Cold-induced ethylene in relation to chilling injury and chilling sensitivity in the non-climacteric fruit of zucchini (Cucurbita pepo L.)

Zucchini is a non-climacteric fruit which is harvested immature on reaching about 18 cm in length. In the present paper we compare fruit quality parameters in different zucchini cultivars with the production of ethylene and the expression of two ethylene biosynthesis genes (CpACS1 and CpACO1) throughout postharvest storage at 4, 12 and 20 °C. In fruit stored at 12 or 20° ethylene production and expression of CpACS1 and CpACO1 genes remained very low throughout the whole storage period. Ethylene production was also low at 4 °C, but was induced rapidly upon transfer to 20 °C for a minimum of 4 h. The expression of both CpACS1 and CpACO1 genes was also induced by storage at 4 °C. This cold-induced ethylene is not necessary for triggering chilling injury (CI) symptoms in zucchini, since they were already evident in the cold chambers before rewarming of the fruit and, therefore, before the burst of ethylene. However, the level of the cold-induced ethylene was lower in those cultivars that were more tolerant to CI, and it fell in response to temperature conditioning treatments that alleviate CI symptoms.