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

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