DROUGHT TOLERANCE IN CHICKPEA AS EVALUATED BY ROOT CHARACTERISTICS, PLANT WATER STATUS, MEMBRANE INTEGRITY AND CHLOROPHYLL FLUORESCENCE TECHNIQUES

摘要

Root traits, such as depth and root biomass, have been identified as the most promising plant traits in chickpea for terminal drought tolerance. With this objective, five contrasting genotypes of chickpea, viz. ICCV-4958, H-208, HC-5, RSG-931 and CSJ-379, having wide adaptability to drought prone areas at national level were assessed for various root characteristics under two environments, i.e. irrigated and rain-fed. The sampling was done at full bloom stage and there were significant differences in the rooting depth among the genotypes both under irrigated and rain-fed conditions. The chickpea roots penetrated to a minimum depth of 92 cm in CSJ-379 and maximum of 122 cm in ICCV-4958 under rain-fed conditions. The rooting depth remained higher under rain-fed than irrigated environment. Under irrigated conditions, the chickpea roots were able to grow to a maximum depth of 99 and 97 cm in HC-5 and ICCV-4958, respectively. Among the genotypes, biomass per plant of the root was higher in ICCV-4958 (6.7 g) and HC-5 (5.6 g) under rain-fed conditions. Similar observations were recorded for root/shoot ratio, dry weights of stem, leaf, nodules and total dry weight per plant. The moisture stress increased the biomass partitioning towards the roots. The water potential (psi(w)), osmotic potential (psi(s)) and relative water content (RWC %) of leaf were 0.98 MPa, 1.82 MPa and 60%, respectively, in the genotype HC-5, and 1.02 MPa, -1.72 MPa and 64%, respectively, in ICCV-4958 under rain-fed conditions. The rates of photosynthesis, and transpiration, values of the stomatal conductance and photochemical efficiency/quantum yield as indicated by F-v/F-m ratio were in the range of 6.7 to 10.6 (mu mol m(-2) s(-1)), 1.27 to 2.38 (mmol m(-2) s(-1)), 0.23 to 0.48 (mol m(-2) s(-1)) and 0.457 to 0.584, respectively, under rain-fed conditions. Genotypes HC-5 and ICCV-4958 also maintained higher photosynthetic and transpiration rates and F-v/F-m ratio than others. The maximum F-v/F-m values in these genotypes were correlated with the higher photosynthetic rate and dry matter yield per plant. Relative stress injury (RSI %) values in HC-5 and ICCV-4958 noticed were 25.3% and 23.7%, respectively. The results of this study indicate that under rain-fed conditions, genotypes ICCV-4958 and HC-5 had higher dry weight of stem, leaves, roots, nodules and total dry weight per plant, rooting depth, root/shoot ratio, photosynthetic and transpiration rates, photochemical efficiency and better plant water status but lower stomatal conductance than other genotypes. These traits are directly associated with maximum seed yield per plant, i.e. 15.6 g and 14.7 g per plant, respectively, in these genotypes. Therefore, both the genotypes in future can be used in crop improvement programme of chickpea breeding for drought tolerance.