Comparative testing of nested PCR‐based methods with bait‐plant tests for detecting Phytophthora fragariae var. fragariae in infected strawberry roots from fruit crops in the UK*

Abstract

This study compared nested polymerase chain reaction (PCR) methods with the traditional Duncan bait test for the detection of Phytophthora fragariae var. fragariae in 86 root samples representing 30 strawberry fruit crops in England and Wales. DNA was extracted directly from the sampled roots using a cetyltrimethyl ammonium bromide‐based (CTAB) extraction method. Dilutions of the extracted DNA were then amplified using a nested PCR protocol. The PCR results correlated strongly with those of the bait tests, with the PCR methodology appearing to be the more reliable detection method on this type of field material. The PCR test also had the advantage of being a more rapid, less labour and time‐intensive test, compared with the 5‐6 week bait test. Comparisons were also made with a second set of nested PCR primers on DNA extracted from infected roots from the same field material; both primer sets performed equally well.