EFFECTS OF WATER STRESS ON LEAVES AND SEEDS OF BEAN (Phaseolus vulgaris L.)

To determine the changes of nitrogen contents in the leaves and seeds of common bean (Plzaseolus vulgaris L.) genotypes under contrasting moisture regimes, two field experiments were conducted as split-plot in a randomized complete block design with four replications. Two levels of irrigation (irrigation after 55-60 and 100-110 mm evaporation from class A pan, respectively) and eight genotypes including white beans (WA4502-1 and WA4531-17), red beans (Akhtar, D81083 and AND1007) and Chitti beans (KS21486, MCD4011 and COS16) were studied in the main- and sub-plots, respectively. Leaf nitrogen (N) and proline contents were measured at two growth stages (pre-flowering and pod filling period). Grain yield, seed N and seed protein contents were measured at harvest. The results indicated that white beans had lower leaf N and seed protein contents than red and Chitti beans under both irrigation regimes. Under drought conditions, AND1007 and COS16 showed markedly higher levels of accumulation of leaf N and proline. Seed protein was higher in Chitti beans. Water deficit reduced the leaf N by 19% and 28% at two growth stages and grain yield by 39.8%. By contrast, proline content of all genotypes was increased by 105%. Seed N and protein contents had the lowest reductions under drought, while increasing N and proline contents in the leaves increased grain yield under this condition. Besides, lower values of seed N and protein is associated with higher yields of genotypes. Totally, based on the grain yield, red beans were more drought-susceptible than white and Chitti groups.