关键词: 嗜碱假单胞菌, 稻瘟病, 生物防治, 植物病原真菌, 水稻内源激素

Abstract:

【Objective】The objective of this study is to clarify the antagonist activity of Pseudomonas alcaliphila strain Ej2 against various phytopathogens (Fusarium spp., etc.) in vitro, focusing on the control efficacy of P. alcaliphila strain Ej2 against rice blast and influences of endogenous hormones in rice plant. The result will provide new biological control resources for the research and development of fungicides against rice blast. 【Method】P. alcaliphila strain Ej2 was isolated from rice leaf tissue. Antagonistic action of strain Ej2 against Magnaporthe oryzae and other pathogenic fungi such as Fusarium spp., Colletotrichum gloeospoioides, Alternaria alternata which can cause apple spot fallen leaf disease and strawberry black spot, etc, was determined by dual culture assay. In addition, antagonistic activity of volatile substance produced by P. alcaliphila strain Ej2 against M. 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 plot experiments were conducted to verify the growth promoting effect on rice and control efficacy against leaf blast and neck blast of strain Ej2. Targeted metabonomics based on MRM method was used to detect the effect of strain Ej2 on endogenous hormones in rice plant such as stress hormone and cytokinin after spraying fermentation broth for three times. 【Result】The strain and volatile substance significantly suppressed the hypha growth rate of M. oryzae P131. The control efficacy against rice blast under greenhouse condition was 78.26% and it had no significant difference with 75% tricyclazole wettable powder. The control efficacy against rice leaf blast and neck blast in fields was 75.07%-83.67% and 62.79%-75.09%, respectively. It had a 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 strain Ej2 showed strong antagonist activity against other five pathogenic fungi, such as F. oxysporum f. sp. niveum, F. solani, F. moniliforme, C. gloeospoioides, A. alternata. The fermentation broth of P. alcaliphila strain Ej2 significantly increased the germinating rate of rice seeds, plant height, and panicle weight compared with water control. After spraying three times, the levels of the stress hormone in plant such as ethylene (ETH) and abscisic acid (ABA) were significantly increased, but the levels of cytokinin such as zeatin riboside (czR), trans-zeatin riboside (tZR) and N6-isopentenyladenine riboside (iPR) were significantly decreased. In addition, the levels of several endogenous hormones in rice plant including IAA, jasmonic acid (JA), cis-OPDA, jasmonoyl-L-isoleucine (JA-LIE), cis-zeatin (cZ), trans-zeatin (tZ), N6-isopentenyladenine (iP) and salicylic acid (SA) had no significant 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 microorganism against rice blast and other fungi diseases.

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