Genome-Wide Association Mapping for Yield and Related Traits Under Drought Stressed and Non-stressed Environments in Wheat

Understanding the genetics of drought tolerance in hard red spring wheat (HRSW) in northern USA is a prerequisite for developing drought-tolerant cultivars for this region. An association mapping (AM) study for drought tolerance in spring wheat in northern USA was undertaken using 361 wheat genotypes and Infinium 90K single-nucleotide polymorphism (SNP) assay. The genotypes were evaluated in nine different locations of North Dakota (ND) for plant height (PH), days to heading (DH), yield (YLD), test weight (TW), and thousand kernel weight (TKW) under rain-fed conditions. Rainfall data and soil type of the locations were used to assess drought conditions. A mixed linear model (MLM), which accounts for population structure and kinship (PC+K), was used for marker–trait association. A total of 69 consistent QTL involved with drought tolerance-related traits were identified, with p ≤ 0.001. Chromosomes 1A, 3A, 3B, 4B, 4D, 5B, 6A, and 6B were identified to harbor major QTL for drought tolerance. Six potential novel QTL were identified on chromosomes 3D, 4A, 5B, 7A, and 7B. The novel QTL were identified for DH, PH, and TKW. The findings of this study can be used in marker-assisted selection (MAS) for drought-tolerance breeding in spring wheat

Accounting for heading date gene effects allows detection of small-effect QTL associated with resistance to Septoria nodorum blotch in wheat.

In humid and temperate areas, Septoria nodorum blotch (SNB) is a major fungal disease of common wheat (Triticum aestivum L.) in which grain yield is reduced when the pathogen, Parastagonospora nodorum, infects leaves and glumes during grain filling. Foliar SNB susceptibility may be associated with sensitivity to P. nodorum necrotrophic effectors (NEs). Both foliar and glume susceptibility are quantitative, and the underlying genetics are not understood in detail. We genetically mapped resistance quantitative trait loci (QTL) to leaf and glume blotch using a double haploid (DH) population derived from the cross between the moderately susceptible cultivar AGS2033 and the resistant breeding line GA03185-12LE29. The population was evaluated for SNB resistance in the field in four successive years (2018-2021). We identified major heading date (HD) and plant height (PH) variants on chromosomes 2A and 2D, co-located with SNB escape mechanisms. Five QTL with small effects associated with adult plant resistance to SNB leaf and glume blotch were detected on 1A, 1B, and 6B linkage groups. These QTL explained a relatively small proportion of the total phenotypic variation, ranging from 5.6 to 11.8%. The small-effect QTL detected in this study did not overlap with QTL associated with morphological and developmental traits, and thus are sources of resistance to SNB

Molecular detection of QTLs for flour quality traits in two doubled haploid populations in spring wheat under heat stress

Wheat four quality is a complex group of traits of tremendous importance to wheat producers, end-users and breeders. Eight four quality traits; four protein content, wet gluten content, gluten index, dry gluten content, falling number, ash content, test weight and four moisture were measured in two doubled haploid populations (Yecora Rojo X Ksu106 and Klassic × Ksu105) at Riyadh and Al-Qassim locations under heat treatments. Single-nucleotide polymorphism markers have been used to determine the number of QTLs controlling the four quality traits in both populations. Analysis of variance revealed high signifcant diferences (P<0.01) for all traits among wheat genotypes and between locations in both populations. The wheat genotypes × location interaction was high signifcant in both populations. A total of 58 additive QTLs were detected for the eight four quality traits in the Yecora Rojo × Ksu106 population at Riyadh and Al-Qassim locations under heat treatments. They were mainly distributed over the 21 wheat chromosomes except 4B and 4D chromosomes. Moreover, in Klassic × Ksu105 population, there were 69 additive QTLs identifed over the full set of chromosomes except 3D chromosome under two locations. This study will facilitate the generation of improved wheat varieties with good quality via molecular markerassisted breeding

Genome wide genetic dissection of wheat quality and yield related traits and their relationship with grain shape and size traits in an elite × non-adapted bread wheat cross.

The genetic gain in yield and quality are two major targets of wheat breeding programs around the world. In this study, a high density genetic map consisting of 10,172 SNP markers identified a total of 43 genomic regions associated with three quality traits, three yield traits and two agronomic traits in hard red spring wheat (HRSW). When compared with six grain shape and size traits, the quality traits showed mostly independent genetic control (~18% common loci), while the yield traits showed moderate association (~53% common loci). Association of genomic regions for grain area (GA) and thousand-grain weight (TGW), with yield suggests that targeting an increase in GA may help enhancing wheat yield through an increase in TGW. Flour extraction (FE), although has a weak positive phenotypic association with grain shape and size, they do not share any common genetic loci. A major contributor to plant height was the Rht8 locus and the reduced height allele was associated with significant increase in grains per spike (GPS) and FE, and decrease in number of spikes per square meter and test weight. Stable loci were identified for almost all the traits. However, we could not find any QTL in the region of major known genes like GPC-B1, Ha, Rht-1, and Ppd-1. Epistasis also played an important role in the genetics of majority of the traits. In addition to enhancing our knowledge about the association of wheat quality and yield with grain shape and size, this study provides novel loci, genetic information and pre-breeding material (combining positive alleles from both parents) to enhance the cultivated gene pool in wheat germplasm. These resources are valuable in facilitating molecular breeding for wheat quality and yield improvement

