Development of novel management tool to mitigate spotted wilt disease.

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Commodities

• Additional Plants: tobacco

Practices

• Pest Management: Bio Pesticides

Tomato spotted wilt virus (TSWV) is one of the chronic pests listed in the priority list identified by stakeholders and published by the Southern Region Information Exchange Group for IPM (SERA3) members and Integrated Pest Management coordinators from the southern region of the United States. Tomato spotted wilt disease (TSWD) is broadly managed by integrating disease management tools using host-mediated resistance, vector management, and cultural practices. Even with devised management strategies, the disease incidence remains high in peanuts and tobacco. In contrast, the emergence of resistance-breaking isolates in tomato and pepper has resulted in the decline of resistant varieties’ effectiveness as a management strategy. With this study, we aim to develop a Spray-Induced Gene Silencing (SIGS) technique against virulent strains of TSWV. This technique includes the production of double-stranded RNA (dsRNA) molecules, capable of inducing a natural plant defense mechanism against viruses. The dsRNA will be designed against the NSm (encode movement protein) and Gn/Gc (encode glycoproteins) genes of TSWV. The findings from this study may yield a critical component for formulating various products applicable to different crop hosts. Given the widespread occurrence of RNAi, introducing dsRNA targeting TSWV can potentially confer immunity across all its host species, assuming successful uptake of the dsRNA by the host organisms. Due to its precise nature, it promotes green practices by avoiding off-target effects. As we are on the verge of losing important management strategies for TSWD, SIGS developed against TSWV will provide an effective approach to sustainable agriculture.

The aims of this project are:

1. Evaluation of symptom severity and TSWV titer on application of in vitro produced dsRNA against NSm and Gn/Gc genes of TSWV, in tobacco plants.

• In vitro production of dsRNA against NSm and Gn/Gc genes of TSWV.
• TSWV inoculation and application of dsRNA on the tabacum plants.
• Evaluation of symptom severity and TSWV titer in inoculated and systemic leaves.

2. Evaluating dsRNA movement and small RNA (sRNA) population using High Throughput Sequencing (HTS) in the tabaccum on different days post-application.
3. Disseminating the research to the stakeholders for disease management.

Expected Outcome.

Objective 1:

Two different dsRNA molecules will be generated in the first objective. These dsRNA will have sequence similarity to the conserved region of the NSm and Gn/Gc, respectively. The second objective will help to decipher the efficacy of these dsRNA molecules against TSWV. Low disease incidence and severity are expected to be observed upon the treatment of inoculated plants with dsRNA. Further, viral titer in both inoculated and systemic leaves is also anticipated to decrease. This will help us to conclude the performance of dsRNA against NSm and Gn/Gc genes of TSWV at different DPIs.

Objective 2:

The administered dsRNA should move to other parts of the plants for better functioning. So, this project also includes the objective to evaluate its movement. The dsRNA applied is expected to be detected on the systemic leaves above the inoculated leaves. Further, high diversity in the siRNA population is expected. This will keep the concentration of any one siRNA low and help to reduce any off-target effects.

Objective 3:

Stakeholders will receive research results through the UGA extension network and presentations at county agents and growers’ meetings led by the UGA Cotton and Peanut team. Additionally, the results will be shared with growers, consultants, and other stakeholders during the annual GA-FL tobacco tour organized by the Georgia Commodity Commission on Tobacco and the peanut tours conducted by the GA Peanut Commission in the summer and fall. Overall, this objective will provide the crucial information to carry forward this research according to the stakeholders’ needs.