Why do melting temperatures differ between PCR fragments amplified with QIAGEN's QuantiTect SYBR Green PCR Kits and Roche Kits?

The melting temperature of a PCR product depends on the salt concentration of the buffers used for amplification. Buffer compositions differ between QuantiTect SYBR Green PCR Kits and Roche kits, resulting in different PCR product melting temperatures.