Leaf-blight disease caused by the Fusarium oxysporum is an emerging problem in Dendrobium chrysotoxum production in China. Symptoms of leaf blight were observed on seedlings of D. chrysotoxum cultivated in a nursery in Ruili City, Yunnan Province, China. In this study, we isolated the Fusarium sp. associated with leaf-blight disease of D. chrysotoxum from the diseased seedlings. A pathogenicity test was performed to fulfill Koch’s postulates to confirm the pathogenicity of isolated strains and identified using morphological and molecular techniques. The results revealed that all four isolated Fusarium sp. isolates (DHRL-01~04) produced typical blight symptoms followed by marginal necrosis of leaves on the D. chrysotoxum plants. On the PDA medium, the fungal colony appeared as a white to purplish color with cottony mycelium growth. Microconidia are oval-shaped, whereas macroconidia are sickle-shaped, tapering at both ends with 2–4 septations. The phylogenetic trees were construed based on internal transcribed spacer (ITS), translation elongation factor (EF-1α), and RNA polymerase subunit genes RPB1 and RPB2 genes, respectively, and blasted against the NCBI database for species confirmation. Based on the NCBI database’s blast results, the isolates showed that more than 99% identify with Fusarium oxysporum. To our knowledge, this is the first comprehensive report on the identification of Fusarium oxysporum as the causal agent of Dendrobium chrysotoxum leaf blight in Yunnan Province, China, based on morphological and molecular characteristics.

Verticillium-like fungi within the Sordariomycetes hold significant ecological and economic importance, especially in biocontrol. This study describes two novel species, Leptobacillium gasaense and Ovicillium yunnanense, and provides DNA sequence data and identification keys for the genera Leptobacillium and Ovicillium. The genus Muscodor, known for its considerable biotechnological value, comprises endophytes characterized by sterile mycelia that produce antibiotic volatile organic compounds (VOCs). Historically, the classification of Muscodor has relied on culture characteristics, VOC chemical profiles, and molecular phylogenetic analyses. However, culture characteristics and VOC profiles lack a definitive diagnostic value. Although asexual morphological traits are crucial for genus-level classification, no conidiogenous structures have been observed in Muscodor. Here, we report the asexual morphological characteristics of Muscodor and describe M. coffeanus as a new record in China, supported by both its asexual morphology and molecular phylogenetic evidence.

Background: Xanthomonas oryzae pv. oryzae (Xoo) causes rice leaf blight (BLB) and poses a major threat to global rice production. In rice production, tetramycin agents provide good control of rice leaf blight, while the standardization of the reference genes of Xoo under tetramycin stress has not been reported. The aim of this study was to identify the most stable reference genes for quantitative PCR analysis of Xoo under tetramycin stress. Methods: Six candidate reference genes, gyrB (RNA polymerase β gene), GADPH (glyceraldehyde-3-phosphate dehydrogenase gene), recA (recombinase A gene), gyrA (citrate synthase encoding gene), dnaK (molecular chaperone protein gene), and 16S rRNA (16S ribosomal RNA gene) were selected and their expression stability was assessed under tetramycin stress conditions using real-time quantitative PCR (qRT-PCR). GeNorm, NormFinder, BestKeeper and RefFinder were used to assess the expression stability, the relative expression values of the eight genes involved QS (Quorum sensing) pathway under tetramycin stress were used to validate by the rpf (regulation of pathogenic factors) gene family. Results: 16S rRNA expression was most stable under tetracycline stress, whereas GADPH was the least. The rpf gene family showed a highly stable expression level, confirming the reliability of 16S r RNA as a reference gene in the study of Xoo under tetramycin stress. Conclusions: 16S rRNA was identified as the best reference gene for Xoo gene expression analysis under tetramycin stress. It provides a reliable support for the molecular research on the control strategy of rice BLB.