Effect of high CO2 level on the titres of γ-aminobutyric acid, total polyamines and some pathogenesis-related proteins in cherimoya fruit stored at low temperature

Abstract

In this study the effect of treatment with 20% CO2 plus 20% O2 for 3 d on γ-aminobutyric acid (GABA) was analysed and total polyamine titres and the production of some pathogenesis-related proteins (PR-proteins) in cherimoya (Annona cherimola Mill.) fruit stored at low temperature. In immunoassays with anti-PR-Q and PR-2 protein sera, high CO2 levels were found to provoke the co-ordinated accumulation of a chitinase-like protein and 1,3-β-glucanase. Chitinase activity was higher in treated than in untreated fruit. At the end of CO2 treatment, total polyamine and γ-aminobutyric acid content and uptake of O2 were observed to be higher in treated compared to untreated fruit, but the accumulation of these compounds decreased when the fruit was transferred to air. Since this treatment effectively retains the fruit quality (Escribano et al., 1997), high CO2 levels may have a direct effect on the activation of the above-mentioned specific responses that enables cherimoya fruit to overcome chilling temperature. The relationship between the activation of the defence system and the capacity to regulate cytoplasmic pH in CO2-treated fruits was also addressed.