IsArthroderma simiithe perfect state ofTrichophyton quinckeanum?

Abstract

Gymnothecia with asci and ascospores developed repeatedly and in abundance whenever Trichophyton quinckeanum isolates X-392 and IMI 140691 were paired with Arthroderma simii 678 A. However, repeatable fertile crosses did not occur when all of our 19 isolates of T. quinckeanum were paired with 10 other isolates of A. simii comprising A and a mating types. Additional crosses between these 19 isolates of T. quinckeanum with A. simii and with A. benhamiae revealed that 11 of the 19 isolates of T. quinckeanum produced fertile gymnothecia only when crossed with A. simii 678 A but not when crossed with another isolate of A. simii of the A mating type nor when crossed with mating type a. All 19 isolates mated with A. benhamiae mating type A; therefore, all of our T. quinckeanum isolates were of the a mating type. Study of asci and random ascospores, selected with a micromanipulator, from crosses between several isolates of T. quinckeanum and A. simii 678 A revealed irregularities in the maturation of ascospores, poor ascospore germination, and a predominance of the A. simii phenotype and mating type for those ascospores that germinated and produced mature colonies. All these reactions are characteristic of interspecific crosses. In contrast, ascus analysis of the F1 progeny of crosses between these same isolates of T. quinckeanum with A. benhamiae revealed regular maturation of ascospores, better germination, and essentially a 1:1 segregation of mating types and parental phenotypes. This study confirms the concept that T. quinckeanum is not an independent species and that it is best considered to be a variety of T. mentagrophytes, as reported by Ajello, Bostick & Cheng (1968). Furthermore, our data indicate that T. mentagrophytes var. quinckeanum appears to be more closely related to A. simii than the granular variety of T. mentagrophytes, since fertile gymnothecia resulted from crosses between T. mentagrophytes var. quinckeanum and A. simii but not between T. mentagrophytes var. mentagrophytes and A. simii. Further implications of this study suggest the importance of extensive ascospore analysis when investigating the perfect states of fungi in order to avoid creating unwarranted new species.