Estimation of parameters of genetic variation of spring durum wheat (Triticum durum Desf.) on the basis of “number of grains from the main spike”

Aim. To assess the combining ability, features and nature of the inheritance of the trait “number of grains from the main spike” in varieties of spring durum wheat for their further involvement in breeding programs. Methods. The investigations were carried out at the V. M. Remeslo Institute of Wheat of NAAS of Ukraine. Varieties (‘Zhizel’, ‘MIP Raiduzhna’, ‘Kharkivska 27’, ‘Kharkivska 39’, ‘Spadshchyna’, ‘Kuchumovka’, ‘Tera’) of domestic breeding were involved in crossings according to the full diallel scheme (7 ´ 7). Parental components and F1 were studied in the field in 2016, 2017. Results. The analysis of variance of combining ability showed a significant advantage in general combining abili­ty (GCA) effects. The mean square of the specific combi­ning ability (SCA) was significantly inferior to the GCA, but was significant in both years of the study. Consistently high GCA effects in 2016, 2017 were determined in the variety ‘Tera’ (gi = 1.35; 2.37). Non-alelic gene interaction was not found, which made it possible to analyze the main parame­ters of genetic variation. In two years of investigations, in the phenotypic manifestation of the number of grains from the main spike, dominant effects (H1 and H2) survived over additive ones (D). The average degree of dominance indicated overdominance (H1/D). The indicator of the ave­rage degree of dominance in loci () also indicated overdominance. Dominance was significantly oriented. Dominant effects of genes increased the number of grains, while recessive effects decreased them. At least one group of genes has been identified that has led to dominance. In general, dominant genes (F > 0) or groups of genes dominated quantitatively in cultivar investigated. A high coefficient of heritability in a broad sense (H2 = 0.88; 0.90) indicates a significant phenotypic conditionality to genetic factors. The coefficient of heritability in a narrow sense (h2 = 0.31; 0.38) indicates the average contribution of the additive effects of genes over the dominant ones. Conclusions. The identified breeding and genetic features on the basis of the “number of grains from the main spike” trait make it possible to predict the effectiveness of selections aimed at increasing the trait in the newly hybrid material. However, due to the predominance of dominant effects and overdominance in the genetic control of a trait, selection in later generations will be more effective. Varieties ‘Kharkivska 27’, ‘Kharkivska 39’ and ‘Tera’ should be used as genetic sources to increase the trait “number of grains from the main spike”.