An Improved Method for Quantification of Viable Fusarium Cells in Infected Soil Products by Propidium Monoazide Coupled with Real-Time PCR

Fusarium is a soil-borne pathogen that causes root rot disease in cucumber. To date, quantitative real-time PCR (qPCR) is a common tool to detect the content of Fusarium in soil. However, qPCR cannot distinguish between viable and nonviable cells. The aim of this study was to develop a detection technique to pretreat tissue fluid with propidium monoazide (PMA) followed by extract DNA, and then to quantify viable Fusarium cells in contaminated soil. In this work, the specific primer pair F8-1/F8-2 was designed based on the translation elongation factor (EF) gene and a PMA-qPCR assay was established to amplify and quantify soils of viable Fusarium cells. The PMA pretreatment test was optimized, which indicated that the optimal PMA concentration and light exposure time were 50 mmol L(−1) and 15 min, respectively. The lowest limit of viable cells in suspension detected and soil by PMA-qPCR were 82 spore mL(−1) and 91.24 spore g(−1), respectively. For naturally contaminated soil, viable Fusarium cells were detected in eight of the 18 samples, and the Fusarium amount ranged from 10(4) to 10(6) spore g(−1). In conclusion, the PMA-qPCR method has the characteristics of high sensitivity, efficiency, and time saving, which could support nursery plants to avoid Fusarium infection and agro-industry losses.