Primer sensitivity test with (A) pure R. subterranea DNA; (B) spiked soil extracts; (C) spiked grapevine root extracts. (A) PCR products of DNA extracts from R. subterranea. From left to right: 1 ng, 100 pg, 10 pg, 1 pg, 100 fg, 10 fg, 1 fg, negative control (a.d.) and DNA ladder. (B) PCR products of DNA extracts from sterile soil spiked with R. subterranea DNA. From left to right: 1 ng, 100 pg, 10 pg, 1 pg, 100 fg, pure soil extract, 1 pg DNA of R. subterranea (positive control), negative control (a.d.) and DNA ladder. (C) PCR products of DNA extracts from grapevine roots spiked with R. subterranea DNA. From left to right: 1 ng, 100 pg, 10 pg, 1 pg, 100 fg, pure root extract, 1 pg DNA of R. subterranea (positive control), negative control (a.d.) and DNA ladder.