Effect of Ethylene-Insensitive Mutation etr2b on Postharvest Chilling Injury in Zucchini Fruit

Abstract

Zucchini is a vegetable fruit that is very susceptible to postharvest chilling injury, and fruit ethylene production is correlated with chilling injury sensitivity, such that the more tolerant the cultivar, the lower is its ethylene production. It is expected that zucchini fruit with reduced sensitivity to ethylene would have a higher chilling injury tolerance. In this study, we compared the postharvest fruit quality of wild type and ethylene-insensitive mutant etr2b, in which a mutation was identified in the coding region of the ethylene receptor gene CpETR2B. Flowers from homozygous WT (wt/wt), mutant plants in homozygous (etr2b/etr2b) and heterozygous (wt/etr2b) were hand-pollinated, and all fruits were harvested with the same length, at about 8 days after pollination. After harvesting, fruit of each genotype was randomly divided in 3 batches of 12 fruits each (four replications with three fruits each), and then stored at 4 °C and 95% RH. At 0, 7, and 14 days after cold storage, each batch was used to assess ethylene production, respiration rate, weight and firmness loss, chilling injury, and oxidative stress metabolites. The results showed a lower chilling injury associated with lower cold-induced ethylene production in the mutant fruit, in comparison with the WT fruit. These data demonstrated that the ethylene-insensitive etr2b mutant fruit was more tolerant to chilling injury, confirming that basal ethylene in the still undamaged fruit could function as a modulator of post-harvest chilling injury. Moreover, the higher chilling tolerance of the etr2b mutant fruit was not associated with MDA content, but was concomitant with a reduction in the accumulation of hydrogen peroxide in the refrigerated mutant fruit.