Genetic Fruit Weight Regulation in 3 Distinct Tomato (Solanum lycopersicum L.) Market Classes

Fruit weight is a quantitatively inherited trait of great importance in breeding. In tomato, the increase in fruit weight is controlled by multiple quantitative trait loci (QTL) including FW2.2, FW3.2, FW11.3, FASCIATED (FAS) and LOCULE NUMBER (LC). Across tomato domestication and widespread cultivation, several market classes have appeared with specific fruit quality requirements. We focus our efforts in understanding fruit weight regulation in grapes, plums and beefsteaks tomatoes. Increased fruit weight is desired for the plum and beefsteak breeding programs, but not in grapes, where exchanging fruit weight alleles may result in improved germplasm. In order to evaluate the possible effects of different fruit weight gene alleles in distinct genetic backgrounds, we introgressed different fruit weight and shape allele combinations in two selected plum, grape and beefsteak fresh-market class accessions. Since our aim was also to provide insights on the pleiotropic effects of the alleles and usefulness of the pre-breeding materials towards market class improvement, about 6-12 plants for each homozygous combination were selected to be evaluated for fruit weight and shape as well as for horticultural acceptability. For plums, only allelic combinations with the cultivated allele of FW3.2 yielded acceptable fruits. LC per se was not sufficient to increase fruit size when the wild-type allele of FW3.2 was present. Phenotypic data from the 2 other market classes would help us get a more general idea on how the different allele combinations affects the overall acceptability of tomato across market classes.