Genetic variability in some faba bean (Vicia faba L.) genotypes under different levels of drought and during different growth stages

Twenty two faba bean genotypes were tested five water treatments over two locations, Shambat and Hudeiba, during season 2001/02, to estimate the amount of genetic variability, heritability, correlations for drought tolerance parameters (Yw, Yd, Yd/Yw, GMP and SSI) in faba beans under different levels of water stresses. Moreover, the correlation between yield, its components and other traits and yield stability were determined. The water treatments used were watering every 7-days (DO), water stress using intervals of 14-days during vegetative and flowering stage (D2) and pod filling stage (D4). Split plot design with three replications was used. The induction of stress was severe enough to create significant differences under most of water treatments, except D3 which had been of less effect. Significant differences for most of the traits were found among the twenty two genotypes. Heritability exhibited wide range of variation. The highest heritability and genetic advance were recorded for 100-seed weight. Significant positive phenotypic and genotypic correlations were found for seed yield/plant with number of podded nodes/plant, number of pods/plant, number of seeds/plant and harvest index. Genetic variability and heritability are reduced with increase in drought severity. Severe drought as in D2 and D4 treatments decreased the genetic variability compared with D1 and D3. Heritability of drought tolerance parameters increased under non-severe water stresses, which could be atrributed to the increase in genetic variability. Tolerant genotypes during vegetative and flowering could also be tolerant during pod filling based on mild water stress. However, under severe water stress tolerant genotypes under vegetative and flowering could not be tolerant during pod filling. Correlations between yield under the different water stresses treatments differ according to the severity of drought (D1 and D3). Positive and significant correlation was observed with less drought, and negative and non-significant when drought was severe (D2 and D4). The genotypes that possess drought tolerance and high yield stability were D.E.2 under D1, Berber1 under D2, Mass55 under D3, and C.52/1/1 under D4. The high stability and drought tolerance proved that these genotypes are better adapted to drought stress and can be used to improve faba bean drought tolerance