Development and screening of cowpea recombinant inbred lines for seedling drought tolerance

The use of multiple traits for drought study affirms the complexity of drought tolerance in cowpea. Despite the availability of several traits for drought tolerance evaluation, the rapid screening technique used by many scientists for seedling drought in wooden boxes is the simplest method for screening large populations. The objective of this study was to select drought tolerant cowpea recombinant lines developed from a drought tolerant and susceptible parent using the wooden box screening technique. Two hundred Recombinant Inbred Lines (RILS) an F2:6 generation were used for the study. The parents were drought tolerant line crossed with susceptible line. Screening was done in wooden boxes and plants stressed for 4 weeks and in two sessions. Leaf wilting, relative water content, chlorophyll content during stress, and recovery from drought data were taken. Results from this study showed significant differences (p < 0.05) for relative chlorophyll content for the 4 weeks of water stress and relative water content taken on the second week of water stress for all 200 inbred lines, but no significant differences were observed for the parental checks. Relative water contents taken for RILS during water-stress ranged between 70-20% for drought tolerant and drought susceptible lines respectively. The parental lines used as checks both had relative water contents of 60%. Relative water content for the second experiment ranged between 74-22% for tolerant and susceptible RILS respectively. About 12 inbred lines consistently performed well for recovery, 13 RILS were susceptible. RILS that maintained a higher relative water and chlorophyll contents, with high proportion of survived seedlings were 11. Potential seedling drought tolerant RILS have been identified. Key words:  Cowpea, leaf wilting, chlorophyll, recombinant inbred lines, drought tolerance, relative water content.