Tomato fruit generally peak in flavor and texture at the “full ripe” stage. Post-harvest deterioration is due to a number of natural processes that include fruit softening and dehydration, and infection of the fruit by post-harvest disease organisms. In tomatoes shelf life is typically defined as the period of time between when the fruit is at full ripe stage and when the fruit deteriorates to the point of becoming undesirable. Although many heirloom types only maintain good fruit quality for a matter of a few days, some improved types can maintain quality for several days longer.
The ripening process in tomatoes is greatly influenced by the plant hormone ethylene. Increased levels of ethylene in the plant promote both the positive changes associated with ripening, such as fruit coloration, sugar accumulation and production of flavor compounds – but also negative post harvest changes, such as fruit softening. RIN (Ripening Inhibitor) and Nor (Non Ripening) are two master regulatory genes in tomato that control both ethylene production and numerous downstream ripening processes. Mutations in the RIN and Nor genes have been identified as candidates for extending shelf life in tomatoes. The rin and nor mutants (alleles) cause a non-ripening phenotype in the inbred parent, but an extended shelf life phenotype in hybrids with a rin or nor inbred parent.
In our breeding program we have identified both rin and nor parent lines that, in combination with careful selection of conventional parents, provide for a fully flavored hybrid fruit with a very significant (14-21 day) improvement in shelf life. We are using the XSL trademark and logo to identify our hybrids that have this extended shelf life trait.
|fruit of wild type parent and XSL hybrid 35d after harvest|