Abstract:[Objective] Melanose caused by Diaporthe citri is one of the major fungal diseases in citrus. D. citri mainly undergoes three developmental stages, including mycelial growth stage (10 d, T1), pycnidium development stage (20 d, T2), and conidial sporulation stage (30 d, T3). The metabolomics analysis of the markers and key metabolites during the development of D. citri can provide clues for clarifying the sporulation mechanism and metabolic regulation of D. citri. [Methods] Ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) was employed to analyze the metabolic changes during the development of D. citri. Then, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed to screen the differential metabolites. Finally, KEGG pathway enrichment analysis was conducted for the differential metabolites. [Results] A total of 1 090 metabolites were identified at the three developmental stages of D. citri. According to the thresholds of VIP≥1 and fold change≥2 or ≤0.5, 265, 456, and 580 differential metabolites were screened out for T1 vs. T2, T2 vs. T3, and T1 vs. T3, respectively. The differential metabolites mainly included organic acids, triglycerides, fatty acids, and amino acids, which were closely associated with the morphological development of the pathogen. Linoleic acid and its metabolites (13-HpODE, 9(S)-HODE, 9-oxoODE, 13-oxoODE, 9-HpODE, 9(S),12(S),13(S)-TriHOME, 9,10-DiHOME, and γ-linoleic acid), as well as arachidonic acid and its metabolites (20-COOH-AA, LXB4, 15-keto prostaglandin F2α, 20-carboxy LTB4, 15-deoxy-δ-12,14-PGJ2), might play a role in the sporulation of D. citri. [Conclusion] The morphological development of D. citri was closely associated with the changes of metabolites during different developmental stages, and the oxylipid metabolites (linoleic acid, arachidonic acid and their metabolites) were the key metabolites for sporulation.
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