Real-time PCR amplification and standard curve of apx gene. Upper panel: real-time PCR logarithmic plot resulting from the amplification of four three-fold serial dilutions of a tomato standard DNA (see Methods for details) using the apx-specific primers and probe described in Table 5. Each sample was run in triplicate. Lower panel: Standard curve obtained for the same samples. Correlation coefficient and slope values are indicated. The calculated TC values were plotted versus the log of each starting quantity.