ARS | Publication request: RAPD FINGERPRINTING AND PHYLOGENETIC ANALYSIS OF DIDYMELLA BRYONIAE AND PHOMA SPECIES

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 1996
Publication Date: N/A

Technical Abstract: D. bryoniae, the causal agent of gummy stem blight (GSB), and nonpathogenic Phoma spp. frequently are confused because both can be isolated simultaneously from cucurbits with GSB symptoms. The process of differentiating and identifying these fungi is difficult and time-consuming. Random amplified polymorphic DNA (RAPD) analysis with random oligonucleotide primers was used to "fingerprint" 61 isolates of these fungi from SC, NY, NC, FL, AZ and WI. Phylogenetic analysis using parsimony (PAUP) of RAPD data resulted in three clusters: D. bryoniae (35 isolates) and Phoma (14 isolates) clusters and an unidentified cluster (12 isolates). Pathogenicity tests conducted in a growth chamber indicated that only isolates of D. bryoniae caused disease on cantaloupe seedlings. Unique RAPD fragments are being cloned and will be sequenced to generate nested primers to enable PCR detection of the three clusters. PCR detection will provide a more rapid and reliable method of distinguishing among isolates in these three clusters and, therefore, will aid in accurate diagnosis.