Diagnostic Sensitivity of Phytophthora ×alni from Environmental Samples Using Conventional and Real-Time PCR

The study aims to compare the sensitivity of conventional and real-time PCR in detecting Phytophthora ×alni DNA in plants, peat substrate, and water. The accuracy of the detection of DNA isolated from pure cultures of P. ×alni and the influence of DNA isolated from Alnus tissue and peat substrate on the sensitivity of P. ×alni detection are assessed. Real-time PCR is 100-fold more sensitive than conventional PCR in the reaction with DNA extracted from plants and peat. Adding 1 µL and 3 µL of plant and peat DNA, respectively, reduces the sensitivity of P. ×alni detection by 100 times when using conventional PCR and by 10 times when using real-time PCR. The conventional PCR technique allows for the detection of P. ×alni on the day the first necrosis symptoms become visible or two days before they appear on artificially inoculated shoots. The real-time PCR technique allows for the detection of P. ×alni, depending on the zoospore concentration and isolate, 2, 4, 6, 8, and 12 days before necrosis appears. Conventional and real-time PCR allow for the detection of 250 and 100 P. ×alni zoospores, respectively, in a 0.5 g peat substrate sample and 25 and 10 spores, respectively, in 100 µL water.