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Laboratory and screenhouse assays for evaluating cowpea resistance to the legume pod borer
Two resistance screening assays were developed for evaluating cowpea Vigna unguiculata (L.) Walp resistance to the legume pod borer (MPB), Maruca testulalis Geyer, one of the most intractable pest problems of this important food crop. The first assay, the dual-choice arena test (DCAT), provided a choice of two varieties to the MPB larva for 72 h. A preference hierarchy representing the resistance ranking of test varieties was obtained using a preference ratio. The relative resistance of a given test line when compared with either the susceptible or resistant check or another test line, was determined using a feeding index. Two wild cowpea relatives, TVNu 72 and TVNu 73, were identified with high levels of resistance using the preference ratio and feeding index. The second assay, the intact pod test (IPT), was a no-choice test conducted in the screenhouse. About 2 weeks are needed to complete the test, but important and conclusive information on seed damage was obtained after 72 h of feeding exposure. In this test TVNu 72 showed resistance similar to that determined by the DCAT. The two assays are complementary and provide useful information on antixenosis and antibiosis, and can therefore be used in sequence. Various attributes of the DCAT and IPT are discussed.
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Permanent link to this itemhttps://hdl.handle.net/20.500.12478/5931
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