Tomatoes are the second most widely cultivated vegetable crop in the world. However, they face severe challenges from soil-borne diseases, with bacterial wilt posing the greatest threat to yield. As most commercial tomato varieties currently lack strong disease resistance, farmers often resort to grafting onto disease-resistant eggplant rootstocks to maintain tomato production. Yet, due to the widespread use of saved seeds by farmers, the resistance of some eggplant rootstocks has shown signs of degeneration.

To support the industry in improving the quality and disease resistance of grafted seedlings, the Taiwan Seed Improvement and Propagation Station (hereinafter referred to as TSIPS) has conducted systematic disease resistance testing and genetic reinforcement of commonly used eggplant rootstock materials. The results are expected to enhance the stability of domestic tomato production.

TSIPS selected commonly used eggplant rootstock varieties from nurseries and seed companies and conducted artificial inoculation trials with bacterial wilt. Results showed that commercial hybrid varieties such as 'Feng-shan No. 3' and 'Tainan No. 1' performed consistently well, with disease incidence rates below 20%. The inbred line EG195, developed by the World Vegetable Center, also demonstrated outstanding resistance, significantly outperforming other farmer-saved seed sources.

To ensure the stable transmission of disease resistance in rootstocks, TSIPS conducted seed-borne pathogen testing (e.g., viroids) on individual plants that showed outstanding disease resistance and selected clean, pathogen-free seed sources (SPF: Specific Pathogen Free). Second-generation seeds were collected, and trial results confirmed that these exhibited significantly better resistance than the first generation. This indicates that through selection and seed sanitization, core germplasm with stable resistance can be successfully established, providing a reliable seed source for nurseries.

To improve breeding efficiency, TSIPS not only established core disease-resistant eggplant germplasm but also began developing molecular markers. After analyzing 40 sets of SSR markers from literature, the SSR marker emb01J19 with the highest polymorphism was identified. Two potential SNP loci in that region have been successfully detected, and further development is underway to create selection tools suitable for breeding and seed testing.

Through a three-pronged strategy—verification of eggplant rootstock resistance, purification of inbred seed sources, and marker-assisted selection—the prevention of bacterial wilt in tomatoes can be effectively addressed at the root. TSIPS encourages farmers and nurseries to prioritize the use of stable, disease-resistant eggplant rootstocks to reduce disease losses, improve yields and profits, and move toward a high-quality, safe, and resilient vegetable production system.

▲Figure 1. Eggplant roots are highly resistant to bacterial wilt and are widely used as disease-resistant rootstocks.

▲Figure 2.Differences in resistance or susceptibility among eggplant rootstock materials become clearly visible within seven days after inoculation. Resistant material (left) vs. susceptible material (right); control (top) vs. treated (bottom).