Quantitative Detection of Pathogen DNA of Verticillium Wilt on Smoke Tree Cotinus coggygria

Verticillium dahliae is a ubiquitous soilborne fungus and the causal agent of smoke tree vascular wilt, which presents a major threat to the famous "red-leaf" scenery of the Fragrant Hills Park in Beijing, China. In this study, we detected the presence of the fungus based on the amount of fungal DNA in planta and in the soil by using quantitative nested real-time polymerase chain reaction (QNRT-PCR). The QNRT-PCR assay results were highly specific for V. dahliae and could detect disease wilt dynamics over time in different plant tissues. Tests with QNRT-PCR in infested soils showed the detection of soil inoculum densities as low as 1 microsclerotium/g of soil. The QNRT-PCR data showed strong correlation between the quantity of pathogen DNA and the Verticillium wilt disease severity rating, suggesting that quantification of V. dahliae soil inoculum could be conducted to assess Verticillium wilt risk before planting. These data indicate that QNRT-PCR is a sensitive and reliable method to monitor the soilborne pathogen V. dahliae in planta and in soil. The results of this study can be useful in the development of new disease control measures for Verticillium wilt and assessment of the risk of V. dahliae infection of smoke tree before planting.