Postharvest fruit quality in ethylene insensitive mutants of zucchini squash

Three ethylene insensitive mutants (Ein1, Ein2 and Ein3) were isolated from an EMS mutant library of zucchini squash by screening for a negative triple response of etiolated seedlings to ethylene. The ethylene insensitive mutations were isolated from other mutations in each one of the lines by backcrossing (BC) with the background genotype. To gain insight into the involvement of ethylene in postharvest fruit quality, WT and mutant fruit from BC3 generation was compared for different fruit quality parameters during 14 days of cold storage, including loss of weight and firmness, chilling injury (CI), and ethylene and CO2 production. The oxidative status of the fruit was also analysed. The mutations stimulated the production of ethylene in rewarmed fruit after cold storage but, given that ethylene response pathway was partially blocked in the mutants, some fruit quality parameters were improved, concomitantly with a reduction of oxidative stress metabolites such as hydrogen peroxide and malonyl dialdehyde (MDA). The Ein1 and Ein3 mutant fruit exhibited reduced chilling injury, and Ein1 also reduced the fruit respiration rate during cold storage. Weight loss was not altered in any of the ethylene mutants. The involvement of ethylene in postharvest deterioration of zucchini fruit quality, including CI and oxidative damage, is discussed.