Screening of Cowpea ( Vigna unguiculata L. Walp) Genotypes for Rust ( Uromyces phaseoli var. vignae ) Resistance in Ghana

Abstract

The demand for cowpea (Vigna unguiculata L. Walp) is higher than supply in Ghana due to low yields caused by pathogenic diseases, predominantly rust disease. The use of rust resistant cultivars is the most effective method to control cowpea rust. Genetic variations among cowpea genotypes may be potential sources of rust resistance to control cowpea rust and increase cowpea yield and production in Ghana. The study assessed rust disease incidence and severity among cowpea genotypes and determined resistance to cowpea rust under field conditions. Twenty-four cowpea genotypes were sowed in four agro-ecological zones in two cropping seasons in Ghana. Cowpea rust incidence, severity, area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) were significantly (p < 0.05) higher in the semi-deciduous forest and minor cropping season compared with deciduous forest, coastal savannah, Sudan savannah and major cropping season. The cowpea genotypes also showed significant differences (p < 0.05) in response to rust infection. Positive and negative correlations existed in rust incidence, severity, AUDPC and rAUDPC within the agro-ecological zones and cropping seasons. The differences observed were due to variations in climatic conditions and genetic composition of the cowpea genotypes. Five cowpea genotypes were better slow rusting, eleven cowpea genotypes were slow rusting and eight cowpea genotypes were fast rusting. Interestingly, eleven cowpea genotypes showed resistance and eight cowpea genotypes showed moderate resistance to cowpea rust. The rust resistant cowpea genotypes identified in this work can be recommended for farmers to cultivate and used in breeding programmes to further improve the crop. This will maximize yields and increase cowpea production particularly in rust prone areas.