MUTATION BREEDING FOR EARLINESS IN IAC-8 SOYBEAN CULTIVAR

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.