Ecophysiological response of Mungbean cultivars to drought stress under different solfate potassium levels in Khouzestan

In order to assess the eco-physiological response of mungbean genotypes to drought stress in tropical climate of Khouzestan, an experiment was conducted as a factorial split plot complete randomized block design with three replications during the summer seasons of 2010-11 in Safiabad Agricultural Research Center of Dezful. Different irrigation levels and rates of potassium fertilizer application were placed in main plot as factorial while genotypes were distributed in sub-plots. Levels of irrigation included irrigating at 120,180 and 240 mm of evaporation as the main factor. The sub-plot included the application of potassium fertilizer in three levels: 0, 37.5 and 75 kg/ha. Five mungbean genotypes included Partow and Indian heap cultivars, and VC6173, CN95 and KPS1 promising lines which were considered as the other sub-plot. Evaluated characteristics included seed yield and yield components, protein percentage, biological yield, leaf area index (LAI), harvest index (HI), a, b and ab chlorophyll content, total chlorophyll content in flowering and pod setting stages, stomatal conductance, stress tolerance indices and traits related to the seed vigor in normal storage and deteriorative conditions. Results showed that water deficit stress significantly affected seed to pod ratio,biological yield, seed yield, protein percentage, HI and physiological traits including LAI, average chlorophyll content and mild drought stress reduced the seed yield by 30.4 and 21.9% compared to optimal conditions, respectively. The application of potassium increased water deficit stress tolerance due to its positive role in better absorption of other nutrients especially nitrogen and phosphorus and improved most of the traits compared to no fertilization treatment. stress had generally a negative significant correlation with mungbean physiological characteristics and these characteristics had a significant effect on seed yield components too. The application of potassium improved yield components significantly due to its significant positive correlation with plant's physiological characteristics. The difference of physiological traits' and yield components' changes among genotypes were significant. Among the studied treatments, irrigation at 120 mm, the application of 37.5 kg/ha potassium and using the Partow and Indian heap cultivars and, VC6173 promising line is recommended in order to obtain an economic mungbean yield in Khuzestan.