QTL Mapping for Some Morphological Traits under Salt Stress Condition in Recombinant Inbred Lines of Bread Wheat

Salinity stress is one of the most important abiotic stresses that have harmful effects on plant performance and quality. So that according to the predictions made until 2050, 50% of agricultural lands will lose their ability to be cultivated due to salinity. Due to the complexity of salinity resistance traits, there is little information about the number of genes, their chromosomal location, and the relative contribution of each gene in the incidence and phenotypic distribution. Locating quantitative genes can break down this complex genetic model into individual genetic components, in which case quantitative traits will also be investigated like monogenic traits.

In order to identify QTLs controlling some root and shoot traits under salinity stress in bread wheat, 148 recombinant inbred lines of spring bread wheat obtained from the cross of Yecora Rojo cultivar (early and dwarf as a parent of American origin) and genotype No.49 (late and tall as a parent originating from Sistan and Baluchestan) were studied with the parents. This research was carried out in 2020 in the research greenhouse of Mohaghegh Ardabili University under salinity and non-stress conditions in pitmas and perlite culture medium and factorial based on a completely randomized design with five replications. Traits measured in this experiment included root length, root fresh weight, root dry weight, fresh and dry weight of shoots. In this study, linkage map was used based on 202 markers (177 SSR markers and 51 Retro transposon Markers). The map length was about 691.36 cM with the average distance of 3.42 cM in every marker pair, and 21 chromosomes covered in bread wheat. QTL analysis was done based on composite interval mapping (CIM) method, and additive effects were estimated for the identified QTLs.

The results of QTL analysis showed that in stress-free conditions, one QTL for root dry weight and shoot dry weight, two QTL shoot fresh weight and three QTL for root wet weight and root length were identified. Under salinity stress conditions, one QTL was identified for root dry weight and root length, two QTLs for shoot dry weight and three QTLs for shoot fresh weight. Among the QTLs identified, QRFW6A.n had the highest additive effect under normal conditions and QSFW2A.s under salinity stress conditions. For shoot dry weight and root fresh weight under normal conditions and shoot fresh weight under salinity stress, the positive additive effect of the located QTL s showed the inheritance of the desired allele at this site from Yecora Rojo's parent. The phenotypic variance justified by these QTLs varied from 5.43 to 8.97 under normal conditions and from 5.51 to 7.43 percent under salinity stress.

In this study, the number of QTLs identified for root and shoot-related characteristics was low, which could be due to the high number of low-impact QTLs, interactions, and environmental effects.