The isolation of the antagonistic strain Bacillus australimaris CQ07 and the exploration of the pathogenic inhibition mechanism of Magnaporthe oryzae

Biological control as a promising method to combat plant disease has gained public attention in recent years. In the present study, we isolated 12 strains resistant to Magnaporthe oryzae from western Sichuan subalpine soil. Among them, CQ07 exhibited remarkable activity against M. oryzae. The result of 16S rRNA sequence analysis revealed that CQ07 is approximately 99% similar to Bacillus australimaris. The sterilized culture filtrate of CQ07 inhibited the growth of M. oryzae, which motivated us to deduce the influence of CQ07 on the pathogenicity of M. oryzae. As shown by experimentation, sterilized culture filtrate (10 μl/ml) of CQ07 can delay and even suppress the germination of conidia and prevent the formation of appressorium in vitro and in vivo. In addition, by simulative field tests, the spraying of conidia suspension diluted with sterilized culture filtrate of CQ07 reduced infection of rice blast. To better control rice blasts, understanding the infection mechanism of M. oryzae and inhibiting the mechanism of the antagonistic strain is of great importance.

近年来，生物防治作为防控植物病害的极具潜力的策略，已受到学界与社会的广泛关注。本研究从川西亚高山土壤中分离得到12株抗稻瘟病菌（Magnaporthe oryzae）的菌株，其中菌株CQ07对该病原菌表现出显著的拮抗活性。经16S rRNA序列分析，CQ07与澳大利亚芽孢杆菌（Bacillus australimaris）的序列相似度约为99%。CQ07的无菌培养滤液可抑制稻瘟病菌的生长，这促使我们进一步探究该菌株对稻瘟病菌致病性的影响。实验结果表明，浓度为10 μl/ml的CQ07无菌培养滤液可延缓甚至抑制稻瘟病菌分生孢子（conidia）的萌发，并在体外与体内实验中阻断附着胞（appressorium）的形成。此外，通过模拟田间试验发现，使用CQ07无菌培养滤液稀释的分生孢子悬浮液进行喷施，可有效降低稻瘟病的侵染程度。为更好地防控稻瘟病，解析稻瘟病菌的侵染机制并明确该拮抗菌株的抑菌作用机制具有重要意义。