Using Vigna unguiculata genotypes to relate photosynthetically active radiation, chlorophyll content index and stomatal conductance

Abstract

Crop response to environment is determined by genetic characteristics of developed cultivars. Phenotypic markers have been shown to be directly linked to genotypic markers. The objective of this study was to use local cowpea (Vigna unguiculata L.) germplasm to determine relationship between intercepted photosynthetically active radiation (PAR), a microenvironment factor, with chlorophyll content index (CCI), stomal conductance and crop growth under field conditions. These physiological factors are useful for enhancing the value of phenotypic and genetic markers. Multivariate analysis confirmed the significant differences between three cowpea genotypes (p ≤ 0.05) in terms of response to microenvironment and grain yield. The patterns of change in temperature, rainfall and evapotranspiration were related to those of PAR, CCI and stomatal conductance during crop growth. Despite the consistent pattern of change in PAR, CCI and stomatal conductance in relation to plant growth during the season, regression analysis indicated weak correlation between plant growth PAR, microclimate-related variables across genotypes. However, the positive relationship between PAR and early plant growth could be explained in the context of a highly significant correlation between CCI and stomatal conductance. Consequently, the study was able to provide evidence of linkage between a cowpea morphological trait and productivity in a manner that also differentiated the three cowpea varieties for future pedigree determination research.