Abstract: To clarify the control effects of 13 agents against viral diseases caused by the co-infection of ToMV, ToBRFV, and ToMMV in tomatoes, and to evaluate their impacts on physiological and biochemical indices, safe biopesticides with high efficiency were screened. The occurrence of viral diseases in tomato seedlings without seed disinfection was investigated, revealing a disease incidence of 94.60% and a disease index of 25.71. Mild mosaic symptoms were identified as the primary manifestation, accounting for 42.20%. It was revealed by DAS-ELISA detection indicated that the concentrations of the three viruses increased as symptoms intensified, with ToMV concentrations generally higher than those of ToBRFV and ToMMV. The control efficacy trials demonstrated that after tomato seedlings (pretreated by root dipping for 20 min and colonized for 10 d) were sprayed twice at 10-day intervals, biopesticides lentinan, ningnanmycin, amino-oligosaccharins, and atailing and chemical fungicides dufulin and kedubao exhibited the best control efficacy, reaching 75.29%, 73.79%, 80.31%, 77.27%, 71.26%, and 69.97% at 30 d post treatment, respectively. It was found that the virus concentrations and relative expression levels of virus coat protein (CP) in tomato leaves were reduced by the six treatments, while chloroplast pigment contents and defense enzyme activities were enhanced. The optimal performance was exhibited by the amino-oligosaccharins treatment. Under this treatment, the concentrations of the three viruses were recorded at 35.53, 37.13, and 30.36 U/g·FW, the inhibition rates of virus proliferation were 64.98%, 76.16%, and 73.74%, and the CP inhibition rates reached 76.35%, 76.67%, and 73.17%, respectively. Furthermore, the contents of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were determined to be 1.12, 0.68, 1.58, and 8.96 mg/g, while the activities of SOD, POD, and PAL were measured at 36.84 U/g FW, 301.50 U/min/g FW, and 136.52 U/g FW, all of which were significantly higher than those of the control CK and other treatments. In this study, four highly effective immune inducers amino-oligosaccharins, lentinan, atailing, and dufulin and two antiviral agents ningnanmycin and kedubao were screened for the management of tomato viral diseases. This study provides an optimized application strategy for seedling protection, combining root-dipping with two scheduled spray treatments.

Key words: tomato, virus disease, biopesticide, chemical pesticide, control effect