Establish an efficient inoculation system of tomato yellow leaf curl virus to assist tomato resistance breeding

Tomato yellow leaf curl virus (TYLCV) endangers the production of tomato in the world, which is largely overcome by cultivating resistant tomato cultivars. Since virus evolves fast and may disrupt the resistance in resistant cultivars, tomato resistance breeding against emerging TYLCV isolates is a long-term task, which requires an efficient inoculation system of TYLCV to screen and identify resistant tomato plants. Previous Agrobacterium-mediated TYLCV infectious clone is to construct the viral genome in the binary vector, and does not have high infection efficiency. In this study, we integrate TYLCV genome in pTRV2GW vector containing partial genome of Tobacco Rattle virus, and generate an Agrobacterium-mediated infectious clone pTRV2GW-TYLCV. Tomato plants are infected by vacuum infiltration with the Agrobacterium culture of infectious clone. PCR analysis with all TYLCV ORFs in infected plants reveals distinct detection of each ORF at different infection stages and a final 100 % infection rate of this inoculation method. Infected tomato plants have typical TYLCV disease symptoms including yellowing, curling, and smaller leaves. Plant growth and leaf photosynthesis are repressed in infected plants compared to non-infected plants. Moreover, the inoculation system is successfully applied for differentiating TYLCV resistant and susceptible cultivars, which can assist tomato resistance breeding.