20. Study of the ecological valence of Virginia tobacco hybrids through mathematical approaches

Tobacco (Nicotiana tabacum) is one of the most widespread non-food plants in the world – a raw material for the production of tobacco products. Tobacco is one of the traditional and economically important crops in Bulgaria. Four varieties are grown in the country – Oriental Basma and Kaba Kulak Tobacco and broad-leaved – Flue-cured – Virginia and Air Cured – Burley. Flue-cured tobacco is essential for the tobacco industry. It is a major ingredient of American blend cigarettes.

The study of the „genotype-environment“ interaction allows the assessment of the degree of stability of tobacco genotypes to environmental factors, according to some biometric and chemical indicators. A single-factor analysis of variance and a Duncan test were applied to perform this assessment. With respect to the plant height indicator, X33 is the most stable. This is the genotype that has a maximum height (161.1 cm) among the three newly selected forms. It was found that the hybrid X33 not only surpassed the control one by the number of plant leaves (24,75), but is also more resistant according to this indicator.

Hybrid X33 has a maximum leaf length (62.29 cm), making it preferred for future selection practices. The most resistant with regard to the leaf width is X33, with a second width by size (34.47 cm). The most stable with respect to nicotine content is X51, which has the lowest one (2.25%). Genotype X33 is relatively stable and has low content of total nitrogen (2.47%). X51 has the highest sugar content (13.12%), but it is unstable with regard to this indicator. The most stable is X33, but it has sugars in minimal quantities (11.34%).