芝麻立枯病内生生防细菌的筛选

Screening of endophytic bacteria against damping-off of the sesame caused by Rhizoctonia solani

利用表面消毒涂布平板的方法从大田健康芝麻根内分离芝麻内生细菌399株。平板对峙试验结果显示,176株细菌对立枯丝核菌(Rhizoctonia solani)有不同程度的拮抗能力,其中编号为B16、b10、D31、e23、G10I、10的6个菌株在PDA平板上对于立枯丝核菌具有极强的抑制作用,对西瓜枯萎病菌、西瓜炭疽病菌、小麦全蚀病菌和油菜菌核病菌也表现出广谱的抑菌作用。利用胶体几丁质和胶体壳聚糖作为唯一碳源,测定了上述6株细菌产生几丁质酶和壳聚糖酶的能力,发现b10和G10具有产壳聚糖酶的能力,I10有产几丁质酶的能力。活体盆栽试验测定了上述6株细菌对芝麻立枯病的生防效果,结果显示测定的6株细菌均具有一定的防治效果,其中G10的生防效果最好,可达到52%。利用胶体壳聚糖作为唯一碳源的选择性培养基测定了G10菌株在芝麻根系内部的定殖动态,发现G10在芝麻根部可以长期定殖。

Three hundred and ninety-nine endophytic bacteria were isolated from the inner roots of healthy sesame grown in the field by the methods of surface disinfection and spread plate. Antagonistic activity of endophytic bacteria against Rhizoctonia solani were assayed on dual culture plates, and the results showed that 176 endophytic bacteria isolates had antagonistic activities toward the R. solani to some extent. Six isolates （B16, b10, D31, e23, G10 and I10） could strongly inhibit the growth of R. solani and other pathogenic fungi, including Fusarium oxysporium, Colletotrichurn orbiculare , Gaeumannornyces graminis var. tritici and Sclerotinia sclerotiorum. The ability of the six isolates to produce chitinase and chitosanase was also assayed on culture plates with colloidal chitin and colloidal chitosan as the sole carbon source, which revealed that the strains of bl0, G10 and I10 could produce both chitosanase and chitinase. The biological control potential of the six isolates against the damping-off caused by R. solani was tested in vivo, and the results indicated that all of the six isolates could control the damping-off to some extent, and the best control efficiency was achieved by the isolate G10, reaching to 52%. Endophytic colonization of G10 within sesame roots was tested on selective media with colloidal chitosan as the sole carbon source, and the results indicated that the isolate G10 could persistently survive on the roots.