Sulfur dioxide enhances postharvest grape resistance to Botrytis cinerea by promoting glutathione level

Gray mold, a fungal disease caused by Botrytis cinerea, is held responsible for postharvest decay of table grape that seriously reduces the edible quality and commercial value of berries. Sulfur dioxide (SO2) treatment is a globally employed and effective method for controlling gray mold. Nevertheless, the potential mechanism underlying its inhibitory effect has not been completely understood. With the aim of investigating the impact of SO2 on enhancing the postharvest grape resistance to B. cinerea, 'Munage grape' (Vitis vinifera L.) was initially treated by SO2 fumigation then inoculated with B. cinerea. The results indicated that 200 μL/L SO2 pretreatment effectively delayed the increase in lesion diameter. Further studies found that SO2 increased enzymes activity by upregulating the transcription levels of related genes in glutathione (GSH) synthesis and GSH-cycling pathways, thereby maintaining high GSH levels and GSH/GSSG (oxidized glutathione). SO2 also increased the activity and gene expression levels of GSH-S-transferase, a key enzyme for detoxification. The upregulation of pathogenesis-related genes further demonstrated the enhancement of disease resistance induced by SO2. Subsequent correlation analysis showed that GSH was conducive to inhibit the development of gray mold. Our results preliminarily confirm that SO2 enhances postharvest grape resistance to B. cinerea by promoting GSH level, and the results enrich the understanding of the biological effect of SO2.