Identification of endophytic Trichoderma species (Hypocreaceae, Hypocreales) and their application against leaf blight of host Platycladus orientalis

Ancient Platycladus orientalis holds significant historical, cultural, ecological, and landscape value. Leaf blight caused by Alternaria spp. is the most common disease of P. orientalis . However, no reports are currently available on the screening and application of biocontrol agents for controlling this disease. In this study, several Trichoderma isolates were obtained from ancient P. orientalis in Beijing. Based on morphological characteristics and phylogenetic analyses of the concatenated ITS, tef 1-α and rpb 2 loci, four Trichoderma species were identified, including T. citrinoviride , T. obovatum , T. nordicum , and T. platycladi . Of these, T. platycladi is a species new to science, whereas T. nordicum and T. obovatum are new host records. Plate antagonism tests showed that representative strains of the four Trichoderma species exhibited significant inhibitory effects against colonies of Alternaria alternata and A. cantlous , the causal agents of leaf blight of ancient P. orientalis . Evaluation of the control effects on 1-year-old P. orientalis seedlings showed that these Trichoderma strains significantly controlled leaf blight, and T. nordicum CGMCC3.28772 exhibited the highest relative control effect under the same inoculation conditions.