Pseudomonas aurantiaca ST-TJ4 against crown gall caused by Agrobacterium tumefaciens by inducing systemic resistance in cherry blossom

• We explored the P. aurantiaca ST-TJ4 control effect on cherry blossom crown gall. • ST-TJ4 inhibited the number of crown gall caused by Agrobacterium tumefaciens . • P. aurantiaca ST-TJ4 reduced the oxidative damage in cherry blossom. • ST-TJ4 had the potential to be applied for biocontrol of cherry blossom crown gall. Cherry blossom crown gall has caused serious damage to plant growth, and is highly contagious and extremely difficult to control. The antagonism of pathogens by rhizosphere bacteria has attracted widespread attention. However, there is still limited research on the cherry blossom crown gall. In this study, we explored the control effect of rhizosphere bacteria Pseudomonas aurantiaca ST-TJ4 on cherry blossom crown gall. We also investigated the long-term survival status of ST-TJ4 in the cherry blossom roots and the induction of plant defense resistance. The results showed that ST-TJ4 had obvious inhibition effect on the population of Agrobacterium tumefaciens , which could reduce the number of A. tumefaciens by 70% to 90%, and its population kept the advantage in the rhizosphere soil and cherry blossom roots. The incidence of crown gall in the therapy group and the prevention group was reduced by 37.5% and 50%, respectively, and the disease index was reduced from 80 to 20 and 10, respectively. At the 150th day, ST-TJ4 could still be isolated from the rhizosphere soil and root surface, indicating that ST-TJ4 could survive in soil for a long time and had long-term performance. Compared with the control group, the therapy group and prevention group could reduce the levels of H 2 O 2 , malondialdehyde (MDA) and the oxidative damage, and up-regulated the expression of active oxygen-related genes DHAR1 , SOD1 , GR1 and CAT to activate defense response. On the other hand, it could up-regulate the expression of SA1 , SA2 and JA1 genes related to the induction of salicylic acid (SA) and jasmonic acid (JA), and lead to the increase of SA hormone level. Collectively, P. aurantiaca ST-TJ4 had the potential to be applied for biocontrol of cherry blossom crown gall by reducing root pathogen colonization and inducing plant resistance.