Sulfur Dioxide Enhances Tobacco Resistance to Black Shank Disease via the Jasmonic Acid Pathway

Tobacco black shank (TBS) disease, caused by Phytophthora nicotianae (P. nicotianae), poses a severe threat to tobacco productivity, necessitating the identification of effective control methods. Sulfur dioxide (SO₂) has emerged as a signaling molecule involved in modulating plant stress responses, yet its role in inducing resistance to TBS in tobacco remains unclear. This study investigated the potential of enhancing TBS resistance through root irrigation with SO₂ derivatives and elucidates the underlying mechanisms. Our findings revealed that SO₂ derivative root irrigation significantly enhanced tobacco resistance to TBS. This was evidenced by reduced malondialdehyde levels, increased hydrogen peroxide accumulation, and elevated activities of antioxidant enzymes such as superoxide dismutase and peroxidase. Moreover, analyses of phytohormones—jasmonic acid (JA), salicylic acid, abscisic acid, and ethylene—indicated a notable increase in endogenous JA levels in SO₂-pretreated plants. The application of the JA biosynthesis inhibitor diethyldithiocarbamate acid (DIECA) significantly decreased JA levels and attenuated the SO₂-induced TBS resistance. Furthermore, transcription of several JA-responsive defense genes was significantly upregulated in SO₂-pretreated plants during P. nicotianae infection. These results demonstrate that SO₂ application elevates endogenous JA levels, thereby activating the antioxidant defense system and enhancing TBS resistance in tobacco plants. This study advances our understanding of SO₂-induced resistance mechanisms and offers an effective, economical, and environmentally friendly strategy for managing soil-borne fungal diseases in crop production.