Genetic Variability and Number of Genes Conditioning Heat Tolerance in Cowpea.

Cowpea is a popular food crop in Texas and other Southern States of USA, and it is a good source of protein, minerals, vitamins, and antioxidants providing good nutrition as well as health benefits. The cultivation of cowpea in the United States is declining due to numerous production constraints including drought, heat, and pests. Therefore, a systematic program has been initiated to develop improved cowpea varieties with tolerance to heat and drought, and resistance to aphid. A total of 41 cowpea varieties were planted in College Station on June 12, 2011. The temperature in July and August covering the reproductive phase of cowpea was above 100⁰F. This temperature range provided excellent opportunity to screen cowpea varieties for heat tolerance, and the results showed significant genetic variability for heat tolerance in the germplasm for heat tolerance. Selected cowpea varieties were grown in the field, as well as, in the hot greenhouse to confirm the genetic variability identified in year 2011, and the results showed that tolerant genotypes (IT98K-205-8 (P1) and GEC) produced significantly higher seed yield/plant compared to susceptible genotypes (IT98K-589-2 (P2) and IT98K-476-8) in two trials. F1, F2, BC1F1P1, and BC1F1P2 populations were developed from P1 and P2, and the developed populations were grown in hot greenhouse to study the inheritance of heat tolerance in summer 2013. The results showed F2 ratio very close to 15 (like P2):1 (like P1), and F1 showed heat susceptibility like P2, which indicated that heat tolerance is controlled by two recessive genes. P2 also dropped significantly higher percentage of flowers compared to P1.