Polyploidy Among Isolates of Phytophthora infestans from Eastern Germany

The ploidy of 101 isolates of Phytophihora infestans from the eastern states of the Federal Republic of Germany (formerly the German Democratic Republic) was determined by Feulgen DNA microdensitometry. The isolates used in this investigation were collected during 11 growing seasons between 1976 and 1990. Fifty hyphal nuclei per isolate were used for DNA measurements. Polyploids predominated throughout the 15-year sampling period. Four of the isolates collected during 1989 were diploid. Based on the results of this investigation, there appears to have been no trend towards a diploid. sexual population during the sampling period.