Identification of genotyping-by-sequencing tags associated with bread-making quality traits in spring wheat under heat stress

The bread-making quality traits of bread wheat underlie into genetic make-up of a variety and are infuenced by environmental factors and their interaction. Identifying QTL that control bread-making traits in wheat under heat stress may help to develop cultivars that are improved for those traits. Two doubled haploid (DH) populations (Yecora Rojo×Ksu106 and Klasic× Ksu105) were used to identify QTL for eight bread-making traits in wheat under heat stress. The phenotyping of bread-making traits was performed under normal and heat stress conditions in Al-Qassim and Riyadh locations, Saudi Arabia. Single nucleotide polymorphism (SNP) markers have been used to determine the number of QTLs controlling the bread-making traits. The genetic analysis of bread-making traits showed considerable variation for measurable traits with transgressive segregation under normal and heat stress conditions in both locations. A total of 60 QTL explained 10–22% of phenotypic variation in the population (Klassic × KSU105). In the population (Yecora Rojo× KSU106), the 98 QTL explained 10–23% of phenotypic variation. In the population (Klassic×KSU105), eleven co-located QTLs were identifed on chromosomes 2A, 3A, 3D, 5B and5D. The BBS QTL under heat stress co-located with QTLs for BCC and BSY under heat stress and normal conditions, respectively, in Riyadh location. Nineteen QTL clusters were identifed on chromosomes 1D, 2A, 2B, 2D, 3B, 3D, 4A, 4D, 5A, 5B, 6A, 7A and 7D based on Map 2 in the population (Yecora Rojo× KSU106). Interestingly, one locus (JD_c4438_839) on the chromosome 5D was identifed in both populations and was considered stable QTL. This locus was associated with QLFV.hs and QSLFV.hs in the population (Klassic× KSU105) and QLFW.n in the population (Yecora Rojo×KSU106). The fnding of SNP marker (JD_c4438_839) has an important signifcant for marker-assisted selection of bread-making quality traits under heat stress

Genotyping of U.S. Wheat Germplasm for Presence of Stem Rust Resistance Genes Sr24, Sr36 and Sr1RSAmigo

The stem rust resistance genes Sr24, Sr26, Sr36, and Sr1RSAmigo confer resistance to race TTKSK (= Ug99) of Puccinia graminis f. sp. tritici Pers. (Pgt). A collection of 776 cultivars and breeding lines of wheat (Triticum aestivum L.) from all growing regions of the United States were screened with simple sequence repeat and sequence tagged site markers linked to Sr24, Sr26, Sr36, and Sr1RSAmigo to determine frequencies of these genes in U.S. wheat germplasm. Marker efficacy in predicting the presence of these genes was evaluated via comparison with assayed seedling infection type. Among the lines evaluated, the most predominant gene is Sr24, present in hard winter, hard spring, and soft winter wheat lines. Resistance in soft winter wheat is primarily due to Sr36. The 1RS·1AL rye translocation carrying Sr1RSAmigo is present at equal frequencies in hard winter and soft winter wheat. Utilization of marker-assisted selection for stem rust resistance genes can hasten the development of wheat cultivars resistant to TTKSK and its variants and allow for the development of resistance gene pyramids for more durable stem rust resistance

Effect of Pre-Harvest Sprouting on Physicochemical Properties of Starch in Wheat

Pre-harvest sprouting (PHS) in wheat (Triticum aestivum L.) occurs when physiologically mature kernels begin germinating in the spike. The objective of this study was to provide fundamental information on physicochemical changes of starch due to PHS in Hard Red Spring (HRS) and Hard White Spring (HWS) wheat. The mean values of α-amylase activity of non-sprouted and sprouted wheat samples were 0.12 CU/g and 2.00 CU/g, respectively. Sprouted samples exhibited very low peak and final viscosities compared to non-sprouted wheat samples. Scanning electron microscopy (SEM) images showed that starch granules in sprouted samples were partially hydrolyzed. Based on High Performance Size Exclusion Chromatography (HPSEC) profiles, the starch from sprouted samples had relatively lower molecular weight than that of non-sprouted samples. Overall, high α-amylase activity caused changes to the physicochemical properties of the PHS damaged wheat