Simulation of Genetic Gain from Marker-Assisted Seedling Selection for Quantitative Trait Improvement in Rosaceae Tree Fruit

The Rosaceae family includes most temperate tree fruit of economic value, such as apple, apricot, peach and nectarine, pear, and sweet cherry. Traditional seedling selection (TSS) is challenging for rosaceous tree fruit as most fruit-related traits can only be phenotyped when seedlings reach maturity after long juvenility. With the assistance of trait-predictive DNA markers, marker-assisted seedling selection (MASS) makes early seedling selection possible. Successful application of MASS enables breeders to increase the chance of identifying truly superior seedlings as potential cultivars by improving genetic gain from seedling selection, which is the increase in the mean genetic value of selected versus original seedling population.

A major challenge in applying MASS is lack of knowledge about the relative genetic gain from MASS compared to TSS under different selection scenarios. This study is the first in rosaceous tree fruit to investigate how genetic gain from MASS compared to TSS on a single trait is influenced by (1) broad-sense heritability of the trait (H), (2) the proportion of genotypic variance explained by marker (P), and (3) selection intensity. Results based on analytical deduction and stochastic simulation in the context of rosaceous tree fruit breeding both indicate that genetic gain from MASS tends to be higher than TSS with the same selection intensity when P/H is greater than one. Conclusions from this study provide breeders with guidance in designing efficient MASS schemes.