FIRST GENERATION OF RECURRENT SELECTION IN APPLE: ESTIMATION OF GENETIC PARAMETERS

Increasingly complex breeding programs coupled with pressure on breeders to reduce costs and improve returns have made knowledge of the performance of breeding population imperative.
Knowledge of genetic parameters including heritability, genotype x environment (g x e) interaction and phenotypic and genetic correlations is important for the interpretation of breeding and testing work as well as for the development of a selection index for multiple trait selection.
Here we report on the estimation of these parameters for major tree (including disease resistance) and fruit quality traits in a recurrent selection program in apple.
To our knowledge, this is the first comprehensive report of estimation of genetic parameters in a breeding population in apple.
In total, eight tree, three disease resistance, and 19 fruit quality, traits were assessed in at least some of the sublines in this program.
The families (502 in all in 4 sublines) were planted at three sites in a randomized incomplete block fashion.
Fruit weight had the highest heritability of approximately unity in subline 91. Heritability estimates for tree traits ranged from 0.19 to 0.92. Disease resistance traits had low to moderate (0.14–0.37 for fireblight) to high heritability (0.51 for scab). Heritability of fruit appearance was mostly moderate to high (0.26–0.54). Heritability of fruit texture ranged from 0.10 to 0.62. The range of heritability for mineral concentration was very wide, from 0.03 (magnesium) to 0.99 (calcium) and also for disorders: from 0.12 (chilling injury) to 0.82 (superficial scald). Trait genetic correlations were mostly low in sublines 92 and 93. The genetic correlations between sites were generally high.
The implications of these estimates for apple breeding are discussed.