Antagonism of plant pathogenic fungi by endophytic fungi is a well-known phenomenon. In plate assays, the antagonism could be due to mycoparasitism, competition for space or antibiosis, involving a chemical diffusate, or a volatile organic compound (VOC). In this study, we demonstrate that besides mycoparasitism, VOCs play a major role in antagonism of pathogenic fungi by four endophytic fungi belonging to the genus Trichoderma. Using a double-plate assay, we show that all the four endophytic Trichoderma species significantly inhibited mycelial growth of three of the four pathogens, (Sclerotinia sclerotiorum-TSS, Sclerotium rolfsii-CSR and Fusarium oxysporum-CFO), while that of Macrophomina phaseolina-CMP was not affected. GC–MS analysis of the pure cultures of one of the endophytic fungi studied, namely, Trichoderma longibrachiatum strain 2 (Acc. No. MK751758) and the pathogens, F. oxysporum-CFO and M. phaseolina-CMP revealed the presence of several VOCs including hydrocarbons, alcohols, ketones, aldehydes, esters, acids, ethers and different classes of terpenes. In mixed double plates, where the endophyte was grown along with either of the two plant pathogens, F. oxysporum-CFO or M. phaseolina-CMP, there was an induction of a number of new VOCs that were not detected in the pure cultures of either the endophyte or the pathogens. Several of these new VOCs are reported to possess antifungal and cytotoxic activity. We discuss these results and highlight the importance of such interactions in endophyte-pathogen interactions.

内生真菌对植物病原真菌的拮抗作用是众所周知的现象。在平板测定中，拮抗作用可能是由于支原体寄生，竞争空间或抗微生物作用，涉及化学扩散物或挥发性有机化合物（VOC）引起的。在这项研究中，我们证明了除真菌副寄生虫外，VOC在木霉属的四种内生真菌拮抗病原真菌方面也起着重要作用。使用双板分析，我们表明，所有四个内生木霉种显著抑制三四个病原菌的菌丝生长，（菌核病sclerotiorum- TSS ，白绢病-CSR和尖孢镰刀菌-CFO），而中，巨噬性菜豆-CMP不受影响。对所研究的一种内生真菌，即长木木霉菌株2（Acc。No. MK751758）和病原体oxysporum- CFO和M. phaseolina -CMP的纯培养物的GC-MS分析表明存在几种VOC包括碳氢化合物，醇，酮，醛，酯，酸，醚和不同种类的萜烯。在混合双板中，内生菌与两种植物病原体中的任何一种一起生长，即：F。oxysporum- CFO或M. phaseolina-CMP，诱导了在内生菌或病原体的纯培养物中未检测到的许多新的VOC。据报道，这些新型VOC中的几种具有抗真菌和细胞毒性活性。我们讨论这些结果，并强调内生菌-病原体相互作用中此类相互作用的重要性。