Effect of timing of drought stress on growth and grain yield of extra-short-duration pigeonpea lines

Four extra-short-duration (ESD) pigeon pea (Cajanus cajan) lines in 1991 and eight ESD lines in 1992 were grown with adequate soil moisture throughout their growth or subjected to drought coinciding with the vegetative, flowering and pod-filling stages under rainout shelters (India). In both years, drought stress treatments significantly reduced dry matter accumulation and seed yield. The extent of reduction in seed yield varied with the line and stage of stress imposition. Drought stress at the flowering stage caused greater reduction in total dry matter and seed yield than the stress imposed during the preflowering and pod-filling stages. Drought stress coinciding with the flowering stage reduced seed yield by 40-55% in 1991 and 15-40% in 1992 in different lines. ESD genotypes could extract moisture from up to a metre depth during preflowering and flowering stage stress but less during the pod-filling stage stress. Genotype ICPL 88039, followed by ICPL 89021, consistently showed the lowest sensitivity to drought stress at flowering. Protracted drought stress commencing from the preflowering to flowering or from the flowering to pod-filling stages was more harmful than stress at the individual stages. The reduction in yield under drought stress could be attributed mainly to less total dry matter accumulation, but also increased abscission of plant parts. The results suggest variation in sensitivity of ESD lines in relation to timing of stress, which should facilitate targeted screening for different intermittent moisture stress environment