Effects of Mixed Infection of Tomato Chlorosis Virus and Tomato Yellow Leaf Curl Virus on Disease Incidence and Growth of Two Tomato Cultivars When Infected at Different Growth Stages

The occurrence of mixed infection with tomato chlorosis virus (ToCV) and tomato yellow leaf curl virus (TYLCV), transmitted by the whitefly vectors Bemisia tabaci Mediterranean is not uncommon in cultivated tomatoes. Mixed infection of those viruses resulted in increased disease severity and reduced plant growth, as synergistic interactions. However, the impact of ToCV+TYLCV mixed infection at different growth stages on tomato growth and fruit yield has not been examined. Therefore, from September to November 2024, we surveyed the spread of single and mixed virus infections in tomato plants in the region of Docheok-myeon, Gwangju-si, Gyeonggi-do; we also conducted field trials to evaluate quantify damage and yield losses incurred by a susceptible (SuperDotaerang) and resistant (TY Giants) tomato cultivar when ToCV+TYLCV mixed infection at seedling stage (SS) and fruiting stage (FS). We observed that the monthly incidence rate of single ToCV infection remained ranged from 29.7% to 46.1% during the experiments, while the incidence rate of ToCV+TYLCV mixed infection on both cultivars significantly increased to about 50% in October. In SuperDotaerang, ToCV+TYLCV mixed-infected tomato plants at the seedling stage showed more severe symptoms compared with those in ToCV-infected plants in both SS and FS, which led to significant yield losses as plant height and leaf area decreased. Thus, this study provides information on management strategies targeted at preventing mixed infection with ToCV and TYLCV in seedling stage tomato crops and highlights that resistant cultivars should not be relied upon as the sole management practice for viral diseases.