Phenotypic and molecular characterization of Striga Gesnerioides resistance among cowpea (Vigna unguiculata l. Walp.) breeding lines

Abstract

In Ghana, cowpea (Vigna unguiculata) production is constrained by Striga gesnerioides infestation. Though some Striga-resistant cowpea varieties exist, they are predominantly small to medium seed sizes, but consumer preference is tailored towards large to extra-large seeds. This study aimed to evaluate cowpea breeding lines and select for Striga resistance and improved agronomic traits. Data from the field were subjected to analysis of variance (ANOVA) and correlation. The variations in the quantitative and qualitative traits and molecular markers distinguished the cowpea genotypes. Genetic diversity and Striga-resistant cowpeas among the breeding populations were determined by SSR markers. Agro-morphogenetic variations exist among the cowpea breeding lines. The 100 seed weight differed significantly (P < 0.001) among the cowpea breeding lines, ranging from 11 to 26.8 g with a mean of 20.4 g. Grain yield ranged from 1.04 t ha-1 - 2.92 t ha-1. The highest coefficient of variation (CV % > 100) was among the Striga response parameters. Striga resistance efficiency test by pot screening was consistent with the marker-assisted selection (MAS) protocol but not so with the field screening test. SSR-1, C42-2B, CLM1320 and LRR8 were considered to have the best discrimination efficiency (74%-85.5%) to S.gesnerioides resistance. The alleles per primer pair of 2 to 7 with an average of 3, PIC of 0.41 and gene diversity of 0.25 were evidence of genetic variations. On the whole, UC15-01, UC15-02, UC15-19, UC15-22, UC15-28, UC15-35, UC15-43, UC15-43 UC15-47 and UC15-49 associated with large seed sizes, high yield and Striga-resistance traits and were the best-improved cowpea progenies selected for further evaluation.