Ascospore-derived isolate of Arthroderma benhamiae with morphology suggestive of Trichophyton verrucosum.

Sixty-one ascospores were isolated from an ascocarp produced by the mating of two Arthroderma benhamiae strains, RV 26678 and KMU4169, that differed in their mitochondrial DNA (mtDNA) restriction fragment length polymorphism (RFLP) patterns and in the sequences of their nuclear ribosomal internal transcribed spacer (ITS) regions. RV 26678 is a genetically typical A. benhamiae isolate, while KMU4169, though morphologically indistinguishable from A. benhamiae, is an isolate with a deviating ITS sequence and with a mtDNA RFLP profile identical to that of T. verrucosum. One of the 61 progeny ascospores formed a colony, KMU5-46, that was quite different from both parental isolates. KMU5-46 is a faviform colony morphologically similar to Trichophyton verrucosum, although its mtDNA RFLP patterns and ITS sequences were identical to those of A. benhamiae parental strain RV 26678. The morphological alteration manifested in KMU5-46, as well as this isolate's complete loss of sexual response, indicates the possibility that the asexual T. verrucosum and the sexual A. benhamiae are conspecific.