Abstract

Cowpea (Vigna unguiculata L. Walp) is an important grain legume in most parts of Sub Saharan Africa. However, viral diseases are a major limiting production factor causing significant yield losses. An experiment was conducted to evaluate the reaction of 105 different cowpea genotypes to viral infection in different agro-ecological zones of Uganda. The aim was to identify genotypes that could serve as sources of resistance to virus infection. Virus infection in these experiments occurred naturally through insect vectors. Results showed that there were significant differences in disease reaction among genotypes within and among agro-ecological zones in terms of Area Under Disease Progress Curve (AUDPC) and incidence. Interactions of genotype by season (GXS), genotype by location (GXL) and genotype by location by season (GXLXS) also significantly affected reaction to viral infection among genotypes. Introduced cowpea genotypes exhibited a more susceptible viral disease reaction compared to the landraces over the two seasons in the three locations. A number of landraces such as WC32, WC18, NE43, NE15, WC35B consistently showed resistance to virus infection in the three locations and therefore could be good sources of resistance. Low disease pressure (AUDPC) was also recorded on SECOW2W (released variety) as reported by previous studies. The landraces also gave consistently higher grain yield values compared to the introduced genotypes. Overall, data from this study showed that locally adapted cowpea genotypes offer resistance to virus infection and may be desirable germplasm for Ugandan cowpea breeding programs.

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