 2 consecutive years at multiple locations. Trait variation within target environments had the greatest impact on performance. Therefore, mega‐environments could not be derived from target environments despite a clear clustering using weather variables. Short plants and locally optimized flowering biology were main drivers for crop performance and adaptation. Modified Rogers' distances derived from genotyping‐by‐sequencing revealed the genetic divergence between German and ‘Great Plains’ pools. However, variation on GY heterosis could not be explained by this divergence. In general, GY of hybrids was more stable across target environments than for locally adapted material, whereas GY heterosis was higher under harsh climate conditions of the Nebraska's ‘Great Plains’. [ABSTRACT FROM AUTHOR]

Wheat hybrids have been widely demonstrated to have remarkable heterosis or hybrid vigor in increasing yield potential and stability since the 1960s. Two-line hybrid wheat can achieve higher yields than local varieties, especially in marginal environments. However, the commercial application of hybrid wheat is hindered by higher seed costs, primarily due to lower yields in hybrid seed production. Stigma exsertion has been verified as a decisive factor in increasing rice's hybrid seed yield, but more investigation is needed in hybrid wheat breeding and production. In this study, four thermo-photo-sensitive genic male sterile lines, including K41S, K64S, K66S, and K68S, with different stigma exsertion rates (SERs) were used to compare the differences in floral architecture relative to stigma exsertion over two growing seasons. The results revealed that the K41S and K64S exhibited a relatively higher SER at 21.87% and 22.81%, respectively. No exserted stigma was observed in K66S, and K68S had an SER of only 0.82%. This study found that the stigma length, glume width and the length–width ratio of the glume were significantly correlated with the SER, with correlation coefficients of 0.46, −0.46 and 0.60, respectively. Other stigma features such as the branch angle, stretch width and hairbrush length, as well as the glume length, also had a weakly positive correlation with SER (r = 0.09–0.27). For K41S and K64S, the SER was significantly affected by the differences in the stigma branch angle and stigma stretch width among florets. A cross-pollination survey showed that the out-crossing ability of florets with an exserted stigma was about three times as high as that of florets with a non-exserted stigma. As a result, the stigma-exserted florets that accounted for 21.87% and 22.81% of the total florets in K41S and K64S produced 46.80% and 48.53% of the total cross-pollinated seeds in both sterile lines. These findings suggest that a longer stigma combined with a slender glume appears to be the essential floral feature of stigma exsertion in sterile wheat lines. It is expected that breeding and utilizing sterile lines with a higher SER would be a promising solution to cost-effective hybrid wheat seed production. [ABSTRACT FROM AUTHOR]

Main conclusion: TaAGL66, a MADS-box transcription factor highly expressed in fertile anthers of KTM3315A, regulates anther and/or pollen development, as well as male fertility in wheat with Aegilops kotschyi cytoplasm. Male sterility, as a string of sophisticated biological processes in higher plants, is commonly regulated by transcription factors (TFs). Among them, MADS-box TFs are mainly participated in the processes of floral organ formation and pollen development, which are tightly related to male sterility, but they have been little studied in the reproductive development in wheat. In our study, TaAGL66, a gene that was specifically expressed in spikes and highly expressed in fertile anthers, was identified by RNA sequencing and the expression profiles data of these genes, and qRT-PCR analyses, which was localized to the nucleus. Silencing of TaAGL66 under fertility condition in KTM3315A, a thermo-sensitive male sterile line with Ae. kotschyi cytoplasm, displayed severe fertility reduction, abnormal anther dehiscence, defective pollen development, decreased viability, and low seed-setting. It can be concluded that TaAGL66 plays an important role in wheat pollen development in the presence of Ae. kotschyi cytoplasm, providing new insights into the utilization of male sterility. [ABSTRACT FROM AUTHOR]

The use of hybrid wheat is one way to improve the yield in the future. However, greater plant heights increase lodging risk to some extent. In this study, two hybrid combinations with differences in lodging resistance were used to analyze the stem-related traits during the filling stage, and to investigate the mechanism of the difference in lodging resistance by analyzing lignin synthesis of the basal second internode (BSI). The stem-related traits such as the breaking strength, stem pole substantial degree (SPSD), and rind penetration strength (RPS), as well as the lignin content of the lodging-resistant combination (LRC), were significantly higher than those of the lodging-sensitive combination (LSC). The phenylpropanoid biosynthesis pathway was significantly and simultaneously enriched according to the transcriptomics and metabolomics analysis at the later filling stage. A total of 35 critical regulatory genes involved in the phenylpropanoid pathway were identified. Moreover, 42% of the identified genes were significantly and differentially expressed at the later grain-filling stage between the two combinations, among which more than 80% were strongly up-regulated at that stage in the LRC compared with LSC. On the contrary, the LRC displayed lower contents of lignin intermediate metabolites than the LSC. These results suggested that the key to the lodging resistance formation of LRC is largely the higher lignin synthesis at the later grain-filling stage. Finally, breeding strategies for synergistically improving plant height and lodging resistance of hybrid wheat were put forward by comparing the LRC with the conventional wheat applied in large areas.

In order to study the effects of different genetic backgrounds and their hybrids on the field seedling emergence rate, 29 AL-type sterile lines and 25 restorer lines were used as parental materials to prepare a diallel hybrid combination. Comparative analysis of field emergence rates of hybrids and parents was carried out in the manner of 'same mother with many fathers' and 'same father with many mothers'. The results showed that there was no significant difference in field emergence rate among restorer lines, maintainer lines and hybrids with different cytoplasmic genetic backgrounds. There was a significant positive correlation between the field emergence rate of hybrids and both parents, and the field emergence rate of hybrids configured with parents with high field emergence rate showed higher heterosis. The field emergence rate of hybrids should be taken seriously as an important indicator of superior parents. [ABSTRACT FROM AUTHOR]

To ensure food security for ~ 10 billion human population in 2050 a sustainable increase in food production is indispensable. Wheat is the third most consumed cereal crop worldwide after rice and maize. It is estimated that the current wheat yield will be insufficient to cope with future needs. In the past hybrid seed production has revolutionized rice and maize production; however, wheat is still lagging behind other crops, such as rice, corn, soybeans, and canola in terms of variety/hybrid development and trait development. The potential of hybrid wheat is undeniable but these challenges need to be overcome if we want to commercialize it. Despite a century of efforts we still do not have a reliable hybrid breeding system to attempt large-scale production due to certain issues like self-pollination, polyploid nature, low variability in germplasm (less than 1% cross-pollination), and higher seed rates. Moreover, a limited number of GMS genes and their regulatory pathways has narrowed our selection; further research is required to identify and understand the genetic and molecular mechanisms involved. There are few successful examples of hybrid wheat, only 1% of its total wheat growing area is hybrid wheat. There is no simple way to produce a stable wheat hybrid, until this point no one knows how to commercialize wheat on a larger scale. The use of comparative functional genomics and biotechnological tools combined with conventional breeding is likely the possible key to guarantee a stable hybrid wheat breeding and to help overcome global food security issues. This paper would provide an overview of techniques to induce male sterility in wheat and their use in commercialized hybrid seed production systems. [ABSTRACT FROM AUTHOR]

Wheat grain has health-promoting properties that are related to the content of phenolic acids in its composition, among which ferulic acid, syringic acid, p-coumaric acid and vanillic acid predominate acting as potent natural antioxidants. The study evaluated the phenolic acid (PA) content and grain yield of hybrid wheat genotypes (Hyland, Hywin) compared to the common variety (Patras), grown under an integrated system at two nitrogen rates of 60 (N60) and 120 (N120) kg·ha−1, under varying hydrothermal conditions during three growing seasons. The effects of genotype, cultivar and the interaction of cultivar and hydrothermal conditions on the phenolic acid profile, except for synapic acid, phydroxybenzoic acid and salicylic acid, and grain yield were confirmed in favour of the hybrid cultivars. The concentration of total phenolic acids (TPAs) and ferulic acid in the grain of the hybrid cultivar Hyland was higher and, in addition, greater yield stability of this cultivar under varying hydrothermal conditions was shown in the analysed years of the study. The grain of the common variety Patras was characterised by advanced content of p-hydroxybenzoic acid, and that of the hybrid variety Hywin by p-coumaric, caffeic and syringic acids. Higher TPAs content and lower grain yield of the varieties were observed in the 2018/2019 drought season. Higher nitrogen fertilisation (N120) compared to N60 significantly increased TPAs content and grain yield of Hyland and Hywin hybrid varieties. Fertilisation with N120 compared to N60 increased TPAs content by 4.2% and promoted higher concentrations of ferulic and syringic acids in the wheat cultivars tested.

