RAPD-based inter- and intravarietal classification of fungi of the Gaeumannomyces-Phialophora complex

The suitability of randomly amplified polymorphic DNAs (RAPD) for differentiation at the varietal and intravarietal level was tested on several hundred isolates of the Gaeumannomyces-Phialophora (G-P) complex from different geographic locations and host plants. Amplification products obtained using two decamer primers allowed differentiation between Gaeumannomyces graminis and Gaeumannomyces cylindrosporus and between the three varieties of Gaeumannomyces graminis, as well as further division at the intravarietal level. Thus, isolates of the causal agent of take-all on cereals, Gaeumannomyces graminis var. tritici were divided into six subgroups by amplification with these two primers. There is some evidence for an association between host preference and RAPD subgroups but further work is needed to confirm this and to determine the importance of these subgroups. This fast and easy method is a useful tool for investigating the occurrence and distribution of this pathogen and for studying changes in the populations of species and subgroups of Gaeumannomyces in cereal cropping systems.