Delaying Broccoli Floret Yellowing by Phytosulfokine α Application During Cold Storage

During postharvest life, broccoli suffers from floret yellowing confining its economic and nutritional value. The objective of the present study was to explore the mechanisms employed by phytosulfokine α (PSKα) at 150 nM for delaying floret yellowing in broccoli during storage at 4°C for 28 days. Our results showed that the higher endogenous accumulation of hydrogen sulfide (H2S) resulting from the higher gene expression and activities of l-cysteine desulfhydrase (LCD) and d-cysteine desulfhydrase (DCD) in broccoli floret treated with 150 nM PSKα may serve as an endogenous signaling molecule for delaying senescence. Moreover, the suppressed ethylene biosynthesis in broccoli floret treated with 150 nM PSKα might be ascribed to lower gene expression and activities of ACC synthase (ACS) and ACC oxidase (ACO). Furthermore, lower gene expression and activities of Mg2+ dechelatase (MDC), pheophytinase (PPH), and pheophorbide a oxygenase (PaO) might be the reasons for the higher accumulation of chlorophyll in broccoli floret treated with 150 nM PSKα. Based on our findings, exogenous PSKα application could be employed as signaling bioactive hormone for retarding floret yellowing of broccoli during storage at 4°C for 28 days.

Ripening Characteristics and Pigment Changes in Russeted Pear Fruit in Response to Ethylene and 1-MCP

Ripening characteristics and pigment changes were investigated in ‘La France’, ‘Gorham’, and their russeted sports ‘Gold La France’ and ‘Grand Champion’ pears. Fruit were harvested at commercial maturity and ripened at 20 °C. In all cultivars, fruit softening was concomitant with a burst in ethylene production. Interestingly, such changes were delayed in russet pear when compared with their wild-types. Chlorophyll level in russet pear at harvest was the same as in the wild-type. In ‘Gorham’ and ‘Grand Champion’ pears, its level rapidly decreased during ripening. Ethylene or 1-methylcyclopropene (1-MCP) did not affect the color and pigments in ‘La France’ and ‘Gold La France’ pears. In contrast, in ‘Gorham’ and ‘Grand Champion’ pears, chlorophyll degradation was suppressed by 1-MCP treatment, but not completely. These results suggested that chlorophyll degradation was regulated by both ethylene-dependent and ethylene-independent means. The influence of ethylene on the expression of chlorophyll-degradation-related genes seemed to be similar in both russet and wild-type. The Stay green-1 gene was stimulated by ethylene and suppressed by 1-MCP treatment. In contrast, little effect of ethylene or 1-MCP was observed on chlorophyllase 1, pheophytinase, pheophorbide a oxygenase, and NYC1-like genes.