A rapid visual field screening technique for resistance of cowpea (Vigna unguiculata) to the legume pod borer Maruca testulalis (Lepidoptera: Pyralidae)

A rapid visual field screening technique for resistance of cowpea (Vigna unguiculata) to the legume pod borer Maruca testulalis (Geyer) was developed. The methodology involved measurement of two damage parameters: field examination of flowers for signs of M. testulalis injury or larval presence (i.e. rapid visual technique - flowers) and/or a pod evaluation index, from the ratio of pod load to pod damage (i.e. rapid visual technique - pods). Highly significant (P <0.01) correlations were obtained between the rapid visual field screening technique and the existing field screening technique. The latter is recommended as a fast and precise method for initial screening large collections of genotypes while the former should be used for more detailed selection and other resistance studies. The technique described here uses fewer variables than the previous method and thereby reduces costs while improving efficiency and precision.