Abstract:

【Objective】 The present study was aimed at evaluating the hybrid heterosis, inbreeding depression and combining ability performed in F1－F3 generations of 14 yield and quality traits among parental materials of soybean in Huang-Huai velleys so as to provide guidelines of parental selection and early generation selection in breeding of hybrid cultivars and inbred line cultivars. 【Method】 A set of eight parental cultivars chosen from Huang-Huai valleys and the US along with their 28 diallel crosses were tested in 2005. The mid-parent heterosis and high-parent heterosis as well as inbreeding depression were evaluated for each of the 14 traits. DIALLEL-SAS05 was used to carry out the combined analysis of variance of combining ability of eight traits in F1, F2 and F3 generations. 【Result】 The obtained results were as follows: (1) There appeared hybrid heterosis and inbreeding depression for yield-related traits, among them, yield heterosis was the largest, that of number of pods per plant and seeds per plant the next, while no obvious heterosis for 100-seed-weight was observed. The traits with high F1 heterosis performed high inbreeding depression in F2 and F3, therefore, were not appropriate for utilization of heterosis in F1-derived generations. But there showed no obvious hybrid heterosis in maturity and quality (protein and oil contents) traits. (2) There existed significant GCA×Generation and SCA×Generation interaction in yield, therefore, the parental cultivars with high combining ability performed in F1 were not necessary with high combining ability in derived inbred generations, while no significant GCA×Generation and SCA×Generation interaction of quality traits were observed, therefore, the combining ability performed in F1 could predict that in derived inbred generations. (3) The yield of the parental materials per se could not be used as an indicator of its GCA, but the protein and oil contents of them per se could be used as an indicator of its GCA. 【Conclusion】 The heterosis of yield was the largest among the traits studied, but that in F1-derived generations declined and, therefore, not useful in production. There might be different superior parental materials and crosses in F1 hybrid cultivars and derived inbred line cultivars. In breeding for line cultivars, selection pressure can be put on early hybrid generations for the effective improvement of the quality traits.

Key words: soybean')">soybean, heterosis, inbreeding depression, combining ability×generation interaction