GENOTYPIC CONTROL OF CARBON ACCUMULATION IN ACTINIDIA DELICIOSA GENOTYPES

Dry matter is an important quality trait in kiwifruit as it correlates with the consumer’s perception of fruit flavour and hence is used in New Zealand as one of the determinants of growers’ returns as well as a key screening criterion for new varieties. Dry matter is a complex trait under polygenic control and is often negatively correlated with fruit size, hampering selection of large, high dry matter kiwifruit varieties. Total non-structural carbohydrates (mainly starch) and organic acids make up about 75% of fruit dry matter. We have found that high dry matter genotypes are characterised by the ability to accumulate more starch during fruit development compared with low dry matter genotypes. Examining the starch metabolic pathway in fruit from these contrasting genotypes showed that higher expression levels of a sucrose synthase gene and an ADP-glucose pyrophosphorylase large subunit gene were observed early in fruit development, immediately before a dramatic increase in starch concentrations in fruit from high dry matter genotypes. Preliminary results from this work will be presented.