Is fruit anatomy involved in variation in fruit starch concentration between Actinidia deliciosa genotypes?

ABSTRACT

The role of anatomical traits in carbohydrate accumulation was investigated in fruit of Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson (kiwifruit) var. deliciosa by comparing high and low dry matter (DM) accumulating genotypes. DM was shown previously to be correlated with starch concentration in these fruit. Volume proportions of the three fruit tissues (outer pericarp, inner pericarp and central core) did not vary significantly between genotypes or contribute to variation in total fruit DM. The outer pericarp of the kiwifruit berry contains both small and large cells the size of these cells was not correlated with final fruit size. In high DM genotypes, the relative volume of outer pericarp tissue occupied by small cells (50%) was significantly greater than that in low DM genotypes (43%). Small cells have a higher starch concentration than large cells the larger proportion of small cells in the outer pericarp of fruit from high DM genotypes accounted for approximately +25% of the measured differences in fruit starch concentration between high and low DM genotypes. We conclude that, although anatomical traits contribute to variation in fruit starch concentration between kiwifruit genotypes, differences in starch content per small cell are important and worthy of further investigation. This is the first time anatomical investigations have been used to examine differences in fruit carbohydrate accumulation in kiwifruit.