Effects of temperature and varietal resistance on latent period of tobacco bacterial wilt

To explore the occurrence pattern of tobacco bacterial wilt (TBW), spread plate method was used to determine the concentration of bacteria suspension. The pot experiments on cv. K326, Honghuadajinyuan, Yunyan 85 and Yunyan 87 were carried out to screen out the optimal artificial inoculation method. The key factors influencing the infection threshold and latent period of TBW were determined using this method. The results showed that root-dipping was the optimal artificial inoculation method for Ralstonia solanacearum. The occurrence time of TBW with root-dipping inoculation was 8 days earlier than that with root-irrigation inoculation. Through the inoculation tests of different concentrations, the infection threshold of R. solanacearum was determined as 3×10² cfu/mL. Further, the results of the pot experiments in the artificial climatic incubator indicated that four tobacco varieties had a similar pattern: the latent period of TBW was significantly affected by temperature, latent period decreased with the rising of temperature. In the optimal occurrence time, the latent period of TBW was between 20-28 days, with 24 days on average. The latent period in varieties with a higher disease resistance was longer.