Wheat hybrids have been widely demonstrated to have remarkable heterosis or hybrid vigor in increasing yield potential and stability since the 1960s. Two-line hybrid wheat can achieve higher yields than local varieties, especially in marginal environments. However, the commercial application of hybrid wheat is hindered by higher seed costs, primarily due to lower yields in hybrid seed production. Stigma exsertion has been verified as a decisive factor in increasing rice’s hybrid seed yield, but more investigation is needed in hybrid wheat breeding and production. In this study, four thermo-photo-sensitive genic male sterile lines, including K41S, K64S, K66S, and K68S, with different stigma exsertion rates (SERs) were used to compare the differences in floral architecture relative to stigma exsertion over two growing seasons. The results revealed that the K41S and K64S exhibited a relatively higher SER at 21.87% and 22.81%, respectively. No exserted stigma was observed in K66S, and K68S had an SER of only 0.82%. This study found that the stigma length, glume width and the length–width ratio of the glume were significantly correlated with the SER, with correlation coefficients of 0.46, −0.46 and 0.60, respectively. Other stigma features such as the branch angle, stretch width and hairbrush length, as well as the glume length, also had a weakly positive correlation with SER (r = 0.09–0.27). For K41S and K64S, the SER was significantly affected by the differences in the stigma branch angle and stigma stretch width among florets. A cross-pollination survey showed that the out-crossing ability of florets with an exserted stigma was about three times as high as that of florets with a non-exserted stigma. As a result, the stigma-exserted florets that accounted for 21.87% and 22.81% of the total florets in K41S and K64S produced 46.80% and 48.53% of the total cross-pollinated seeds in both sterile lines. These findings suggest that a longer stigma combined with a slender glume appears to be the essential floral feature of stigma exsertion in sterile wheat lines. It is expected that breeding and utilizing sterile lines with a higher SER would be a promising solution to cost-effective hybrid wheat seed production.

In Romania, climate changes have determined in recent years, the intensification of water deficits (very often associated with drought) during the vegetation of agricultural crops, in almost all areas of the country. Cultivating autumn wheat varieties that can withstand drought and heat well and adapting cultivation technology to climate changes are decisive factors in obtaining stable and economically efficient productions. In the agricultural year 2022-2023, in A.R.D.S. Secuieni, Neam? County, a multifactorial experiment of the 10 x 3 x 1 type was established, which aimed to determine an optimal density depending on the varieties used and the climatic conditions. The experiment was laid out according to the method of parcels subdivided into 3 repetitions, with the following factors: Factor A - variety, cu 10 graduations (a1 = Trublion; a2 = Centurion; a3 = Katarina; a4 = Glosa; a5 = Aspekt; a6 = Izvor; a7 = Avenue; a8 = Solehio; a9 = Alcantara; a10 = Hyxperia); Factor B - plant density, with 3 graduations: (b1 = 250 germinable kernels/sm; b2 = 360 germinable kernels/sm and b3 = 500 germinable kernels/sm.); Factor C - location, cu 1 graduation: c1 = Secuieni. Productivity elements are influenced by sowing density, variety and experimental conditions. The Glosa variety is the common winter wheat variety with the largest share in the structure of varieties grown in the all the Romania country. It achieves high and stable yields (8,559 kg/ha), with a protein contain 14.2, the highest average protein contain on the tested varieties. For the northern part of the country, good results were obtained when 250 g.g/m2 were used for the variety Centurion, a yield production of 10,008 kg/ha. The hybrid wheat, Hyxperia variety obtained the highest yields (8,745 kg/ha) regardless of the climatic conditions of the year, proving ecological stability and plasticity, with a protein content of 11.9%. [ABSTRACT FROM AUTHOR]

To extend the contemporary understanding into the grain yield heterosis of wheat, the current study investigated the contribution of deleterious alleles in shaping mid-parent heterosis (MPH). These alleles occur at low frequency in the genome and are often missed by automated genotyping platforms like SNP arrays. The deleterious alleles herein were detected using a quantitative measurement of evolutionary conservation based on the phylogeny of wheat and investigations were made to: (1) assess the benefit of including deleterious alleles into MPH prediction models and (2) understand the genetic underpinnings of deleterious SNPs for grain yield MPH using contrasting crosses viz. elite × elite (Exp. 1) and elite × plant genetic resources (PGR; Exp. 2). In our study, we found a lower allele frequency of moderately deleterious alleles in elites compared to PGRs. This highlights the role of purifying selection for the development of elite wheat cultivars. It was shown that deleterious alleles are informative for MPH prediction models: modelling their additive-by-additive effects in Exp. 1 and dominance as well as associated digenic epistatic effects in Exp. 2 significantly boosts prediction accuracies of MPH. Furthermore, heterotic- quantitative trait loci’s underlying MPH was investigated and their properties were contrasted in the two crosses. Conclusively, it was proposed that incomplete dominance of deleterious alleles contributes to grain yield heterosis in elite crosses (Exp. 1).

The sterile lines used in the production of two-line hybrid wheat in China are mainly photoperiod-thermo sensitive male sterile (PTSMS), and it is of great significance to study the sterile features and mechanisms of novel sterile lines for wheat hybrid breeding. XN291S, a spontaneous mutant of XN291, was sterile under long-day/high-temperature and fertile under short-day/low-temperature. In this study, its male sterility was mainly controlled by the high temperature, and occurred in the binucleate stage. The sterility gene at high temperature was a major recessive XNms-6B gene located on 6BS by genetic analysis and molecular marker genetic mapping, and the large fragment deletion at the end of 6BS was proved by genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH) and further genomic resequencing. This fragment corresponded to the 0–88.3 Mb physical interval of the Chinese Spring Reference Genome (IWGSCv1.0), and contained 1077 high-confidence genes. The results of multi-omics association analysis showed that starch and sucrose metabolism, phenylpropane biosynthesis, linoleic acid metabolism, and secondary metabolite biosynthesis were the key pathways, and the deleted genes involved in heat stress response and anther development directly or indirectly resulted in the male sterility of XN291S. This study will contribute to further study of XNms-6B, and lay a foundation for the application of this sterile line in hybrid wheat breeding. [ABSTRACT FROM AUTHOR]

This study was carried out at the experimental farm of Sakha Agricultural Research Station, ARC, Egypt, to identify the best parents with high combining ability and superior hybrid cross combinations under Egyptian conditions. Three thermo-photosensitive genic male sterile (TPSGMS) lines as female parents and 49 restorer lines as males were crossed according to the line tester hybridization method. The ratio of general combining ability (GCA) to specific combining ability (SCA) variances showed values less than unity for all studied traits, indicating predominantly non-additive gene effects in controlling their inheritance. The GCA values for sterile line S1 were higher than those of lines S2 and S3 in seven out of ten characters. The restorer line R16 and both lines R31 and R34 had a significantly positive GCA in eight and seven characters, respectively. The crosses S1/R8 and S3/R42 had the highest positive SCA values in three characters, including grain yield. In this study, heterosis over the Sakha 95 check variety reached 80.63, 71.27, 55.16, 26.07, and 24.49% for KS, SW, GY, TKW, and SP-1, respectively. The crosses S2/R34 and S1/R16 showed the highest significant positive heterosis estimates (55.16 and 54.43%, respectively) over the standard check for grain yield. Also, the crosses of S1/R16 and S1/R37 had the highest significant positive heterosis estimates over both the better parent (65.81 and 46.64%, respectively) and the mid parent (70.75 and 52.55%, respectively) for grain yield. The results showed a significant increase in heterosis over Sakha 95 check in twelve hybrids, and we recommend evaluating these hybrids in multiplications representing environmental conditions to benefit from them in raising wheat productivity in wide areas in Egypt. [ABSTRACT FROM AUTHOR]

