Graduate Researcher University of Florida Horticultural Sciences Dept. Gainesville, Florida
Body of Abstract: Many tomato (Solanum lycopersicum) varieties demonstrate a susceptibility to the development of firm, internal white tissue (IWT) in their ripe fruits. The white tissue is difficult to chew and flavorless, making it an undesirable trait for consumers and reducing the marketability of varieties exhibiting this trait. Prior research suggests a potential relationship between IWT and “yellow shoulder,” a ripening abnormality, as well as an association with heat stress. With climate change threatening to increase temperatures and unpredictable weather patterns, there is high potential for an increase in environmentally induced IWT formation. The objective of this research is to identify specific genetic region(s) that contribute to IWT development. ‘Tasti-Lee’, a F1 hybrid developed at the University of Florida, is a variety that was selected for high lycopene content and good flavor (Scott et al., 2008 HortScience 43:2228). When cross-sectional images of ripe tomato fruit from Fla. 8059 and Fla. 7907B – the parents of ‘Tasti-Lee’ – were analyzed, they showed a distinct difference in the extent of IWT with FL8059 having “high” IWT and FL7907B having “low” IWT. The F2 population derived from self-pollinating ‘Tasti-Lee’ segregated for IWT, ranging from 11.70% to 70.91%. F2 plants with extreme IWT phenotypes were self-pollinated, and ripe fruits from the resulting F3 plants were analyzed. Comparison of the F3 plants with their filial generation revealed a narrow sense heritability (h2) of 0.6 (p-value < 0.001). After confirming the IWT trait is heritable, bulked segregant analysis of plants with “high” and “low” IWT and high heritability were used to identify key genetic regions. Subsequent investigation revealed a small region in chromosome 7 that is linked to the IWT trait. Fine mapping this region will reveal the causative factor(s) of IWT formation and enable fruit quality improvement for tomato varieties produced by our breeding program.