Phytopathogenic Mollicutes

Recent reports indicate as essential information, that must be submitted with the manuscripts about quantitative PCR the quantification cycle (Cq), corresponding to threshold cycle (Ct), of the samples named no template control (NTC), containing the mix without DNA template. Moreover if all samples without templateshow different Cq valuesfor at least threetimes, thereisahigh probability of contamination due to human error during the plate loading. In this case, samples that resulted positive in analytical PCR can differ only of one Ct from the NTC samples. This problem was found in checking two couples of primers to quantify ‘Candidatus Phytoplasma pyri’ in DNAs samples extracted from pear leaves that were positive in nested PCR assays. The possibility of a contamination of one of the reagents was excluded since the Ct values of NTC samples were not close to each other and the melting curve analysis did not reveal the presence of primer dimers at low temperatures. The analyses of NTC samples were determinant suggesting to not further promote the use of the two couples of primers.