Authors
N. A.
Peres
,
University of Florida, Gulf Coast Research and Education Center, Wimauma 33598
;
R.
Harakava
,
Instituto Biológico, São Paulo, Brazil
;
G. C.
Carroll
,
Department of Biology, University of Oregon, Eugene 97403
;
J. E.
Adaskaveg
,
Department of Plant Pathology, University of California, Riverside 92521
; and
L. W.
Timmer
,
University of Florida, Citrus Research and Education Center, Department of Plant Pathology, Lake Alfred 33850
ABSTRACT
Citrus black spot, caused by Guignardia citricarpa, is a serious fruit spot disease and is widely distributed in Asia, southern Africa, and South America, but does not occur in North America or the Mediterranean region. A nonpathogenic species, G. mangiferae, is cosmopolitan with a wide host range and can colonize citrus fruit and leaves saprophytically. Detection and identification of Guignardia spp. on citrus fruit is necessary for epidemiological, management, and regulatory purposes. In this study, we compared published and unpublished polymerase chain reaction primer sets for their specificity and sensitivity in the detection and differentiation of the two Guignardia spp. All primers evaluated successfully identified the two species using purified DNA from fungal cultures or mycelia as source materials. However, some primer sets were not highly effective in detecting G. citricarpa when DNA was extracted directly from single characteristic black spot lesions on fruit. Thus, new primer pairs for both species were designed from the internal transcribed spacer region that were highly sensitive and specific for detection of G. citricarpa using DNA recovered from single lesions on fruit by a rapid DNA extraction procedure.
