一株萎缩芽孢杆菌在小麦中的定植及对赤霉病的防治

Bacillus atrophaeus strain’s colonization in wheat plant and its inhibition efficiency to Fusarium head blight

从小麦的叶片中筛选获得了一株抗赤霉病菌株XM5,经16S-23SrDNAITS序列的扩增比对,鉴定其为萎缩芽孢杆菌(Bacillusatrophaeus)。通过逐步提高抗生素浓度驯化,使该菌株获得了利福平和链霉素的双抗性标记,同时针对其ITS序列的特异性区段,设计了特异性引物L6SF、L6SR。采用抗抗生素和特异性PCR双重标记,研究了XM5在小麦中的内生定植状况,发现根施的XM5能长期定植于室内小麦苗和室外植株中,但定植菌的数量随时间呈递减趋势。为研究穗部的防治效果,分别以XM5的菌悬液和发酵液喷施幼穗,结果表明:10d后两个处理组在穗部表面残余的活菌数量均已不足起始量的5%,但在喷施菌悬液组,麦穗内部定植的XM5的数量不断增加,由5.2×103持续增加至4.8×104cfu·穗-1,其对赤霉病的防效在7d时可达到68.3%。

An antagonism strain XM5 which can strongly inhibit Fusarium graminearum was iso- lated from wheat leaves at jointing stage. The strain was identified as Bacillus atrophaeus by 16S- 23S internal transcribed spacer （ITS） nucleotide sequences. To track the XM5 colonized in wheat plant, a dual-antibiotic-marker resistant to rifampicin and streptomycin was induced by gradually increasing the concentration of antibiotics in the medium for XMS. Meanwhile, the ITS sequence of XM5 was used as a DNA marker. A pair of specific primers L6SF and L6SR was adopted for PCR test. With the double labels of the dual antibiotic resistance and the specific PCR test, the amount of XM5 colonized in wheat plant was measured. The results showed that XM5 could colonize in wheat plant for a long time, but the amount of XM5 in seedlings decreased with time. To measure the bio-control efficiency of XM5 to Fusarium head blight （FHB）, the XM5 cell suspension and cultured broth （with cells） were sprayed on the heading wheat, respec- tively, and the amount of endophytic XM5 in wheat ear and the resistance efficiency against FHB were surveyed. In the two treatments, the amount of XM5 on the surface of wheat ear decreased with time, only less than 5% XM5 being survived 10 days later, but in the cell suspension treat- ment, the amount of colonized XM5 in wheat ear increased unceasingly from 5.2xlO3 to 4.8~104 cfu ~ head-j , and the biological control efficiency to FHB reached 68.3% after 7 days.