Estimation of genetic parameters of apple (Malus domestica) fruit quality from open-pollinated families

Abstract

Variance components of Julian harvest date, fruit weight, and eight sensory fruit traits (amount of over-colour, russet, firmness, crispness, juiciness, acidity, sweetness, and astringency) were estimated on two of the four initial sublines of the Apple Genetics Population in New Zealand. The sublines, both established at three sites, consisted of 119 and 50 families with sufficient fruiting trees, and had a median of c. 40 trees/family. These families were derived from open-pollinated seed from apple cultivars (Malus domestica Borkh.), as well as crab apples (Malus spp.) from a number of countries. Fruit weight was taken as the mean of six fruit, and sensory traits were scored on a 0 (no detectable presence) to 9 (full expression) scale by a pair of assessors in one laboratory. Additive and variance stabilising (AVAS) transformations were performed for scored traits before analysis. Genotype-by-environment interaction variance was less than half that among families. Heritability estimates of harvest date and fruit weight were high (>0.70), but those of the sensory traits were, at most, moderate (russet 0.35–0.54 and firmness 0.26–0.59). Estimates from the two sublines were in broad agreement, and exclusion of the crab apple families generally made little difference to the estimates. Phenotypic and genetic correlations were similar, and mostly below 0.3 in magnitude (median magnitude 0.12). © 2002 Taylor & Francis Group, LLC.