A Trichoderma longibrachiatum strain with antagonistic effects against three soil-borne pathogenic fungi

To enrich the microbial resources of Trichoderma spp. for biocontrol, a dominant Trichoderma strain was isolated from the rhizosphere soil of a landscape plant, Sedum spectabile Boreau. The isolated Trichoderma strain was identified using colonial-and micro-morphological observations, ribosomal DNA (rDNA)-internal transcribed spacer (ITS) sequence alignment, and homology analysis using a Neighbour-Joining method. An agar disk diffusion method was used to investigate the antagonism between the isolated Trichoderma strain and three other soil-borne pathogenic fungi, Sclerotinia sclerotiorum, Rhizoctonia solani, and Alternaria alternata. The tissue-cultured plantlets of Populus davidiana×P. alba var. Pyramidalis were further inoculated with the isolated Trichoderma strain and the resistance of the inoculated seedling leaves against A. alternata was evaluated in vitro. The results demonstrated that the isolated Trichoderma strain was Trichoderma longibrachiatum and it exhibited evident and differential antagonistic effects against each of the three tested soil-borne pathogenic fungi. We designated the isolated Trichoderma strain as Tl-70. The antifungal activity of Tl-70 against S. sclerotiorum was a 77.71% inhibition, which was the highest and significantly higher than that against R. solani or A. alternata (P<0.05). The antifungal activity against R. solani was a 58.56% inhibition, and significantly higher than that against A. alternata (P<0.05, 53.32%), which was the lowest of the three tested strains. Moreover, inoculation with Tl-70 enhanced the disease resistance of the leaves of tissue-cultured Populus davidiana×P. alba var. Pyramidalis seedlings against the pathogen A. alternata. Our results suggest that Tl-70 is a potential biocontrol strain.