The study aimed to investigate the effects of thifluzamide (2.67 mg/L) on ‘Huangguan’ pear fruit rot caused by Rhizoctonia solani during storage, as well as the activities of polygalacturonase (PG), pectin methylesterase (PME), polygalacturonic acid trans-eliminase (PGTE), pectin methyl trans-eliminase (PMTE), xylanase, and pectate lyase (PL) secreted by R. solani. The results showed that thifluzamide treatment significantly inhibited the activities of PG, PME, PGTE, PMTE, xylanase, and PL secreted by R. solani after 3 days in vitro culture, compared to the control. Thifluzamide also increased the activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate CoA ligase (4CL), and the contents of flavonoids and total phenolic compounds in pear fruit. Furthermore, thifluzamide increased the expression of PcPAL, PcC4H, Pc4CL, Pcβ-1,3-GA, PcLCH, PcF3H, and PcDFR involved in phenylpropanoid metabolism in pear fruit. In conclusion, thifluzamide treatment reduced the infection ability of R. solani by inhibiting the expression of the genes encoding cell wall-degrading enzymes in R. solani. At the same time, it inhibited the activities of cell wall-degrading enzymes induced resistance against R. solani infection in ‘Huangguan’ pears by promoting phenylpropane metabolism.

Laccase (LAC), a copper-containing polyphenol oxidase, is an important pathogenic factor of pathogenic fungi, and has been identified as an important virulence factor in numerous pathogenic fungi. LAC is encoded by a gene family and belongs to the class of multicopper oxidases. The study aimed to identify the LAC genes in Athelia bombacina (Link) Pers, and their interactions with the host. The expression levels of the LAC genes were quantified using RT-qPCR. The LAC activity, level of malondialdehyde (MDA) and activities of protective enzymes in ‘Huangguan’ pears during the interaction were measured. The AbLac4 gene deletion mutant strain was constructed. Six LAC genes were identified in A. bombacina, distributed across three chromosomes. Interspecies collinearity analysis suggested that LAC genes could serve as crucial pathogenic factors in A. bombacina. The LAC gene family can be classified into three distinct subgroups. Among the subgroups, variations were observed in their characteristic sequences and conserved motifs. However, the LAC genes within the same subgroup exhibited a high degree of conservation. The genes showed diverse expression profiles, with their promoters harboring multiple stress-responsive elements. Signal peptide prediction showed that all LAC proteins, with the exception of the AbLac3 protein, possessed signal peptides, indicating that they are secretory proteins. The subcellular localization analysis showed that all LAC proteins may be localized extracellularly. RT-qPCR revealed differential expression patterns among LAC genes; specifically, AbLac1 and AbLac4 exhibited distinct expression dynamics during the infection process. The LAC activity first increased and then decreased, with the highest increase rate occurring in the early stage of culture. The MDA content and catalase (CAT) activity at the inoculated site were found to be significantly higher than the uninoculated control. In addition, the deletion of AbLac4 gene reduced the growth rate and pathogenic ability of A. bombacina. This investigation found that AbLac1 and AbLac4 may play pivotal roles in mediating host interactions, and the fruit may combat pathogen infection through increasing the activities of CAT, phenylalanine ammonia lyase and peroxidase. This study provides valuable new insights into the pathogenic mechanisms of A. bombacina, significantly contributing to the field.