Saprophytic, leaf endophytes, and orchid mycorrhizal fungi as biocontrol agents of the phytopathogenic fungi Rhizoctonia solani and Fusarium circinatum

Pathogenic fungi cause approximately 80% of crop diseases worldwide. Among these, Rhizoctonia solani and Fusarium circinatum have a significant economic impact, affecting major crops and Pinus species. Traditional fungicides pose health and environmental risks, therefore, sustainable approaches such as biocontrol are necessary. This work explores the biocontrol potential of saprophytic, endophytic, and orchid mycorrhizal fungi (OMF), including C. rigida, P. ostreatus and E. nigrum, on the pathogenic fungi F. circinatum and R. solani. It also examines their volatile organic compound (VOC) profiles of biocontrolling fungi and pathogens during the biocontrol process. The results show that all fungi exhibited an in vitro biocontrol effect on both pathogenic fungi, similar to that of the known biocontroller fungi T. harzianum, except for the OMF isolated from the orchid Chloraea lamellate. A representative amount of the VOCs corresponded to terpenes, present in most individual and dual cultures. Dual cultures presented specific volatile, which may be related to the inhibitory effect. This research contributes to the knowledge about the biotechnological potential of saprophytic fungi and OMFs in the control of agriculturally important pathogenic fungi. The preliminary study of VOCs allowed us to explore one of the possible mechanisms that explain the biocontrol process.