产几丁质酶香蕉枯萎病拮抗菌的筛选、鉴定及抑菌作用

Screening and identification of chitinase-producing bacterium and its antagonistic activity against Fusarium oxysporum f. sp. cubense

为了筛选出对枯萎病菌有拮抗作用的几丁质酶产生菌,分别以香蕉枯萎病镰刀菌细胞壁和几丁质为唯一碳源进行几丁质酶产生菌初筛和复筛,然后通过平板对峙试验,从几丁质酶产生菌中筛选出一株香蕉枯萎病拮抗菌。通过形态特征和分子生物学分析,确定其为枯草芽孢杆菌并将其命名为XW-2。研究了不同温度、pH值及碳源对XW-2菌株发酵液抑菌活性的影响,结果表明,发酵液在初始pH为7～8,温度为31～34℃时活性最高,几丁质诱导的发酵液活性高于病原菌细胞壁。发酵液能明显抑制病原菌菌丝的生长,拮抗试验可见病原菌菌丝缢缩、消解、顶端膨胀,菌丝体畸形、断裂。

In order to screen ehitinase-producing bacteria which could inhibit the growth of pathogen, chitinase-produeing strains were isolated by double screen with the chitin and pathogen cell wall as sole carbon, and then, by dual culture, an antagonistic bacillus against Fusarium oxysporum f. sp. cubense was isolated from chitinase-producing strains. Based on morphological characteristics and the homology analysis of 16S rDNA sequence, the strain was identified as Bacillus subtilis and was named XW-2. In order to study the effects of environmental factors on the antagonistic substance activity of fermentation filtrate, the culture conditions of XW-2, such as temperature, pH and medium were studied. The results showed that an initial range of pH 7.0 to 8.0 in the liquid culture and a temperature range of 31 to 34 ℃ were most favorable for the production of antagonistic substance. It was also indicated that the chitin was better than cytoderm for the induction of antagonistic activity. The study showed that the myeelium growth of fungi was inhibited seriously with the fermentation filtrate, and microscope observation of antagonistic action revealed that the fungi hypha were constricted, dissolved, and had an inflated tip, mycelium was deformed mid fractured to small segments.