Plant viruses can infect various types of plants, including food and oil crops, and ornamental flowers, threatening agricultural production and food supply. Cross-protection is an efficient strategy against severe viral strains. Due to distinct infection mechanisms, cross-protection cases involving RNA viruses and DNA viruses often rely on the utilization of corresponding attenuated strains for control purposes. In this study, we utilized cucumber mosaic virus (CMV), a member of the RNA virus group, as the foundational framework for developing attenuated vaccines. We developed four vaccines by inserting relevant sequences from tomato yellow leaf curl virus (TYLCV), a DNA virus. All vaccines demonstrated effective prevention against TYLCV infection, with relative control efficacies exceeding 80%. Subsequently, we evaluated the preventive effects of these vaccines on mixed infections of CMV and TYLCV. Our findings demonstrated that CMV (R2-2bPTI-TYC1C4), CMV (R2-2bPTII-TYC1C4), and CMV (R2-2bPTIII-TYRep) displayed significant efficacy in preventing mixed infections. Following pre-inoculation with these vaccines, the disease index of tomato plants decreased from 100 to 56. This work provides theoretical foundations and tangible resources for controlling TYLCV through cross-protection while suggesting a feasible strategy for utilizing weak RNA virus vaccines to control DNA viruses.

Plant viruses are major plant pathogens and account for nearly half of emerging plant diseases worldwide. To date, few effective management measures are available for the efficient control of plant viral diseases. Cross-protection based on attenuated vaccine is an effective strategy to prevent plant viral diseases. The primary requirement for the development of attenuated vaccines is a vector with excellent characteristics, such as low pathogenicity, genetic stability, and the capacity for stable insertion of exogenous fragments. In this study, the cucumber mosaic virus (Fny strain) was genetically modified to serve as an attenuated vaccine vector. Based on pre-termination of the 2b protein-coding region and deletion of the 3′ UTR in CMV RNA2, six RNA2 mutants, designated R2-2bPTI, R2-2bPTII, R2-2bPTIII, R2-2bPTIV, R2-2bPTV, and R2-2bPTVI, were constructed. Experiments with different lengths tobacco phytoene desaturase (PDS) fragment insertion evaluated the capacity of each mutant to accommodate exogenous fragment. Based on the R2-2bPTIV, a viral fragment insertion mutant R2-2bPTIV-TMPYTVPX targeting cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), potato virus Y (PVY), tobacco vein banding mosaic virus (TVBMV), and potato virus X (PVX) was constructed. This mutant provided effective cross-protection against these targeted virulent viruses. This study developed a series of CMV-based vaccine vector, providing materials and data for the development of plant viral diseases attenuated vaccines.