PHYSIOLOGICAL-BASIS OF YIELD VARIATION IN SHORT-DURATION PIGEONPEA GROWN IN DIFFERENT ENVIRONMENTS OF THE SEMIARID TROPICS

Five short-duration pigeonpea (Cajanus cajan (L.) Millsp.) genotypes w ere grown at three plant populations in three locations during the 198 6 and 1988 rainy seasons, to determine the physiological basis of obse rved variations in yield. Significant differences were found in seed y ield (Y), crop growth rate(C), and the durations of vegetative (Dv) an d reproductive (Dr) growth, and partitioning (P). These were attributa ble to genotypes and their interactions with environments (except for C). Variation in C, Dr; and P together explained 78 % of the observed variation in Y due to different genotypes and environments. Crop growt h rate alone contributed about 71 % of the variation in Y, and reached an optimum value of around 6.5 kg ha(-1) degrees Cd-1. Crop growth ra tes increased with the duration of the vegetative period and with plan t population. However, a negative relationship between C and P resulte d in plant population having little effect on seed yield. The maximum- yielding genotype, ICPH 8 had the highest C and an intermediate P.