Genetic diversity and population structure of elite drought tolerant bread wheat (Triticum aestivum L.) genotypes

The objective of this study was to assess genetic diversity and population structure of 47 bread wheat genotypes obtained from the International Maize and Wheat Improvement Centre (CIMMYT) using 10 polymorphic simple sequence repeat (SSR) markers. Data was subjected to analysis for generating a dissimilarity matrix by the Jaccard index for clustering by the Neighbour-joining algorithm on DARwin 6.5 software. GenAlex Software was used to analyse the number of detected alleles (Na), number of effective alleles (Ne), observed heterozygosity (Ho), expected heterozygosity (He), genetic distance (GD), genetic identity (GI), gene flow (Nm), fixation index (F), Shannon’s Information Index (I), Analysis of molecular variance (AMOVA) and polymorphic information content (PIC). Results revealed that, at the locus level, marker Xgwm 132 had the highest Na (21), Ne (14.5), Ho (1.0) and He (0.94), while at the population level, Population III had the highest Na (21), Ne (5.59), He (0.83), and I (1.78). The mean PIC recorded was 0.80, and ranged from 0.63 (Wmc 78) to 0.93 (Xgwm 132). AMOVA revealed significant differences in genetic variation allocated within individuals (60%), across different individuals (37%) and across populations (3%) (P < 0.001). Four populations were distinguished based on pedigrees with GD ranging from 0.01 (Populations III and IV) to 0.31 (Populations II and III), while GI ranged from 0.74 (Populations II and III) to 0.99 (Populations III and IV). The selected markers successfully distinguished test genotypes with the most informative marker being Xgwm 132. Populations II and III were most distinct, thus suitable for parental selection and further drought tolerance breeding.