Regional Centre of Agricultural Research of Sidi Bouzid, CRRA, Gafsa Road Km 6, B.P. 357, Sidi Bouzid, 9100, Tunisia.
Department of Plant Protection and Biological Sciences, Higher Agronomic Institute of Chott-Meriem, University of Sousse, Sousse, Tunisia.
BMC Microbiol. 2023 Apr 20;23(1):108. doi: 10.1186/s12866-023-02855-4.
In our continuing search for biologically active natural enemies from North of Africa with special reference to Tunisian fungi, our teamwork screened fungi from different ecological habitats in Tunisia. Our previous study on the comparative effectiveness of filamentous fungi in the biocontrol of Meloidogyne javanica, a taxon (Lecanicillium) showed high potentiality against M. javanica. We undertook the present study to evaluate the ability and understand the mechanism of this fungal parasite as a biological control candidate against the root-knot nematode M. javanica. This study used in vitro bioassays with fungal filtrate cultures, scanning electron microscopy (SEM) observation, and isobaric tag for relative and absolute quantitation (iTRAQ) methodology to characterize the biological and molecular features of this fungus.
The microscopic and SEM observation revealed that Lecanicillium sp. exhibited exceptional hyperparasitism against M. javanica eggs. The hyphae of this fungi penetrated the eggs, causing destructive damage to the outer eggshell. The exposure to five concentrations of Lecanicillium sp. filtrate cultures showed high inhibition of egg hatching, which increases depending on the exposure time; the best results are recorded at 50%, 75%, and 100% dilutions after seven days of exposure. The SEM observation of nematode-parasitized eggs and juveniles suggests that the production of lytic enzymes degrades the egg cuticle and fungal hyphae penetrate unhatched M.javanica juveniles. Forty-seven unique proteins were identified from the Lecanicillium sp. isolate. These proteins have signalling and stress response functions, bioenergy, metabolism, and protein synthesis and degradation.
Collectively, Lecanicillium sp. had ovicidal potentiality proved by SEM and proteomic analysis against root-knot nematode' eggs. This study recommended applying this biological control candidate as a bio-agent on vegetable crops grown in situ.
在我们继续从北非寻找具有生物活性的天然捕食者的过程中，特别关注突尼斯真菌，我们的团队筛选了来自突尼斯不同生态栖息地的真菌。我们之前对丝状真菌在防治爪哇根结线虫（Meloidogyne javanica）方面的比较效果的研究表明，该真菌对爪哇根结线虫具有很高的潜力。我们进行了本研究，以评估这种真菌寄生虫作为防治爪哇根结线虫的生物防治候选物的能力，并了解其机制。本研究使用真菌滤液培养物的体外生物测定、扫描电子显微镜（SEM）观察和等压标记相对和绝对定量（iTRAQ）方法来表征这种真菌的生物学和分子特征。
微观和 SEM 观察表明，Lecanicillium sp. 对爪哇根结线虫卵表现出异常的超寄生作用。该真菌的菌丝穿透卵，导致卵外壳的破坏性损伤。暴露于五种浓度的 Lecanicillium sp. 滤液培养物显示出对卵孵化的高度抑制作用，这种抑制作用随着暴露时间的增加而增加；在暴露七天后，50%、75%和 100%稀释度的效果最佳。对寄生有根结线虫的卵和幼虫的 SEM 观察表明，溶酶体酶的产生降解卵壳，真菌菌丝穿透未孵化的爪哇根结线虫幼虫。从 Lecanicillium sp. 分离株中鉴定出 47 种独特的蛋白质。这些蛋白质具有信号转导和应激反应功能、生物能量、代谢以及蛋白质合成和降解。
综上所述，Lecanicillium sp. 通过 SEM 和蛋白质组学分析对根结线虫的卵具有杀卵潜力。本研究建议将这种生物防治候选物作为生物制剂应用于原位种植的蔬菜作物上。
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