Influence of the direction of crossing on heterosis and transgression events in relation to the length of the vegetative period of Burley tobaccos variety group

Y. Dyulgerski2, T. Radoukova2*, L. Dospatliev3

1Tobacco and Tobacco Products Institute, Markovo, 4108 Plovdiv, Bulgaria
2Department of Botany and MOB, Faculty of Biology, Plovdiv University “Paisii Hilendarski”, 24 Tzar Assen, 4000 Plovdiv, Bulgaria
3Department of Pharmacology, Animal Physiology and Physiological Chemistry, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria

Abstract. Investigated are manifestations of real and hypothetical heterosis in terms of the length of vegetative period in ten hybrid combinations involving indigenous and introduced varieties of Burley tobacco. Each of them is represented by forward and reverse cross. The results show that more than half of the Burley tobacco hybrid combinations observed significant negative heterosis. Heterozis effect is influenced positively by distance of parents used for hybridization, and the participation of a variety Burley 1344, regardless of whether maternal or paternal component. The direction of crossing influences manifestations of heterosis effect in terms of length of the vegetative period at cross examined Burley tobacco. Heterosis effect is more pronounced when a local variety or line is used as a mother component and an imported variety is used as a father component. Transgressive manifestations in the studied hybrids in the second generation in terms of length of the vegetative period presented by degree and frequency are relatively low presented and do not have great importance for the selection practice. The direction of crossing influences the degree and to a lesser extent the frequency of transgressive events. Strong relationship between manifestations of heterosis and transgression has not been observed.