Traits for Screening and Selection of Cowpea Genotypes for Drought Tolerance at Early Stages of Breeding

Abstract

The association of leaf water content with yield-attributes such as pod setting and number of pods/plant and seed yield in cowpea was examined using midday drop of leaf relative water content (RWC) determined from morning (800 h) and midday (1330 h) measurements of RWC. Midday drop of RWC was significantly correlated to pod setting ratio (R² = 0.80, P < 0.01), number of pods/plant (R2 = 0.87, P < 0.01) and seed yield (R² = 0.37, P < 0.05). There was a significant genotypic variation for leaf water potential (LWP) at 800 and 1330 h and for RWC at 1330 h. Significant genotypic differences were also observed in pod setting ratio, number of pods/plant, number of seeds/pod, 1000-seed weight, biomass and seed yield. Pod setting ratio was significantly and positively correlated with number of pods/plant (R² = 0.80, P < 0.01) and seed yield (R² = 0.38, P < 0.05). These results showed that the genotypes with a smaller reduction in midday drop of RWC produced a larger number of pods/plant and consequently had higher seed yield as compared with a larger midday drop of RWC. The results also showed that there was a large genotypic variation in the midday drop of RWC, which was correlated with yield-attributes and seed yield. It may therefore be possible to use midday drop of RWC as a screening and selection trait for drought tolerance of cowpea genotypes.