High Specific Combining Ability Effects Research Articles

Genetics of nodulation in Chickpea (Cicer arietinum L.)

Combining ability, components of genetic variance and graphic analysis revealed that nodulation in the cultivars of Chickpea (Cicer arietinum L.) under study, was predominantly under the control of non-additive gene action although substantial additive effect was also present. The crosses giving high specific combining ability effects also manifested highly significant positive heterosis. The parents F-61, Giza and Annegiri possessed mostly dominant alleles while Phule G-5, NEC-249 and N-31 possessed mostly recessive alleles having positive effect on nodule weight.

GENOTYPE × ENVIRONMENT INTERACTIONS IN SMOOTH BROMEGRASS. I. YIELD

Twenty-one progenies and the parents of a 7 × 7 half diallel cross of smooth bromegrass (Bromus inermis Leyss.) were evaluated at four locations in Alberta in each of two years, for genetic variation and genetic by environment interactions in the expression of their yield potentials. Years, locations and their interactions were highly significant in the combined analysis of variance. Combining ability analysis revealed that general combining ability (GCA) and specific combining ability (SCA) were both important in the expression of yield, including spring, fall and annual yield, whereas GCA was more important than SCA for yield per area. Although the genotype × environment interactions were all highly significant, variation accounted for by combining ability effects was generally higher than the interaction effects of GCA and SCA respectively, with environments. High average GCA effects for spring, fall and annual yield were demonstrated for the clones UA5, UA9 and B42. These together with the high average SCA effects suggested that the three clones could be included in a synthetic to develop high yielding cultivars. The results suggested that recurrent selections involving multi-location and multi-year testing seems necessary in breeding for high yielding bromegrass cultivars in Alberta.

Parental generation in relation to combining ability analysis in spring barley

A comparison between Griffing's (1956) Method 1, Model I, and Method 3, Model I, using data from a 10 × 10 diallel of spring barley grown in eight different environments, revealed that inclusion of the parental generation (Method 1) caused considerable upward bias in the estimates of both the general and specific combining ability variances, whereas its exclusion (Method 3) from the analysis resulted in similar GCA∶SCA ratios in all the environments. This investigation supports the exclusion of the parental generation in combining ability analyses. The proportion of general combining ability variance was much higher than that of the specific combining ability variance although both were statistically significant. The interaction of the former with environment was much higher than that of the latter. Except for combining ability variances, the estimates of GCA and SCA effects were found to be alike in both Method 1 and Method 3. Mean performance was correlated with the general combining ability effects. Variety Cb 824 proved to be the best general combiner for earliness; it could be usefully exploited in future breeding programmes to induce earliness, as this variety possesses mostly dominant genes for earliness. Early varieties such as Otis, Bonus M-12a and Line 7-2 were also good combiners for earliness. Crosses between these varieties generally showed high specific combining ability effects.

Inheritance of in vitro Digestibility and Associated Characteristics in Medicago sativa L.1

The progenies of 10 Medicago sativa L. clones were analyzed to determine the type of gene action conditioning in vitro dry matter digestibility (IVDMD) and related chemical components and the relationship to total digestible units (TDU) per unit area. The mean squares for both general and specific combining ability were significant for IVDMD. Usually, if the general combining ability effects for IVDMD of the clone were positive, the effects for yield were negative. The 10 crosses highest in sea effects for IVDMD had negative (low) specific combining ability effects for yield with one exception. Three of the 10 crosses with the highest specific combining ability effects for yield had positive sea effects for IVDMD. The other seven were negative.