INDUCTION OF MUTATIONS FOR EARLINESS IN THE SOYBEAN CULTIVAR PARANA

Mutation induction breeding through gamma ray seed treatment (22 krad) was used to obtain earliness in the soybean cultivar Parana. Plants f lowering earlier than Parana were selected at the M3 generation. Eight mutant lines were isolated by further selections through several gene rations and tested in four yield trials carried out in 85/86 (Piracica ba) and 86/87 (Piracicaba, Sertaozinho and Assis) in Sao Paulo State. The following data were taken in these trials: number of days to flowe ring, yield, total plant height and height to pod insertion, flower co lor, pod pubescence and seed and plant growth type. Two of the mutants are of agronomic interest because they were, on average, seven to 10 days earlier in maturity than the control in all trials. Except for sh orter plant height, the other agronomic characteristics remained unalt ered.