Seasonal trends of starch and soluble carbohydrates in fruits and leaves of 'Abbé Fétel' pear trees and their relationship to fruit quality parameters

- Starch trend in 'Abbé Fétel' pears follows an accumulation pattern and degradation already described for different species.
- Soluble carbohydrates concentrations in fruits is related to the different vigor induced by rootstocks and sink strength.
- The maximum starch concentrations, always corresponding to the onset of its degradation, is seasons dependent.
- The starch degradation in fruits is correlated with fruit weight, soluble sugars content, flesh firmness and IAD index.

Plants mainly store carbohydrates, a product of photosynthesis, as starch and the amount of distribution of starch differs between organs and species. The objective of this research was to study changes in carbohydrate reserves, mainly starch, in the fruits and leaves of 'Abbé Fétel' pear trees at different physiological stages during the 2012-2013 growing seasons. Trees were trained as a spindle system and grafted on two rootstocks, Sydo® and Quince C. The evolution of starch degradation in fruit was correlated with the fruit quality parameters, soluble sugars and organic acids. Starch in fruit started accumulating early, 50 days after full bloom (DAFB), and reached a maximum concentration during the middle phase of fruit development, 110 DAFB, several weeks before harvest. As starch degradation began, a constant increase of soluble carbohydrates occurred. The two rootstocks did not induce significant differences in starch concentrations, but were different in their amounts of soluble carbohydrates. Further, the starch degradation in fruits was highly related to fruit weight, soluble solids content, flesh firmness and Index of Absorbance Difference. Among soluble sugars and organic acids, glucose, fructose, sucrose and quinic acid were related to starch hydrolysis during fruit maturation. Understanding the changes in carbohydrate creation and degradation among vegetative and reproductive organs could lead to optimization of yield efficiency and production.