THE USE OF NONDESTRUCTIVE MEASUREMENT AND PHYSIOLOGICAL MODELS OF YIELD DETERMINATION TO INVESTIGATE FACTORS DETERMINING DIFFERENCES IN SEED YIELD BETWEEN GENOTYPES OF DESI CHICKPEAS (CICER-ARIETINUM)

Mathematical models for yield determination are most commonly used to estimate the probable final crop yield in a given circumstance based on measured physiological parameters but the reverse may be done. Simple models of yield determination may be used to estimate the model parameters associated with a measured final product. One can then obtain a better understanding of the physiological attributes of large numbers of genotypes without the labour intensive destructive measurements usual to interpretive physiology. This approach has been demonstrated using 120 chickpea genotypes. The total mass, seed yield, vegetative (D(v)) and reproductive (D(r)) durations were observed and the crop growth rates (C) and partitioning to seed (p) estimated. The contribution of variation in C, D(r), and p to the variations in seed yield were analysed by regression techniques. Contrary to expectations based on other crops, the variations in C were an important source of yield variation, rather than variations in p and D(r). Counteracting relationships existed between the parameters of the yield model; C was inversely related to D(r) and p. The influence of these features of chickpea yield determination on genotype by environment interactions and maximising yield are discussed.