Identificação de famílias mutantes de arroz (Oryza sativa L.) para características de importância agronômica e tolerância a baixas temperaturas na germinação

Abstract

The existence of variability is essential for successful breeding. The use of mutagens can increase the mutation frequency, enabling the development of variation for traits of interest. The occurrence of low temperatures is a common stress in rice cultivation in temperate regions, therefore the tolerance to low temperatures is a desirable feature of Brazilian rice genotypes grown in the South, where low temperatures affect the germination and crop establishment causing reductions in the grain yield. This work aimed to identify mutants of rice genotypes for traits of agronomic importance and to evaluate the low temperature stress tolerance of genotypes on germination stage. In stage germination, 400 M3 families and control genotypes BRS Querência, BR IRGA 409 and Nourim Mochi, were subjected to treatments with different temperatures (13 C and 25 C) and compared for their relative performance, measured by the coleoptile, root and shoot length. To evaluate the traits of agronomic importance, M3 rice seeds were sown in the experimental field at Embrapa Clima Temperado. The experimental design was a completely randomized block with four replications. Seven traits of agronomic importance were evaluated: length of main panicle in cm, weight of main panicle in g; grain mass of the main panicle in g, length of flag leaf, in cm, width of flag leaf, in cm, plant height, in cm, and stem length, in cm. The results indicate that the ethylmethanesulfonate mutagen (EMS) was effective in generating mutants of rice for six of the traits, except for the character length of the flag leaf, which did not show increase in genetic variability. The induction of mutation was also efficient in generating genetic variability for tolerance to low temperatures at the stage of germination, but the results also indicated the occurrence of a large number of deleterious mutations, affecting negatively the performance of the mutant families.