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广东省桐花树叶尖枯病病原菌鉴定及拮抗细菌筛选

Identification of Neofusicoccum ribis Causing Leaf Tip Blight on Aegiceras corniculatum and Screening of Its Antagonistic Bacteria in Guangdong Province

  • 摘要:
    目的 为明确引起广东省湛江市桐花树叶尖枯病的病原菌种类,揭示病原菌的生物学特性,并筛选拮抗菌,为该病的防控提供依据。
    方法 采用组织分离法和单孢分离法进行病原分离纯化,通过形态学和多基因系统发育分析 (ITS、TEF-1αTUB2) 相结合的方法对分离菌株进行鉴定,通过人工接种测定其致病性。用菌丝生长速率法研究其生长特性,利用平板对峙法进行拮抗菌的筛选。
    结果 28 ℃条件下该菌在PDA培养基上的生长速度较快,3 d即可长满培养基,培养基正面气生菌丝初期为白色,随后变成灰色,背面初期为白色,随后菌落中心变为黑色。菌丝有隔,厚垣孢子链状,分生孢子椭圆形至梭形,薄壁半透明,大小为(15.19~19.66) × (4.59~6.07)μm(n=100)。根据形态特征和多基因系统发育分析将分离菌株鉴定为新壳梭孢菌(Neofusicoccum ribis)。人工接种分离菌株,可以引起桐花树叶片发病,症状与林间一致。新壳梭孢菌菌株THJK1A3最适生长温度为28 ℃,但该菌的适宜生长温度范围较窄,温度低于20 ℃或高于30 ℃时,菌丝生长显著受到抑制。最适pH值为4。解淀粉芽孢杆菌68对菌株THJK1A3的菌丝生长抑制率为(68.71 ± 2.56)%。
    结论 明确了 N. ribis 是引起广东省湛江市桐花树叶尖枯病的致病菌,解淀粉芽孢杆菌68对菌株THJK1A3的拮抗效果较好。

     

    Abstract:
    Objective To identify the pathogen causing tip blight on Aegiceras corniculatum in Zhanjiang City, Guangdong Province, China. The study involves elucidating the biological and molecular characteristics of the pathogen and screening for antagonistic bacteria, aiming to provide a basis for disease prevention and control.
    Methods Isolation and purification of the pathogen were carried out using infected tissue samples and single spores. The isolated fungal strains were identified through morphological observations and phylogenetic analysis of concatenated gene sequences, including ITS, TEF-1α and TUB2. Biological characteristics such as growth rate, colony diameter, and growth morphology in different environmental conditions were assessed. Pathogenicity was confirmed by artificial inoculation on detached leaves of A. corniculatum. Antagonistic bacteria were screened using dual culture assays to identify potential candidates for controlling leaf tip blight.
    Results  The isolated fungi displayed rapid growth on PDA medium at 28 °C, fully covering the Petri dish within 3 days. The aerial mycelium initially appeared white amd later turned gray, while the underside transitioned from white to a black center. Microscopic observation revealed septate hyphae forming thick-walled, spore chain-like structures. The conidia were oval to spindle-shaped, thin-walled, semi-transparent, and measured (15.19~19.66) × (4.59~6.07) μm (n=100). Morphological characteristics and phylogenetic analysis identified the strain as N. ribis. Artificial inoculation with the isolate caused symptoms identical to those observed in naturally infected leaves. The optimal growth temperature for the N. ribis strain THJK1A3 was 28 °C, with a narrow growth range; hyphal growth was significantly inhibited below 20 °C or above 30 °C. The optimal pH condition was determined to be 4. Finally, Bacillus amyloliquefaciens 68 demonstrated a 68.71 ± 2.56% inhibition of the hyphal growth of strain THJK1A3, suggesting its potential as a promising biocontrol agent for practical application.
    Conclusion The causative agent of tip blight in A. corniculatum in Zhanjiang City, Guangdong Province, China, was identified as N. ribis strain THJK1A3. Additionally, B. amyloliquefaciens 68 demonstrated strong antagonistic activity against THJK1A3, making it a promising candidate for the biological control of this disease.

     

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