Tomato breeding for organic systems: development and selection of promising genotypes for open field cultivation

Abstract Tomato cultivation in organic production systems faces production challenges related to the low availability of genotypes adapted to the particularities of this system. This study aimed to present a breeding program and select promising tomato lines for cultivation in an organic open-field system in Southern Brazil. Different combinations of crosses were obtained from three non-hybrid genotypes and one commercial hybrid, and the genotypes of interest were determined by visual selection. In the F6 generation, four parental genotypes (CH, GA, BGT_16 and BGT_37) and ten experimental lines (1731, 1732, 1733, 1724, 1725, 1716, 1717, 1718, 1729 and 17,210) were evaluated in open-field organic production management in a randomized complete block design with four replications. Various morpho-agronomic traits were evaluated, and nine traits of importance for the organic system were selected from a subset that underwent multicollinearity analysis. Using these traits, association analyses between traits, genetic diversity, and the Mulamba and Mock selection index were performed, focusing on the selection of superior traits such as commercial fruit production, soluble solids/titratable acidity ratio, foliage density, and a*/b* colour parameter ratio. Cluster analysis identified a promising cross between CH and BGT_37 for obtaining desirable genotypes. The selection index determined lines 1732, 1733, 1717, and 17,210 as the most promising for the breeding program's objectives, and 1733 stood out with satisfactory values for all traits with the highest economic weights for selection. By improving these lines, we aim to develop genotypes adapted to organic production with characteristics of interest to both farmers and the consumer market.