VARIABILIDADE FENOTÍPICA E MOLECULAR EM GENÓTIPOS DE ARROZ COM DIFERENTES REAÇÕES AO FRIO PHENOTYPIC AND MOLECULAR VARIABILITY OF RICE GENOTYPES WITH DIFFERENT COLD REACTIONS

Marker assisted selection for cold tolerance is of high interest in rice due to the difficulties of selection under field conditions and to the fact that tolerance may vary according to the developmental stage of the plant. The aim of this study was to characterize rice cold tolerance at different periods of development in six rice genotypes, to determine the correlation between these periods and to identify the most adequate population for molecular mapping of cold tolerance based on the polimorphism of RAPD markers and phenotypic traits. Three genotypes belonged to the Japonica subspecies and the other three to the Indica one. Cold tolerance was evaluated at germination, vegetative and reproductive periods through measure of ten traits. Results showed that the Japonica genotypes were more cold tolerant than the Indica ones in all periods of development studied. Phenotypic correlations varied according to the evaluated trait and were higher when the traits differentiated cold tolerant from cold sensitive genotypes. Jaccard coefficients indicated a low degree of similarity between Japonica and Indica genotypes, so based on RAPD markers any Japonica x Indica cross would be suitable for cold tolerance mapping. Phenotypic traits, in contrast, did not separate completely the genotypes, and based on them, the most divergent population for cold tolerance mapping would be the cross involving the tolerant Quilla 64117 and the sensitive IRGA 417.