Plant and Microbial Biology, North Carolina State University, 112 Derieux Place, Raleigh, NC 27607.
Biology Department, Indiana University, 1001 East 3rd St, Bloomington, IN 47405-7107.
FEMS Microbiol Ecol. 2019 Feb 1;95(2). doi: 10.1093/femsec/fiy237.
Endophytic microbiota are potentially useful plant symbionts for conferring biotic or abiotic stress tolerance. Common approaches to identify putatively beneficial functions of endophytes rely on lab-based assays. However, if functional roles are context-dependent, lab-based assessments may not accurately represent functional outcomes under variable field conditions. Our objective was to test whether antagonism by bacterial endophytes towards a plant pathogen in vitro would be predictive of disease outcomes in live plant tissue. We challenged Fusarium graminearum, a fungal pathogen of wheat, against bacterial endophytes isolated from wheat plants in two in vitro assays. A subset of isolates, with in vitro antagonistic activity ranging from weak to strong, was selected for testing in live plant tissue (detached wheat heads). Assays were performed under different temperature and/or carbon dioxide conditions to test environmental dependency in the plant-endophyte-pathogen interactions. The two in vitro assays produced contrasting measures of pathogen inhibition, and neither predicted pathogen load reductions in the detached wheat head assay. Additionally, outcomes were environment-dependent and varied among bacterial isolates. Thus, endophytic impacts on plant performance cannot be easily inferred from simplified in vitro assays, and environmental gradients should be incorporated into future testing of microbial interactions in plant hosts.
内生微生物群是具有潜在用途的植物共生体，可以赋予生物或非生物胁迫耐受性。鉴定内生菌的推定有益功能的常用方法依赖于基于实验室的检测。然而，如果功能作用取决于上下文，那么基于实验室的评估可能无法准确代表在可变的田间条件下的功能结果。我们的目标是测试细菌内生菌对活体植物组织中植物病原体的拮抗作用是否可以预测疾病结果。我们挑战了小麦真菌病原体禾谷镰刀菌，针对从小麦植物中分离出的细菌内生菌进行了两项体外检测。选择了具有体外拮抗活性强弱不同的一组分离株，用于活体植物组织（分离的小麦头）测试。在不同的温度和/或二氧化碳条件下进行了检测，以检测植物-内生菌-病原体相互作用中的环境依赖性。这两种体外检测产生了截然不同的病原体抑制措施，并且都不能预测在分离的小麦头检测中病原体载量的减少。此外，结果取决于环境，并且在细菌分离株之间存在差异。因此，不能从简化的体外检测轻易推断内生菌对植物性能的影响，并且应该将环境梯度纳入未来对植物宿主中微生物相互作用的测试中。
