Bioactivities evaluation of an endophytic bacterial strain Bacillus tequilensis QNF2 inhibiting apple ring rot caused by Botryosphaeria dothidea on postharvest apple fruits

Apple ring rot, one of the most common apple postharvest diseases during storage, is caused by Botryosphaeria dothidea. Presently, the disease management is primarily dependent on chemical fungicide application. Here we demonstrated an endophyte bacterium Bacillus tequilensis QNF2, isolated from Chinese leek (Allium tuberosum) roots considerably suppressed B. dothidea mycelial growth, with the highest suppression of 73.56 % and 99.5 % in the PDA and PDB medium, respectively in vitro confront experiments. In in vivo experiments, B. tequilensis QNF2 exhibited a control efficacy of 88.52 % and 100 % on ring rot disease on postharvest apple fruits inoculated with B. dothidea disc and dipped into B. dothidea culture, respectively. In addition, B. tequilensis QNF2 volatile organic compounds (VOCs) also manifested markedly inhibition against B. dothidea mycelial growth and the ring rot on postharvest apple fruits. Moreover, B. tequilensis QNF2 severely damaged the mycelial morphology of B. dothidea. Finally, B. tequilensis QNF2 significantly repressed the expression of six pathogenicity-related genes, such as adh, aldh, aldh3, galm, pdc1, pdc2, involved in glycolysis/gluconeogenesis of B. dothidea. The findings of the study proved that B. tequilensis QNF2 was a promising alternative for controlling apple ring rot of postharvest apple fruit.