酥瓜果实细菌性斑点病的病原鉴定

为明确安徽省淮南市地区酥瓜果实斑点病的病原菌,采用常规平板划线法从酥瓜果实病组织分离细菌,通过生理生化特征、分子生物学特性和致病性试验对其进行鉴定.结果表明,从采集的病果中获得36株菌落形态特征相似的细菌分离物,测试菌株均能诱导烟草叶片产生过敏性坏死.采用牙签刺伤法将测试菌株接种健康酥瓜果实,可导致接种点处产生水浸状病斑.BLAST结果表明,2株菌株的16S rRNA序列分别与短小芽胞杆菌Bacillus pumilus GR-8(CP009108),ATCC 7061(ABRX01000003)的同源性为99.93％和99.58％,2株菌株的 gyrB 基因序列与 B.pumilus C4(CP011109)的同源性达99.39％.基于gyrB基因的聚类分析证实2株菌株与B.pumilus(C4和GR-8)紧密的聚在一个分支.生理生化试验结果进一步显示,该细菌与文献报道的短小芽胞杆菌的生理生化特征相吻合.结合细菌生理生化特征、16S rRNA和gyrB基因的序列分析,以及柯赫氏法则验证,确定引起酥瓜果实细菌性斑点病的病原为B.pumilus.

Identification of the pathogen causing bacterial fruit spot of crisp melon

To clarify the causal agent of bacterial fruit spot of crisp melon, it was conducted for the bacterial isolation from the symptomatic fruits by plate streaking method in this study. The isolates were tested for pathogenicity assays on the fruit of crisp melon, and the identification by physiological and biochemical tests and molecular methods. A total of 36 bacterial isolates with consistent appearance were recovered from symptomatic tissues. The tested isolates induced hypersensitive reactions on tobacco leaves within 48 h after infiltration and caused water-soaked necrosis in the fruit tissues with the toothpick inoculation method. BLAST results showed that the sequences of 16S rRNA of the two representative strains were 99.93% and 99.58% identity with B. pumilus GR-8 (CP009108) and ATCC 7061(ABRX01000003), respectively. And the sequences of gyrB gene of the two strains were 99.39% identity with that of B. pumilus C4 (CP011109). Furthermore, a phylogenetic analysis of the gyrB sequences showed that the two strains were most closely related to B. pumilus C4 and GR-8 in the phylogenetic tree. The physiological and biochemical tests indicated the characteristics of these bacterial isolates were consistent with those of reference strains of B. pumilus. Based on the physiological and biochemical characteristics, sequences analysis of 16S rRNA and gyrB gene, and verified identified Koch''s postulate, the pathogen causing fruit spot of crisp melon was identified as B. pumilus.