Use of carbon isotope discrimination technique to sustain rice productivity under stressed and low land irrigated ecosystem of Pakistan

Carbon isotope discrimination (δ) is an indirect screening tool for breeding cultivars against water stressed conditions. previous studies exhibited that leaf and straw δ,under water stress,have positive and significant association with grain yield in rice genotypes. current study was performed to assess the efficiency of δ technique at farmer's field level. five rice genotypes (rsp-1,rsp-2,rsp-3,rsp-4 and rsp-5),grown in lysimeters under well,medium and low water conditions,were subjected to δ analysis for selection of high yielding water use efficient genotypes. rsp-1 and rsp-2 were identified as the high yielding (4.22 and 4.23 tons ha-1 respectively) and water use efficient genotypes (9.48 and 8.87 gm/m2/mm respectively) under lysimeters. for field study,three yield trials were conducted. in preliminary yield trial,under curtained water supply of 900mm for a complete crop cycle),rsp-1 and rsp-2 produced 6.73 and 7.27 tons ha-1 paddy yields respectively. a multi location yield trial,to test the yield stability,indicated above average and average stability of rsp-1 and rsp-2 respectively. yield performance of rsp-2 (4.1 tons ha-1) under highly saline field conditions (ec: 10dsm-1) opened the prospects for simultaneous selection of rice genotypes against water limited and saline conditions. according to our knowledge,this is the first report depicting the utility of δ technique to select the rice cultivar for water limited and saline soil conditions of low land irrigated rice ecology of pakistan.