2.2.3
EYESPOT POPULATION VARIABILITY IN THE CZECH REPUBLIC
I POLISENSKA1, P VEJL2, M VANOVA1

1ARI, Agricultural Research Institute Kromeriz, Ltd., Havlickova 2787, 767 01 Kromeriz, Czech Republic; 2Czech Agricultural University, Faculty of Agronomy, Kamycka 957, 165 21 Prague 6-Suchdol, Czech Republic

Background and objectives
Eyespot, caused by Tapesia yallundae and Tapesia acuformis, is a common disease on winter cereals. Yield losses can be of different levels in relation to crop rotation, sowing date, soil fertility, weather factors and inherent susceptibility of the cultivar to the lodging. At present, the eyespot pathogen is classified in two species. The earlier W (N) type of the Pseudocercosporella herpotrichoides anamorph corresponds with T. yallundae, R (L) type corresponds with T. acuformis [1]. Field populations taken from infected stems usually contain both species in various ratios. They differ by in pathogenicity, fungicide sensitivity and show different culture morphology in vitro. In this respect, it is necessary to determine a ratio of species and their sensitivity to the fungicidal active ingredients applied. The species may be clearly distinguished using molecular markers.

Materials and methods
For 3 years (1995, 1996 and 1997) infected stem parts of winter wheat were collected at various locations across the Czech Republic. Pure colonies of the fungus were cultivated from these on potato-dextrose agar, then visually classified in individual species and tested for their sensitivity to MBC fungicides. Some isolates of T. yallundae and T. acuformis, as well as two isolates of Fusarium culmorum, Microdochium nivale and Rhizoctonia spp. were examined using RAPD markers.

Results and conclusions
A total of 450 isolates of T. yallundae and T. acuformis were obtained. The proportion of isolates resistant to MBC fungicides was about 25%. However, there was considerable variability between locations and T. acuformis isolates exhibited resistance more frequently.

The RAPD method allowed differentiation of F.&mbspculmorum, M. nivale and Rhizoctonia spp., which can also be found on stem bases of winter cereals. The variability observed in RAPD patterns of T. yallundae and T. acuformis correlated with visual assessment of colony morphology of these species.

Acknowledgements
Research is supported by the Grant Agency of the Czech Republic, project no. 522/97/0636

References
1. Dyer PS, Nicholson P, Lucas JA, Peberdy JF, 1996. Mycological Research 100, 1219-1226.