Feasibility of using tobacco hybrids of the Dark tobacco type
The species Nicotiana tabacum, known as tobacco, is one of the crops with the highest economic value in the world among non-food species. Since 2000, Brazil has become the world’s second largest tobacco producer. Brazilian production is mainly concentrated in the South region. The main tobacco types are produced in Brazil, such as Dark, which, despite representing a small percentage of the total production in Brazil, is economically important because of a high added value. Until now the only available cultivar is a line that despite having a desirable alkaloid content, has low productivity. In an effort to help improve production, we estimated the heterosis of diallel crosses involving tobacco lines of the Dark tobacco type. A complete diallel cross was made involving 10 lines from the British American Tobacco company breeding program. The 45 hybrid combinations, together with the 10 parental lines and nine other commercial controls, were evaluated at four sites in Southern Brazil, using a triple lattice experimental design (8 x 8). The characteristics evaluated included: green leaf mass (Productivity - YLD), and total alkaloid content (ALK), and the selection index was obtained by the sum of standardized variables (SSV), considering a weight of 70% for YLD and 30% for ALK. Estimated correlation between YLD and the ALK was -0.66. The use of the selection index allowed simultaneous gains in both traits, although they were of less magnitude than selection for each characteristic individually. The average heterosis was 8.6% for productivity, -1.4% for the total alkaloid content, and 5.3% for the selection index. However, considering the selection index, hybrids were obtained with an average heterosis greater than 10%. Under these conditions, the use of hybrids should be encouraged not only to combine favorable phenotypes, but also to explore the beneficial effects of heterosis.