Wood-associated fungi produce volatile organic compounds toxic to root-knot nematode

ABSTRACT Since volatiles do not leave residues in food and cause low toxicity to humans, they can act as a skeleton for new nematicidal molecules, once they have demonstrated activity against phytonematodes. The aim of this study was to evaluate the effect of volatile organic compounds (VOCs) released by wood-associated fungi on controling second-stage juveniles (J2) of Meloidogyne incognita. All 28 wood-associated fungi isolates produced VOCs which caused in excess of 76 % immobility in exposed J2 of M. incognita. The fungus isolate VOCs also caused significant mortality compared to control when J2 were exposed to them. After 6 h of exposure, the fungus species Epicoccum nigrum and Schizophyllum commune produced VOCs that immobilized exposed J2 compounds, in relation to the control. When J2 were inoculated into tomato under greenhouse conditions, the M. incognita infectivity and reproduction were reduced by exposure to the VOCs. Volatiles produced by most of the fungi isolates and analyzed by gas chromatograph coupled to a mass spectrometer (CG-MS), included alcohols, esters, terpenes, and ketones. Certain compounds appeared only in S. commune or in E. nigrum suggesting their involvement in the high level of damage caused to nematode reproduction on tomato. Volatiles emitted by wood fungi demonstrated another mode of action of these microorganisms in nature.

摘要 鉴于挥发性物质不会在食品中残留且对人体毒性较低，一旦被证实具有抗植物线虫（phytonematodes）的活性，便可作为新型杀线虫分子的核心骨架。本研究旨在评估木栖真菌释放的挥发性有机化合物（Volatile Organic Compounds, VOCs）对南方根结线虫（Meloidogyne incognita）二龄幼虫（second-stage juveniles, J2）的防控效果。所有28株木栖真菌分离物均可产生挥发性有机化合物，对受试的南方根结线虫二龄幼虫的麻痹率均超过76%。与对照组相比，经真菌分离物挥发性有机化合物处理的二龄幼虫死亡率亦显著升高。暴露6小时后，黑团壳霉（Epicoccum nigrum）和裂褶菌（Schizophyllum commune）产生的挥发性有机化合物对受试二龄幼虫的麻痹效果显著优于对照组。在温室条件下将二龄幼虫接种至番茄植株后，经挥发性有机化合物处理的线虫其侵染能力与繁殖能力均受到显著抑制。经气相色谱-质谱联用仪（Gas Chromatograph Coupled to a Mass Spectrometer, CG-MS）分析的多数真菌分离物所产生的挥发性成分，涵盖醇类、酯类、萜类与酮类物质。部分挥发性成分仅在裂褶菌或黑团壳霉的代谢产物中被检出，提示这些成分可能参与了对线虫在番茄植株上繁殖的强效抑制作用。木栖真菌释放的挥发性物质，揭示了这类微生物在自然环境中发挥作用的另一重机制。