Genetic similarity among Cercospora apii-group species and their detectionin host plant tissue by PCR/RFLP analyses of the rDNA internal transcribedspacer (ITS)

The objective of this study was to determine the genetic relatedness among the Cercospora and Pseudocercospora species closely related to Cercospora a pii by using a polymerase chain reaction/restriction fragment length polymo rphism (PCR/RFLP) analysis of the internal transcribed spacer (ITS) region. A single PCR fragment (about 550 bp) was obtained from all Cercospora spec ies categorized as the C. apii-group, Pseudocercospora purpurea, Pseudocerc ospora conyzae, and Pseudocercospora cavarae. Cercospora caricis yielded a 680 bp PCR fragment, The similarity in the PCR fragment size and RFLP profi les among the C. apii-group isolates, including Pseudocercospora purpurea, and Pseudocercospora conyzae strongly suggests that these species are consp ecific. Synonymy with C. apii (lectotype) at a subspecific rank has been pr oposed. Amplified ITS regions of genomic DNA extracted from spinach leaves showing 12 and 23% leaf spot disease symptoms caused by Cercospora beticola yielded two PCR fragments (i.e., one from the fungus and one from the host plant) and were resolved by electrophoresis of the PCR product in 3% LMP a garose. Digestion of the total PCR product with Hinfl restriction enzyme yi elded RFLP profiles similar to those obtained from amplified DNA from the c ausative agent, C. beticola, The method described in this preliminary study offers rapid detection and diagnosis of fungal infections in plants for di sease prediction and management and screening of plant materials for quaran tine purposes.