Mating type-correlated molecular markers and demonstration of heterokaryosis in the phytopathogenic fungus Thanatephorus cucumeris (Rhizoctonia solani) AG 1-IC by AFLP DNA fingerprinting analysis

The destructive soil-borne plant pathogenic basidiomycetous fungus Thanatep horus cucumeris (Frank) Donk [anamorph: Rhizoctonia solani Kuhn] is not a h omogeneous species, but is composed of at least twelve anastomosis groups ( AG), which seem to be genetically isolated. The genetics of several T. cucu meris anastomosis groups has been studied by analysis of heterokaryotic tuf t formation in the area of contact between homokaryotic single-spore isolat es, revealing that AG 1 is heterokaryotic and bipolar. To prove that tuft f ormation is due to heterokaryosis, AFLP DNA fingerprinting has been applied to a heterokaryotic T. cucumeris AG 1-IC isolate, its homokaryotic single spore-derived progeny, and newly formed heterokaryons. By means of AFLP mar kers, it is demonstrated that fluffy tufts formed upon pairing of homokaryo ns from different mating types are newly formed heterokaryons. Mating type- correlated markers have also been found, which will be useful for future st udies of the genetics of this fungal species complex. (C) 1999 Elsevier Sci ence B.V. All rights reserved.