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.
