Abstract: A specific real-time PCR assay based on the ITS region of rDNA was established to quantitatively detect Verticillium dahliae of cotton in a naturally infested soil. The standard curve of the realtime PCR system was constructed by a 324 bp PCR amplification product and the specificity, sensitivity and reproducibility of the method were evaluated. The results showed that the realtime PCR assay had good specificity and sensitivity and the detection limit was
100 copies·μL^-1. The correlation coefficient of the standard curve was 0.994 and the PCR amplification efficiency reached 91.5%. Using the realtime PCR assay, soil samples from a transgenic cotton field and nontransgenic one were detected. The results indicated that the amount of V. dahliae in the transgenic cotton field was significantly higher than that of conventional cotton, which showed consistency with the observations achieved in the two cotton fields. As a reliable and sensitive assay, the realtime PCR system provided an effective method for the rapid detection of V. dahliae and the control of cotton diseases.

Key words: evolution principle, hydrologicalfrequency., moment, non-consistency, hydrological gene