Mutation breeding through ethyl methanesulphonate seed treatment (0.05
M) was conducted in order to obtain earliness in the soybean Glycine
max cultivar IAC-8 in a way that the other plant characteristics remai
n unchanged. At the M2 generation, ten plants with less number of days
to flowering than IAC-8, were selected. By further selections and adv
ancing the generations, five mutant lines were selected and tested in
four yield trials carried out in 85/86 (Piracicaba), 86/87 (Piracicaba
, Sertaozinho and Assis) in Sao Paulo, Brazil. In these trials, the fo
llowing data were noted: number of days to flowering and maturity, yie
ld, total plant height and length to the first pod insertion, colour o
f flower, pod pubescence and seeds and type of plant growth. The resul
ts indicated that among the mutants, two of them (mutants numbers 2 an
d 9) were of interest because on the average of the four trials, showe
d earliness of seven to ten days in maturity in comparison with the or
iginal cultivar. With the exception of plant height, which was shorter
than the control, these mutants maintained unchanged the other charac
teristics of the original cultivar IAC-8.