QTL MAPPING OF WHEAT (TRITICUM AESTIVUM L.) IN RESPONSE TO SALT STRESS

Abstract

Molecular markers provide a rapid approach to breeding for desired traits. To use them, it is necessary to determine the linkagebetween quantitative trait loci (QTL) and such markers. This study was conducted to investigate the geneticbasis of salinity responses in Egyptian bread wheat (Triticum aestivumL.). In this context, a doubled haploid (DH) population (SGDH) of 139 individuals was produced from the cross between two Egyptian breeding cultivars (Sakha 93,salttolerant) and (Gemmeza7, saltsusceptible). The DH populationwas tested under saline hydroponics culture and various plant responsesweremeasured.A molecular genetic map of the SGDHpopulationcovering 3645.3cM, was constructed using Restriction Fragment Length Polymorphism (RFLP), Microsatellite or Simple Sequence Repeats (SSR), and Amplified Fragment Length Polymorphism (AFLP)markers.In total, 325locialong the 21 wheat chromosomes weremapped. The B genome showed the highest number of mapped markers followed by the A and the D genomes respectively. Interval and composite interval mapping (using QTL cartographer) were used to identify the genomic regions controlling traits related to salt tolerance with a threshold of LOD 3. Analysis of QTLs has revealed the approximate location of the significant markers associated with 12traits related to salt tolerance traits across the A, B and D genomes.Fifty five significant QTL were detected on 15 of the 21 chromosomes mapped in this study, for some of these more than one QTL was identified. In many cases QTL were mapped very close to each other, indicating possible gene clustering or pleiotropy. For some traits, the total percentage of phenotypic variation explained by all QTL exceeded 50-60% but on average it was in the region of 15%. Chromosomes of homologues groups2and 5exerted the biggest effect on most phenotypic traits, especially chromosomes2Band 5B.Theresults indicatedthat there is considerable potential for improving salttolerance of hexaploidwheat byusing marker-assisted selection