Variation in Canopy Temperature and Its Relationship with Drought Tolerance in Cowpea [Vigna unguiculata (L.) Walp] Recombinant Inbred Lines

Aim: The objective of the study was to develop drought tolerant cowpea inbred lines using leaf canopy temperature and grain yield under contrasting soil moisture conditions in the field.

Study Design: Split plot design was used for the experiment.

Place and Duration of the Study: The study was carried out in February and December 2016 and 2017 at Golinga and Libga irrigation sites respectively in the Guinea Savanna ecology of Ghana.

Methodology: The watering regimes at two levels were the main plots and the 22 recombinant inbred lines, with 2 parental checks, were the subplot factor. Treatment was completely randomized and in 3 replications given a total of 144 plots. Various agronomic data were taken and statistical analysis was done using Genstat edition 12. Leaf canopy temperature was used to calculate stress susceptibility index during the period of stress imposition.

Results: The genotypic and phenotypic correlations between yield and chlorophyll were r = -0.69 and r = -0.528 respectively. Negative correlations indicate that moisture stress delayed the onset and time to flowering and consequently reduction in yield. Under well-watered conditions, the susceptible lines had yields of 1.69t ha-1 whereas the low temperature inbred lines had mean yields of 1.9 t ha-1. The mean yields of drought susceptible inbred lines (high temperature) lines had 1.1t ha-1, while that of the drought tolerant (low temperature) lines had mean yields of 1.24t ha-1.

Conclusion: The study revealed that genotypes exhibited variation in mean canopy temperature across the two watering regimes. Watering regimes for canopy temperature were significant for days 39, 45, 48 and 54 days after planting. Leaf canopy temperature has proven to be a useful physiological index for selecting drought tolerant cowpea under field conditions.