Assessment of maximum amplicon length: PCR product yield. Mean relative yield (%) of 200, 400 and 600 bp PCR products of 4 materials (A, B, C and D). The prot. K + QIAamp extraction's yield was set at 100%. The +/ and -/ indicate the use of proteinase K digestion or no digestion, respectively. The different extraction methods are indicated by: heat-treatment =/-, QIAamp DNA extraction =/Q, EasyMAG DNA extraction =/EM, Gentra DNA extraction =/G.