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保持加拿大林业的竞争力至关重要。虫害和疾病每年造成大量可销售木材的损失，采取措施减少虫害和疾病造成的损失有助于提高森林生产力。在不列颠哥伦比亚省和阿尔伯塔主要的商业树种--小杆松对西瘿锈病的病原体--哈氏内孢霉（Endocronartium harknessii）特别敏感。这种病原体在加拿大各地都有发现，导致生长迟缓、茎畸形和死亡。我们已经确定，西方类型的E。哈氏菌比东方型更毒。 在不列颠哥伦比亚省和阿尔伯塔发生山松甲虫爆发后，大规模的松树再生正在增加景观中幼年松树的比例，这是西部瘿锈病感染和死亡的最大风险。 对西部瘿锈病的抗性是可遗传的，种植西部瘿锈病抗性砧木有很大的希望减少这种病原体造成的产量损失。阿尔伯塔省政府已将抗西部瘿锈病确定为树木育种的优先事项，该政府已授权在该省进行树木改良。 针对这一优先事项，该项目的目标是发现美国黑松和美国黑松×短叶松杂交种的西方瘿锈病抗性的基因组特征，并将这些发现转化为树木育种的基因组工具。 我们将通过进行基因组选择和关联遗传分析，确定与抗性相关的松树基因，这些基因具有一套独特的分子标记和幼苗和成熟树木家族的疾病严重程度数据。 然后，我们将通过结合松树基因表达的基因组尺度分析和E. harknessii病原体类型或多或少可能导致疾病。 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方胆锈病抗性。 这些基因组工具可能是第一个在阿尔伯塔实施的，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.