Analysis of softening in air- and ethylene-treated rin, nor and wild-type tomato fruit

Authors: Smith, David; Gross, Kenneth; Whitaker, Bruce

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2008
Publication Date: 8/4/2008
Citation: Smith, D.L., Gross, K.C., Whitaker, B.D. 2008. Analysis of softening in air- and ethylene-treated rin, nor and wild-type tomato fruit. Postharvest Biology and Technology. 49(2):314-317.

Interpretive Summary: Fruit ripening includes many structural and metabolic alterations that lead to changes in texture, color, flavor, aroma and susceptibility to decay. Firmness is a major component of texture and a primary determinant of shelf-life is the loss of firmness during ripening. The precise mechanisms of fruit softening are not well understood, but in tomato and many other fruits softening is partly regulated by ethylene, a natural gaseous ripening hormone. In this study we compared the external and internal softening profiles of normal and non-ripening mutant tomato fruit, exposed to ethylene or not. The results showed that loss of whole fruit firmness and softening of internal fruit tissues clearly involve separate mechanisms, the latter being much more dependent on gene regulation by ethylene. These findings will help plant scientists develop an experimental system for discovery of new genes involved in fruit softening. Ultimately, this knowledge may be applied, either through traditional breeding programs or genetic manipulation, to extend shelf-life while preserving optimal sensory and nutritional quality.

Technical Abstract: Rin; ripening-inhibitor and nor; non-ripening are previously identified spontaneous mutations that affect the primary regulation of tomato fruit ripening. Mutations at these loci result in fruit that are either partially or completely inhibited in their ability to ripen. Both internal and whole fruit firmness of air- and ethylene-treated wild-type fruit declined as expected and previously reported. Firmness of whole rin and nor fruit decreased slightly after nine days of air-treatment and, interestingly, internal fruit firmness did not change. Ethylene-treated rin and nor whole fruit softened significantly over nine days, but substantially less than wild type. At harvest and after air or ethylene treatment, firmness was significantly greater in nor than in rin fruit. Surprisingly, slices from ethylene-treated rin and nor fruit softened much more than whole fruit, and fruit slice firmness was not significantly different between rin and nor.