The present study was conducted during the 2020/2021 and 2021/2022 wheat growing seasons at Shandaweel Agricultural Research Station, Sohag governorate, Egypt. Three cytoplasmic male sterile (CMS) lines, namely Vorobey A-line, Navojoa A-line and Neloki A-line of wheat having Triticum Timopheevi cytoplasmic male sterility source (three-lines system A, B and R) were crossed with twenty-five wheat genotypes as testers in line × tester fashion to identify maintainer and restorer lines for the CMS lines. Based on the evaluation of 75 hybrid combinations for pollen and spikelet fertility percent, results indicated that the identified wheat genotypes as effective maintainers were Shandaweel 1, Misr 3, Misr 4, Giza 168, Gemmeiza 11, Gemmeiza 12, Kutz, Line 1, Line 2, Line 3, Line 4 and Line 5 for all the three CMS lines, Sids 14, Giza 171, Sakha 1001, Nadi and Kenya Sunbird for Vorobey A-line and Navojoa A-line, Misr 1, Kachu #1, Francolin #1 and Baj #1 for Navojoa A-line and Neloki A-line and Sids 12 for Neloki A-line and these genotypes could be converted into new CMS lines through backcross breeding method. On the other side, the identified wheat genotypes as effective restorers were Sakha 95 for Vorobey A-line and Neloki A-line, and Kachu #1, Francolin #1 and Baj #1 for Vorobey A-line, therefore these genotypes could be used to develop promising wheat hybrids. Consequently, the presence of maintainer and restorer lines among the studied wheat genotypes indicates the possibility of developing wheat hybrids using CMS system in Egypt. [ABSTRACT FROM AUTHOR]

Cytoplasmic male sterility (CMS) is a crucial means for the utilization of heterosis, which is of great significance for improving the yield and quality of hybrids. Currently, fertility restoration has been extensively investigated in crops, but fertility restoration of CMS wheat with Aegilops juvenalis cytoplasm is poorly understood. Here, a backcross population BC1F1 derived from a cross between the male-sterile line Ju706A, its maintainer line 706B, and restorer line LK783 was used to map the Rfd1 locus by bulked segregant analysis and wheat 660K single nucleotide polymorphism genotyping. Ju706A displayed complete male sterility, and its fertility can be restored by LK783 with a pair of dominant genes Rfd1Rfd1. The locus was located to a 2.4 Mb region on chromosome 1BS by markers AX-174254104 and AX-111201011. Combined with transcriptomic analysis and quantitative real-time PCR assay, TraesCS1B02G197400LC , the most likely candidate gene for Rfd1 , was found to encode a pectinesterase that was localized in the cell wall, and was highly expressed in fertile anthers. The silencing of Rfd1 resulted in decreased fertility, and heterogeneous expression of Rfd1 promoted pollen germination and affected vegetative growth. This implies that Rfd1 is required for anther or pollen development and male fertility in CMS wheat with Ae. juvenalis cytoplasm. Furthermore, a 7 bp deletion in Ju706A was employed to develop a specific marker, Xnwafu1 , for molecular marker-assisted selection of restorers. This study provides a new understanding for exploring the fertility restoration mechanism of CMS. [ABSTRACT FROM AUTHOR]

To extend the contemporary understanding into the grain yield heterosis of wheat, the current study investigated the contribution of deleterious alleles in shaping mid-parent heterosis (MPH). These alleles occur at low frequency in the genome and are often missed by automated genotyping platforms like SNP arrays. The deleterious alleles herein were detected using a quantitative measurement of evolutionary conservation based on the phylogeny of wheat and investigations were made to: (1) assess the benefit of including deleterious alleles into MPH prediction models and (2) understand the genetic underpinnings of deleterious SNPs for grain yield MPH using contrasting crosses viz. elite - elite (Exp. 1) and elite - plant genetic resources (PGR; Exp. 2). In our study, we found a lower allele frequency of moderately deleterious alleles in elites compared to PGRs. This highlights the role of purifying selection for the development of elite wheat cultivars. It was shown that deleterious alleles are informative for MPH prediction models: modelling their additive-by-additive effects in Exp. 1 and dominance as well as associated digenic epistatic effects in Exp. 2 significantly boosts prediction accuracies of MPH. Furthermore, heterotic-quantitative trait loci's underlying MPH was investigated and their properties were contrasted in the two crosses. Conclusively, it was proposed that incomplete dominance of deleterious alleles contributes to grain yield heterosis in elite crosses (Exp. 1). [ABSTRACT FROM AUTHOR]

Abstract Background Histone methylation usually plays important roles in plant development through post-translational regulation and may provide a new visual field for heterosis. The histone methyltransferase gene family has been identified in various plants, but its members and functions in hybrid wheat related in heterosis is poorly studied. Results In this study, 175 histone methyltransferase (HMT) genes were identified in wheat, including 152 histone lysine methyltransferase (HKMT) genes and 23 protein arginine methyltransferase (PRMT) genes. Gene structure analysis, physicochemical properties and subcellular localization predictions of the proteins, exhibited the adequate complexity of this gene family. As an allohexaploid species, the number of the genes (seven HKMTs orthologous groups and four PRMTs orthologous groups) in wheat were about three times than those in diploids and showed certain degrees of conservation, while only a small number of subfamilies such as ASH-like and Su-(var) subfamilies have expanded their members. Transcriptome analysis showed that HMT genes were mainly expressed in the reproductive organs. Expression analysis showed that some TaHMT genes with different trends in various hybrid combinations may be regulated by lncRNAs with similar expression trends. Pearson correlation analysis of the expression of TaHMT genes and two yield traits indicated that four DEGs may participate in the yield heterosis of two-line hybrid wheat. ChIP-qPCR results showed that the histone modifications (H3K4me3, H3K36me3 and H3K9ac) enriched in promoter regions of three TaCCA1 genes which are homologous to Arabidopsis heterosis-related CCA1/LHY genes. The higher expression levels of TaCCA1 in F1 than its parents are positive with these histone modifications. These results showed that histone modifications may play important roles in wheat heterosis. Conclusions Our study identified characteristics of the histone methyltransferase gene family and enhances the understanding of the evolution and function of these members in allohexaploid wheat. The causes of heterosis of two-line hybrid wheat were partially explained from the perspective of histone modifications.

The utilization of heterosis plays an important role in improving wheat yield. Hybrid breeding in wheat is an important development direction for seed production. At present, great progress has been achieved in the strong heterosis combination of hybrid wheat. There are issues such as lack of excellent parents for hybrid combination and hybrid seed production system for high yield and high efficiency wheat, which leads to low seed production efficiency in large area. Therefore, to explore the development of hybrid seed production technology system, germplasm improvement of parental resources and seed production process standards will be conducive to summarizing the overall trend of the development bottleneck and future development direction of hybrid seed production. In this paper, the influencing factors of hybrid breeding in wheat are reviewed. Through the comparison between commercial hybrid crops and superior seed from novel hybrid wheat, some effective suggestions for rapid commercialization of hybrid wheat are put forward, and its future development trend is forecasted. [ABSTRACT FROM AUTHOR]

Thermo-sensitive cytoplasmic male sterility (TCMS) plays a crucial role in hybrid production and hybrid breeding; however, there are few studies on molecular mechanisms related to anther abortion in the wheat TCMS line. In this study, FA99, a new wheat thermo-sensitive cytoplasmic male sterility line, was investigated. Fertility conversion analysis showed that FA99 was mainly controlled by temperature, and the temperature-sensitive stage was pollen mother cell formation to a uninucleate stage. Further phenotypic identification and paraffin section showed that FA99 was characterized by indehiscent anthers and aborted pollen in a sterile environment and tapetum was degraded prematurely during the tetrad period, which was the critical abortion period of FA99. The contents of O2−, H2O2, MDA and POD were significantly changed in FA99 under a sterile environment by the determination of physiological indexes. Furthermore, through transcriptome analysis, 252 differentially expressed genes were identified, including 218 downregulated and 34 upregulated genes. Based on KOG function classification, GO enrichment and KEGG pathways analysis, it was evident that significant transcriptomic changes in FA99 under different fertility environments, and the major differences were "phenylalanine metabolism", "phenylpropanoid biosynthesis", "cutin, suberine and wax biosynthesis", "phenylalanine, tyrosine and tryptophan biosynthesis" and "citrate cycle (TCA cycle)". Finally, we proposed an intriguing transcriptome-mediated pollen abortion and male sterility network for FA99. These findings provided data on the molecular mechanism of fertility conversion in thermo-sensitive cytoplasmic male sterility wheat. [ABSTRACT FROM AUTHOR]

