Combining ability in snap bean lines in Brazil
The search for genetic material of snap beans with desirable yield traits is of utmost importance for yield increase in Brazil. We evaluated 12 snap bean genotypes by diallel crosses that presented characteristics of interest, so as to select the best genitors to generate productive populations in the snap bean breeding program of the Universidade Estadual do Norte Fluminense in Rio de Janeiro state, Brazil. Diallel crosses were performed applying Method 2 of Griffing. The F1 generation, composed of 36 hybrid combinations, was evaluated in a greenhouse, in a completely randomized design with two replicates. The traits evaluated were: pod weight, length, width and thickness, number of seeds and seed weight. There were significant differences among genotypes for most variables, indicating genetic variability between snap bean lines. The following genitor genotypes proved to be the most suitable when the trait to be improved was yield: Top Seed Blue Line, UENF 1445, UENF 7-20-1, and UENF 7-10-1. The hybrids with higher values of combining ability estimates are indicated to generate promising segregating populations. Thus L3 (Top Seed Blue Line) × L18 (UENF 9-24-2), and L12 (UENF 7-14-1) × L1 (UENF 1445) hybrid combinations showed the best estimates of specific combining ability for the traits under evaluation, suggesting a high probability of obtaining superior genotypes. The efficiency of selection for these traits is based on additive genic action and demonstrates progress in the of snap bean breeding program.