Breeding For Resistance To Fusiform Rust In Loblolly Pine

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Download or read book Major Gene Detection for Fusiform Rust Resistance Using Segregation Analysis and Linkage Analysis in Loblolly Pine written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fusiform rust, a disease caused by Cronartium quercuum f.sp. fusiforme, is the most economically important disease for loblolly pine (Pinus taeda L.) in the southern U.S. Identification and breeding of loblolly pines that are genetically resistant to fusiform rust are important for successful establishment of commercial plantations. This research developed a new analytical approach to detect major genes for rust resistance using complex segregation analysis in a diallel progeny population. Molecular markers were examined for association with the potential rust resistance genes. Loblolly pines from a six-parent half-diallel mating were planted in a randomized complete block field design at four test sites. Rust infection (gall presence / absence) was recorded annually through age 8. Time trends and genetic differences for rust infection were analyzed based on a polygenic model using a Bayesian logistic approach. For genetic control of rust infection among families, the parental general combining ability (GCA) due to additive effect was much more important than specific combining ability (SCA) due to none-additive effect in full-sib combinations. Large genetic differences among parents and full-sib families were found for rust infection. Among six parents, parent A showed consistent low infection rates over time and across four sites, which indicated high genetic resistance to fusiform rust due to strong polygenic effects and / or major gene effects. A Bayesian analysis of a threshold model was developed and used to make inference about a mixed inheritance model (MIM) that included both polygenic effects and major gene effects. The MIM was compared with a pure polygenic model. Marginalizations were achieved by means of Gibbs sampler. A parent block sampling has been implemented to improve mixing. Results showed that the MIM was a better model to explain the inheritance of rust-resistance than the pure polygenic model in the diallel population. A large major gene vari.