Summary: Transcriptional gene silencing (TGS) can offer a straightforward tool for functional analysis of plant genes, particularly in polyploid species such as wheat, where genetic redundancy poses a challenge in applying mutagenesis approaches, including CRISPR gene editing. In this study, we demonstrate efficient TGS in wheat, mediated by constitutive RNA expression of a promoter inverted repeat (pIR). pIR‐mediated TGS of two anther‐specific genes, TaMs45 and TaMs1, abolished their function resulting in male sterility. Whilst TGS of TaMs45 required transcriptional silencing of all three homoeologs, a B‐genome‐specific pIR for TaMs1 was sufficient to confer male sterility. We further show that the pIRs effect TGS of TaMs45 gene through DNA methylation of homologous promoter sequence, successfully suppressing transcription of all three homoeologs. Applying pIR‐mediated TGS in wheat, we have generated a dominant male fertility system for production of hybrid seed and demonstrated the efficacy of this system under greenhouse and field conditions. This report describes the first successful TGS in wheat, whilst providing a dominant negative approach as alternative to gene knockout strategies for hybrid wheat breeding and seed production. [ABSTRACT FROM AUTHOR]

Domestication of wheat started with the dawn of human civilization. Since then, improvement in various traits including resistance to diseases, insect pests, saline and drought stresses, grain yield, and quality were improved through selections by early farmers and then planned hybridization after the discovery of Mendel's laws. In the 1950s, genetic variability was created using mutagens followed by the selection of superior mutants. Over the last 3 decades, research was focused on developing superior hybrids, initiating marker-assisted selection and targeted breeding, and developing genetically modified wheat to improve the grain yield, tolerance to drought, salinity, terminal heat and herbicide, and nutritive quality. Acceptability of genetically modified wheat by the end-user remained a major hurdle in releasing into the environment. Since the beginning of the 21st century, changing environmental conditions proved detrimental to achieving sustainability in wheat production particularly in developing countries. It is suggested that high-tech phenotyping assays and genomic procedures together with speed breeding procedures will be instrumental in achieving food security beyond 2050. [ABSTRACT FROM AUTHOR]

Hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future, and population construction is an important factor affecting their yield heterosis formation. In order to clarify the effect of population regulation of hybrid wheat on source–sink systems, the two-line hybrid wheat variety Jingmai 6 was used to carry out relevant research in this experiment. The leaf area index (LAI) of Jingmai 6 showed an increasing trend, while the tiller-spike rate exhibited a downward trend with the increase of planting density. The total accumulation of dry matter at maturity increased with the increase of planting density, among which the relative proportion of dry matter pre-anthesis gradually increased, while that after anthesis gradually decreased. The sink capacity and spikes number of hybrid wheat were positively correlated with the grain yield. There was higher sink capacity, spike to leaf ratio and grain to leaf ratio under A2 and A3 conditions. With the increase of planting density, the hybrid wheat yield showed a unimodal curve, and A3 had the highest grain yield. Combined with the change trend of dry matter accumulation before and after anthesis, it was proved that suitable planting density was the key to obtaining high yield of hybrid wheat. [ABSTRACT FROM AUTHOR]

In order to explore the effects of different ratios of restoring lines on seed production，purity and heterosis of F1 yield in hybrid wheat production with strong heterosis combinations，three AL（Alborubrum Korn）-type CMS（cytoplasmic male sterility）wheat hybrid combinations were used as materials in the sterile line（female parent ♀）. The seeds were mixed with different proportions of restoring line（male parent♂）seeds for sowing. The yield of hybrid seed production，the purity of seed production，and the change of hybrid F1 yield heterosis were studied. The results showed that the two hybrid combinations 36A×2014AR5 and 002A×99AR142-1 were mixed with different proportions of restoration line seed production，the yield of hybrid seed production increased with the increase of the mixed male parent ratio，and the seed purity of the hybrids gradually decreased. When the male parent’s mixed sowing proportion was 5%，it reached the requirement of 96% of field seed purity，and the seed production yield was also higher. The yield of the F1 generations produced by the two hybrid combinations with different mixed sowing ratios was compared，and the mixed seeding production. The seed yields of mixed sowing and mixed harvesting were higher than those of the hybrid control of the same combination and row ratio seed production，and the yield advantage of F1 with mixing ratios of 12% and 9% was more significant. The SSR molecular markers Wmc474，which were linked to the restorer gene（qRf-2A-1） and located on chromosomes 2A，were used to predict the seed purities via mixed sowing and mixed harvesting under different mixing ratios. Concurrently，the prediction results of the regression equation for purity detection of AL-type three-line hybrid wheat hybrids established by the SSR marker Xbarc8 linked to the restorer gene（qRf-1B-1）on chromosome 1B were compared，showing that the two regression equations established with the two molecular markers can be used in the identification of the purity of the seed production of mixed restorer lines. [ABSTRACT FROM AUTHOR]

Chemical hybridization and genic male sterility systems are two main methods of hybrid wheat production; however, complete sterility of female wheat plants cannot be guaranteed owing to the influence of the growth stage and weather. Consequently, hybrid wheat seeds are inevitably mixed with few parent seeds, especially female seeds. Therefore, seed purity is a key factor in the popularization of hybrid wheat. However, traditional seed purity detection and variety identification methods are time-consuming, laborious, and destructive. Therefore, to establish a non-destructive classification method for hybrid and female parent seeds, three hybrid wheat varieties (Jingmai 9, Jingmai 11, and Jingmai 183) and their parent seeds were sampled. The transmittance and reflectance spectra of all seeds were collected via hyperspectral imaging technology, and a classification model was established using partial least squares-discriminant analysis (PLS-DA) combined with various preprocessing methods. The transmittance spectrum significantly improved the classification of hybrids and female parents compared to that obtained using reflectance spectrum. Specifically, using transmittance spectrum combined with a characteristic wavelength-screening algorithm, the Detrend-CARS-PLS-DA model was established, and the accuracy rates in the testing sets of Jingmai 9, Jingmai 11, and Jingmai 183 were 95.69%, 98.25%, and 97.25%, respectively. In conclusion, transmittance hyperspectral imaging combined with a machine learning algorithm can effectively distinguish female parent seeds from hybrid seeds. These results provide a reference for rapid seed purity detection in the hybrid production process. Owing to the nondestructive and rapid nature of hyperspectral imaging, the detection of hybrid wheat seed purity can be improved by online sorting in the future. [ABSTRACT FROM AUTHOR]

Wheat is one of the most important staple crops, facing to the challenge of dramatically increasing yield to meet the demand of continually expanding human population. The utilization of heterosis is considered to be an important way to increase the yield per unit area of wheat. In recent years, with the continuous innovation of strong-dominant wheat hybrids, hybrid wheat has shown strong yield stability and stress resistance in production and application. By two-line hybrid wheat bred based on the photo thermo sensitive sterile line, the industrialization of hybrid wheat has been initially realized. With the continuous deepening of its extension and application, further breakthroughs in hybrid wheat parent line improvement, seed production, and high-yield cultivation techniques have become the key to the rapid industrialization of hybrid wheat. In this article, the research and application status of hybrid wheat in recent years including the important breakthroughs of variety creation and research on industrialization of hybrid wheat were reviewed, the main technological problems in the process of industrialization of hybrid wheat were proposed, and the new progress of practical technology and methods in the process of industrialization of two-line hybrid wheat was systematically summarized from the aspects of hybrid wheat variety creation, parental outcrossing biological characteristics and rational allocation, mechanized seed production technology and high-yield green supporting cultivation technology. It is believed that the industrialization development of hybrid wheat in the future can integrate traditional breeding, biotechnology, physiological regulation, intelligent agricultural machinery and other technical means, so as to realize the successful application of wheat heterosis. [ABSTRACT FROM AUTHOR]

