Combining Ability of Different Agronomic Traits and Yield Components in Hybrid Barley
Selection of parents based on their combining ability is an effective approach in hybrid breeding. In this study, eight maintainer lines and nine restorer lines were used to obtain 72 crosses for analyzing the general combining ability (GCA) and special combining ability (SCA) for seven agronomic and yield characters including plant height (PH), spike length excluding awns (SL), inter-node length (IL), spikes per plant (SP), thousand kernel weight (TKW), kernel weight per plant (KWP) and dry matter weight per plant (DWP). The results showed that GCA was significantly different among parents and SCA was also significantly different among crosses. The performance of hybrid was significantly correlated with the sum of female and male GCA (TGCA), SCA and heterosis. Hu1154 A, Mian684 A, 86F098 A, 8036 R and 8041 R were excellent parents with greater general combining ability. Five crosses, Hu1154 A×8032 R, Humai10 A×8040 R, Mian684 A×8037 R, Mian684 A×8041 R and 86F098 A×8037 R, showed superior heterosis for most characters.
Studies on the Heterosis of Barley (Hordeum vulgare L.)——I. Superiority of Hybrid F_1 from Mid-Parent or over Better-Parent
The heterosis performance of 12 barley quantitative traits, including plant height (abbreviated to PH), spike length excluding awns (SL), internode length below spike (IL), spikes per plant (SP), kernels on main spike (KMS), kernels per plant (KP), kernel weight per plant (KWP), dry mater weight per plant (DWP), 1 000-grain weight (KW), kernel yield (KY), protein content (PC) and lysine content (LC), was investigated in 7 CMS lines and corresponding maintainers, 4 restorers and their 7×4=28 F_1 hybrids. The superiority values of hybrid F_1 from mid-parent, H_m, and that over better-parent, H_b, were used to describe the heterosis, and the occurrence rate of the significant H_m or H_b described the heterosis potence of a trait. The results showed that the H_m often existed and the occurrence rates of positively and negatively significant H_m were 46% and 12%, respectively. On the other hand, the occurrence rate of the significant H_b was 28% on average, ranging from 0% (PH and KMS) to 79% (IL), varied with the traits. In the present study, the crosses of 3×10 and 6×8 had strong heterosis, and they belong to the combinations of 6-row×6-row types and 2-row×2-row types, respectively. It seems that the hybrid with strong heterosis could be easier to be found in the combinations of 6-row×6-row or 2-row×2-row barley types than that of 6-row×2-row or 2-row×6-row barley types. The relationship between the heterosis and genetic effects was also discussed briefly.
Comparison of F2 and F∞ diallel analyses in barley
A study was conducted in barley (Hordeum vulgare L.) to compare the relative magnitudes of heterosis to additive × additive epistasis and to compare F2 and F∞, diallel analyses. Both F2 and F∞, progenies were derived from 7 × 7 diallel crosses. Progenies and their parents were evaluated for grain yield, heading date, plant height, and the number of spikes per hill in hill plots with five replications at Elora (Ontario) in 1978. Results suggested that additive × additive epistasis were present for these traits and its magnitude was similar to that of heterosis estimated in F2. Both F2 and F∞ analyses detected the presence of epistasis. Both analyses provided similar estimates of the additive genetic variance for heading date and the number of spikes per hill, but the F2 analysis provided higher estimates than the F∞ analysis for grain yield and plant height. The estimate for grain yield and plant height obtained from the F2 analysis could be biased upward because of the invalid assumption of no epistasis. ...