Application of plant survival-promoting and pathogen-suppressing Trichoderma species for crop biofertilization and biocontrol of root rot in Panax notoginseng

In this study, the biological activity of Trichoderma atroviride 1126, Trichoderma harzianum , and Trichoderma koningiopsis T5-1 against pathogens involved in root rot in sanqi ginseng ( Panax notoginseng ) were evaluated, in vitro and in the field. The in vitro effects of the three Trichoderma strains were analyzed through dual culture, assessment of volatile organic compounds (VOCs), and scanning electron microscopy. Ginseng growth and sanqi ginseng root rot (SRR) control were evaluated in terms of biomass and disease indices, respectively; plant survival was also assessed. Among the three tested strains, T. atroviride 1126 showed the strongest inhibition of Phytophthora cactorum (76%), and its VOCs inhibited P. cactorum growth by 68.93%. In a 2015 field test, Trichoderma increased total belowground fresh and dry weights by up to 28.20% and 24.81%, respectively, in 1-year-old sanqi ginseng and by up to 22.03% and 42.29% in 2-year-old sanqi ginseng. In the 2-year field study, the three Trichoderma strains significantly increased seedling survival at harvest, by up to 37% in 2016 and 14% in 2017. The SRR disease index was reduced by 44% and 60% in 1-year-old plants in 2016 and 2-year old plants in 2017, respectively. These results suggest that the three Trichoderma strains are important candidate biocontrol agents that could be supplied to soil for biofertilization, particularly in forests cultivated for organic traditional Chinese medicines.