The Northern Ireland Phytophthora infestans population 1998–2002 characterized by genotypic and phenotypic markers |
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| Authors: | L R Cooke D J Carlisle C Donaghy M Quinn F M Perez K L Deahl |
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| Institution: | Department of Applied Plant Science, Faculty of Science and Agriculture, The Queen's University of Belfast Newforge Lane, Belfast, BT9 5PX;;Applied Plant Science Division, Department of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX, UK;and;USDA, ARS, PSI, Vegetable Laboratory, Beltsville, MD 20705, USA |
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| Abstract: | A total of 204 isolates of Phytophthora infestans from Northern Ireland, almost all from commercial potato crops, were collected over 5 years (1998–2002). Phenotypic diversity was assessed using mating type and metalaxyl resistance; genotypic diversity was assessed using two allozyme loci (glucose-6-phosphate isomerase, Gpi, and peptidase, Pep ), mitochondrial DNA haplotype and the multilocus RFLP probe RG57. All isolates were A1 mating type and Gpi 100/100 . The majority were Pep 100/100 , but four Pep 83/100 and six Pep 96/100 isolates were identified. Three mtDNA haplotypes were detected; haplotype IIa was the most common, but each year up to 2001 its frequency declined, with a concomitant increase in Ia isolates. Three isolates had the rare haplotype IIb, but this was only detected in 1998. Metalaxyl resistance and mtDNA haplotype were markedly associated: most haplotype Ia isolates were metalaxyl-resistant, whereas haplotype IIa was more commonly associated with metalaxyl sensitivity. Analysis of a subsample of 91 isolates revealed nine RG57 genotypes, three associated exclusively with haplotype IIa and six exclusively with haplotype Ia. The most common RG57 genotype (51% of isolates) comprised both metalaxyl-resistant and -sensitive haplotype IIa isolates. However, of haplotype Ia isolates, all metalaxyl-resistant phenotypes belonged to one of four RG57 types, one of which was the second most frequent overall (29% of isolates), while all metalaxyl-sensitive isolates belonged to one of two other types. The P. infestans population in Northern Ireland appears to consist of a limited number of clones related to, but differentiated from, the populations in mainland Britain and elsewhere in Europe. |
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| Keywords: | allozymes mating type metalaxyl sensitivity mitochondrial DNA haplotype potato-late blight RG57 analysis |
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