拮抗细菌Bacillus subtilis B5423-R抑制水稻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

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Rhizoctoniasolani,采用不同的方法 (喷雾次数、间隔期 )喷雾B542 3 R(B542 3的标记菌株 ,为利福平Rifampicin抗性的突变体 ) ,在接种 1d后 ,采用 2d喷 1次、连续 3～ 4次喷雾的方法 ,使B542 3 R在稻株上的群体数量在 6～ 7d内维持在 1× 10 6 cfu/g以上 ,在 2 5d内显著地降低相对病斑高率 ;而采用 5d喷1次、连续 3～ 4次喷雾的方法 ,B542 3 R在稻株上的群体数量在 15d内维持在 1× 10 5 ～ 10 6cfu/g,在 2 5d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～ 7d内 ,在稻株上B542 3 R维持在 1× 10

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- r esistant mutant ) to suppress vertical spread of sheath blight was conducted b y inoculating R. solani and spraying B5423-R in different methods (includin g spraying times, and spraying intervals). Successive 3-4 times spraying with a n interval of one day made the population sizes of B5423-R on rice stems be hi gher than 1×10 6 cfu/g within 6-7 days, and significantly reduced rela tive 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 fluct uate from 1×10 6 to 1×10 5 cfu/g within 15 days, and not cause any sig nificant reduction of RLH of rice sheath blight in 25 days. The above results r evealed that the population threshold of B5423-R to suppress rice sheath blig ht should be higher than 1×10 6 cfu/g during the early infection of R. so lani (within 6-7 days).