Domestication of wheat started with the dawn of human civilization. Since then, improvement in various traits including resistance to diseases, insect pests, saline and drought stresses, grain yield, and quality were improved through selections by early farmers and then planned hybridization after the discovery of Mendel’s laws. In the 1950s, genetic variability was created using mutagens followed by the selection of superior mutants. Over the last 3 decades, research was focused on developing superior hybrids, initiating marker-assisted selection and targeted breeding, and developing genetically modified wheat to improve the grain yield, tolerance to drought, salinity, terminal heat and herbicide, and nutritive quality. Acceptability of genetically modified wheat by the end-user remained a major hurdle in releasing into the environment. Since the beginning of the 21st century, changing environmental conditions proved detrimental to achieving sustainability in wheat production particularly in developing countries. It is suggested that high-tech phenotyping assays and genomic procedures together with speed breeding procedures will be instrumental in achieving food security beyond 2050.

Background: Histone methylation usually plays important roles in plant development through post-translational regulation and may provide a new visual field for heterosis. The histone methyltransferase gene family has been identified in various plants, but its members and functions in hybrid wheat related in heterosis is poorly studied. Results: In this study, 175 histone methyltransferase (HMT) genes were identified in wheat, including 152 histone lysine methyltransferase (HKMT) genes and 23 protein arginine methyltransferase (PRMT) genes. Gene structure analysis, physicochemical properties and subcellular localization predictions of the proteins, exhibited the adequate complexity of this gene family. As an allohexaploid species, the number of the genes (seven HKMTs orthologous groups and four PRMTs orthologous groups) in wheat were about three times than those in diploids and showed certain degrees of conservation, while only a small number of subfamilies such as ASH-like and Su-(var) subfamilies have expanded their members. Transcriptome analysis showed that HMT genes were mainly expressed in the reproductive organs. Expression analysis showed that some TaHMT genes with different trends in various hybrid combinations may be regulated by lncRNAs with similar expression trends. Pearson correlation analysis of the expression of TaHMT genes and two yield traits indicated that four DEGs may participate in the yield heterosis of two-line hybrid wheat. ChIP-qPCR results showed that the histone modifications (H3K4me3, H3K36me3 and H3K9ac) enriched in promoter regions of three TaCCA1 genes which are homologous to Arabidopsis heterosis-related CCA1/LHY genes. The higher expression levels of TaCCA1 in F1 than its parents are positive with these histone modifications. These results showed that histone modifications may play important roles in wheat heterosis. Conclusions: Our study identified characteristics of the histone methyltransferase gene family and enhances the understanding of the evolution and function of these members in allohexaploid wheat. The causes of heterosis of two-line hybrid wheat were partially explained from the perspective of histone modifications. [ABSTRACT FROM AUTHOR]

Breeding hybrids with maximum heterosis requires efficient cross-pollination and an improved male sterility system. Renewed efforts have been made to dissect the phenotypic variation and genetic basis of hybrid floral traits, although the potential of tailoring the appropriate flower design on seed setting is less known. To this end, elite wheat genotypes were crossed using a chemical hybridizing agent at different doses. A total of 23 hybrids were developed from a partial diallel design; and planted in an alpha lattice design with their parents at two locations in Morocco, for two years, to evaluate for yield components, heterosis and combining abilities. The 13.5 L ha−1 dose induced a maximum level of sterility (95%) and seed set showed large phenotypic variation and high heritability. In parallel, seed set showed tight correlation with pollen mass (0.97), visual anther extrusion (0.94) and pollen shedding (0.91) (p < 0.001), allowing direct selection of the associated traits. Using the combined data, mid-parent heterosis ranges were −7.64–14.55% for biomass (BM), −8.34–12.51% for thousand kernel weight (TKW) and −5.29–26.65% for grain yield (YLD); while best-parent heterosis showed ranges of −11.18–7.20%, −11.35–11.26% and −8.27–24.04% for BM, TKW and YLD, respectively. The magnitude of general combining ability (GCA) variance was greater than the specific combining ability (SCA) variance suggesting a greater additive gene action for BM, TKW and YLD. The favorable GCA estimates showed a simple method to predict additive effects contributing to high heterosis and thus could be an effective approach for the selection of promising parents in early generations. [ABSTRACT FROM AUTHOR]

Straw cereals, especially wheat (Triticum aestivum), are the most widely cultivated plant in the world, grown in over 100 countries, and are a prime commercial source. The uses of straw cereals are many and varied. The grains are used for a range of milling products from which a rich assortment of bakery products, pastries and biscuits are made, which constitute basic foods for 35-55% of the world's population, providing 50-55% of calories consumed worldwide, along with other grains grown. The processing of wheat in high-capacity mills results in large quantities of bran, which is a valuable concentrated feed (rich in protein, lipids and mineral salts) and germs high in vitamins, which is a natural provitamin but also lipids with uses in cosmetics. Straw left over from harvesting can be used to make pulp, bulk feed or bedding for various categories of animals, organic fertilizer after a period of composting or incorporated as such into the soil after harvest, and by briquetting can be used as fuel. The agronomic importance is given by: integral mechanization of the crop; early release of the land and the possibility of summer plowing, being a good precrop for most crops; according to the early varieties, it allows the location of successive crops in certain areas. In this respect, a field experiments were established in the year 2020 at the Agricultural and Development Research Station Secuieni (ADRS Secuieni) located in North Romania (Neam? County) and at Experimental Trials of Saaten Union Romania at Drajna Nouă located in South-East (Călăra?i County). The experimental variants were represented by the nine winter wheat varieties (Trublion, Centurion, Katarina, Glosa, Aspekt, Izvor, Avenue, Solehio, Alcantara) and one hybrid wheat (Hyxperia) in three repetitions in both locations, with the following graduations: a) 250 germinable kernels/sm; b) 360 germinable kernels/sm; c) 500 germinable kernels/sm. The obtained results indicate that at medium density the production results are superior to the variants of low and high density, which implies giving us more profitability. [ABSTRACT FROM AUTHOR]

Changes in climatic conditions would strongly influence the crop duration of many crops including wheat, which necessitates exploration of diversity in crop duration parameters in wheat with particular emphasis on novel sources of genetic variation, including hybrid wheat. The present work was designed to assess the potential of Chinese wheat hybrid germplasm for cultivation across Pakistan. For this purpose, 416 hybrids were assessed for diversity in crop duration parameters in the year 2017-18 and a subset of better performing 108 hybrids were selected and assessed for subsequent assessment. During the first experiment of preliminary testing of 416 Chinese wheat hybrids along with 5 local checks tested during 2017-18, significant variability (P<0.01) was observed for days to jointing and booting, the parameters related to crop duration. The overall impact was negative on the crop duration, resulting in selection of earlier lines. Although selection increased the mean value, the variability decreased for most of the parameters. Variability in Chinese hybrids reflects on the potential of selection for candidate hybrids to be released in Pakistan after proper testing. The variability could also be exploited for generation of further variability in Pakistani wheat germplasm for normal varietal development as a novel source of germplasm to reduce genetic homogeneity. [ABSTRACT FROM AUTHOR]

The exploitation of heterosis, which is associated with the development of hybrid wheat varieties, has a great potential for increasing global wheat grain yields. Nevertheless, common wheat hybrids now account for less than 1% of global wheat production. In practice, two general approaches in hybrid wheat seeds production are being used. The first is based on the application of a chemical hybridizing agent, while the second is based on the use of cytoplasmic-genetic male sterility derived from Triticum timopheevii Zhuk. (G type cytoplasm). In this study, we present the development of R (restorer) lines for an alternative hybrid wheat system based on the cytoplasm of Aegilops crassa Boiss. (D2 type cytoplasm). Considering the cytoplasm types, it was found that different types of experimental F1 crosses required different sources of fertility restorer genes. CMS materials with T. timopheevii cytoplasm achieved the highest productivity in combination with Rf3 gene carriers. On the other hand, CMS materials with D2 cytoplasm in combination with interspecific crosses of synthetic hexaploid wheat accessions and SBEII mutants led to highly heterotic F1 hybrids. D2 cytoplasm based male sterility induction system represents a promising tool for hybrid wheat development. [ABSTRACT FROM AUTHOR]

