Genetic diversity analysis of sorghum [Sorghum bicolor (L.) Moench] genotypes for drought tolerance using SSR markers

Sorghum (Sorghum bicolor (L.) Moench) is considered as a model species for drought tolerance due to its inherent drought tolerant characteristics. The accessions were grouped into 27 major clusters elucidating a high level of genetic diversity which will be useful for identifying suitable genotypes for drought tolerance breeding. The best characterized form of drought tolerance during crop growth is the non-senescence or "stay-green" trait. Genetic diversity analysis carried out with 100 sorghum genotypes for drought tolerance using 13 stay-green specific polymorphic SSR markers revealed high level of polymorphism among the genotypes. A total of 56 scorable alleles were generated of which 55 were polymorphic. The number of alleles produced by different primers ranged from two to seven with an average of 4.0 alleles per primer. The polymorphic loci clearly discriminate all the genotypes. The similarity coefficients based on 13 SSR markers ranged from 0.02 to 1.00. Among the 100 accessions three genotypes viz., IS 29389, IS 29393 and IS 29496 and two other genotypes IS 23392 and IS 23397 showed the highest similarity index (1.00) and the genotypes IS 22005 and IS 24693, showed the least similarity index (0.02). The dendrogram, which classified the hundred sorghum accessions into twenty-seven major clusters and discriminated the drought tolerant genotypes with susceptible genotypes. Cluster analysis categorized the drought resistant and drought susceptible genotypes in to separate clusters. Most of the genotypes in the cluster IV had the better stay-green score. The stay-green specific genes may be present in most of these genotypes and classified as drought tolerant. In general, the genotypes B 35, IS 22212, IS22335, IS 22697, IS 29323, IS 22243, IS 23418, IS 22794, IS 21756 and IS 22339 exhibited drought tolerance phenomenon and were grouped as drought tolerant under molecular level of genetic diversity.