Hydrogen sulfide enhances resistance to Penicillium italicum by activating phenylpropanoid metabolism in postharvest navel orange fruit.

An effective prevention treatment in postharvest fruit diseases is helpful in maintaining fruit quality and prolonging shelf life. In this study, we aimed to investigate whether hydrogen sulfide (H₂S) enhances resistance to Penicillium italicum by activating phenylpropanoid metabolism in postharvest navel orange fruit. The findings showed that 25μL/L H₂S fumigation alleviated the disease symptoms and lesion area of P. italicum-inoculated navel orange fruit. RT-qPCR analysis revealed that H₂S treatment upregulated the transcription levels of phenylpropanoid biosynthesis (CitC4H, Cit4CL, CitCYP98A, CitCAD, CitCHI, and CitCHS) and metabolite-related genes (CitPAL, CitGLU, CitPOD, and CitCSE). Meanwhile, H₂S upregulated the transcripts of MYB and WRKY transcription factors and had similar expression patterns to phenylpropanoid metabolism-related genes. Correlation analysis showed that H₂S-promoted accumulation patterns of total phenols, flavonoids, and lignin were positively correlated...