Development of a glasshouse assay for screening for partial resistance to P. vignae in cowpea

Abstract

A glasshouse-based root inoculation method for screening for partial resistance to P. vignae was developed. By infecting potting mix with 0.01 g dry weight mycelium kg-1 dry weight of mix, inoculum levels comparable to those found under natural conditions of infestation in the field were obtained. This screening assay was used to compare resistance levels of eight cowpea lines with those obtained following hypocotyl inoculation with races 1-4 of P. vignae. One of the lines tested, CPI 84853, expressed partial resistance to all four races in the root inoculation assay, although it was highly susceptible to race 4 following hypocotyl inoculation. This line, along with the root assay described in this paper, form a basis for the development of new cowpea cultivars with more durable resistance to P. vignae.