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.