Figure 6
Quantifying QTL effect on mycelial growth of Setosphaeria turcica in planta using DNA-based real-time PCR. (A) Two standard curves were constructed by mixing a series of S. turcica DNA and 50 ng of maize DNA from non-inoculated B73 and Tx303 plants, respectively. With B73 DNA, Ln[fungal DNA] = 16.912 - 0.606*Ct (R2 = 0.99); with Tx303 DNA, Ln[fungal DNA] = 16.906 - 0.610*Ct (R2 = 0.99). Ln: natural logarithm. Ct: threshold cycle, the number of PCR amplification cycle at which the exponential increase of the product was detected. (B) Measurement of S. turcica DNA ratio in infected leaves collected 9 dpi from maize genotypes B73 (open), Tx303 (gray), TBBC3-38-05F (hatched; the NIL carrying qNLB1.06 Tx303 ) and TBBC3-42-10E-02 (dotted; the NIL carrying qNLB1.02 Tx303 , which is essentially "replacement of qNLB1.02 B73 "). Differences between least square means of different genotypes relative to B73 were determined by two-tailed Student's t test (significance level: * 0.01 <P < 0.05; ** 0.001 <P < 0.01; *** P < 0.001). The proportion data were arcsine transformed for statistical analysis, and the corresponding least squares means and 95% confidence intervals were back-transformed to original scale before plotting. The confidence intervals are bigger than significance levels due to asymmetry resulting from back transformation.