Heritability and correlations among traits in four-way soybean crosses

Recurrent selection programs can use several crossing arrangements to synthesize basic populations for breeding purposes. This study evaluated heritability and correlations among traits in forty-five populations of F-2[4] and F-2:3[4] generations obtained throughout four-way crosses [4] between two dialells among ten semi-late and ten late maturity soybean (Glycine max L. Merrill) genotypes. The generation advance was made by the TSHD (Thinned Single Hill Descent) method and all individual plants were evaluated for the following traits: number of days to flowering (NDF) and maturity (NDM), plant height at flowering (PHF) and maturity (PHM), agronomic value (AV) and seed yield (YLD). Four-way crosses associated with TSHD method provided high genetic variability in the populations with little or no reduction from F-2[4] to F-2:3[4]. The 'narrow sense' heritability estimated using correlations between F-2[4] and F-2:3[4] plants was lower than but closely related to broad- sense estimates. The populations 21 (IAC-4 x IAC-9) x (GO79-1039 x Paranagoiana) and 23 (IAC-4 x Santa Rosa) x (GO79-1039 x Tropical) were the most productive with high variability in F-2[4] and/or F-2:3[4] generations. Genotypic correlations measured were generally high, positive and consistent for the two generations except for those related to AV and YLD. These results indicate that the use of four-way crosses can be an efficient method to increase the genetic base of populations for recurrent selection or cultivar development. Significant AV x YLD correlations indicated visual selection can be used as additional selection criteria for improving populations.