Abstract: 【Objective】This study aimed to definitude the antagonist activity of Pseudomonas alcaliphila strain Ej2 against various phytopathogens concluding Fusarium spp. in vitro, focusing on control efficacy of P. alcaliphila Ej2 against rice blast and influences of endogenous hormones in plant. The research can provide new biocontrol resources for the research and development of fungicides against rice blast.【Method】P. alcaliphila strain Ej2 was isolated from endophytic bacteria into rice leaf tissue. Antagonistic action of strain Ej2 against other five pathogenic fungi, such as Fusarium spp., Colletotrichum gloeospoioides, Alternaria alternate which can cause apple spot fallen leaf disease and strawberry black spot, et al., was determined by dual culture assay. In addition, antagonistic activity of volatile substance produced by P. alcaliphila strain Ej2 against Magnaporthe oryzae and promoting efficacy of fermentation broth increasing the germinating rate of rice seeds were tested in the experiment. The control efficacy of strain Ej2 was determined for the control of rice leaf blast under greenhouse condition by pot-culture method. The pot experiments were used to verify the promoting and control efficacy of strain Ej2 against rice leaf blast and neck blast. Targeted metabonomics based on MRM method was detected effect on endogenous hormones in plant such as stress hormone and cytokinin after fermentation broth sprayed for three times.【Result】The strain and volatile substance suppressed the colony growth rate of M. oryzae P131 significantly. The control efficacy against rice blast under greenhouse condition was 78.26% and it had no significant difference with 75% tricyclazole wettable powder. What’s more, the control efficacy against rice leaf blast and neck blast in field were 75.07%-83.67% and 62.79%-75.09%, respectively. It had significant difference between the control efficacy of strain Ej2 and 20% fenoxanil suspending agent against rice leaf blast. But it had no significant difference between the control efficacy of strain Ej2 and 20% fenoxanil suspending agent against rice neck blast. P. alcaliphila Ej2 showed strong antagonist activity against other five pathogenic fungi, such as F. oxysporum f. sp. niveum, F. solani, F. moniliforme, C. gloeospoioides, Alternaria alternate, et al. The fermentation broth of P. alcaliphila Ej2 significantly increased the germinating rate of rice seeds, plant height, panicle weight and thousand kernel weight. After spraying three times, the level of the stress hormone in plant such as ethylene (ETH) and abscisic acid (ABA) were significantly increased, but the level of cytokinin such as zeatin riboside (czR), trans-zeatin riboside (tZ) and N6-isopentenyladenine riboside (iPR) were evidently decreased. In addition, the level of several endogenous hormones in plant including IAA, JA, cis-OPDA, JA-LIE, cZ, tZ, iP and SA had no evident change.【Conclusion】P. alkalophilis strain Ej2 possesses the application value to control disease, promote crop growth and enhance stress resistance of rice plant, and it is considered to be a biological control nicroorganism against rice blast and other fungi diseases.

Key words: Pseudomonas , alcaliphila, rice blast,  , biological control,  , plant pathogenic fungi,  , endogenous hormones in plant