ADAPTATION OF SPRING-SOWN CHICKPEA TO THE MEDITERRANEAN BASIN .2. FACTORS INFLUENCING YIELD UNDER DROUGHT

Drought during the late vegetative and reproductive stages of developm ent is the major constraint to the productivity of spring-sown chickpe a in the rainfed farming systems of West Asia and North Africa. This p aper examines the contribution of crop traits to yield under drought a nd determines the relative contributions of drought escape, yield pote ntial and a drought response index (DRI) to such yield. In years with mild drought (1986/87 and 1987/88), high biomass, high yield potential and high harvest index were highly correlated with grain yield. Durin g the severe drought of 1988/89, early flowering and low straw yield, high harvest index, yield potential, pod and seed number and seed mass were correlated with rainfed grain yield. Differences among chickpea cultivars in rainfed (drought) yield were partitioned into drought esc ape, yield potential and DRI. Drought escape accounted for 41% in 1986 /87, 37% in 1987/88 and 69% in 1988/89; yield potential accounted for 47%, 37% and 1%, respectively; and DRI accounted for 4%,17% and 17% of the variations, respectively. The three factors combined explained an average of 90% of the variability in grain yield. The DRI was used to quantify tolerance or susceptibility of a cultivar independently of d rought escape (early flowering) and yield potential. Of the traits whi ch were significantly associated with drought yield, high harvest inde x, large number of pod and high seed mass were associated with drought escape (early flowering), while deep root system, high leaf water pot ential at dawn and large number of seeds were associated with drought tolerance (DRI).