Because of the yield increase of 3.5–15% compared to conventional wheat, hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future. In this study, we performed a principal component analysis (PCA) on two-line hybrids wheat and their parents using the grain weight (GW), the length of spike (LS), the kernel number of spike (KSN), and spike number (SPN) as variables. The results showed that the variables could be classified into three main factors, the weight factor (factor 1), the quantity factor 1 (factor 2) and the quantity factor 2 (factor 3), which accounted for 37.1, 22.6 and 18.5%, respectively of the total variance in different agronomic variables, suggesting that the GW is an important indicator for evaluating hybrid combinations, and the grain weight of restorer line (RGW) could be used as a reference for parents selection. The hybrid combination with a higher score in factor 1 direction and larger mid-parent heterosis (MPH) of the GW and its parents were used to carry out the analysis of grain filling, 1-aminocylopropane-1-carboxylicacid (ACC) and polyamine synthesis related genes. The results suggested that the GW of superior grain was significantly higher than that of inferior grains in BS1453×JS1 (H) and its parents. Both grain types showed a weight of H between BS1453 (M) and JS1(R), and a larger MPH, which may be caused by their differences in the active filling stage and the grain filling rate. The ADP-glucose pyrophosphorylase (AGPase), granule bound starch synthase I (GBSSI), starch synthase III (SSS), and starch branching enzyme-I (SBE-I) expression levels of H were intermediated between M and R, which might be closely related to MPH formation of the GW. Compared with R and H, the GW of M at maturity was the lowest. The expression levels of spermidine synthase 2 (Spd2), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) had significantly positive correlations with the grain filling rate (r=0.77*, 0.51*, 0.59*), suggesting their major roles in the grain filling and heterosis formation. These provide a theoretical basis for improving the GW of photo-thermo-sensitive male sterile lines (PTSMSL) by changing the endogenous polyamine synthesis in commercial applications.

Abstract Background Two-line hybrid wheat system using thermo-photo sensitive genic male sterility (TPSGMS) is currently the most promising approach for wheat heterosis utilization in China. However, during past 20 years only few TPSGMS lines were developed in hybrid wheat breeding, which has been the main limiting factor to create heterotic hybrids. Application of doubled haploid (DH) breeding provides a useful strategy to efficiently develop practically usable TPSGMS lines. Results F1s and selected F2 and F3 sterile plants of eight crosses made from two commercial TPSGMS lines were used to produce DH lines. We developed a total of 24 elite DH sterile lines with stable sterility, good outcrossing and yield potential, resistance to yellow rust and powdery mildew, as well as desirable plant height (50–60 cm). These DH lines were developed within 4 years through at least 1 year of evaluation. The stability of male sterility was confirmed for most (20/24) of these elite DH sterile lines by multiple tests in two or 3 years. These lines are expected to be used in hybrid wheat breeding. The percentage of elite lines developed from the tested DH lines produced from filial generations was in the order of F2 > F3 > F1. Conclusions We demonstrate that coupling DH techniques with conventional breeding is an efficient strategy for accelerating the development of more practical wheat TPSGMS lines. Generation of DHs from F2 generation appeared to be the better choice considering the balance of shortening breeding time and overall breeding efficiency.

Abstract Background Aegilops crassa cytoplasm is an important source for investigating cytoplasmic male sterility (CMS). Moreover, the stamens of line C303A exhibit a high degree of pistillody, turning almost white. However, the molecular mechanism that underlies pistillody in C303A remains unclear. Therefore, to obtain a better understanding of pistillody in C303A, the phenotypic and cytological features of C303A were observed to identify the key stage for the homeotic transformation of stamens into pistil-like structures. Transcriptome profiles were determined for stamens using Illumina RNA sequencing. Results Morphological observations of the CMS wheat line with Aegilops crassa cytoplasm C303A showed that the pistils developed normally, but the stamens were ultimately aborted and they released no pollen when mature. According to paraffin section observations, the stamens began to transform into pistils or pistil-like structures in the binucleate stage (BNS). Therefore, the stamens were collected from line C303A and its maintainer 303B in the BNS for transcriptome sequencing. In total, 20,444 wheat genes were determined as differentially expressed in C303A and 303B stamens, with 10,283 upregulated and 10,161 downregulated genes. Gene Ontology enrichment analyses showed that most of the differentially expressed genes (DEGs) were annotated with GO terms comprising metabolic process, cell, cellular process, catalytic activity, and cell part. Analysis based on the Kyoto Encyclopedia of Genes and Genomes database showed that the enriched DEGs were mainly associated with energy metabolism. We also found several essential genes that may contribute to pistillody in C303A. These findings suggest that disrupted energy metabolism and reactive oxygen metabolism induce pistillody and eventually lead to abortion in C303A. Conclusion We determined the complex transcriptome profiles for C303A stamens and demonstrated that disrupted energy metabolism and class B MADS-box genes are related to pistillody. These findings may facilitate future studies of the mechanistic response of the wheat stamen and pollen development in CMS.

Thermo-sensitive cytoplasmic male sterility (TCMS) plays a crucial role in hybrid production and hybrid breeding; however, there are few studies on molecular mechanisms related to anther abortion in the wheat TCMS line. In this study, FA99, a new wheat thermo-sensitive cytoplasmic male sterility line, was investigated. Fertility conversion analysis showed that FA99 was mainly controlled by temperature, and the temperature-sensitive stage was pollen mother cell formation to a uninucleate stage. Further phenotypic identification and paraffin section showed that FA99 was characterized by indehiscent anthers and aborted pollen in a sterile environment and tapetum was degraded prematurely during the tetrad period, which was the critical abortion period of FA99. The contents of O2−, H2O2, MDA and POD were significantly changed in FA99 under a sterile environment by the determination of physiological indexes. Furthermore, through transcriptome analysis, 252 differentially expressed genes were identified, including 218 downregulated and 34 upregulated genes. Based on KOG function classification, GO enrichment and KEGG pathways analysis, it was evident that significant transcriptomic changes in FA99 under different fertility environments, and the major differences were “phenylalanine metabolism”, “phenylpropanoid biosynthesis”, “cutin, suberine and wax biosynthesis”, “phenylalanine, tyrosine and tryptophan biosynthesis” and “citrate cycle (TCA cycle)”. Finally, we proposed an intriguing transcriptome-mediated pollen abortion and male sterility network for FA99. These findings provided data on the molecular mechanism of fertility conversion in thermo-sensitive cytoplasmic male sterility wheat.

Hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future, and population construction is an important factor affecting their yield heterosis formation. In order to clarify the effect of population regulation of hybrid wheat on source–sink systems, the two-line hybrid wheat variety Jingmai 6 was used to carry out relevant research in this experiment. The leaf area index (LAI) of Jingmai 6 showed an increasing trend, while the tiller-spike rate exhibited a downward trend with the increase of planting density. The total accumulation of dry matter at maturity increased with the increase of planting density, among which the relative proportion of dry matter pre-anthesis gradually increased, while that after anthesis gradually decreased. The sink capacity and spikes number of hybrid wheat were positively correlated with the grain yield. There was higher sink capacity, spike to leaf ratio and grain to leaf ratio under A2 and A3 conditions. With the increase of planting density, the hybrid wheat yield showed a unimodal curve, and A3 had the highest grain yield. Combined with the change trend of dry matter accumulation before and after anthesis, it was proved that suitable planting density was the key to obtaining high yield of hybrid wheat.

