Application of a simple crop physiological model based on some yield determinants to assess the productivity of pigeonpea genotypes in northern Ghana

Pigeonpea (Cajanus cajan (L.) Millsp.) is cultivated in northern Ghana mainly on marginal soils towards the end of the rainy season. The crop, therefore, subsists on residual soil moisture for most part of its growth. Little is known, however, about varieties best adapted to this zone under such harsh conditions. Twenty early-maturing pigeonpea lines were, therefore, evaluated in the northern Guinea savanna ecology of Ghana with the objective of determining the physiological basis of their yields. Grain yields (Y), reproductive development (RD), total biomass (T), crop growth rates (CGR), harvest indices (HI) and the rate of partitioning (p) of photosynthates to reproductive sinks were estimated. Wide variations were observed for pod yields and the yield determinants. No direct links were observed between RD and the other parameters. However, there were close correlations between grain yield, T, CGR, HI and p on the other. The possibility of developing genotypes which combine high grain yield, T, CGR, HI and p in a single genetic background is, therefore, achievable. Genotypes with such attributes are most desirable to produce grains for human consumption and fodder for livestock. This study provides an example of how a simple physiological model can enhance the selection efficiency of plant breeders, through a better understanding of the genetic materials that are handled. (Ghana Journal of Agricultural Science, 1997, 30(1): 3-8