Characterization of differential aluminum toler-ance among rice genotypes cultivated in south india

Six genotypes of rice (Oryza sativa L.) commonly cultivated in South India have been subjected to screening for their tolerance to Al toxicity in hydrocultures. Ten-day-old seedlings were exposed to six levels of Al (0, 74, 148, 222, 296, and 370 μmol/L) supplied in the nutrient solutions at pH 4.0. The seedlings were grown under controlled environmental conditions in growth chambers and the nutrient solutions were replenished once a week. After three weeks of A1 stress, growth characteristics of the rice genotypes were compared. The recommended growth parameters such as root and shoot growth, number of roots, leaf tip scorching, dry matter (biomass) production by roots and tops, relative growth reduction in roots (RGRR) and shoots (RGRS), and root tolerance index (RTI) and shoot tolerance index (STI) have been used as markers of A1 response.