Screening of SSR Molecular Markers for Polymorphism in Aphid Resistant and Susceptible Cowpea Varieties

Abstract

The aim of this study was to screen SSR markers for polymorphism in aphid resistant and susceptible varieties. Twenty-Two (22) Simple Sequence Repeat (SSR) markers were screened on aphid resistant (TVNu-1158 and TVu-2876) and susceptible (Aloka Local and Keffi local). varieties. These molecular markers were used to identify polymorphism between the resistant and susceptible cowpea varieties using the PCR technique.  Polymorphic indices of primers were generated on the PICcalc DEMoMa application v2012. Primers showed different banding and clustering patterns. Results showed that 17/22 (77.3%) of the primers produced a total of 79 visible bands. Six (6) primers (27.3%) had PIC >0.50 and were considered polymorphic. They were: EX-78, EX-79, C42-B, RB-45, JL 31/32 and CP-253/254. The first five primers had PIC of 0.99 each as the highest value recorded.The maximum Marker Index (MI) recorded was 2.96 while the Effective Multiplex Ratio (EMR) was highest in CP-253/254. Polymorphism was higher in the aphid susceptible varieties than the resistant varieties in the following order: Keffi Local (27%), Aloka Local (26%), TVu-2879 (24%) and TVNu-1158 (23%). The highly polymorphic primers as stated in this report are effective candidates for developing varieties for aphid resistance in cowpea breeding.