A SIMPLE SCREENING METHOD FOR DROUGHT TOLERANCE IN COWPEA

Abstract

A simple screening method was developed that accurately discriminates between drought tolerant and susceptible cowpea {Vigna unguiculata (L.) Walpl varieties. Wooden boxes (130 cm length. 65 em width. 15 em depth) made of 2.5 em thick planks were lined with polythene sheets, filled with a 12 em layer of soil and sand mixture (1:1) and kept on the table top in a screenhouse. Test materials were planted in the boxes with 10 em between rows and 5 em between plants within the row and watered daily until the partial emergence of the first trifoliate, after which watering was stopped. Percent permanent wilting was recorded at various intervals for each line until all the plants of the most susceptible lines were dead. Watering was then resumed and percent plant recovery in each line recorded. Based on the days taken to permanent wilting and percent recovery, cowpea lines IT9OK-59-2, Kanannnado, Dan IIa, TVu 11979 and TVu 11986 were drought tolerant while TVu 7778 and TVu 8256 were susceptible., Field and pot testing of these lines gave a close correspondence between drought tolerance in seedling stage and reproductive stage. The method has additional advantage that seedlings from the wooden boxes can be saved and transplanted for further progeny testing and selection.