Based on diallelic crosses we obtained 36 combinations, which highlighted the best high heterosis effect. We analyzed segregation of the best forms released from heterosis by fixing them through apomixis and by abnormality use for further breeding.

The best hybrid combinations from crosses of 4-5 N. alata F1 plants were subjected to apomixis and their seeds were sown for further A1 analysis and compared with the parent forms F1.

Apomictic A1 9/10 Burley / Burley 7 / N. alata showed apomictic segregation. We obtained 24.7% of apomictic hybrid plants with similar level of morphological feature display as in their parent form (10 plants), planted on the same plot. Other plants with different abnormality expression in excessive or decreased productivity were amphimictic. Among these plants 3.2% were regarded as mutants with high performance, especially plants that exceed maternal by abnormal color (dark green or light yellow leaf with dense venation). 15.3% of amphimictic plants were diseased or of poor quality and they were immediately removed from plot. Less productive dwarf plants accounted 56.8%. The apomictic plants were isolated and their flowers underwent castration to produce seeds to test generation A2, in which constancy of quantitative traits was observed.

The segregation in apomictic A1 Pologi Shargo/Spectr/N. alata was estimated. 25.6% of plants found similar to the parent form with apomixis. Amphimictes comprised 74.4%. This combination expressed only 1.8% mutants with only slightly higher rates of productivity without abnormalities in micro-features and in flower. 25% of the plants were affected by diseases (bronze of tomato, clorosis, etc.). Plants with poor productivity accounted 47.6%. This hybrid is less interesting for breeding as it manifested poor qualities.

Apomictic segregation of A1 Zhovtolysty 36/Berley 9/10/N. alata resulted in the findings of high percentage (73.3%) of apomictic plants. The amphimictic set comprised 26.7%. The share of mutants accounted 4.9% of plants with very distinctive micro-features of white colored leaf, high leaf matter and dense canopy with large inflorescences in contrast to the parent form, with sprawling inflorescence. This hybrid is a valuable for further multiplication and fixation through apomixis. Mutants will be in place of the parent form. This hybrid provided 23.9% of plants with maternal characteristics and 76.1% of plants were amphimictic. Deviations from the parent form towards improving of plant quality amounted to 3.8% plant without canopy or flowers abnormalities, which might be prospective for breeding.

Thus, 27.5% of the observed plants were of parent-type and 72.5% of them were amphimictic. In this case, a very interesting type was abnormal dense canopy, some plant height reached 2 m, some plants possess abnormal flowers (stamen sprouted a pink leaf and flower corolla separations, especially, in central).

We devoted special attention here to the abnormal expression of traits and some plant forms were secured through apomixis for further selection process.

Splitting in apomictic A1 Burley 9/10/Spectrum/N. alata resulted in expression of mutations as dense venation, white central vein, white stems, large flowers and very sprawling inflorescence. There were no abnormalities in flowers. As a result of the analysis of specific segregation in A1 forms, we noted that each hybrid combination had its specific segregation pattern and there were no correlations in feature expression pattern as it was observed in the second hybrid generation.

Thus, we obtained the best hybrid combinations (Burley 9/10 / Spectrum / N.alata, Spectrum / Burley 9/10 / N.alata and Zhovtolystnyy 36 / Burley 9/10 / N.alata). They contained high percentage of apomictic plants with confirmed morphological mutations. This allowed us to expand the material source for breeding of tobacco through fixing these deviations by apomixis.

Key words: tobacco, varieties, apomixis, segregation, fixation of heterosis.