1.8.35
THE FIRST LINKAGE MAP OF MYCOSPHAERELLA GRAMINICOLA (ANAMORPH SEPTORIA TRITICI), EUROPE'S MAJOR FUNGAL WHEAT PATHOGEN

GHJ KEMAL1, S HAMZA2, PJM BONANTS1, C WAALWIJKI1, M HAGENAAR-DE WEERDT1, ECP VERSTAPPEN1 and TAJ VAN DER LEE3

1DLO-Research Institute for Plant Protection, PO Box 9060, 6700 GW Wageningen, The Netherlands; 2Institut National Agronomique de Tunisie, Tunis, Tunisia; 3Wageningen Agricultural University, Laboratory of Phytopathology, The Netherlands

Background and objectives
Genetic variation within and between local populations of Mycosphaerella graminicola is vast [1, 2]. Recently, development of a procedure to cross isolates of the fungus showed that M. graminicola has a heterothallic bipolar mating system [3]. Furthermore, we crossed isolates IP0323 (avirulent, MAT1-11) and IP094269 (virulent, MAT1-21) and isolated a large F1 progeny, and back-crosses and sib-crosses were made to produce BC1 and F2 populations, respectively. These populations were used to study the genetics of avirulence, to determine the mating types of individual progeny isolates, to create a linkage map of the M. graminicola genome, and to map the above-mentioned loci.

Materials and methods
All progeny isolates were tested on bread wheat cultivars Taichung 29 (susceptible), Kavkaz/K4500 (resistant) and Shafir, Veranopolis and Kavkaz (differential). The AFLP technique, using fluorescent primers, was applied to generate a mapping data set. The parental isolates IP0323 and IP094269 were screened with 64 primer combinations, of which 11 were selected to screen 68 F1 isolates. The data were analysed using JoinMap software.

Results and conclusions
Avirulence for each differential cultivar segregated as a monogenic character. In addition, the tested populations merely showed parental phenotypes, hence avirulence on cultivars. Shafir, Veranopolis and Kavkaz co-segregated. Since these cultivars do carry at least one different resistance gene [2], we hypothesize a complex locus with at least three tightly linked avirulence genes. This locus segregated independently from the mating-type locus. The AFLP experiments resulted in 317 polymorphic markers. JoinMap placed 303 markers on the map and calculated 24 linkage groups, slightly more than the 16-18 chromosomes visualized by pulsed field gel electrophoresis. The avirulence and mating-type loci, and several closely linked markers, were mapped on small linkage groups.

References
1. McDonald BA, Pettway RE, Chen RS et al., 1995. Canadian Journal of Botany 73 (suppl), S292-S301.
2. Kema GHJ, Annone JG, Sayoud R et al., 1996. Phytopathology 86, 200-212.
3. Kema GHJ, Verstappen ECP, Todorova M, and Waalwijk C, 1996. Current Genetics 30, 251-258.