Aldana Juan A, Moa Belaid, Mattsson Jim, Russell John H, Hawkins Barbara J
School of Arts, Science, and Education, Medicine Hat College, Medicine Hat, AB, Canada.
Electrical and Computer Engineering Department, University of Victoria, Victoria, BC, Canada.
Front Plant Sci. 2024 Feb 6;15:1309762. doi: 10.3389/fpls.2024.1309762. eCollection 2024.
Western redcedar () is an important species in the Cupressaceae both at economic and cultural levels in the Pacific Northwest of North America. In adult trees, the species produces one of the most weathering-resistant heartwoods among conifers, making it one of the preferred species for outdoor applications. However, young plants are susceptible to infection with cedar leaf blight (), an important foliar pathogen that can be devastating in nurseries and small-spaced plantations. Despite that, variability in the resistance against in has been documented, and such variability can be used to breed for resistance against the pathogen.
This investigation aimed to discern the phenotypic and gene expression differences between resistant and susceptible seedlings to shed light on the potential constitutive resistance mechanisms against cedar leaf blight in western redcedar.
The study consisted of two parts. First, the histological differences between four resistant and four susceptible families that were never infected with the pathogen were investigated. And second, the differences between one resistant and one susceptible family that were infected and not infected with the pathogen were analyzed at the chemical (C, N, mineral nutrients, lignin, fiber, starch, and terpenes) and gene expression (RNA-Seq) levels.
The histological part showed that seedlings resistant to had constitutively thicker cuticles and lower stomatal densities than susceptible plants. The chemical analyses revealed that, regardless of their infection status, resistant plants had higher foliar concentrations of sabinene and α-thujene, and higher levels of expression of transcripts that code for leucine-rich repeat receptor-like protein kinases and for bark storage proteins.
The data collected in this study shows that constitutive differences at the phenotypic (histological and chemical) and gene expression level exist between seedlings susceptible and resistant to . Such differences have potential use for marker-assisted selection and breeding for resistance against cedar leaf blight in western redcedar in the future.
北美乔柏（Western redcedar）在北美太平洋西北部的经济和文化层面都是柏科中的重要物种。在成年树木中，该物种产生针叶树中最耐风化的心材之一，使其成为户外应用的首选物种之一。然而，幼树易感染雪松叶枯病（cedar leaf blight），这是一种重要的叶部病原体，对苗圃和小间距种植园可能具有毁灭性。尽管如此，已记录到北美乔柏对雪松叶枯病抗性的变异性，这种变异性可用于培育抗该病原体的北美乔柏。
本研究旨在辨别抗性和易感北美乔柏幼苗之间的表型和基因表达差异，以揭示北美乔柏对雪松叶枯病潜在的组成型抗性机制。
该研究包括两个部分。首先，调查了四个从未感染病原体的抗性家族和四个易感家族之间的组织学差异。其次，在化学（碳、氮、矿质营养、木质素、纤维、淀粉和萜类）和基因表达（RNA测序）水平上分析了一个感染病原体和一个未感染病原体的抗性家族与易感家族之间的差异。
组织学部分表明，对雪松叶枯病具有抗性的北美乔柏幼苗比易感植株具有组成型更厚的角质层和更低的气孔密度。化学分析表明，无论感染状态如何，抗性植株叶中桧烯和α-侧柏烯的浓度更高，编码富含亮氨酸重复序列受体样蛋白激酶和树皮储存蛋白的转录本表达水平更高。
本研究收集的数据表明，易感和抗性北美乔柏幼苗在表型（组织学和化学）和基因表达水平上存在组成型差异。这些差异未来在北美乔柏抗雪松叶枯病的标记辅助选择和育种中具有潜在用途。
