Introduction: Endophytic fungi were isolated from medicinal plants on the assumption that these would possess the ability to produce a diverse array of secondary metabolites that might help deter the plant pathogens.
Methods: The plant Pterocarpus santalinus was collected from the campus of the University of Agricultural Sciences, GKVK, Bengaluru (13.0801° N, 77.5785° E), in the year 2014-15. Endophytic fungi were isolated from the leaf, stem and flower (if available), as described by Shweta et al. (2010). Endophytes were screened against the soil-borne plant pathogens by a dual culture assay and a double-plate assay. Mechanisms were confirmed using SEM and GC-MS. Data were statistically analyzed.
Result: In this study, involving four pathogenic fungi and an endophytic fungus, Trichoderma harzianum isolated from Pterocarpus santalinus, show that besides mycoparasitism, VOCs play a major role in antagonism. In the double-plate assay, the endophytic T. harzianum significantly inhibited the mycelial growth of three of the four pathogens (Sclerotinia sclerotiorum, Sclerotium rolfsii, and Fusarium oxysporum), while that of Macrophomina phaseolina was not affected. The GC-MS profile of the VOCs of the endophytic T. harzianum and their interaction with pathogens showed the presence of different classes of VOCs. The VOC profiles of endophyte–pathogen depended on the interacting pathogen, suggesting a species-specific response. In the presence of M. phaseolina, the VOC repertoire was subdued and in some cases not detected. Such dynamism in the chemical warfare between the endophyte and pathogenic fungi is little known and could be potentially interesting for unraveling the molecular mechanisms of VOC induction. Soybean seeds pre-treated with the endophyte T. harzianum showed significantly reduced mortality upon infection with S. rolfsi and S. sclerotiorum compared with those not enriched with the endophytes.
Conclusion: Understanding the immediate mechanisms involved in this endophyte-mediated resistance against pathogens could lead to a more effective use of endophytes in disease control in the future.
