An experiment was carried out in an acid hydromorphic soil (Gley humic) at Campinas, State of São Paulo, Brazil, in the period November 1980-February 1981, testing 25 cultivars in a duplicated simple lattice design. Soil concentrations of Al, P and K were high. A single row plot two meters long was used with spacing of 60 centimeters between rows and 20 plants per meter. The soybean cultivars were seeded in November in order to insure the maximum vegetative growth. The parameters measured were: dry matter weight, plant height, primary root length and scores of root coloration and leaf scorching at 60 days after planting. The cultivars IAC-9, Biloxi, IAC-Santa Maria 702, IAC-2 and PI 274.454 had higher dry matter weight, plant heigth and lower scores on leaf scorching, aluminum and manganese contents and better indices than other genotypes. Althought the root lenght and scores on root color showed differences, they were not as good as the former parameters. There was a significant correlation between dry matter weight and leaf scorching suggesting the utilization of this criteria in soybean breeding for resistance to soil acidity. This method also takes into account the importance of symbiotic nitrogen fixation in the increase of dry matter weight of those cultivars resistant to leaf scorching since the plants were grown in natural environment.
soybean breeding; soil acidity; acidity resistance