Main conclusion: Bioinformatic analysis identified the function of genes regulating wheat fertility. Barley stripe mosaic virus-induced gene silencing verified that the genesTaMut11andTaSF3are involved in pollen development and related to fertility conversion. Environment-sensitive genic male sterility is of vital importance to hybrid vigor in crop production and breeding. Therefore, it is meaningful to study the function of the genes related to pollen development and male sterility, which is still not fully understand currently. In this study, YanZhan 4110S, a new thermo-sensitive genic male sterility wheat line, and its near-isogenic line YanZhan 4110 were analyzed. Through comparative transcriptome basic bioinformatics and weighted gene co-expression network to further identify some hub genes, the genes TaMut11 and TaSF3 associated with pollen development and male sterility induced by high-temperature were identified in YanZhan 4110S. Further verification through barley stripe mosaic virus-induced gene silencing elucidated that the silencing of TaMut11 and TaSF3 caused pollen abortion, finally resulting in the declination of fertility. These findings provided data on the abortive mechanism in environment-sensitive genic male sterility wheat. [ABSTRACT FROM AUTHOR]

Anther extrusion (AE) is the most important male floral trait for hybrid wheat seed production. AE is a complex quantitative trait that is difficult to phenotype reliably in field experiments not only due to high genotype-by-environment effects but also due to the short expression window in the field condition. In this study, we conducted a genome-wide association scan (GWAS) and explored the possibility of applying genomic prediction (GP) for AE in the CIMMYT hybrid wheat breeding program. An elite set of male lines (n = 603) were phenotype for anther count (AC) and anther visual score (VS) across three field experiments in 2017–2019 and genotyped with the 20K Infinitum is elect SNP array. GWAS produced five marker trait associations with small effects. For GP, the main effects of lines (L), environment (E), genomic (G) and pedigree relationships (A), and their interaction effects with environments were used to develop seven statistical models of incremental complexity. The base model used only L and E, whereas the most complex model included L, E, G, A, and G × E and A × E. These models were evaluated in three cross-validation scenarios (CV0, CV1, and CV2). In cross-validation CV0, data from two environments were used to predict an untested environment; in random cross-validation CV1, the test set was never evaluated in any environment; and in CV2, the genotypes in the test set were evaluated in only a subset of environments. The prediction accuracies ranged from −0.03 to 0.74 for AC and −0.01 to 0.54 for VS across different models and CV schemes. For both traits, the highest prediction accuracies with low variance were observed in CV2, and inclusion of the interaction effects increased prediction accuracy for AC only. In CV0, the prediction accuracy was 0.73 and 0.45 for AC and VS, respectively, indicating the high reliability of across environment prediction. Genomic prediction appears to be a very reliable tool for AE in hybrid wheat breeding. Moreover, high prediction accuracy in CV0 demonstrates the possibility of implementing genomic selection across breeding cycles in related germplasm, aiding the rapid breeding cycle.

Breeding hybrids with maximum heterosis requires efficient cross-pollination and an improved male sterility system. Renewed efforts have been made to dissect the phenotypic variation and genetic basis of hybrid floral traits, although the potential of tailoring the appropriate flower design on seed setting is less known. To this end, elite wheat genotypes were crossed using a chemical hybridizing agent at different doses. A total of 23 hybrids were developed from a partial diallel design; and planted in an alpha lattice design with their parents at two locations in Morocco, for two years, to evaluate for yield components, heterosis and combining abilities. The 13.5 L ha−1 dose induced a maximum level of sterility (95%) and seed set showed large phenotypic variation and high heritability. In parallel, seed set showed tight correlation with pollen mass (0.97), visual anther extrusion (0.94) and pollen shedding (0.91) (p < 0.001), allowing direct selection of the associated traits. Using the combined data, mid-parent heterosis ranges were −7.64–14.55% for biomass (BM), −8.34–12.51% for thousand kernel weight (TKW) and −5.29–26.65% for grain yield (YLD); while best-parent heterosis showed ranges of −11.18–7.20%, −11.35–11.26% and −8.27–24.04% for BM, TKW and YLD, respectively. The magnitude of general combining ability (GCA) variance was greater than the specific combining ability (SCA) variance suggesting a greater additive gene action for BM, TKW and YLD. The favorable GCA estimates showed a simple method to predict additive effects contributing to high heterosis and thus could be an effective approach for the selection of promising parents in early generations.

Hybrid wheat shows promise to increase yield potential, but many questions remain about the hybrid system. One of the most important is how hybrids will perform in terms of diseases such as Fusarium head blight (FHB). It is unknown if a hybrid produced from a resistant by susceptible cross will express acceptable resistance levels. This experiment tested hybrids produced from four resistant parents crossed with a common susceptible parent (2398). The results indicated that the hybrids were resistant compared with the susceptible parent and mid-parent, while they were less resistant compared with their respective resistant parent. The hybrids were between the mid-parent and resistant parent in resistance to FHB traits. This may indicate that the resistance in the hybrids may be controlled by partial dominance gene action. The findings also indicated that accumulation of more resistance genes provided improved resistance to FHB. In conclusion, successful hybrids with a good level of FHB resistance could be produced through crossing parents with contrasting resistance to this disease. [ABSTRACT FROM AUTHOR]

Resistance breeding is crucial for sustainable control of wheat leaf rust and single nucleotide polymorphism (SNP)-based genome-wide association studies (GWAS) are widely used to dissect leaf rust resistance. Unfortunately, GWAS based on SNPs often explained only a small proportion of the genetic variation. We compared SNP-based GWAS with a method based on functional haplotypes (FH) considering epistasis in a comprehensive hybrid wheat mapping population composed of 133 parents plus their 1574 hybrids and characterized with 626 245 high-quality SNPs. In total, 2408 and 1 139 828 significant associations were detected in the mapping population by using SNP-based and FH-based GWAS, respectively. These associations mapped to 25 and 69 candidate regions, correspondingly. SNP-based GWAS highlighted two already-known resistance genes, Lr22a and Lr34-B , while FH-based GWAS detected associations not only on these genes but also on two additional genes, Lr10 and Lr1. As revealed by a second hybrid wheat population for independent validation, the use of detected associations from SNP-based and FH-based GWAS reached predictabilities of 11.72% and 22.86%, respectively. Therefore, FH-based GWAS is not only more powerful for detecting associations, but also improves the accuracy of marker-assisted selection compared with the SNP-based approach. [ABSTRACT FROM AUTHOR]

Anther extrusion (AE) is the most important male floral trait for hybrid wheat seed production. AE is a complex quantitative trait that is difficult to phenotype reliably in field experiments not only due to high genotype-by-environment effects but also due to the short expression window in the field condition. In this study, we conducted a genome-wide association scan (GWAS) and explored the possibility of applying genomic prediction (GP) for AE in the CIMMYT hybrid wheat breeding program. An elite set of male lines (n = 603) were phenotype for anther count (AC) and anther visual score (VS) across three field experiments in 2017–2019 and genotyped with the 20K Infinitum is elect SNP array. GWAS produced five marker trait associations with small effects. For GP, the main effects of lines (L), environment (E), genomic (G) and pedigree relationships (A), and their interaction effects with environments were used to develop seven statistical models of incremental complexity. The base model used only L and E, whereas the most complex model included L, E, G, A, and G × E and A × E. These models were evaluated in three cross-validation scenarios (CV0, CV1, and CV2). In cross-validation CV0, data from two environments were used to predict an untested environment; in random cross-validation CV1, the test set was never evaluated in any environment; and in CV2, the genotypes in the test set were evaluated in only a subset of environments. The prediction accuracies ranged from −0.03 to 0.74 for AC and −0.01 to 0.54 for VS across different models and CV schemes. For both traits, the highest prediction accuracies with low variance were observed in CV2, and inclusion of the interaction effects increased prediction accuracy for AC only. In CV0, the prediction accuracy was 0.73 and 0.45 for AC and VS, respectively, indicating the high reliability of across environment prediction. Genomic prediction appears to be a very reliable tool for AE in hybrid wheat breeding. Moreover, high prediction accuracy in CV0 demonstrates the possibility of implementing genomic selection across breeding cycles in related germplasm, aiding the rapid breeding cycle. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Wheat is grown on more land than any other crop in the world. Current estimates suggest that yields will have to increase sixty percent by 2050 to meet the demand of an ever‐increasing human population; however, recent wheat yield gains have lagged behind other major crops such as rice and maize. One of the reasons suggested for the lag in yield potential is the lack of a robust hybrid system to harness the potential yield gains associated with heterosis, also known as hybrid vigor. Here, we set out to identify candidate genes for a genic hybrid system in wheat and characterize their function in wheat using RNASeq on stamens and carpels undergoing meiosis. Twelve genes were identified as potentially playing a role in pollen viability. CalS5‐ and RPG1‐like genes were identified as pre‐ and post‐meiotic genes for further characterization and to determine their role in pollen viability. It appears that all three homoeologues of both CalS5 and RPG1 are functional in wheat as all three homoeologues need to be knocked out in order to cause male sterility. However, one functional homoeologue is sufficient to maintain male fertility in wheat.

