Effect of unique cytoplasms in reciprocal crosses of soybean

Cytoplasmic inheritance studies concerning agronomic characters and seed quality traits have often produced contradictory results. The use of parental lines with similar cytoplasms may explain the seeming discrepancies, since differences among the cytoplasms were not identified in previous studies. Differences among cytoplasms have been identified in soybean [Glycine max (L.) Merr.] by means of chloroplast DNA (cpDNA) restriction fragment length polymorphism (RFLP) patterns. This study was conducted to determine if cytoplasmic effects exist in soybean. Ten soybean lines representing five cpDNA cytoplasmic groups were crossed to 'Harosoy 63' and 'Clark 63' to produce 40 [F.sub.1] and reciprocal [F.sub.1] populations. Ten Harosoy 63 [F.sub.1] and reciprocal [F.sub.1] populations were advanced to the [F.sub.2] generation for evaluation in the following year. The parents, crosses, and reciprocal crosses were evaluated for the following agronomic characters: developmental stages, height, leaflet characteristics, and seed size. The population means and variances of each reciprocal cross were examined. Reciprocal cross means were significantly different for agronomic characters in only 8% of the crosses. Reciprocal crosses rarely differed with respect to the variances. Protein, oil, fatty acid, and amino acid composition were examined in composite samples of seed for each line. Significant differences were observed for only a few reciprocal crosses. Protein and oil concentration each differed in only one reciprocal cross. Oleate and linoleate concentration differed the most often, accounting for eight of the 10 significant reciprocal cross differences observed for fatty acid types in the [F.sub.1] and [F.sub.2] generations. Reciprocal cross differences involving the aliphatic amino acids were observed in four of the five cytoplasmic groups, but were not consistent with the cpDNA RFLP groupings. Consistent cytoplasmic effects, based on cpDNA RFLP groupings, were not observed for any of the traits examined. The significant differences that were observed may have been due to nuclear x cytoplasmic interactions, short-lived maternal effects, or Type I error.