CONICET | Buscador de Institutos y Recursos Humanos

Kiwifruit has a climacteric maturation; while the fruit ripens, the pulp becomes less green and firm and increases the level of sugars and flavours. As there is no external colour change that can be appreciated, the total soluble solids (TSS) is the most widely used index of harvest maturity. The dry matter content of the fruit (% DM) would be more related to sensory quality and storage potential, so it is desirable to count with management tools that promote its accumulation. Phosphites (Phi) induce many responses involved in the plants? defense mechanism and secondary metabolism. This study evaluated the effect of the application of potassium phosphite on maturity indexes at harvest, fruit quality at shelf life and tolerance to gray mold. Six weekly foliar applications of 0.3% (v/v) of Phi (30% P2O5, 20% K2O) or water (Control) were done in a commercial mature orchard of kiwifruit 'Hayward'. We evaluated the % DM, firmness (in N, with a hand penetrometer), colour of flesh (CIELab), SST (in %, by refractometry) and titratable acidity (TA, % citric acid) at the day of harvest and after 10 days at 20°C (shelf life). Fruit treated with Phi and control was inoculated with Botrytis cinerea to assess the effect on the severity of gray mold. The application of phosphites increased the % DM at harvest (Control: 15.6%; Phi: 17.4%), TSS (Control: 5.8%; Phi: 6.5%) and colour, while no changes in fruit firmness occurred (Control: 75.5 N; Phi: 78.5 N). Kiwifruit treated with phosphites were more tolerant to gray mold development. Treated fruit also showed better quality in terms of TSS and firmness compared to Control at shelf life. These preliminary results indicate that the use of phosphites may induce metabolic changes associated with better flavor and texture and less susceptibility to decay.