Detection of Phytophthora nicotianae and P. palmivora in citrus roots using PCR-RFLP in comparison with other methods
Bowman. K. D Albrecht. U Graham. J. H Bright. D. B
European Journal of Plant Pathology ; 2007 [Vol.119] Pages:143-158
Abstract
Phytophthora nicotianae and P. palmivora are the most important soil-borne pathogens of citrus in Florida. These two species were detected and
identified in singly and doubly infected plants using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of internal transcribed spacer (ITS) regions of ribosomal DNA. The sensi-
tivity of the PCR-RFLP was analyzed and the usefulness of the method evaluated as an alternative or supplement to serological methods and recovery
on semi-selective medium. In a semi-nested PCR with universal primers ITS4 and ITS6, the detection limit was 1 fg of fungal DNA, which made it 1000· more sensitive than a single-step PCR with primers
ITS4 and DC6. The sensitivity of detection for P. nicotianae was shown to be ten-fold lower than for P. palmivora, limiting its detection with restriction profiles in plants infected by both fungal species. Phytophthora nicotianae was detected with species-
specific primers in all samples inoculated with this species despite the absence of species-specificpatterns in RFLP. In contrast, the incidence of
detection of P. palmivora in the presence of P. nicotianae was considerably lower using plating and morphological detection methods. Due to its high sensitivity, PCR amplification of ribosomal ITS regions is a valuable tool for detecting and identifying Phytophthora spp. in citrus roots, provided a thorough knowledge of reaction conditions for the
target species is established prior to the interpretation of data.
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