Optimization of a VIGS System Suitable for the Functional Study of Resistance Genes of Chinese Cabbage Against Clubroot Disease

Clubroot disease caused by Plasmodiophora brassicae has greatly affected the quality and yield of Chinese cabbage. Excavating the key resistance genes and verifying their function is important for clarifying disease resistance mechanisms. Virus-induced gene silencing (VIGS) technology has been widely used in gene function research. However, the VIGS system specifically designed for the functional analysis of clubroot resistance genes is currently unavailable. In this study, it was found that the vacuum infiltration VIGS method is more effective for gene silencing than the seed soaking method. When seedlings were VIGS-treated using vacuum infiltration for 10 min, genes were effectively silenced on the 6th-35th days (d) after treatment, ensuring high seedling survival rate and plant transformation rate. To investigate the optimal inoculation time with P. brassicae, plants were inoculated 3, 6, 9, and 15 d after VIGS treatment. Results showed that the difference of clubroot resistance between gene-silenced and control plants was most significant when plants were inoculated 6 d after VIGS treatment. This result suggests that, when the target gene began to silence (6 d after VIGS), immediate inoculation with P. brassicae should be suitable for the functional study of clubroot-resistance genes.