Evaluation of Yield and Yield Components of Some Pinto bean (Phaseolus vulgaris L.) Genotypes under Late Season Water Deficit Conditions

Introduction Drought or water deficit stress is the most important environmental factor which has severe negative impacts on crop yields, especially when the water stress occurs in the flowering stage. Iran is located in arid and semi-arid areas, therefore, attention to the effects of water deficit stress in different stages of plants growth seems necessary. Bean (Phaseolus vulgaris L.) is one of the most important legumes that has a major contribution to human diet and provides an important part of the human protein. According to studies, cultivation areas of legumes in Iran are about 97300 hectares and its total production is about 208350 tons of grain. Bean is a fast-growing plant (Tran and Singh, 2002), thus soil water must be sufficiently available to ensure its desirable growth and yield. The aim of this study was to investigate the effect of drought stress on yield and yield components of some pinto bean (Phaseolus vulgaris L.) cultivated in Zanjan province. Materials and methods An experiment was conducted as spilt plot based on randomized complete block design with four replications in Zanjan university research farm. Irrigation levels (control and drought stress) and genotypes (Local khomein, Sadri, Ks21193 and Ks21189) were set in the main and subplot, respectively. Water deficit stress was applied during flowering stage (50% of the plants were at anthesis). Sampling was performed to measure yield and yield components at the end of the growth period and final maturity. In this experiment number of pod per Plant, numberof grain per pod, 100 grain weight, grain yield, biological yield and harvest index were measured. Results and Discussion In this experiment it was observed that drought stress, genotype and interact irrigation×genotyps were significantly for all traits except biological yield. Drought stress reduced number of pod perplant, number of grain per pod, 100 grain weight, grain yield, biological yield and Harvest Index. Results indicated that Ks21189 genotype showed maximum number of pod perplant (9.2), number of grain per pod (2.91), 100 grain weight, grain yield (741.6 Kg.Ha-1), biological yield (2857 Kg.Ha-1) and Harvest Index (27.31%) under drought stress conditions. In addition, this genotype had the least reduction for all traits under water limitation conditions in comparison to control. These findings confirm the resistance of Ks21189 genotype to drought stress and stimulating this genotype to least reduction in Grain yield under water limitation conditions. Minimum number of pod per plant (4.52), number of grain per pod (1.62), grain yield (503.1 Kg.Ha-1), biological yield (2301.6 Kg.Ha-1) and Harvest Index (22.66%) was obtained in sadri genotype under drought conditions. Sadri genotype was identified as water deficit stress sensitive genotypes with reduction of yield up to 80.18%. In all genotypes, water deficit stress reduced grain yield due to reduced yield components (number of pod per plant, number of grain per pod and 100 grain weight). Conclusion The results of this experiment showed that water deficit stress on yield and yield components of bean genotypes had a negative effect. The highest and lowest yield and yield components were obtained from normal irrigation and drought stress treatments, respectively. Ks21189 genotype was more stable in water deficit treatment than other genotypes; however grain yield reduce in normal irrigation treatment was lower than other genotypes. Therefore, it seems that this genotype can be used as an appropriate genotype for supplemental evaluation in water deficit stress conditions. Correlation analysis showed significant and positive correlation between biological yield, number of pods per plant, number of grains per pod with grain yield. We concluded that genotypes with higher biological yield under drought stress conditions can produce maximum number of pods per plant, number of grains per pod and grain yield. Acknowledgments We would like to express our thanks to the Faculty of Agriculture, Sari Agricultural Sciences and Natural Resources University for supporting this study