Caldwell Denise, Kim Bong-Suk, Iyer-Pascuzzi Anjali S
Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47906.
Phytopathology. 2017 May;107(5):528-536. doi: 10.1094/PHYTO-09-16-0353-R. Epub 2017 Mar 21.
Ralstonia solanacearum is the causal agent of bacterial wilt and infects over 200 plant species in 50 families. The soilborne bacterium is lethal to many solanaceous species, including tomato. Although resistant plants can carry high pathogen loads (between 10 and 10 CFU/g fresh weight), the disease is best controlled by the use of resistant cultivars, particularly resistant rootstocks. How these plants have latent infections yet maintain resistance is not clear. R. solanacearum first infects the plant through the root system and, thus, early root colonization events may be key to understanding resistance. We hypothesized that the distribution and timing of bacterial invasion differed in roots of resistant and susceptible tomato cultivars. Here, we use a combination of scanning electron microscopy and light microscopy to investigate R. solanacearum colonization in roots of soil-grown resistant and susceptible tomato cultivars at multiple time points after inoculation. Our results show that colonization of the root vascular cylinder is delayed in resistant 'Hawaii7996' and that, once bacteria enter the root vascular tissues, colonization in the vasculature is spatially restricted. Our data suggest that resistance is due, in part, to the ability of the resistant cultivar to restrict bacterial root colonization in space and time.
青枯雷尔氏菌是青枯病的病原菌，可侵染50个科的200多种植物。这种土壤传播的细菌对包括番茄在内的许多茄科植物是致命的。尽管抗性植株可携带高病原菌载量（每克鲜重10到10个菌落形成单位），但该病最好通过使用抗性品种，特别是抗性砧木来控制。这些植物如何发生潜伏感染却仍保持抗性尚不清楚。青枯雷尔氏菌首先通过根系侵染植物，因此，早期根系定殖事件可能是理解抗性的关键。我们假设抗性和感病番茄品种根系中细菌入侵的分布和时间不同。在此，我们结合扫描电子显微镜和光学显微镜，研究接种后多个时间点土壤种植的抗性和感病番茄品种根系中青枯雷尔氏菌的定殖情况。我们的结果表明，抗性品种‘Hawaii7996’根维管束的定殖延迟，并且一旦细菌进入根维管组织，维管系统中的定殖在空间上受到限制。我们的数据表明，抗性部分归因于抗性品种在空间和时间上限制细菌根系定殖的能力。
