Regulation of BTH Treatment on Redox Status and Disease Resistance in Postharvest Strawberries

To determine the relevant mechanism involved in the inhibition effects of benzothiadiazole (BTH) on grey mold decay in strawberry, the present research was performed to analyze the regulation of redox status and disease resistance by BTH in postharvest strawberries during the storage at 20℃. The results exhibited that the treatment of 0.1 mmol/L BTH could effectively induce the increase in activities of G6PDH and 6PGDH as well as MDHAR、DHAR、GR and APX, known as key enzymes in pentose-phosphate pathway (PPP) and ascorbate-glutathione cycle (AsA-GSH) respectively, thus resulting in the increase in contents of reductive substances such as NADPH, GSH and AsA while inhibiting the synthesis of oxidative products such as NADP⁺, GSSG and DHA for the enhancement of the internal redox status. The expression levels of PRs such as FaPR1, FaPR5, FaCHI-1 and Faβglu in the BTH-treated fruits displayed a remarkably increase and the disease incidence caused by B. cinerea was significantly suppressed (p<0.05). Activities of enzymes involved in PPP and AsA-GSH cycle in the BTH-treated fruits following a inoculation of a pathogen B. cinerea were more significantly enhanced compared with those in BTH-treated samples (p<0.05);meanwhile, the disease incidence in BTH-treated and pathogen inoculated fruits deceased significantly (p<0.05). These results indicated that 0.1 mmol/L BTH activated the efficient protection in strawberries against B. cinerea infection through the priming defense. Moreover, the BTH treatment enhanced the activities of the key enzymes in PPP and AsA-GSH, accumulated reductive substance, which provided a high redox status for PRs gene expression.