Data from: Seasonal variation in the biocontrol efficiency of bacterial wilt is driven by temperature-mediated changes in bacterial competitive interactions

1. Microbe-based biocontrol applications hold the potential to become an efficient way to control plant pathogen disease outbreaks in the future. However, their efficiency is still very variable, which could be due to their sensitivity to the abiotic environmental conditions. 2. Here we assessed how environmental temperature variation correlates with the Ralstonia pickettii, an endophytic bacterial biocontrol agent, ability to suppress Ralstonia solanacearum pathogen during different tomato crop seasons in China. 3. We found that the pathogen suppression was highest when the seasonal mean temperatures were around 20 °C and rapidly decreased with increasing mean crop season temperatures. Interestingly, low levels of disease incidence did not correlate with low pathogen or high biocontrol agent absolute densities. Instead, the biocontrol to pathogen density ratio was more important predictor of disease incidence levels between different crop season. To understand this mechanistically, we measured the growth and strength of competition between the biocontrol agent and the pathogen over a naturally occurring temperature gradient in vitro. We found that the biocontrol strain grew relatively faster at low, and the pathogen at high temperature ranges, and that similar to field experiments, pathogen suppression peaked at 20° C. 4. Together our results suggest that temperature-mediated changes in the strength of bacterial competition could potentially explain the variable R. solanacearum biocontrol outcomes between different crop seasons in China. 5. Synthesis and applications. Bacterial strains that can retain their functionality regardless of the environmental conditions (i.e. have flat reaction norms), could be good candidate species for developing more consistent biocontrol applications.

1. 基于微生物的生物防治应用，未来有望成为防控植物病原物病害暴发的高效手段。然而其防控效果仍存在显著波动，这可能与其对非生物环境条件的敏感性有关。2. 本研究针对中国不同番茄种植季，探究了环境温度波动与生防内生细菌皮氏罗尔斯顿菌（Ralstonia pickettii）抑制青枯劳尔氏菌（Ralstonia solanacearum）病原物的能力之间的关联。3. 研究发现，当季平均温度约为20℃时，病原物抑制效果最佳，且随作物季平均温度升高，抑制效果会快速下降。值得注意的是，低病害发生率与低病原物密度或高生防菌绝对密度并无关联；相较而言，生防菌与病原物的密度比，是不同种植季间病害发生率的更重要预测因子。为从机制层面解析这一现象，我们在体外针对自然存在的温度梯度，测定了生防菌与病原物的生长情况及竞争强度。结果显示，生防菌株在低温范围内生长速度相对更快，而病原物则在高温范围内生长更优；且与田间试验结果一致，病原物抑制效果在20℃时达到峰值。4. 综合来看，我们的研究结果表明，温度介导的细菌竞争强度变化，或可解释中国不同作物季中青枯劳尔氏菌生防效果存在差异的现象。5. 综合与应用启示：无论环境条件如何变化均能保持其功能（即反应规范平坦）的细菌菌株，有望成为开发更稳定生物防治应用的优质候选菌种。