Genetic parameters for sugar content in an interspecific pear population

Abstract

Fruit quality and flavour are important targets in all pear breeding programmes. Perceived sweetness is directly influenced by the amount and type of sugar accumulated in fruit. Limited information is available on sugar composition in pear fruit and published studies have been completed using cultivars rather than breeding populations. The objective of this research was to determine the quantitative genetic parameters of sugar content in fruit of interspecific hybrids from families making up a pear breeding population. Glucose, fructose, sucrose and sorbitol contents were measured in mature fruit. Most of the sugars, except for sorbitol, showed genetic variability and a relatively high (i.e., > 0.5) ratio between the estimated additive genetic variance and the total variance. Sorbitol showed a high negative genetic correlation (–0.65) with fructose. It could be suggested that the main product of sorbitol conversion was fructose. Sucrose showed a negative genetic correlation with glucose (–0.37) and fructose (–0.16), which would be expected given that sucrose is metabolised into fructose and glucose. Two parents with 100 % European parentage showed the highest empirical breeding values (eBV)s for fructose and total sugars. The parent with 100 % Asian parentage showed the lowest eBV for sorbitol. The mean percentages of the sugars across the entire population were: glucose 13 %, fructose 59 %, sucrose 8 % and sorbitol 20 %, indicating fructose was the main sugar with sucrose less prominent.