Screening for resistance to <i>Maruca testulalis</i> Geyer in cowpea (<i>Vigna unguiculata</i> L.) Walp

Abstract

Summary Screening methods were devised to select cowpea genotypes with resistance to yield loss oaused by larvae of Maruca testulalis (Lepidoptera, Pyralidae). More emphasis was placed on flower damage than on pod damage. One hundred and forty genotypes of wild and cultivated cowpeas and four of related Vigna speoies were screened in the first year; 25 of these were selected for rescreening in the second year. Resistance to flower damage was assessed by the ratio of number of pods under unsprayed conditions to number of pods under sprayed conditions and resistance to overall post-flowering damage by ratio of seed yield under unsprayed conditions to seed yield under sprayed conditions. The absolute numbers of pods and seed yields from unsprayed plots were also taken into account. Several genotypes of moderate resistance and one of high resistance were located among cultivars of different origins. It is suggested that the empirical approach to the search for insect resistance, particularly the comparison of unprotected with protected yields, has great potential, especially for seriously damaged crops.