Abstract
Two heat-tolerant cowpea [Vigna unguiculata (L.) Walp.] lines (Prima and TVu 4552) and three heat-sensitive lines (Magnolia, 7964, and Bambey 23) were assessed in the field and in growth chambers in 1987 and 1988 for their tolerance to heat. The average daily minimum and maximum air temperatures in the field were 24ºC and 43ºC, respectively. In the growth chambers the day and night temperatures were 33 and 30 (±2)ºC, respectively. Only Prima and TVu 4552 produced high pod numbers per peduncle under field and growth-chamber conditions, which were 2.2 and 1.3 (Prima) and 1.0 and 1.1 (TVu 4552) pods per peduncle, respectively. The heat-sensitive lines Bambey 23, Magnolia and 7964 produced individually about 0.6 pods per peduncle in the field and 0.22, 0.65 and 0.5 in the growth chamber, respectively. A strong correlation was observed between field and growth-chamber conditions for pod productivity (r = 0.81) but not for floral bud development (r = -0.19). These figures indicate that selecting for hear-tolerant cowpea genotypes for high pod yields under field conditions is as effective as using growth chambers with controlled environments.
