Oregon State University, Department of Botany and Plant Pathology, Corvallis, OR 97331.
U.S. Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, 3420 NW Orchard Avenue, Corvallis, OR 97330.
Plant Dis. 2021 Sep;105(9):2494-2502. doi: 10.1094/PDIS-09-20-1873-RE. Epub 2021 Oct 17.
Phytophthora root rot is a destructive disease of rhododendron that causes substantial losses of this nursery crop in infested field and container production areas. Historically, was considered the main causal agent of the disease. However, a recent survey of soilborne species from symptomatic rhododendrons in Oregon revealed that is more common than , and that several other species may be involved. We investigated the ability of the five most abundant species from the survey to cause root rot: , , , , and . Three to four isolates were selected for each species from across six Oregon nurseries. Media of containerized 'Boursault' was infested with single isolates in a randomized complete block design in a greenhouse. , and rapidly caused ≥90% of severe root rot, whereas caused more moderate disease (46% of severe root rot). failed to produce enough inoculum and was used at a lower inoculum density than the other four species; however, occasionally, it caused severe root rot (5% incidence). No differences in virulence were observed among isolates of the same species, except for one isolate of that caused less disease than other isolates. This study demonstrates that all five species, which were representative of 94% of the survey isolates, are capable of causing severe root rot and plant death, but that not all species are equally virulent.
植物疫霉根腐病是一种毁灭性的杜鹃花病害，会导致受感染的田间和容器生产区的这种苗圃作物大量损失。历史上，被认为是该病的主要病原体。然而，最近对俄勒冈州受感染的杜鹃花中的土壤传播疫霉物种的调查显示，比更为常见，可能还有其他几种 物种也参与其中。我们调查了调查中来自五个最丰富的物种的能力，以引起根腐病：，，，，和。从俄勒冈州的六个苗圃中选择了每个物种的三到四个分离株。在温室中，采用随机完全区组设计，用容器化的“Boursault”侵染单一分离株的培养基。和迅速引起≥90%的严重根腐病，而引起更中度的疾病（46%的严重根腐病）。未能产生足够的接种物，并且接种密度低于其他四个物种；然而，偶尔它会引起严重的根腐病（5%的发病率）。除了一种引起的疾病比其他 分离株少的 分离株外，同一物种的分离株之间没有观察到毒力差异。这项研究表明，所有五种疫霉物种，它们代表了调查分离株的 94%，都能够引起严重的根腐病和植物死亡，但并非所有物种的毒力都相同。
