Characterization of differential aluminum tolerance among rice genotypes cultivated in South India

Abstract

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 Al 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 Al response.

The rice genotypes tested revealed a wide range of responses to Al. Although only six levels of Al were employed, a good degree of separation in the responses of rice genotypes was observed only at 222 μmol/L. Therefore, this concentration was chosen for evaluating the relative responses. The genotypes IR 50, IET 1444, Co 31, and Co 37 gave increases in root growth, while IR 60 and ADT 36 showed inhibition with Al stress. Further, the RGRR and RGRS data also indicated that the growth of Co 31 and Co 37 was increased by Al, whereas in the remaining genotypes, Al inhibited growth. The RTI and STI data also substantiated this observation. The extent of leaf tip scorching was lesser in Co 31 and Co 37, while it was greater in the other genotypes. Based on the overall comparison of these data, the rice genotypes tested have been ranked as to then‐tolerance to Al toxicity: Co 37 > Co 31 > IET 1444 > IR 60 > IR 20 > ADT 36. Co 37 was the most tolerant and ADT 36 was the most susceptible to Al.

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