Antagonistic fungal endophytes and their metabolite-mediated interactions against phytopathogens in rice

Endophytes regulate physiological activities of host plants by conferring resistance against abiotic stress, insect, nematode, and diseases. Besides, they produce novel natural bioactive compounds with potential applications in agriculture, medicine, and food industry. In the present study, seven antagonistic fungal endophytes showing anti-fungal and anti-bacterial activities were isolated from rice leaves and identified as Paecilomyces tenuis EF1, Talaromyces pinophilus EF2, Nigrospora sphaerica EF3, Nigrospora oryzae EF4, Trichoderma longibrachiatum EF5, and EF7 and Aspergillus terreus EF6. Of these, T. longibrachiatum EF5 had the highest growth inhibition activity against the tested fungal (23%-82%) and bacterial plant pathogens (13%-46%). Soluble metabolites such as aliphatic organic acids, (e.g., lactic, acetic, hydroxyl-methyl valeric acids, ethyl hexyl acetate, salbutamol sulfate, dodecanone, octadecanoic, octaheptanoic and butanenoic acids), aromatic nitroamino compounds (Benzyl gly-cinate), and volatile metabolites, (e.g., 2,3butanediol dinitrate, pentadecane, tetramethyl hexahydro napthalenone, 1-iodo-2-methylundecane) were detected through FT-IR and GC-MS-TD, respectively. The metabolite induced antagonistic activity of EF5 was much pronounced against phytopathogens such as Magnaporthe grisea, Rhizoctonia solani, and Macrophomina phaseolina. Also, the volatile organic compounds (VOCs) of T. longibrachiatum EF5 enhanced the lateral root formation by modulating auxin biosynthesis.