Fusiform rust disease, caused by the endemic fungus Cronartium quercuum f. sp. fusiforme, is the most damaging disease affecting economically important pine species in the southeast United States. Unlike the major epidemics of agricultural crops, the co-evolved pine-rust pathosystem is characterized by steady-state dynamics and high levels of genetic diversity within environments. This poses a unique challenge and opportunity for the deployment of large-effect resistance genes. We used trait dissection to study the genetic architecture of disease resistance in two P. taeda parents that showed high resistance across multiple environments. Two mapping populations (full-sib families), each with ~1000 progeny, were challenged with a complex inoculum consisting of 150 pathogen isolates. High-density linkage mapping revealed three major-effect QTL distributed on two linkage groups. All three QTL were validated using a population of 2057 cloned pine genotypes in a 6-year-old multi-environmental field trial. As a complement to the QTL mapping approach, bulked segregant RNAseq analysis revealed a small number of candidate nucleotide binding leucine-rich repeat genes harboring SNP associated with disease resistance. The results of this study show that in P. taeda, a small number of major QTL can provide effective resistance against genetically diverse mixtures of an endemic pathogen. These QTL vary in their impact on disease liability and exhibit additivity in combination.

梭形锈病，由地方性真菌Cronartium quercuum f. 引起。sp。梭形目病是影响美国东南部具有重要经济意义的松树树种的最具破坏性的病害。与农作物的主要流行病不同，共同进化的松锈病病害系统的特点是稳态动态和环境内的高水平遗传多样性。这为大效应抗性基因的部署带来了独特的挑战和机遇。我们使用性状解剖来研究两种P. taeda的抗病遗传结构在多种环境中表现出高抵抗力的父母。两个绘图种群（全同胞家族），每个都有约 1000 个后代，用由 150 种病原体分离物组成的复杂接种物进行挑战。高密度连锁作图揭示了分布在两个连锁群上的三个主效QTL。在为期 6 年的多环境田间试验中，使用 2057 个克隆的松树基因型种群对所有三个 QTL 进行了验证。作为 QTL 作图方法的补充，批量分离 RNAseq 分析揭示了少量候选核苷酸结合富含亮氨酸的重复基因，这些基因含有与抗病性相关的 SNP。这项研究的结果表明，在P. taeda, 少数主要 QTL 可以对地方性病原体的遗传多样性混合物提供有效的抗性。这些 QTL 对疾病易感性的影响各不相同，并且在组合时表现出可加性。