Irreversibility of chilling injury in zucchini squash (Cucurbita pepo L) could be a programmed event long before the visible symptoms are evident

Oxidative Stress Associated with Chilling Injury in Immature Fruit: Postharvest Technological and Biotechnological Solutions

Immature, vegetable-like fruits are produced by crops of great economic importance, including cucumbers, zucchini, eggplants and bell peppers, among others. Because of their high respiration rates, associated with high rates of dehydration and metabolism, and their susceptibility to chilling injury (CI), vegetable fruits are highly perishable commodities, requiring particular storage conditions to avoid postharvest losses. This review focuses on the oxidative stress that affects the postharvest quality of vegetable fruits under chilling storage. We define the physiological and biochemical factors that are associated with the oxidative stress and the development of CI symptoms in these commodities, and discuss the different physical, chemical and biotechnological approaches that have been proposed to reduce oxidative stress while enhancing the chilling tolerance of vegetable fruits.

Individual Shrink Wrapping of Zucchini Fruit Improves Postharvest Chilling Tolerance Associated with a Reduction in Ethylene Production and Oxidative Stress Metabolites

We have studied the effect of individual shrink wrapping (ISW) on the postharvest performance of refrigerated fruit from two zucchini cultivars that differ in their sensitivity to cold storage: Sinatra (more sensitive) and Natura (more tolerant). The fruit was individually shrink wrapped before storing at 4°C for 0, 7 and 14 days. Quality parameters, ethylene and CO2 productions, ethylene gene expression, and oxidative stress metabolites were assessed in shrink wrapped and non-wrapped fruit after conditioning the fruit for 6 hours at 20°C. ISW decreased significantly the postharvest deterioration of chilled zucchini in both cultivars. Weight loss was reduced to less than 1%, pitting symptoms were completely absent in ISW fruit at 7 days, and were less than 25% those of control fruits at 14 days of cold storage, and firmness loss was significantly reduced in the cultivar Sinatra. These enhancements in quality of ISW fruit were associated with a significant reduction in cold-induced ethylene production, in the respiration rate, and in the level of oxidative stress metabolites such as hydrogen peroxide and malonyldialdehyde (MDA). A detailed expression analysis of ethylene biosynthesis, perception and signaling genes demonstrated a downregulation of CpACS1 and CpACO1 genes in response to ISW, two genes that are upregulated by cold storage. However, the expression patterns of six other ethylene biosynthesis genes (CpACS2 to CpACS7) and five ethylene signal transduction pathway genes (CpCTR1, CpETR1, CpERS1, CpEIN3.1 and CpEN3.2), suggest that they do not play a major role in response to cold storage and ISW packaging. In conclusion, ISW zucchini packaging resulted in improved tolerance to chilling concomitantly with a reduction in oxidative stress, respiration rate and ethylene production, as well as in the expression of ethylene biosynthesis genes, but not of those involved in ethylene perception and sensitivity.

The chilling injury induced by high root temperature in the leaves of rice seedlings

Root temperature is found to be a very important factor for leaves to alter the response and susceptibility to chilling stress. Severe visible damage was observed in the most active leaves of seedlings of a japonica rice (Oryza sativa cv. Akitakomachi), e.g. the third leaf at the third-leaf stage, after the treatment where only leaves but not roots were chilled (L/H). On the other hand, no visible damage was observed after the treatment where both leaves and roots were chilled simultaneously (L/L). The chilling injury induced by L/H, a novel type of chilling injury, required the light either during or after the chilling in order to develop the visible symptoms such as leaf bleaching and tissue necrosis. Chlorophyll fluorescence parameters measured after various lengths of chilling treatments showed that significant changes were induced before the visible injury. The effective quantum yield and photochemical quenching of PSII dropped dramatically within 24 h in both the presence and absence of a 12 h light period. The maximal quantum yield and non-photochemical quenching of PSII decreased significantly only in the presence of light. On the other hand, L/H chilling did not affect the function of PSI, but caused a significant decrease in the electron availability for PSI. These results suggest that the leaf chilling with high root temperature destroys some component between PSII and PSI without the aid of light, which causes the over-reduction of PSII in the light, and thereby the visible injury is induced only in the light.