Major Gene Detection for Fusiform Rust Resistance using Bayesian Complex Segregation Analysis in Loblolly Pine

Presence of major genes affecting rust-resistance of loblolly pine was investigated in a progeny population that was generated with a half-diallel mating of six parents. A Bayesian complex segregation analysis was used to make inference about a mixed inheritance model that included polygenic effects and a single major gene effect. Marginalizations were achieved by means of Gibbs sampler. A parent block sampling by which genotypes of a parent and its offspring were sampled jointly was implemented to improve mixing. The mixed inheritance model was compared with a pure polygenic model based on Bayes factor. Results showed that the mixed inheritance model was a better model to explain the inheritance of rust-resistance than the pure polygenic model in the diallel population. A large major gene variance component estimate (> 50 % of total variance), indicated existence of major genes for rust resistance in this loblolly pine population studied. Based on estimations of parental genotypes, it appears that there may be two or more major genes affecting disease phenotypes in this diallel population