Abstract
The objectives of the present study were to compare the application and utility of random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) marker techniques for analysis of genetic diversity among Saudi wheat genotypes under drought stress, compare genetic diversity estimated using molecular markers with agronomic performance under water stress to establish the degree of association between these techniques and develop drought tolerance-associated DNA markers. Twelve wheat genotypes were used in this study. They were evaluated phenotypically for drought tolerance and were planted under four irrigation treatments over two seasons to expose genotypes to different levels of drought stress during the grain filling period. The UPGMA dendrogram generated from the standardized agronomic data separated the twelve wheat genotypes into three main groups, which diverged at a similarity index of 0.42. The average genetic similarity among the twelve wheat genotypes was 0.50, with value ranging from 0.34 to 0.68. Two types of molecular markers, RAPD and ISSR, were assayed to determine the genetic diversity of 12 wheat genotypes. A high level of polymorphism was found with both RAPD and ISSR markers. In RAPD analyses, a total of 322 fragments were produced by the 30 primers. Of these 322 amplified fragments, 18.63% were not polymorphic; whereas, the remaining bands (81.37%) were polymorphic in one or more in the twelve genotypes. In ISSR analyses, 192 out of 238 bands (80.67%) were polymorphic. The dendrogram based on RAPD markers was not in accord with the dendrogram based on ISSR markers. The combined dendrogram agreed better with the groups of the wheat genotypes based on pedigree analysis than the dendrogram generated by ISSR or RAPD data alone. The correlation coefficient between RAPD and ISSR matrix was highly significant (0.534**, p > 0.001). Additionally, both RAPD and ISSR matrices showed significantly positive correlation (r = 0.94** and r = 0.77**, respectively) with RAPD+ISSR matrix. Specific RAPD and ISSR markers were developed successfully to identify drought tolerance genotype (Ksu103 and Ksu105) from drought sensitive genotype (Yecora Rojo). Thus, the markers identified in this study should be applicable for marker-assisted selection for the drought tolerance in wheat breeding programs.