拮抗细菌Bacillus subtilis B5423-R 抑制水稻纹枯病的阈值群体数量

 在菲律宾国际水稻研究所实验农场田间条件下，通过人工接种Rhizoctonia solani,采用不同的方法(喷雾次数、间隔期)喷雾B5423-R（B5423的标记菌株，为利福平Rifampicin抗性的突变体），在接种1 d后，采用2 d喷1次、连续3～4次喷雾的方法，使B5423 R在稻株上的群体数量在6～7 d内维持在1×10sup]6/sup]cfu/g以上，在25 d内显著地降低相对病斑高率；而采用5 d喷1次、连续3～4次喷雾的方法，B5423-R在稻株上的群体数量在15 d内维持在1×10sup]5/sup]～106cfu/g，在25 d内相对病斑高率未能显著降低。表明在纹枯病侵染早期的6～7 d内，在稻株上B5423 R维持在1×10sup]6/sup]cfu/g以上是抑制纹枯病的阈值群体数量。

Threshold Population Sizes of Bacillus subtilis B5423-R to Suppress the Occurrence of Rice Sheath Blight

The mechanism of Bacillus subtilis B5423 to suppress the occurrence of rice sheath blight is mainly by means of antibiotics produced by B5423. Under field conditions, the experiment of B5423-R(marker strain of B5423, a Rifampicin-resistant mutant ) to suppress vertical spread of sheath blight was conducted by inoculating R. solani and spraying B5423-R in different methods (including spraying times, and spraying intervals). Successive 3-4 times spraying with an interval of one day made the population sizes of B5423-R on rice stems be higher than 1×10⁶ cfu/g within 6-7 days, and significantly reduced relative lesion height (RLH) of rice sheath blight. On the other hand, successive 3- 4 times spraying with an interval of four days made B5423-R on rice stems fluctuate from 1×10⁶ to 1×10⁵ cfu/g within 15 days, and not cause any significant reduction of RLH of rice sheath blight in 25 days. The above results revealed that the population threshold of B5423-R to suppress rice sheath blight should be higher than 1×10⁶ cfu/g during the early infection of R. solani (within 6-7 days).