Characterization of Mexican wheat landraces for drought and salt stress tolerance potential for future breeding

One of the several impediments to increasing wheat productivity challenge is the low genetic diversity in modern wheat. Successful breeding requires the identification of donor germplasm in genetically diverse pools highlighting the importance of selection and use of diverse genotypes in a breeding program. In this investigation, we attempted to characterize a set of Mexican wheat landraces for drought and salt stress under controlled conditions at seedling stage to identify the drought and salt-tolerant genotypes. Drought stress at 14% PEG and saline stress at 125 mM NaCl caused significant reduction in all the traits investigated, i.e., germination %, root and shoot length, root and shoot fresh weight and vigor index. Association analyses revealed a total of 71 significantly associated SNPs with different traits. In addition, the cluster analysis of the germplasm for drought and salt stress identified three sub-groups based on the first two principal components which explained 51.5% and 44.3% variation, respectively. The best accessions under drought stress were number 13, 70, 71, 83, 85, 86, 87, 129, 141 and 142 carrying 8-22 positive alleles from a total possible of 24 positive alleles of the associated SNPs. Moreover, accessions 71 and 83 were carrying 22 positive alleles in total. This group also showed a mean increase of 22.54% in all the traits as compared to the population mean. Likewise, the ten best performed accessions under salt stress were 13, 14, 20, 26, 34, 35, 128, 130, 132 and 139 that carried from 17 to 28 from a possible of 35 alleles where accession number 20 carried maximum 28 favorable alleles. The phenotypic performance of these accessions indicated a mean increase of 16.43% from the population mean. Realizing the potential of these accessions, they can be included in future breeding programs to breed drought and salt stress-tolerant cultivars.