CALLI INDUCTION, REGENERATION AND RAISING OF MUTANT POPULATION IN INDICA RICE CULTIVARS FOR SCREENING UNDER SALT STRESS Apekshita Singh*, Ashwani Pareek 1 and Suman Sharma 2 Amity Institute of Biotechnology, Amity University, Sector-125, Noida, India. 1 School of Life Sciences, Jawaharlal Nehru University, New Delhi - 110 067, India. 2 Ramjas College, University of Delhi, Delhi - 110 007, India. Abstract Rice (Oryza sativa L.) is one of the most important food crops in the world. The successful regeneration protocols are important for introgression of new traits and development of better cultivars. Therefore, in vitro callus induction and regeneration was studied in three indica rice varieties, Swarna, Pokkali and IR 64, widely grown in Indian continent. The highest percentage of calli induction and regeneration was reported in Pokkali. The calli induction varied from 80% to 89% across three varieties. The MS (Murashige & Skoog) medium supplemented with various plant growth regulators such as 2,4-D (auxin), BAP (benzyl aminopurine) has been successfully used in the study. The two factors that stimulated the large percentage of callus induction are concentrations of 2,4-D and casein hydrolysate (CH). The best conditions for the maximum regeneration in the three varieties varied from using only MS with two hormones or additional supplements just as in calli induction media. The combinations for regeneration were MS + BAP + NAA; MS + CH + BAP + proline; MS + BAP + NAA + kinetin, respectively in Pokkali, Swarna and IR 64. The percentage of regeneration varied from 70 to 90%. The present study also analysed the effect of gamma irradiation and thereby raised a mutant population in cv IR 64. Rice mutant population showed variation for different characters, which can be utilized for forward genetics approach. Calli and field mutants were also screened for salt stress. Key words : Rice cultivars, in vitro calli induction, regeneration, mutation, salt stress. Plant Archives Vol. 16 No. 1, 2016 pp. 321-326 ISSN 0972-5210 Introduction Rice (Oryza sativa L.) one of the most important staple food crops in the world, is consumed by more than one third of the world population. It is an annual grass belonging to family Poaceae. There are two varieties of rice – indica and japonica . The recent years have witnessed research in rice biotechnology to produce transgenic rice plants with improved yield and quality, increased resistance to biotic and abiotic stresses and value added grains such as golden rice (Lee et al., 2002). There is an ever increasing demand of rice in the growing population in India and China (IRRI, 2014). Rice covers half of the arable land used for agriculture in many Asian countries. It is estimated that rice production has to be increased by at least 50% by 2025. The most viable option is to increase the yield potential of cultivars as well as better agronomic characters. Recent advancement in biotechnology has enhanced the introgression of new and potentially beneficial genes into cultivated varieties. Routine transformation in rice is difficult and it is genotype specific. Therefore, successful regeneration in recalcitrant plants is important biotechnological advancement to raise new varieties with better tolerance to stresses. The chosen material in the present study are three indica rice varieties IR64, Pokkali and Swarna. IR 64 is grown in the tropics. It is an elite variety carrying many valuable agronomic traits related to yield, plant architecture, grain quality, and good taste. It is a moderately salt sensitive variety. Pokkali rice, with a Geographical Indication registration, is known for its salt-resistant genes and is cultivated in the water-logged coastal regions of Kerala, India. Rice has also established itself as a model crop (Shimamoto et al., 2002). The availability and screening of large mutagenesis population is prerequisite for genetic *Author for correspondence : E-mail: asingh20@amity.edu