The study assessed the quality parameters of grain and flour, the rheological properties of dough and the quality of bread prepared from flour of hybrid cultivars of wheat in comparison with population cultivars of wheat. As the interest in wheat hybrids cultivars from the agricultural and milling industry is growing, their technological value of grain and flour was evaluated at two levels of nitrogen fertilisation (N1—110 kg/ha, N2—150 kg/ha). Increasing the fertilisation (N2) produced a significant influence on the crude protein and gluten content in the flour, as well as the moisture of the crumb and the yield of the dough without impacting other rheological traits and parameters of bread baking process. The performed principal component analysis (PCA) allowed for identification of the best cultivars among the studied wheat cultivars (Hybery and Hyvento). The hybrid cultivar Hyvento was characterised by favourable qualitative traits of the grain (vitreousness, crude protein content) and rheological parameters of the dough (bread volume), however, it had lower baking quality parameters. Among the hybrid cultivars, the best applicability for baking purposes was Hybery due to the favourable values of the baking process parameters and bread quality (bread yield, bread volume, Dallmann porosity index of crumb). Hybrid cultivars of wheat can therefore be used for the production of bread and be an alternative in agricultural production for population cultivars, which will contribute to filling the knowledge gap for the hybrid wheat cultivars. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is the basic element of a wheat cultivation technology, affecting the volume and quality of grain yield. The aim of this study, conducted in 2016-2019, was to assess the yield, quality parameters and chemical composition of the grain of hybrid cultivars fertilized with higher doses of nitrogen compared to a winter wheat population cultivar. The experiment was established on brown peat with the textural composition of silt loam (2016/2017 and 2018/2019) and clay loam (2017/2018). The soil was classified as a Fluvic Cambisol (CMfv). The first factor studied was nitrogen fertilization at doses: N150 – 150 kg ha-1 (three applications: 60+50+40) and N200 – 200 kg ha-1 (four applications: 60+80+40+20). The second factor was four cultivars of winter wheat: hybrid cultivars Hyking, Hypocamp and Hyvento, and a population variety Artist. The grain of the hybrid cultivars had good quality parameters (Hyking, Hyvento) and higher yields as well as a greater content of iron, copper, zinc and phosphorus in the grain (Hypocamp) compared to the population cultivar. The weather conditions with less rainfall, including a very dry period during wheat grain formation and maturation, depressed the grain yield but resulted in better quality traits and a higher content of macro- and micronutrients (Fe, Zn, Cu) in the grain. The application of a nitrogen dose of 200 kg ha-1 compared to 150 kg ha-1 caused an increase in the yield and quality of the hybrid wheat grain, without differentiating the mineral composition of grain in terms of the content of K, Ca and Mg as well as Zn and Mn. [ABSTRACT FROM AUTHOR]

The photoperiod/temperature‐sensitive genic male sterile (P/TGMS) character is important for use of heterosis in hybrid wheat. In the present study, the fertility of 172 doubled haploid (DH) lines derived from the cross between a P/TGMS wheat line BS366 and a restorer wheat line Baiyu149 was investigated under both fertile and sterile environments during three cropping seasons. The phenotype was recorded based on the international seed setting rate. A total of 167 SSR and 1,278 SNP markers were used to construct a linkage map, with a total length of 3,748.94 cM and an average marker interval of 2.59 cM. Three QTLs were identified and designated as QF.bhw‐2DS, QF.bhw‐4BS and QF.bhw‐7Al, explaining 6.9%–12.8%, 19.7%–25.6% and 7.2%–8.8% of the phenotypic variances, respectively. These results lay a good basis for application of male sterility‐related molecular markers in improvement of two‐line hybrid wheat breeding system. [ABSTRACT FROM AUTHOR]

Summary: Resistance breeding is crucial for a sustainable control of leaf rust (Puccinia triticina) in wheat (Triticum aestivum L.) while directly targeting functional variants is the Holy Grail for efficient marker‐assisted selection and map‐based cloning. We assessed the limits and prospects of exome association analysis for severity of leaf rust in a large hybrid wheat population of 1574 single‐crosses plus their 133 parents. After imputation and quality control, exome sequencing revealed 202 875 single‐nucleotide polymorphisms (SNPs) covering 19.7% of the high‐confidence annotated gene space. We performed intensive data mining and found significant associations for 2171 SNPs corresponding to 50 different loci. Some of these associations mapped in the proximity of the already known resistance genes Lr21, Lr34‐B, Lr1 and Lr10, while other associated genomic regions, such as those on chromosomes 1A and 3D, harboured several annotated genes putatively involved in resistance. Validation with an independent population helped to narrow down the list of putative resistance genes that should be targeted by fine‐mapping. We expect that the proposed strategy of intensive data mining coupled with validation will significantly influence research in plant genetics and breeding. [ABSTRACT FROM AUTHOR]

Background: Two-line hybrid wheat system using thermo-photo sensitive genic male sterility (TPSGMS) is currently the most promising approach for wheat heterosis utilization in China. However, during past 20 years only few TPSGMS lines were developed in hybrid wheat breeding, which has been the main limiting factor to create heterotic hybrids. Application of doubled haploid (DH) breeding provides a useful strategy to efficiently develop practically usable TPSGMS lines. Results: F1s and selected F2 and F3 sterile plants of eight crosses made from two commercial TPSGMS lines were used to produce DH lines. We developed a total of 24 elite DH sterile lines with stable sterility, good outcrossing and yield potential, resistance to yellow rust and powdery mildew, as well as desirable plant height (50–60 cm). These DH lines were developed within 4 years through at least 1 year of evaluation. The stability of male sterility was confirmed for most (20/24) of these elite DH sterile lines by multiple tests in two or 3 years. These lines are expected to be used in hybrid wheat breeding. The percentage of elite lines developed from the tested DH lines produced from filial generations was in the order of F2 > F3 > F1. Conclusions: We demonstrate that coupling DH techniques with conventional breeding is an efficient strategy for accelerating the development of more practical wheat TPSGMS lines. Generation of DHs from F2 generation appeared to be the better choice considering the balance of shortening breeding time and overall breeding efficiency. [ABSTRACT FROM AUTHOR]

Environment-sensitive genic male sterility is a valid tool for hybrid production and hybrid breeding, but there are no previous reports of the molecular mechanism of fertility conversion. In this study, RNA-seq, phenotypic and cytological observations, and physiological indexes were applied to analyze thermo-sensitive genic male sterility line 4110S under different temperature conditions to explore the fertility transformation mechanism. In total, 3420 differentially expressed genes (DEGs) were identified comprising 2331 upregulated genes and 1089 downregulated genes. The DEGs were apparently distributed among 54 Gene Ontology functional groups. The phenylpropanoid, long-chain fatty acid, and jasmonic acid (JA) biosynthesis pathways were related to male sterility, where their downregulation blocked the synthesis of sporopollenin and JA. Phenotypic and cytological analyses showed that pollen wall defects and anther indehiscence at high temperatures induced sterility. Moreover, enzyme-linked immunosorbent assay results indicated that the abundance of JA was lower in 4110S under restrictive conditions (high temperature) than permissive conditions (low temperature). A possible regulated network of pathways associated with male sterility was suggested. These results provided insights into the molecular mechanism of fertility conversion in the thermosensitive male sterility system. [ABSTRACT FROM AUTHOR]