Variation and transgressive variability of the stem length in F1 and F2 soft spring wheat under conditions of forest-steppe of Ukraine

The paper highlights the question of the stem length variability in F1 and F2 soft spring wheat and the detection of transgressive forms in the second generation of hybrids. The complicated character of stem length determination in F1 is defined, since in this process not only genes of additive type of action are involved, but also alleles of genes with stronger specific interaction. In the hybrid combinations Struna Myronivska/Elehiia Myronivska were at parental level, in the combination Struna Myronivska/Azhurnaia treated as inferior to the parental form on 10.9%, indicating the probability of maternal organism’s effect on the trait formation due to the content of short-stem genetic factors in cytoplasm. It was established that the coefficient of variation of stem length in first-generation hybrids when reciprocal crosses was in the range from 6.8% (Simkoda Myronivska/Struna Myronivska) to 9.3% (Azhurnaia/Struna Myronivska), indicating a slight variation of this index. Only in combinations of crosses Lehuan/Struna Myronivska, Heroinia/Struna Myronivska and Kolektyvna 3/Struna Myronivska variation of stem length is average and account for 15.8, 11.3 and 11.1% respectively. A significant reciprocal effect was also noted – shorter-stem hybrids F1 obtained in combinations when using low-growth varieties as a maternal form. The smallest range of stem length was found in second-generation hybrids in the combination Struna Myronivska/Kolektyvna 3 – 16.1 cm with low variance 22.1 and the largest one – in the combination Heroinia/Struna Myronivska (34.1 cm) with variance 81.0. The complex genetic nature of the stem length determination in the studied hybrids F1 and F2 was established. Starting from F2, a significant form-creating process in the stem length can be traced in hybrids. In the majority of reciprocal crosses, a significant reduction of the stem length in F2 hybrids is observed, when maternal form was a variety with shorter stem length. This indicates the influence of the maternal cytoplasm on this trait formation. High-growth transgressions were found in the second generation of a third of soft spring wheat hybrids. In F2 hybrids, the degree of transgression was in the range 2.1-6.2% with a frequency 6.0-10.0% in the hybrid combinations Struna Myronivska/Simkoda Myronivska, Simkoda Myronivska/Struna Myronivska, Elehiia Myronivska/Struna Myronivska, Kolektyvna 3/Struna Myronivska. Thus, it can be argued that the highest rates of transgressive variability based on the stem length were found in those hybrids which had heterosis in F2.