Identification of SSR markers associated with morphological traits in cowpea (Vigna unguiculata L. Walp) genotypes under drought stress condition

In the current investigation, 22 SSR primer pairs were used to identify molecular markers associated with morphological traits in cowpea (Vigna unguiculata L.) based association analysis, markers produced 186 locations in 32 cowpea genotypes. 22 SSR primers pair amplified 8.45 for each primer location and the average polymorphism information content (PIC) ranged from 0.445 to 0.25 (Vm25) and 0.625 (Vm5) were varied, respectively. Cluster analysis based on Dice, Jaccard and Simple Maching similarity coefficients based on molecular traits revealed primarily two major groups. Stepwise regression analysis between molecular data as independent variables, and morphological data as dependent variables was performed to identify informative markers associated with the studied traits. SSR loci associated with economic and biological yield, in normal conditions and in drought stress condition were Vm70 and Vm33, and Vm3 and Vm26 respectively. In drought stress condition the maximum variation of number of days to 50% flowering, days to 50% maturity of pods and pod length (99.9%, respectively) was accounted by Vm22, Vm31 and Vm26 markers. While in the normal condition the maximum variation of traits sheath thickness, width of pod and days to 50% flowering (99.9%) was accounted by Vm14, Vm34 and Vm34 markers. In both normal and drought conditions most of the used SSR primers showed significant association with the studied traits, so we can use these markers along with morphological traits in breeding cowpea genotypes to identify drought tolerant and hardy cultivars suitable for the preparation and use mapping populations.