Effects of benzothiadiazole on disease resistance and soluble sugar accumulation in grape berries and its possible cellular mechanisms involved

• 0.1 or 1 mmol L−1 BTH treatment inhibited Botrytis cinerea infection in grape berries.
• BTH treatment induced a series of SAR responses in grape suspension cells.
• BTH elicitations affected soluble sugars components in both grape cells and berries.
• BTH elicitations led to the change in activities of the cellular sucrose-metabolizing enzymes.

This study was conducted to investigate the effects of benzo-thiadiazole-7-carbothioic acid S-methyl ester (BTH) treatments on disease resistance against Botrytis cinerea infection and soluble sugar accumulation in grape berries and to analyze the possible cellular mechanisms involved. In grape berries, the results indicated that BTH treatments at 0.1 or 1 mmol L−1 could effectively inhibit B. cinerea infection possibly by directly inhibiting pathogen growth and indirectly inducing disease resistance. However, an obvious change in the composition of the soluble sugars was simultaneously observed in the BTH-treated berries. In parallel, addition of BTH at 0.1 or 1 mmol L−1 to the medium could effectively trigger a SAR defense response in grape suspension cells, and the defense included a cellular H2O2 burst, VvNPR1.1 and PR1 genes expression, and the accumulation of stilbene phytoalexins. The 0.1 or 1 mmol L−1 BTH treatment induced higher activity of sucrose-hydrolyzing enzyme SS-cleavage and lower activities of sucrose-synthesizing enzymes such as SS-synthesis, SPS and SPP than the controls, contributing to the gradual increase in sucrose hydrolysis, a decrease in the glucose content and the accumulation of fructose in grape cells. Therefore, our results suggest that BTH exerts its effect on reducing fruit decay perhaps through the cellular SAR response. Moreover, the presence of costs in terms of altered soluble sugar components in grape berries may be attributed in changing activities of cellular sucrose-metabolizing enzymes after effective BTH elicitations.