CONICET | Buscador de Institutos y Recursos Humanos

Phosphites (Phi) are salts of P2O5 or K2O, listed as fertilizers or fungicides, with several physiological effects reported in plants. It has been demonstrated that foliage spray of Phi delays softening in ?Hayward? kiwifruit which was associated to a lower ethylene production in relation to untreated fruits. The objective of this research was to evaluate the effect of Phi (30% P2O5, 20% K2O) as spray at foliage, postharvest dipping or their combination on ?Hayward? fruit ripening and quality indices. Treatments were: T1: non-treated fruits; T2: fruits treated on the plant during fruit growth with six weekly sprays at foliage (0.3% v/v Phi); T3: postharvest fruit dipping (1% v/v Phi); T4: T2 and T3 combined.Firmness (N), color (CIELab), total soluble solids content (SSC) and titratable acidity (%) were analyzed at harvest, after 4 months of cold storage (0-1°C, 90%RH) and subsequent shelf-life (7 days at 20 °C). Ethylene production and respiration rate were measured during 21 days at 20 °C after cold storage. Foliage spray of Phi did not affect any ripening indices at harvest. All Phi-treated fruits were firmer than control at the end of cold storage, mostly when Phi were applied both at preharvest and postharvest (T4). After shelf-life, firmness for T2 and T4 was higher than for T1, demonstrating that preharvest Phi sprays were as effective as the combined treatment. Delayed softening for Phi treated fruits might be associated to a drastic diminution in ethylene production during shelf life. Control fruits showed a typical climacteric pattern, with an increase in ethylene production, whereas low (T3 and T4) or very low (T2) increases were detected in Phi-treated fruits. These results indicate that Phi delays the climacteric process in ?Hayward? kiwifruit, and could be considered as a useful tool to make fruits more suitable for long-term storage.Keywords: Actinidia deliciosa, ethylene, firmness, climacteric, ripening.