Selection of castor germplasm with important traits for drought tolerance under field conditions

India is the leading producer of castor with major area under rainfed cultivation. To improve the productivity in rainfed areas, varieties and hybrids with drought tolerance and water use efficiency (WUE) have to be developed. Hence, it is essential to select germplasm with important traits viz: for root growth, WUE, drought tolerance etc. Fourteen castor genotypes with more root volume (225–557 cm³), root dry weight (38–122 g/pl) and one poor root check (root volume of 94 cm³, root dry weight of 15.2 g/pl.) identified by screening in root structures were sown in field for 2 years. The experiment was conducted during 2010–2012 in late rabi (November first week) in split plot design with three replications and water stress was imposed from 30 to 90 DAS by withholding irrigation. Results revealed severe growth reduction in terms of reduced plant height, leaf number, stem girth, branches and total dry matter (56% reduction) with water stress. Seed yield of primary spike reduced significantly with water stress, but the reduction was less pronounced in secondaries and compensated in later order spikes. The reduction in total seed yield was 35%, total dry matter at harvest was 10% and harvest index was 14% with drought stress (pooled means). Among the Ricinus germplasm (RG) studied, RG 1494 and RG 2139 recorded <20% reduction in seed yield with low drought susceptibility index of <0.5. The root volume (310, 557 cm³), root dry weight (122, 93 g/pl.) of RG 1494 and RG 2139 recorded in root structures was also more. Chlorophyll content measured with SPAD chlorophyll meter reading and bloom content increased in water stressed plants as an adaptive feature. RG 1494, RG 2139 showed good performance during both years and also recorded better root and shoot growth characters, and can be used in drought breeding programs.