Responses of cow pea (Vigna unguiculata) varieties and their hybrids to variation in day and night temperature regimes

Abstract

SUMMARYThe effects of each of four contrasting combinations of two day (30, 26°C) and two night (24, 19°C) temperatures were studied on four cowpea varieties and their F1 hybrids. Early vegetative development was enhanced by the higher day, higher night temperature and flowering occurred first in plants receiving this treatment. The hybrids showed marked heterosis for leaf area but not for time to flowering. The ten genotypes studied showed correlated responses to increases in night temperature and differed in the degree of their response. The extent of the response (or stability) of varieties was often determined by the character values in the environment with the highest yield and heterotic hybrids were the least stable. Grain yield was highest in the lower day temperature environments but there was variation between genotypes in whether this occurred at the lower or higher night temperature. The pattern of responses shown by hybrids agreed with those of their parents indicating that stability was an inherited character. The results confirmed and extended those in earlier studies and emphasised the importance of a greater understanding of the nature of responses to the environment in selecting new varieties.