Rice mutants and their responses to suboptimal temperatures in the early stages of development

The aim of this study was to verify differences in the tolerance to suboptimal temperatures of eight rice mutant genotypes in relation to their cultivars of origin in the initial stages of development. During the germination period, the germination percentage and the germination rate index were evaluated at temperatures of 25 and 13°C. For the vegetative stage enzymatic indicators, photosynthetic pigment concentration and electrolyte leakage were verified. The relative decrease in the germination percentage of mutants QUE 47, QUE 30 and QUE 33 was significantly lower (p ≤ 0.01) than that of cv. BRS Querencia. The principal component analysis using the values of the relative decreases of the germination percentage and of the germination rate index confirmed this distinction and the mentioned genotypes were classified into the group with a higher cold tolerance than BRS Querencia. The BRS Fronteira genotype did not differ from its mutants for the variables analyzed during germination. In the vegetative stage there were no differences (p ≤ 0.05) between the mutant genotypes and BRS Querencia for the analyzed variables. The induced mutation increased the tolerance to suboptimal temperature in the germination period in the genotypes QUE 47, QUE 30 and QUE 33, but not for the vegetative stage.   Key words: Oryza sativa, mutation, abiotic stress, low temperature.