Genetic Mapping of Quantitative Trait Loci for Agronomical and Morpho-Physiological Traits Under Drought Environments in Spring Barley (Hordeum vulgare L.)

Abstract

Abstract Drought is one of the major abiotic stresses that severely limit barley production which is well adapted to drought conditions in the Mediterranean basin where the unpredictable climatic conditions, particularly rainfall, rainfall distribution and both high and low temperatures, may lead to dramatic decreases in yield. Landraces and wild species, represent an important source of variation for adaptive traits that may contribute to increased yield and yield stability under drought conditions. The study includes mapping of Quantitative QTLs for agronomical and morpho-physiological traits associated with drought tolerance. A total of 76 QTLs identified to 11 traits that describe grain yield, biological yield, harvest index, kernel weight, seed per head, days to heading, kernel filling duration, growth vigor, growth habit, lodging and plant height were mapped using RIL population Arta x Harmal-2//Esp/1808-4L which was evaluated at six dry and semi-dry areas over three years.The linkage map contained 254 markers (80 SSR, 174 AFLP) spanning 691cM. Eighty-Four markers’ loci (38 SSR and 46 AFLP) were used for QTLs mapping using the Simple Interval Mapping (SIM) and Simplified Composite Interval Mapping (sCIM). The QTLs which explained the largest part of the phenotypic variation in the dry areas (rainfall <250 mm) were found on the following chromosomes: 2H for biological yield, 1H for harvest index, 2H, 4H and 5H for kernel weight, 2H for days to heading, 1H for the duration of kernel filling period and plant height. While in the semi-dry areas (rainfall between 250- 400mm) QTLs were identified on chromosomes 6H for grain yield, 2H and 5H for kernel weight, 1H and 6H for seed per head, 2H for days to heading. Some of the QTLs were common to those in other published work and some QTLs seemed specific to this study. Chromosomes 1H, 2H, 4H and 5H harbor more than 60% of mapped QTLs for dry areas. For the first time, QTLs explained the variation for grain yield, biological yield, harvest index, kernel weight and days to heading in very dry areas with rainfall less than 150 mm. An understanding of coincidental locations of QTL for correlated phenotypes allows a genetic dissection of different traits and better prediction of the loci most amendable for selection in a breeding program. The identification of marker-trait associations provides suitable opportunities for marker-assisted selection of genomic regions to improve adaptation to low rainfall environments provided interactions with other loci and with the target environments are reasonably well understood.