Phytophthora infestans in Poland from 1987–1989; Nuclear DNA Content, Mating Type Distribution and Response to Metalaxyl |
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| Authors: | C. D. Therrien D. L. Ritch L. S. Sujkowski L. J. Spielman W. E. Fry S. S. Daggett J. H. Sim P. W. Tooley |
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| Affiliation: | Departments of Biology and Plant Pathology, The Pennsylvania State University, University Park, PA 16802, USA;Department of Human Biology, University of Wisconsin-Green Bay, Green Bay, WI 54311-7001, USA;Department of Genetics and Parental Line Breeding, Institute for Potato Research, Mlochow, 05-832, Rozalin, Poland;Department of Plant Pathology, Cornell University, Ithaca, NY 14853-5908, USA;US Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research, Ft. Detrick, Frederick, MD 21702, USA. |
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| Abstract: | Isolates of Phytophthora infestans were collected from all potato growing regions of Poland during the blight seasons of 1987—1989. All 1987 isolates were of Al mating type and were sensitive to metalaxyl. In 1988 and 1989, 46.5 % and 55.3 % of the isolates were sensitive to metalaxyl, respectively. The percentage of highly resistant (R) isolates increased from 25.6 % in 1988 to 39.5 % in 1989; however the percentage of intermediately resistant (I) isolates decreased during that period from 27.9 % to 5.3 %. A significant association was observed between the A1 compatibility type and metalaxyl resistance. The A2 mating type first appeared in 1988, and its frequency increased from 4.7 % of the population in 1988 to 47.6 % in 1989. Coincident with this change in mating type frequency, changes in ploidy levels of isolates were observed. Whereas 3 % of the 1988 isolates were diploid, 90 % of the 1989 A2 isolates and 28.6 % of the 1989 Al isolates were diploid. The approximate 1:1 ratio of the two mating types encountered in 1989, and the predominance of diploidy, indicates that the Polish population of P. infestans has the potential to become sexual. |
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