ADVANCES IN GENOMIC MAPPING OF PHYTOPHTHORAINFESTANS.

Previously a genetic linkage map of the heterothallic oomycetous plant pathogen Phytophthora infestans was constructed using only one cross from two Dutch field isolates (cross 71) and 73 F1 progeny. The map is based on polymorphic DNA markers generated by the DNA fingerprinting technique AFLP. The 183 AFLP markers and the 7 RFLP markers were comprised in 10 major and 7 minor linkage groups covering a total of 827 cM. Non Mendelian segregation ratios were found for the mating type locus and for 13 AFLP markers, all of which are located on the same linkage group as the mating type locus. A new genetic map was constructed using 56 individuals derived from a cross between two Mexican isolates (cross 68). The Mexican parental isolates are genetically more diverse than the Dutch ones. Approximately 300 segregating markers were scored. Although the number of markers present in the map of the cross 68 and cross 71 is limited, preliminary analysis indicate that parts of genome are colinear. To further investigate whether we can construct an integrated map, we are increasing the number of the markers in both cross 71 and cross 68.