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

可持续的、可预测的木材供应对保持加拿大林业的竞争力至关重要。病虫害每年造成商品木材的大量损失，减少病虫害损失的措施有助于提高森林生产力。黑松是不列颠哥伦比亚省和阿尔伯塔省的一种主要的商业树种，它特别容易受到西部胆锈病的病原体——哈克纳西内分泌菌的影响。这种病原体在加拿大各地都有发现，会导致生长迟缓、茎部畸形和死亡。我们已经确定，西部的哈克尼斯大肠杆菌比东部的毒力更强。在不列颠哥伦比亚省和阿尔伯塔省爆发山松甲虫之后，大量的松树更新正在增加景观中幼松的比例，这些幼松最容易受到西部瘿锈病感染和死亡。小麦瘿锈病的抗病性是遗传的，种植小麦瘿锈病抗病性砧木对减少小麦瘿锈病造成的产量损失有很大的希望。抗西部瘿锈病已被艾伯塔省政府确定为树木育种的优先事项，该政府负责该省的树木改良。为了解决这个问题，这个项目的目标是发现黑松和黑松杂交品种抗西部胆锈病的基因组特征，并将这些发现转化为树木育种的基因组工具。我们将利用一套独特的分子标记和疾病严重程度数据，对幼苗和成熟树木的家庭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。然后，我们将通过结合松树基因表达的基因组规模分析和更可能或更不可能引起疾病的哈克奈希杆菌病原体类型的基因组比较，确定松树抗性和病原体严重程度的分子机制。这项研究的结果将用于开发DNA标记和统计模型，以预测树木育种计划中的西部胆锈病抗性。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森林树木的改善。

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.