Reaction of selected cowpea (Vigna unguiculata L. Walp) bfeedinglihcs to Xanthomonas campestrispv. vignicola

Abstract

Disease pressure in a cowpea screening field in Kano, a Sudan Savanna region of Nigeria, was increased by early planting of spreader lines of cowpea varieties susceptible to bacterial blight incited by Xanthomonas vignicola. Fourty five cowpea lines, previously found to be resistant to canker and blight (only 0 - 5 % of leaves with leaf spot) in the regular screening fields in 1993 and 1994 were screened in fields with high disease pressure. Nine cowpea breeding lines were confirmed as resistant to bacterial blight. Others were susceptible at varying degrees. Sixteen breeding lines were found to be resistant to canker induction and 12 were resistant to both blight and canker. Field screening under increased disease pressure by planting spreader lines two weeks earlier was more effective than the regular screening in fields with relatively low inoculum level, when spreader lines were planted along with breeding lines under test.