Effect of Drought Stress and Plant Density on Yield and Some Physiological Characteristics of Pinto Bean (Phaseolus vulgaris L.) in Yasouj Region

In order to investigate the effects of drought stress and plant density on yield and some physiological characteristics of pinto bean (Phaseolus vulgaris L. cv. C.O.S16), a field experiment was conducted in split plot arrangement based on randomized complete blocks design with three replications at Research Farm of Yasouj University, Yasouj, Iran, in 2010. Treatments were conventional irrigation, drought stress at growth stage and drought stress at reproductive stage as main plots and plant density at four levels (15, 25, 35 and 45 plants/m2) as subplots. In this experiment, mean grain and biological yield, chlorophyll a, chlorophyll b, proline, carotenoid and protein content were measured. Result showed that there was significant interaction between drought stress and plant density on biological yield, grain yield and harvest index. Maximum biological yield and grain yield (11235 and 3368 kg/ha, respectively) was recorded at 35 plants/m2 density in conventional irrigation treatment, which had no significant difference with 45 plants/m2 density. The highest grain yield due to drought stress in growth and reproductive stages (2520 and 2260 kg/ha, respectively) was observed at 35 plants/m2 density and the lowest yield (2066 and 1953 kg/ha, respectively) was obtained at 15 plants/m2. Drought stress at growth and reproductive stages reduced grain yield and chlorophyll a content, and increased carotenoid content, chlorophyll b, proline and protein content of seeds. In general, density of 35 plants/m2, without any drought stress, and density of 25 plants/m2 at all drought-stress levels, is recommended for pinto bean (cultivar C.O.S.16) in similar environmental conditions to this experiment.