Phytopathology. 1999 Oct;89(10):974-80. doi: 10.1094/PHYTO.1999.89.10.974.
ABSTRACT The crown gall pathosystem was used to evaluate a model that describes the dose-response relationship between biological control agents and plant pathogens. The model predicts that this relationship can become asymptotic, such that increased antagonist doses cannot compensate for deficiencies in disease suppression. Wounded roots of tomato (Lycopersicon esculentum) and cherry (Prunus mahaleb) plants were dipped into different concentrations of the biological control organism Agrobacterium radiobacter strain K84 prior to inoculation with the pathogen A. tumefaciens. Pathogen strains sensitive or resistant to the antibiotic agrocin 84 were used, and for tomato experiments, a derivative of A. radiobacter strain K84 that does not produce agrocin 84 also was included as an experimental treatment. As predicted by the dose-response model, the amount of disease suppression per unit of antagonist decreased with increasing antagonist dose and became asymptotic at high antagonist densities. Control of crown gall of tomato was nearly complete with the combination of A. radiobacter K84 and an agrocin 84-sensitive strain of A. tumefaciens. Pathogen resistance to agrocin 84 or lack of agrocin 84 production by A. radiobacter resulted in antagonist dose-crown gall incidence relationships that were apparently asymptotic at levels of control significantly less than 100%. For field-grown cherry, similar dose-response relationships were observed with higher asymptotic levels of disease suppression obtained when trees were inoculated with an agrocin 84-sensitive A. tumefaciens strain compared with an agrocin 84-resistant pathogen strain. The differences among bacterial strain combinations in the magnitude of the asymptote defined by the dose-response relationships suggest that A. radiobacter impacts a smaller proportion of the pathogen population when the activity of agrocin 84 is muted.
本研究利用根癌农杆菌诱导冠瘿瘤病体系，评估了一种用于描述生物防治剂与植物病原菌相互作用剂量-效应关系的模型。该模型预测，这种关系可能会达到渐近线，即增加拮抗菌剂量不能弥补病害抑制的不足。在接种病原菌之前，将番茄（Lycopersicon esculentum）和樱桃（Prunus mahaleb）的受伤根系浸入不同浓度的生物防治剂根癌农杆菌（Agrobacterium radiobacter）K84 中。使用对抗生素农杆菌素 84 敏感或抗性的病原菌菌株，并且对于番茄实验，还包括根癌农杆菌 K84 的衍生物，该衍生物不产生农杆菌素 84，作为实验处理。正如剂量-效应模型所预测的那样，每单位拮抗菌的病害抑制量随着拮抗菌剂量的增加而减少，并在高拮抗菌密度下达到渐近线。根癌农杆菌 K84 与农杆菌素 84 敏感型根癌农杆菌的组合几乎完全控制了番茄的冠瘿瘤病。病原菌对农杆菌素 84 的抗性或根癌农杆菌缺乏农杆菌素 84 的产生导致拮抗菌剂量-冠瘿瘤发病率关系在明显低于 100%的控制水平下呈渐近线。对于田间生长的樱桃，当用农杆菌素 84 敏感型根癌农杆菌菌株接种时，与农杆菌素 84 抗性病原菌菌株相比，观察到类似的剂量-效应关系，并且获得了更高的病害抑制渐近水平。在剂量-效应关系所定义的渐近线幅度方面，不同细菌菌株组合之间的差异表明，当农杆菌素 84 的活性减弱时，根癌农杆菌对病原菌种群的影响比例较小。
