Dufulin Impacts Plant Defense Against Tomato Yellow Leaf Curl Virus Infecting Tomato

<i>Tomato yellow leaf curl virus</i> (TYLCV) poses a significant threat to tomato production, leading to severe yield losses. The current control strategies primarily rely on the use of pesticides, which are often nonselective and costly. Therefore, there is an urgent need to identify more environmentally friendly alternatives. Dufulin, a novel compound that has been effective in controlling viral diseases in tobacco and rice, has not yet been tested against TYLCV. This study assessed the efficacy of dufulin in controlling TYLCV over a three-year span from 2021 to 2023 through field trials, by monitoring disease symptoms and viral titers. Additionally, this study assessed the expression levels of genes associated with systemic acquired resistance (SAR), specifically <i>proteinase inhibitor II</i> (<i>PI II</i>) and <i>non-expressor of pathogenesis-related genes 1</i> (<i>NPR1</i>), using real-time qRT-PCR. The chlorophyll and nitrogen content in the leaves were also measured. Plants treated with dufulin showed reduced symptomatology and lower viral titers compared to the controls. Analysis of gene expression revealed that <i>NPR1</i> was upregulated in the dufulin-treated plants, whereas <i>PI II</i> expression was consistently downregulated in the TYLCV-infected plants. Interestingly, <i>PI II</i> expression increased in the healthy plants following a seven-day post-treatment with dufulin. Moreover, the treated plants exhibited a higher chlorophyll content than the controls, though no significant differences in the nitrogen levels were observed between the dufulin-treated and water-treated plants. Overall, the application of dufulin significantly bolstered the plant's defense response, effectively reducing TYLCV symptoms and enhancing resistance.