Paraburkholderia sp. GD17 improves tomato plant growth and resistance to Botrytis cinerea-induced disease

Background and aims The plant growth promoting rhizobacteria have been repeatedly addressed in improving plant growth and resistance against pathogens. This study explored the role of Paraburkholderia sp. GD17 in improving tomato plant growth and resistance to Botrytis cinerea. Methods Tomato roots were inoculated with GD17 strain, and then the leaves of well-colonized plants were infected with B. cinerea. Physiological and biochemical parameters, and gene expression were analyzed. Results In the absence of B. cinerea, GD17 efficiently improved plant growth, and increased photosynthetic efficiency. In the presence of B. cinerea, GD17-bacterized plants exhibited an enhanced resistance, as indicated by 67% of disease index in non-bacterized plants, while by 24% in bacterized ones. In response to B. cinerea, the defense reaction was reinforced in bacterized plants, as shown by enhanced antioxidative capacity and mitigated oxidative damage, as well as increased PR gene expression in bacterized plants compared with control. Photosynthesis was inhibited by B. cinerea, while it was substantially attenuated in bacterized plants. In the presence of B. cinerea, contents of soluble sugar significantly increased in non-bacterized plants, while it was controlled in bacterized plants. The carbohydrate catabolism-related genes, including starch degradation, photorespiration, and pentose phosphate pathway, generally presented a higher expression in bacterized plants under B. cinerea attack. Conclusions GD17 strain improved tomato plant growth by increasing the photosynthetic efficiency. GD17 enhanced plant resistance against B. cinerea-induced disease by increasing defense and alleviating oxidative damage. Additionally, GD17 optimized the trade-off between plant growth and defense by strengthening carbohydrate metabolic regulation.