Effects of Thifluzamide Treatment on the Production of Cell Wall Degrading Enzymes in Rhizoctonia solani and Phenylpropane Metabolism in Pear Fruit

The study aimed to investigate the effects of thifluzamide (2.67 mg/L) on 'Huangguan' pear fruit rot caused by <i>Rhizoctonia solani</i> 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 <i>R. solani</i>. The results showed that thifluzamide treatment significantly inhibited the activities of PG, PME, PGTE, PMTE, xylanase, and PL secreted by <i>R. solani</i> 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 <i>PcPAL</i>, <i>PcC4H</i>, <i>Pc4CL</i>, <i>Pcβ-1,3-GA</i>, <i>PcLCH</i>, <i>PcF3H</i>, and <i>PcDFR</i> involved in phenylpropanoid metabolism in pear fruit. In conclusion, thifluzamide treatment reduced the infection ability of <i>R. solani</i> by inhibiting the expression of the genes encoding cell wall-degrading enzymes in <i>R. solani</i>. At the same time, it inhibited the activities of cell wall-degrading enzymes induced resistance against <i>R. solani</i> infection in 'Huangguan' pears by promoting phenylpropane metabolism.