Mapping of QTLs Associated with Yield and Yield Related Traits in Durum Wheat (Triticum durum Desf.) Under Irrigated and Drought Conditions

Abstract

Global durum wheat consumption (Triticum durum Desf.) is ahead of its production. One reason for this is abiotic stress, e.g., drought. Breeding for resistance to drought is complicated by the lack of fast, reproducible screening techniques and the inability to routinely create defined and repeatable water stress conditions. Here, we report the first analysis of dissection of yield and yield-related traits in durum wheat in Pakistan, seeking to elucidate the genetic components of yield and agronomic traits. Analysis of several traits revealed a total of 221 (160 with logarithm of odds (LOD) > 2 ≤ 3 and 61 with LOD > 3) quantitative trait loci (QTLs) distributed on all fourteen durum wheat chromosomes, of which 109 (78 with LOD > 2 ≤ 3 and 31 with LOD > 3) were observed in 2016-17 (S1) and 112 (82 with LOD > 2 ≤ 3 and 30 with LOD > 3) were observed in 2017-18 (S2). Allelic profiles of yield QTLs on chromosome 2A and 7B indicate that allele A of Xgwm895 and allele B of Xbarc276 can enhance the Yd up to 6.16% in control and 5.27% under drought. Moreover, if combined, a yield gain of up to 11% would be possible.

Molecular Mapping and Genomics of Grain Yield in Durum Wheat: A Review

“…Given that a large number of molecular markers are necessary for higher resolution and precision in the genetic mapping of complex traits, hundreds of thousands of markers have been developed in wheat, including a wheat 90K SNP iSelect assay containing 81,587 SNP markers [ 26 ]. SNPs have been widely used to dissect the genetic basis of several economically important traits [ 15 , 17 , 18 , 20 ], and to develop a high-density durum wheat consensus map [ 27 ].…”

“…Thus, the genetic basis of GY has been investigated through the three main yield components which will be explored in this review: kernel weight, kernels number and kernels number per unit area [ 28 , 31 ]. A total of 665 QTLs (100 with a pleiotropic effect) were identified and associated with grain yield and its components ( Table S1 ) [ 7 , 14 , 15 , 17 , 18 , 30 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ]. Specifically, nine additional yield components were considered: kernel length (KL), kernel width (KW), thousand-kernel weight (TKW) associated with the kernel weight, kernels number per spike (KNS), kernels number per spikelet (KNSL), spikelets number per spike (SLNS) associated with the kernels number, grain yield (GY), kernels number per square meter (KNM) and spike number per square meter (SNM) related to the kernels number per unit area ( Figure 1 ).…”

“…This can be explained considering that the increase in kernel number per unit area or per spike results in a lower availability of photo-assimilates synthesized during grain filling for each kernel, which leads to decreases in individual kernel weight due to competition effects [ 87 ]. In addition, four genomic regions on chromosomes 3A (at 43.4 and 93.8 cM), 3B (at 12.4 cM) and 5B (at 103.8 cM) presented co-localization of QTLs for KNS and GY, which explained between 7% and 38% of the phenotypic variance, and the additive effect for both traits was positive [ 18 , 44 ].…”

“…More recently, two genomics regions located on chromosomes 2A and 7B linked with the markers Xgwm895 (at 125 cM) and Xbarc276 (at 219 cM) were associated with GY in an RIL population derived from the cross between “Omrabi” and “Belikh2”. These markers can increase the GY up to 6.16% and 5.27% under irrigated and drought conditions, and in a combined manner, a yield rise of up to 11% is possible [ 18 ]. However, it is necessary to verify if these markers segregate in elite populations used in genetic improvement programs of durum wheat.…”

“…Finally, the stable QTLs identified to date for grain yield-related traits of durum wheat grown under normal or irrigated, drought and high-temperature conditions are shown in Table S2 [ 7 , 14 , 18 , 33 , 35 , 47 , 79 , 131 ]. Therefore, these genomic regions are important to study (fine mapping and characterization of genes) for durum wheat breeding programs to produce new varieties well-adapted to drought stress and/or high temperatures, a relevant productive problem in most of the regions where durum wheat is cultivated.…”