Evangelos Sfakiotakis

Ethylene Biosynthesis and its Regulation in Ripening “Hayward” Kiwifruit

Ethylene plays a crucial role in ripening of kiwifruit, and the elucidation of the controlling factors in ethylene biosynthesis is important in prolonging the storage life and keeping the fruit quality during the handling operations.

Ascorbic Acid, Soluble Solids and Dry Matter Content in Sweet Pepper Fruit: Change During Ripening

ABSTRACT The ascorbic acid, dry matter and soluble solids content of sweet pepper (Capsicum annuum L.) fruit from two cultivars (‘P-14’ and ‘Florinis’) were determined at the immature, commercially mature and physiologically mature stages of ripening. The ascorbic acid content in fruits of ‘P-14’ increased with ripening, while in fruits of ‘Florinis’ it showed an increase only at the commercially mature stage of ripening. The dry matter content in fruit of ‘P-14’ varied little from the immature to the commercially mature stages of ripening, while a large increase was observed at the physiologically mature stage of ripening. Fruit of ‘Florinis’ showed an increase in dry matter content at the commercially mature stage of ripening, while at the physiologically mature stage it varied with harvest date. The soluble solids content in fruit of ‘P-14’ increased with ripening. In contrast with ‘P-14’, fruit of ‘Florinis’ showed an increase in soluble solids content at the commercially mature stage of ripening, while at the physiologically mature stage it varied with harvest date. In both cultivars, the maturation and ripening related changes in ascorbic acid was positively correlated with the changes in dry matter and the soluble solids.

Differential Effects of Low Temperature Inhibition on Kiwifruit Ripening and Ethylene Production

Our previous studies [7] have shown that there is an inhibition of propylene-induced ethylene production in kiwifruit below a critical temperature range of 11-14.8°C. The aim of this research was to identify the biochemical basis of inhibition of the propylene-induced ethylene production in kiwifruit, below the above mentioned critical temperature range. “Hayward” kiwifruit were treated with 130μl/l propylene or air free of propylene and ethylene at 10°C and 20°C. Ethylene production as well as ACC synthase and ACC oxidase activities were measured during a period of 312 hours. Changes in soluble solid content (SSC) and flesh firmness were also monitored during the same time-course period. RNA blot hybridisations using specific probes for ACC synthase and ACC oxidase were performed with total RNA from untreated fruit as well as from those that had received 192 hours of propylene treatment, at 10°C and 20°C. We propose that the main reasons for the inhibition of the propylene-induced (autocatalytic) ethylene production in kiwifruit at low temperature (<11°C) are: a) primarily the inhibition of the expression of the propylene-induced ACC synthase gene and b) the possible post-transcriptional modification(s) of ACC oxidase, since expression of the propylene-induced ACC oxidase gene existed at the low temperature storage.