Capacidade de combinação entre linhagens de tabaco dark

Abstract

The species Nicotiana tabacum, known as tobacco, is one of the crops with the highest economic value in the world among non-food species. The main tabaco types planted in Brasil are Virginia and Burley. However, there are some varietal groups such as Dark Tobacco, which despite representing a small percentage of the total production is considered economically important. The Dark tabaco types is mostly used to manufacture the so-called "Snus", which are tobacco saches for ingestion. This study aimed to estimate the magnitude of genetic parameters, mainly the heterosis of F1 hybrids, the general combining capacities (GCA) and the specific combining capacities (SCA), through diallel crossings using method 2, proposed by Griffing. For this, a complete diallel crossing was used, 10 parental strains belonging to the Dark varietal group. The 45 hybrids from the diallel together with the 10 parental strains and 9 more controls, totaling 64 treatments with three replications in 4 sites. They were evaluated in the 2016/17 crop at three sites in western Paraná and one at the company's experimental farm in Mafra/SC. The design used was the triple lattice (8 x 8). The experiments were conducted according to the technological package that the company uses for Dark Tobacco, the characteristics evaluated were: green weight of leaves (productivity), and total alkaloids, and for obtaining the index was used the weight of 70% for green weight and 30% for total alkaloids. It was verified that, although heteroses were on average 5% the hybrids with higher averages were not those with higher heteroses, that is, the additive effects were the main contributors to the performance of the hybrid. Both the effects of CGC and SCA were significant for the SVP index, reinforcing the presence of additive and dominant effects for this characteristic. By applying the SVP index it is possible to obtain gains for productivity and alkaloids simultaneously, although they are of lesser magnitude than the selection for each characteristic individually. Therefore, the use of hybrids should be encouraged not only for the combination of phenotypes, but also to explore heterosis. The Dark Tobacco breeding program should focus on increasing the performance of the 'per se' strains, then test all possible combinations to find the best hybrid.