Canadian Journal of Plant Pathology (1998) 20, 259-273

R.D. Peters, H.W. Platt and R. Hall (1998)
Characterization of changes in populations of Phytophthora infestans in Canada using mating type and metalaxyl sensitivity markers
Canadian Journal of Plant Pathology 20 (3), 259-273
Abstract: Isolates of Phytophthora infestans were obtained from individual fields of potato and tomato and from potato storages across Canada in 1994 (142 samples yielding 555 isolates), 1995 (185 samples yielding 914 isolates), and 1996 (300 samples yielding 1013 isolates). Characterization of these isolates according to mating type and sensitivity to metalaxyl revealed the changing nature of P. infestans populations in Canada. In 1994, isolates of the traditional A1, metal axyl-sensitive (MS) phenotype were common, but by 1996, they were no longer recovered from any tissue samples. Isolates of the A2 mating type, which were predominantly insensitive to metalaxyl (MI), were prevalent in 1996, except in British Columbia (B.C.). In B.C., A1 isolates highly insensitive to metalaxyl predominated. Isolates of the A1, MI phenotype were also found in a sample of tomatoes from Ontario in 1996. New populations composed of the A2 mating type were predominantly insensitive to metalaxyl, but they showed an intermediate response between the high sensitivity of the original A1 population and the highly insensitive A1 populations in B.C. The exception was a few A2, MS isolates obtained from B.C. in 1996. The correlation between recovery of MI isolates and metalaxyl use was poor. There was a tendency for the proportion of MI isolates from fields managed with or without metalaxyl to increase as the growing season progressed. Both mating types of P. infestans were found in the same tissue sample a maximum of three times in a given year, self-fertile isolates were not recovered. Of 627 tissue samples examined over 3 years, one was found to have oospores of P. infestans present, indicating that sexual reproduction had occurred. These results demonstrate that populations of P. infestans in Canada have changed dramatically from 1994 to 1996 and that the original A1, MS population was rapidly displaced.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Rick D. Peters, H.W. (Bud) Platt

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora infestans	Potato (Solanum tuberosum)	Canada (west)
	Phytophthora infestans	Tomato (Solanum lycopersicum)	Canada (east)