DEVELOPMENT, MATURATION, AND POSTHARVEST RESPONSES OF ACTINIDIA-ARGUTA (SIEB. ET ZUCC.) PLANCH. EX MIQ. FRUIT

Fruit from a range of seedling selections of Actinidia arguta, or hybr ids between A. arguta and A. melanandra were compared for fruit growth , maturation, and postharvest storage. Timing and duration of the flow ering period varied. Long fruit had greater maximum growth rates than round fruit, but the timing of maximum growth (25-30 days after anthes is (DAA)) tended to be similar for all selections and was similar to t hat for other Actinidia species. A smaller second peak in growth rate occurred around 60-80 DAA. Fruit on the vine progressed from a slow to a rapid increase in soluble solids concentration, typical of commerci al kiwifruit. This occurred at the time when temperatures in New Zeala nd are at their highest (February), indicating a primarily physiologic al cause for an increase in soluble solids concentration rather than a response to lowered temperatures as generally postulated for commerci al kiwifruit (A. deliciosa). Maximal dry matter accumulation also vari ed according to selection, with some selections able to continue to ac cumulate carbohydrate during on-vine ripening. There was variation bet ween selections in rate of on-vine softening, with the most rapid bein g 4 days. Fruit with A. melanandra in their parentage sometimes develo ped reddening of the skin or flesh or both as they matured and ripened . Fruit softening and reddening began at either the stem end or the st ylar end depending on selection. Soft fruit stored 2 weeks at 0 degree s C, whereas firm fruit lasted at least 6 weeks. There was no differen ce in storage longevity between 0 and 3 degrees C. Compressive and pun cture tests showed similar patterns of softening, however compressive tests were non-destructive, more sensitive, and hence more useful. No major disorders or diseases were noted, and shrivel (water loss) was t he most significant cause of potential commercial loss. In red cultiva rs, the ability to colour after harvest was severely retarded if fruit were held at low temperatures. These results indicate there will be s ome difficulty in selecting a suitable maturity parameter that will al low a commercial postharvest life for A. arguta types.