中文摘要：

为挖掘用于稻瘟病防治的微生物资源,从感病水稻品种湘早籼24号的健康植株茎叶中用稀释分离法获得527个菌株。采用平板对峙法筛选出对稻瘟病菌具有拮抗作用的菌株60个,其中菌株YN145对稻瘟病菌菌丝生长抑制率达84.31%。经形态学和生理生化鉴定及16S rDNA序列分析,将菌株YN145鉴定为枯草芽胞杆菌Bacillus subtilis。生物活性测定表明,该菌株继代培养25代后,对稻瘟病菌菌丝抑菌效果仍在80%以上。菌株YN145发酵离心上清液经40、60、80、100和120℃处理30 min后,对稻瘟病菌的抑制率分别为91.50%、92.35%、91.78%、90.93%和86.97%;同样发酵上清滤液分别在pH 3、5、7、9和11处理30 min后,对稻瘟病菌的抑制率分别为91.50%、92.92%、92.92%、92.35%和92.63%。表明抗菌物质能耐高温、耐酸碱,菌株YN145作为稻瘟病生防制剂研发具有一定的价值。

英文摘要：

In order to explore the microbial resources for controlling rice blast, caused by Magnaporthe oryzae, 527 strains were isolated from healthy rice plants of the susceptible cultivar Xiangzaoxian 24 by the method of plate dilution. 60 strains with antagonistic activity against the blast fungus were obtained. The strain YN145 showed the strongest inhibition activity on mycelium growth with the rate of 84.31%. Based on the morphological analysis, physiological and biochemical characteristics, and 16S rDNA phylogeny, the strain YN145 was identified as Bacillus subtilis. Biological activity test showed that YN145 still had the inhibition rate of more than 80% on mycelium growth after 25 generations of subcultures. Fermentation supernatant of the strain could inhibit the mycelium growth by the rate of 91.50%, 92.35%, 91.78%, 90.93% and 86.97%, respectively, after treated at 40, 60, 80, 100 and 120 ℃ for 30 min. Meanwhile, the fermentation filtrate could inhibit the mycelium growth by the rate of 91.50%, 92.92%, 92.92%, 92.35% and 92.63%, respectively, after treated by pH 3, 5, 7, 9 or 11 for 30 min. The results suggested that antifungal substance of YN145 may be resistant to high temperatures and anti-acid and alkali. Thus, the strain YN145 is worthy for further research and development as rice blast bio-control agents.