1 Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; and.
2 Scion Forest Protection, Private Bag 3020, Rotorua 3046, NZ.
Phytopathology. 2019 Mar;109(3):446-455. doi: 10.1094/PHYTO-06-18-0195-R. Epub 2019 Jan 8.
Swiss needle cast is a foliar disease of Douglas-fir (Pseudotsuga menziesii) that results in premature foliage loss and reduced growth. The causal fungus, Nothophaeocryptopus gaeumannii, was first detected in New Zealand in 1959 and spread throughout the North and South Islands over the following decades. The contemporary genetic structure of the N. gaeumannii population in New Zealand was assessed by analyzing 468 multilocus SSR genotypes (MLGs) from 2,085 N. gaeumannii isolates collected from 32 sites in the North and South Islands. Overall diversity was lower than that reported from native N. gaeumannii populations in the northwestern United States, which was expected given that N. gaeumannii is introduced in New Zealand. Linkage disequilibrium was significantly higher than expected under random mating, suggesting that population structure is clonal. Populations of N. gaeumannii in the North and South Islands were weakly differentiated, and the isolates collected from sites within the islands were moderately differentiated. This suggests that gene flow has occurred between the N. gaeumannii populations in the North and South Islands, and between the local N. gaeumannii populations within each island. Eighteen isolates of N. gaeumannii Lineage 2, which has previously been reported only from western Oregon, were recovered from two sites in the North Island and four sites in the South Island. The most likely explanation for the contemporary distribution of N. gaeumannii in New Zealand is that it was introduced on infected live seedlings through the forestry or ornamental nursery trade, as the fungus is neither seed borne nor saprobic, and the observed population structure is not consistent with a stochastic intercontinental dispersal event.
瑞士针枞枯梢病是道格拉斯枞（Pseudotsuga menziesii）的一种叶部病害，可导致过早落叶和生长受阻。病原菌为胶膜菌属（Nothophaeocryptopus）的长喙胶膜菌（N. gaeumannii），于 1959 年在新西兰首次被发现，并在随后的几十年中蔓延至南北岛。通过分析从南北两岛 32 个地点采集的 2085 个长喙胶膜菌分离株的 468 个多位点 SSR 基因型（MLGs），评估了新西兰长喙胶膜菌种群的当代遗传结构。与美国西北部的原生长喙胶膜菌种群相比，新西兰长喙胶膜菌的总体多样性较低，这是由于长喙胶膜菌是引入的物种。连锁不平衡显著高于随机交配下的预期值，表明种群结构呈克隆型。南北两岛的长喙胶膜菌种群分化较弱，而在岛内各地点采集的分离株分化程度中等。这表明，北岛和南岛的长喙胶膜菌种群以及每个岛内的本地长喙胶膜菌种群之间发生了基因流。从北岛的两个地点和南岛的四个地点回收了 18 株先前仅在俄勒冈州西部报道过的长喙胶膜菌谱系 2 菌株。长喙胶膜菌在新西兰的当代分布最可能的解释是，它通过林业或观赏苗圃贸易，以感染活苗的形式引入，因为该菌既不是种子传播的，也不是腐生的，而且观察到的种群结构与偶然的洲际扩散事件不一致。
