Finding loci associated to partial resistance to white pine blister rust in sugar pine (Pinus lambertiana Dougl.)

White pine blister rust (WPBR) is an exotic disease threatening five-needle pines in North America. In spite of its relatively recent introduction, some five-needle pines such as sugar pine (Pinus lambertiana) have developed both complete (major) gene resistance and partial (quantitative) resistance to WPBR. While significant effort has been dedicated to clone and locate the position of the major gene of WPBR resistance in sugar pine, the genetic basis of quantitative resistance remains largely unknown in all Strobus pines. In this work, we took a preliminary approach to identify potential genotype × phenotype associations using the results of long-term survival and symptoms of infection in both experimental and applied breeding populations. Our study found significant associations between several genes and WPBR disease symptoms such as normal active cankers and blights, important symptoms in the development of partial resistance. No significant associations were found with percentage of survival, probably due to the complex inheritance of the disease and long time to infection. With this study, we hope to lay the ground for further genome-wide association studies using large phenotypic data sets in sugar pine and other Strobus pines.