Comparative Assessment of Synthetic-derived and Conventional Bread Wheat Advanced Lines Under Osmotic Stress and Implications for Molecular Analysis

Drought is one of the most important environmental factors limiting wheat yield in many parts of the world. Progress in breeding to improve drought tolerance has been limited by its high sensitivity to environmental factors, low heritability, and the complexity and size of wheat genome. Two genetically diverse sets of wheat genotypes were evaluated to identify genetic resources maintaining physiological and metabolic stability under osmotic stress. Data on 13 different morphological and physiological traits under control and osmotic stress clearly depicted the superiority of wheat lines derived from synthetic hexaploid wheats (SHWs) as compared to conventional bread wheats. Accordingly, all lines were genotyped with simple sequence repeat (SSR) markers to assess the diversity and identify the marker-trait associations (MTAs). Structure analysis partitioned the germplasm into two sub-populations (K = 2) based on Delta K and LnP(D) values. Association mapping was performed using Q + K matrix as covariates by applying mixed linear model (MLM). In total, 39 MTAs over 20 SSR loci were detected by the strict MLM model, which were reduced to 12 MTAs over 6 SSR loci after strict Bonferroni adjustments. MTAs detected under osmotic stress conditions indicated the effectiveness of association mapping to identify loci for different attributes under low-moisture conditions. Conclusively, this study has demonstrated that synthetic-derived wheats harbor valuable alleles that can enrich the genetic base of cultivated wheat and improve its adaptation under water stress conditions. The MTAs detected may have the candidate genes responsible for drought adaptation, thus providing a unique resource which can be manipulated for developing drought-tolerant cultivars.