This paper reports results from the evaluation of 900 F7:6 inbred lines of soybean [Glycine max (L.) Merrill], derived from 45 diallel crosses, 20 of each one, and ten parental genotypes: FT-Cristalina, EMGOPA-301, IAC-4, IAC-5, IAC-6, IAC-8, IAC-9, IAC-11, Santa Rosa, and SS-1. The experiments were carried out in two localities (Anhembi and Areão Experimental Stations, Piracicaba county, State of São Paulo, Brazil), contrasting for aluminium saturation; Anhembi showed high aluminium saturation (>Al) whereas Areão showed low saturation (<Al). Four traits were evaluated: seed yield (PG), days to maturity (NDM), plant height at maturity (APM) and agronomic value (VA). The VA character was evaluated through a visual score considering: pod number, plant height, vigor, lodging, leaf retention, pod dehiscence, and disease symptoms. It was used an augmented design with 20 blocks, each one with 45 lines (regular treatment) and the ten parental genotypes as checks (common treatment); the experimental plot consisted of one row with length of 2.0 m x 0.5 m between row. The augmented design proved to be easily implemented in this phase, where many progenies were tested but few seeds were available. The effect of aluminium saturation on the means of the genetics parameters was dependent on the genotype and the character considered. The heritability estimates for the set of 900 lines were respectively in Anhembi and Areão: 0.58 and 0.84 for NDM; 0.64 and 0.62 for APM; 0.50 and 0.36 to VA; 0.38 and 0.38 to PG. Three crosses involving EMGOPA-301 with FT-Cristalina, IAC-4 e Santa Rosa, exceeded by having superior values of heritability for PG, in both localities, relatively to the set of 900 lines tested. In Anhembi, the genotypic correlations between number of days to maturity (NDM), plant height (APM), agronomic value (VA) and grain yield (PG) at F7:6 inbred lines level varied from 0.54 to 0.95 and they were superior in relation to phenotypic ones. The VA/PG genotypic correlation was distinguished (0.82), indicating that VA could be used for indirect selection of seed yield. Thus, for initial tests, the VA is of advantage, specially when having many entries in evaluation.
soybean; Glycine max; soils of low fertility; aluminium saturation; heritability; correlations among characters; augmented design
