Investigation of Factors Determining Genotypic Differences in Seed Yield of Non-irrigated and Irrigated Chickpeas Using a Physiological Model of Yield Determination

Physiological attributes determining yield, both under drought and under irrigated conditions, of some advanced chickpea lines of recent origin were investigated over two seasons using a physiological model. Total shoot biomass, grain yield, and vegetative (D_v) and reproductive (D_r) durations were measured and the crop growth rates (C) and the rate of partitioning to seed (p) were estimated. The contribution of model parameters to variations in grain yield were determined by path analysis, and the relationships of the yield determinants with seed yield were obtained by regression techniques. The model was found to be suitable for chickpea, and when the parameters were fitted the model explained 98% of the variation. Irrigation enhanced D_r and C. While C was the major single yield determinant, the combination of C and p in non-irrigated environments explained most of the grain yield variation. D_v and D_r exhibited a negative relationship while C and p exhibited a positive relationship under drought stress and a negative relationship in the irrigated environment. There were indications of the existence of an optimum D_v for maximum C among the genotypes, suggesting the need to select for optimum duration genotypes. As high values for p and C in severe drought stress and D_r and C in the irrigated environments are advantageous for high yield, separate breeding strategies are needed for different soil water environments.