Development, maturation, and postharvest responses of Actinidia arguta (Sieb. et Zucc.) Planch, ex Miq. fruit

Abstract

Fruit from a range of seedling selections of Actinidia arguta, or hybrids between A. arguta and A. melanandra were compared for fruit growth, maturation, and postharvest storage. Timing and duration of the flowering period varied. Long fruit had greater maximum growth rates than round fruit, but the timing of maximum growth (25–30 days after anthesis (DAA)) tended to be similar for all selections and was similar to that 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 commercial kiwifruit. This occurred at the time when temperatures in New Zealand are at their highest (February), indicating a primarily physiological cause for an increase in soluble solids concentration rather than a response to lowered temperatures as generally postulated for commercial kiwifruit (A. deliciosa). Maximal dry matter accumulation also varied according to selection, with some selections able to continue to accumulate carbohydrate during on‐vine ripening. There was variation between selections in rate of on‐vine softening, with the most rapid being 4 days. Fruit with A. melanandra in their parentage sometimes developed 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 stylar end depending on selection. Soft fruit stored 2 weeks at 0°C, whereas firm fruit lasted at least 6 weeks. There was no difference in storage longevity between 0 and 3°C. Compressive and puncture 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 the most significant cause of potential commercial loss. In red cultivars, the ability to colour after harvest was severely retarded if fruit were held at low temperatures. These results indicate there will be some difficulty in selecting a suitable maturity parameter that will allow a commercial postharvest life for A. arguta types.