烟草叶围细菌的分离及其对Alternaria alternata的拮抗作用

分离到烟草叶围细菌136株,通过对峙培养实验筛选出对烟草赤星病菌A.alternata有较强拮抗活性的9个菌株.离体叶片生防测定实验表明,9株细菌均能不同程度地减轻烟草赤星病的发生.其中菌株Tpb88具有较强和稳定的拮抗作用,无菌滤液实验表明,叶围细菌Tpb88在一定浓度范围内能有效抑制A.alternata菌丝生长、孢子萌发和芽管伸长,且浓度越高,抑制能力越强,结果表明Tpb88对烟草赤星病菌的拮抗机制可能为抗菌物质的产生.

Screening of antagonistic bacteria from phylloshere and its resistance to Alternaria alternata

The possibility of employing antagonistic bacteria for controling tobacco brown spot was studied. Approximately 136 strains of bacteria were isolated from phyllospheres of tobacco and 9 of these possessed high level of antagonistic properties. They significantly reduced brown spot in detached tobacco leaves when artificially inoculated with Alternaria alternata. Culture filtrate of the most effective bacterial isolate which designated as Tpb88 was shown to be very efficient in inhibiting mycelial growth of A. alternata in dual cultures. Culture filtrate of Tpb88 inhibited germination and germ tube elongation of A. alternata. The results showed that the culture filtrate directly inhibited spore germination of A. alternata, especially during the early hours of the paired cultivation. The rate of antagonistic activity of culture filtrate of Tpb88 depended on its concentration in the mixture. The greatest inhibition of spore germination was observed at the highest concentration of filtrate (filtrate to fungal spores inocula mixed in proportion 1:50). These suggested that the hypothetic mechanism of Tpb88 against tobacco brown spot was induced by antagonistic substances.