G3: Genes, Genomes, Genetics, Apr 1, 2018
Predicting phenotypes based on genotypes and understanding the effects of complex multilocus trai... more Predicting phenotypes based on genotypes and understanding the effects of complex multilocus traits on plant performance requires a description of the underlying developmental processes, growth trajectories, and their genomic architecture. Using data from Brassica rapa genotypes grown in multiple density settings and seasons, we applied a hierarchical Bayesian Function-Valued Trait (FVT) approach to fit logistic growth curves to leaf phenotypic data (length and width) and characterize leaf development. We found evidence of genetic variation in phenotypic plasticity of rate and duration of leaf growth to growing season. In contrast, the magnitude of the plastic response for maximum leaf size was relatively small, suggesting that growth dynamics vs. final leaf sizes have distinct patterns of environmental sensitivity. Consistent with patterns of phenotypic plasticity, several QTL-by-year interactions were significant for parameters describing leaf growth rates and durations but not leaf size. In comparison to frequentist approaches for estimating leaf FVT, Bayesian trait estimation resulted in more mapped QTL that tended to have greater average LOD scores and to explain a greater proportion of trait variance. We then constructed QTL-based predictive models for leaf growth rate and final size using data from one treatment (uncrowded plants in one growing season). Models successfully predicted non-linear developmental phenotypes for genotypes not used in model construction and, due to a lack of QTL-by-treatment interactions, predicted phenotypes across sites differing in plant density. KEYWORDS Function-Valued Traits quantitative genetics Brassica rapa leaf development high-throughput phenotyping, phenotypic plasticity, Bayesian vs. frequentist, genotype to phenotype Expressed phenotypes reflect the independent and combined effects of genetic and environmental inputs over time. However, understanding the relationship between genotype, the environment, and phenotype can be complicated. For example, phenotypic plasticity generated via genotype-by-environment interactions can alter the course of development, allowing a single genotype to exhibit multiple distinct phenotypes (BRADSHAW 1965; SCHLICHTING AND PIGLIUCCI 1998; DIGGLE 2002). Alternatively, phenotypic traits may be buffered against environmental effects, a phenomenon referred to as canalization (WADDINGTON 1954; RICE 1998; DEBAT AND DAVID 2001; HALL et al. 2007). Predicting phenotypes based on genotypes across multiple environments is therefore complicated by differential environmental sensitivity, yet is critical for understanding and predicting crop yields and evolutionary outcomes (
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Papers by Stephen Welch