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Forward genetic analysis defines candidate genes for fusiform rust resistance in loblolly pine and avirulence in Cronartium quercuum f.sp. fusiforme

Daniel Ence: University of Florida, IFAS

<div>The improved annotated genome of loblolly pine (<em>Pinus taeda</em> L.) may allow fine-mapping of important Mendelian traits such as disease resistance. <em>Cronartium quercuum</em> f.sp. <em>fusiforme </em>(CQF) causes fusiform rust disease on pine, a major disease threat to the timber industry in the southern US. Genetic major gene for gene resistance is the primary approach to control losses. A high priority for breeders and forest managers is to identify candidate resistance genes in pine and avirulence genes in CQF. We conducted bulk segregant analysis of next-generation sequence data from both host and pathogen. In pine, half-sibling progeny from a resistant mother were phenotyped as either resistant or susceptible to CQF. These progeny were sequenced with a custom sequence-capture method targeting a genomic region linked to resistance alleles by prior work. In CQF, analysis of whole-genome sequence of rust grown on resistant or susceptible seedlings identified a 200kbp region containing several likely effector proteins. In pine, we will test any identified candidate R genes for interaction with the candidate avirulence genes identified in CQF. By identifying candidates for an interacting avirulence and resistance gene pair in this conifer-rust pathosystem, we will discover markers that will guide breeding and deployment of resistant pine and enable us to identify additional interacting gene pairs that are known to exist but have yet to be molecularly discovered in this pathosystem.</div>