Western gall rust resistance in pines: using genomics to discover resistance mechanisms and develop new tools for tree breeding

可持续、可预测的木材供应对于保持加拿大林业的竞争力至关重要。减少病虫害损失的措施有助于提高森林生产力，病虫害造成了每年大量的商品木材损失。黑松是不列颠哥伦比亚省和艾伯塔省的主要商业树种，特别容易受到哈克尼西内克纳特菌（西瘿锈病的病原体）的影响。这种病原体遍布加拿大各地，会导致生长发育不良、茎畸形和死亡。我们已经确定，西部类型的哈克尼希艾美耳球虫比东部类型的毒性更强。 不列颠哥伦比亚省和艾伯塔省山松甲虫爆发后，大范围的松树再生正在增加景观中幼松的比例，这些幼松是西部瘿锈病感染和死亡的最大风险。 对西瘿锈病的抗性是可遗传的，种植抗西瘿锈病的苗木有望减少这种病原体造成的产量损失。阿尔伯塔省政府已将西瘿锈病抗性确定为树木育种的优先事项，并负责该省的树木改良。 针对这一优先事项，该项目的目标是发现黑松和黑松与短叶松杂交种的西部瘿锈病抗性基因组特征，并将这些发现转化为树木育种的基因组工具。 我们将通过对幼苗和成熟树科的一组独特的分子标记和疾病严重程度数据进行基因组选择和关联遗传分析，来识别与抗性相关的松树基因。 然后，我们将通过将松树基因表达的基因组规模分析与或多或少可能引起疾病的哈克内斯桉病原体类型的基因组比较相结合，确定松树抗性和病原体严重性的分子机制。 这项研究的结果将用于开发 DNA 标记和统计模型，预测树木育种计划的西部瘿锈病抗性。 这些基因组工具可能是第一个在艾伯塔省实施的工具，因此有可能为我们的合作伙伴改变林木改良。

A sustainable, predictable timber supply is vital to maintain competitiveness of Canada's forest industry. Measures that reduce losses to pests and diseases, which account for substantial annual losses of merchantable timber, can help improve forest productivity. Lodgepole pine, a major commercial species in British Columbia and Alberta, is particularly susceptible to Endocronartium harknessii, the causative agent of western gall rust. This pathogen, which is found across Canada, causes stunted growth, stem deformity and mortality. We have determined that western types of E. harknessii are more virulent than eastern types. Extensive pine regeneration that is occurring in the wake of the mountain pine beetle outbreak in British Columbia and Alberta is increasing the proportion of juvenile pines on the landscape, which are at greatest risk for western gall rust infection and mortality. Resistance to western gall rust is heritable, and planting of western gall rust-resistant stock has great promise to reduce yield losses to this pathogen. Western gall rust resistance has been identified as a priority for tree breeding by the Government of Alberta, which has the mandate for tree improvement in the province. Addressing this priority, the goal of this project is to discover genomic signatures of western gall rust resistance in lodgepole pine and lodgepole x jack pine hybrids, and translate these discoveries into genomic tools for tree breeding. We will identify pine genes associated with resistance by conducting genomic selection and association genetic analyses with a unique set of molecular marker and disease severity data for families of seedlings and mature trees. We will then identify molecular mechanisms of pine resistance and pathogen severity through combining genomic scale analyses of pine tree gene expression with genome comparisons of E. harknessii pathogen types that are more or less likely to cause disease. Outcomes from this research will be used to develop DNA markers and statistical models that predict western gall rust resistance for tree breeding programs. These genomic tools may be the first to be implemented in Alberta, and therefore have the potential to transform forest tree improvement for our partners.