Assessing drought tolerance and regional patterns of genetic diversity among spring and winter bread wheat using simple sequence repeats and phenotypic data

This study was conducted to assess drought tolerance and regional-based patterns of diversity of bread wheat accessions and to identify new sources of diversity that could accelerate the development of improved wheat varieties better suited to meeting the challenges posed by changing climate in Southern and Eastern Europe. For this, genetic diversity assessed by simple sequence repeats (SSR) markers was compared with diversity evaluated using 19 phenotypic traits averaged over irrigated and drought-stress field conditions. Thirty-six SSR were used to profile 96 wheat genotypes from the collection of genetic resources at the Institute of Field and Vegetable Crops, Novi Sad, Serbia. A total of 46 loci and 366 alleles were detected, with a range of 3-21 alleles per locus. The polymorphic information content was estimated to be 0.61. The genetic distance for all possible 4560 pairs of genotypes ranged from 0.06 to 0.91 with an average of 0.65. Genotypes were grouped according to their drought tolerance (high, medium, low) and region of origin. Analysis of molecular variance showed that over 96% of the total variation could be explained by the variance within the drought tolerance and geographical groups. As a whole, genetic diversity among the high drought tolerance genotypes was considerably higher than that among low drought tolerance genotypes. Comparative analysis of SSR diversity among six regional groups revealed that the genotypes from North America exhibited more genetic diversity than those from other regions. Two dendrograms were constructed based on phenotypic and molecular analyses using the Unweighted Pair Group Method with Arithmetic Mean method and were found to be topologically different. Genotypes characterised as highly drought tolerant were distributed among all SSR-based cluster groups. This implied that the genetic basis of drought tolerance in these genotypes was different, thereby enabling wheat breeders to combine these diverse sources of genetic variability to improve drought tolerance in their breeding programs.