Pacific Forestry Centre, Canadian Forestry Service, Natural Resources Canada, Victoria, BC, Canada.
Phytopathology. 2011 Aug;101(8):904-11. doi: 10.1094/PHYTO-10-10-0282.
Multiple families of pathogenesis-related (PR) proteins are believed to contribute to plant quantitative resistance to various pathogens. Along with other host PR proteins, PR3 chitinase is one protein component participating in genetic resistance of western white pine (Pinus monticola) to the white pine blister rust (WPBR) pathogen (Cronartium ribicola). In the present study, we characterized a novel P. monticola class IV chitinase gene (PmCh4B) and further analyzed its nucleotide variations in the open-pollinated seed families of diverse geographical distribution and variable levels of quantitative resistance to C. ribicola infection. PmCh4B showed high haplotype diversity (Hd=0.94) and nucleotide diversity (π=0.00965), similar to those of other conifer genes related to environmental stresses. A low level of intragenic linkage disequilibrium (LD) (but most of the levels with statistical significance) was found within a distance of ≈800 bp. Based on PmCh4B haplotype frequency, moderate to high levels of population structure were observed among P. monticola seed families currently used in breeding programs for WPBR resistance (average FST=0.163, P<0.001). Association analysis revealed that allelic variants and multiple single-nucleotide polymorphisms of PmCh4B were significantly associated with quantitative levels of P. monticola resistance against C. ribicola. This work represents the first association study for quantitative resistance in western white pine pathosystem and provides a potential for marker-assisted selection in white pine breeding.
多个与发病机制相关（PR）的蛋白家族被认为有助于植物对各种病原体的定量抗性。与其他宿主 PR 蛋白一样，PR3 几丁质酶是参与西部白松（Pinus monticola）对白皮松疱锈病（WPBR）病原体（Cronartium ribicola）遗传抗性的一种蛋白成分。在本研究中，我们对一种新型的西部白松 IV 类几丁质酶基因（PmCh4B）进行了表征，并进一步分析了其在不同地理分布和对 C. ribicola 感染定量抗性程度不同的开放授粉种子家族中的核苷酸变异。PmCh4B 表现出高单倍型多样性（Hd=0.94）和核苷酸多样性（π=0.00965），与其他与环境应激相关的针叶树基因相似。在 ≈800 bp 的距离内，发现了低水平的基因内连锁不平衡（LD）（但大多数具有统计学意义）。基于 PmCh4B 单倍型频率，在当前用于 WPBR 抗性育种计划的西部白松种子家族中观察到中等至高种群结构水平（平均 FST=0.163，P<0.001）。关联分析表明，PmCh4B 的等位变异和多个单核苷酸多态性与 C. ribicola 对西部白松抗性的定量水平显著相关。这项工作代表了在西部白松病原系统中进行定量抗性的首次关联研究，并为白皮松育种中的标记辅助选择提供了潜力。
