AimsTo determine whether Venturia effusa, the causative fungal agent of pecan scab, harbours a bacterial symbiont. Methods and ResultsVenturia effusa isolates were maintained on potato dextrose agar amended with antibiotics (chloramphenicol (100gml(-1)) and tetracycline 100(gml(-1))). Genomic DNA extracted from mycelia was used to target eubacterial 16S rDNA. A 14-kbp PCR amplified product using 16S rDNA degenerate primers was cloned, sequenced and found to have 99% identities with Actinobacteria representatives. Attempts to culture the detected bacteria apart from the fungus following agitation and fungal cell lysis were unsuccessful using standard bacteriological media under either aerobic or anaerobic conditions. Fungal structures were visualized using scanning electron microscopy and putative bacterial formations associated with the fungal mycelia were observed. Fluorescence insitu hybridization using 16S rDNA oligonucleotides illuminated spores and portions of the hyphae. ConclusionsThis is the first report to provide both molecular microbiological and microscopic evidence in support of the hypothesis that V.effusa harbours endosymbiotic bacteria. Significance and Impact of the StudyFindings from this research contribute fundamental information regarding the biology of the fungus that may ultimately lead to identifying a target of the pathogen for use in management and/or avoidance strategies.