Responses of two common bean (Phaseolus vulgaris L.) genotypes to deficit irrigation

About 90% of Iran extends over arid and semi-arid areas where drought stress is inevitably suffered by crops such as common bean. Due to limitations in water resources and importance of common bean in Iran, it is essential to evaluate common bean under water-deficit condition. The objective of this study was to determine effects of deficit irrigation on the yield, physiology and biochemistry of two bean genotypes. Experiments were conducted at the Agricultural Experimental Station, Shahr-e-Kord University, Shahr-e-Kord, Iran during 2014 and 2015. The plants were submitted to non-drought stress (NDS), moderate drought stress (MDS) and severe drought stress (SDS) under field conditions. Seed yield, phonological stages, leaf greenness, relative water content (RWC), stomatal conductance (SC), canopy temperature depression(CTD), intercepted PAR (PAR(1)), leaf area index(LAI), radiation use efficiency(RUE), lipid peroxidation, activity of enzymatic antioxidants, water use efficiency(WUE) and water productivity(WP) were recorded. The results indicated that, seed yield decreased due to deficit irrigation; RWC, SC and leaf greenness were lower under MDS and SDS conditions; whereas deficit irrigation had not equal effects on WUE, WP and RUE of the tested genotypes. Under NDS condition, genotype KS21193 is superior than genotype K521486 in many traits including seed yield, RUE, PAR(1), WUE and WP. While, the situation is changed under water deficit conditions, so that K521486 is superior than KS21193 in terms of the majority of traits measured such as seed yield, RWC, RUE, SC and CTD before irrigation, WUE, WP. In fact, genotype KS21486 is more tolerant to water deficit conditions than another genotype. This was attributed to various mechanisms such as stress escape, decreased chlorophyll, LAI and PAR(1), more conversion efficiency of received water and PAR into dry matter and economic yield and more efficient enzymatic antioxidants.