Novel Lead Compound Discovery from Aspergillus fumigatus 1T‑2 against Meloidogyne incognita Based on a Chemical Ecology Study

To
replace biohazardous nematicides, there is an ever-increasing
need to identify natural product-based agents to contain root-knot nematodes
(RKNs) in agriculture. In this chemical ecology study, an antagonistic
fungus Aspergillus fumigatus 1T-2,
which could cause the formation of withering of the gut and vacuole-like
structures in the nematode body, was isolated based on the gradually
increased antagonistic interactions between the soil fungi and RKNs.
Based on these typical morphological characteristics, a potent nematode-antagonistic
compound 2-furoic acid, which had a simple structure, was successfully
identified from 1T-2 fermentation broth by liquid chromatography–mass spectrometry (LC–MS). 2-Furoic
acid showed effective mortality activity in vitro, of which the LC50 value to Megalaima
incognita at 24 h was 37.75 μg/mL. 2-Furoic
acid had similar mortality activity to the positive control fosthiazate
at 30 μg/mL. Continuous 2-furoic acid exposure had obvious negative
influences on both nematode vitality and egg hatchability. Notably,
significant variations were observed in nematodes and eggs with 2-furoic
acid treatment, which might be induced by novel nematocidal mechanisms.
Furthermore, the 1T-2 fermentation broth and 2-furoic acid had significant
control efficacy on M. incognita under
the greenhouse test-tube assay. Overall, these findings provide valuable
insights into the use of 2-furoic acid with biocontrol potential as
a preferable lead structure for the development of innovative nematicides.

为替代具有生物危害性的杀线虫剂，农业领域对筛选基于天然产物的药剂以防控根结线虫（root-knot nematodes, RKNs）的需求日益增长。本化学生态学研究中，基于土壤真菌与根结线虫间逐渐增强的拮抗互作，我们分离得到一株可致使线虫体内肠道萎缩并形成液泡样结构的拮抗真菌——烟曲霉（Aspergillus fumigatus）1T-2。基于上述典型形态学特征，本研究通过液相色谱-质谱联用法（liquid chromatography–mass spectrometry, LC-MS）从1T-2的发酵液中成功鉴定出一种结构简单的高效抗线虫化合物——2-糠酸（2-furoic acid）。2-糠酸在体外展现出优异的杀线虫活性：其在24小时时对Megalaima incognita的半致死浓度（LC50）为37.75 μg/mL。在30 μg/mL浓度下，2-糠酸的杀线虫活性与阳性对照药剂噻唑磷（fosthiazate）相当。持续暴露于2-糠酸会对线虫活力与卵孵化率均产生显著负面影响。值得注意的是，经2-糠酸处理的线虫与虫卵均出现显著变化，这一现象可能由全新的杀线虫机制所介导。此外，在温室试管试验中，1T-2发酵液与2-糠酸均对M. incognita展现出显著的防控效果。综上，本研究结果为将具备生防潜力的2-糠酸开发为新型杀线虫剂的优选先导结构提供了重要理论参考。