Genetic change within populations of Phytophthora infestans in the United States and Canada during 1994 and 1996: role of migration and recombination

• Published in: Phytopathology Vol. 88; no. 9; pp. 939 - 949
• Main Authors: Goodwin, S.B. (USDA, ARS, Crop Production and Pest Control Research Unit, West Lafayette, IN.), Smart, C.D, Sandrock, R.W, Deahl, K.L, Punja, Z.K, Fry, W.E
• Format: Journal Article
• Language: English
• Published: St. Paul, MN American Phytopathological Society 01.09.1998
• Subjects: ALBERTA; ALLOENZYMES; ALLOZYME; ALLOZYMES; ALOZIMAS; ASEXUAL REPRODUCTION; Biological and medical sciences; BIOLOGICAL COMPETITION; BRITISH COLUMBIA; CANADA; COLOMBIE BRITANNIQUE; COLUMBIA BRITANICA; COMPATIBILITY; COMPETENCIA BIOLOGICA; COMPETITION BIOLOGIQUE; COMPETITIVE ABILITY; DIAGNOSIS; DIAGNOSTIC; DIAGNOSTICO; ECHANTILLONNAGE; ENFERMEDADES DE LAS PLANTAS; ETATS UNIS; EUA; FONGICIDE; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; FUNGICIDAS; FUNGICIDE TOLERANCE; FUNGICIDES; GENETIC VARIATION; GENETICA DE POBLACIONES; GENETIQUE DES POPULATIONS; GENOTIPOS; GENOTYPE; GENOTYPES; HOST RANGE; HOSTS; HOTE; HUESPEDES; IDENTIFICACION; IDENTIFICATION; LYCOPERSICON ESCULENTUM; MALADIE DES PLANTES; METALAXIL; METALAXYL; MIGRACION; MIGRATION; MUESTREO; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; PHYTOPHTHORA INFESTANS; PLANT DISEASES; POPULATION GENETICS; RECOMBINACION; RECOMBINAISON; RECOMBINATION; REPRODUCCION ASEXUAL; REPRODUCCION SEXUAL; REPRODUCTION ASEXUEE; REPRODUCTION SEXUEE; RESISTANCE AUX PRODUITS CHIMIQUES; RESISTANCE TO CHEMICALS; RESISTENCIA A PRODUCTOS QUIMICOS; SAMPLING; SEED TUBERS; SEXUAL REPRODUCTION; SOLANUM TUBEROSUM; TUBERCULE; TUBERCULO; TUBERS; USA; VARIACION GENETICA; VARIATION GENETIQUE; North America; America; Fungi; Pathogenicity; Genetic variability; Plant pathogen; Dissemination; Phycomycetes; Phytophthora infestans; Isolate; Epidemiology; Population genetics; Thallophyta
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO.1998.88.9.939

Dramatic changes occurred within populations of Phytophthora infestans in the United States and Canada from 1994 through 1996. Occurrence of the US-8 genotype, detected rarely during 1992 and 1993, increased rapidly and predominated in most regions during 1994 through 1996. US-7, which infected both potato and tomato and made up almost 50% of the sample during 1993, was detected only rarely among 330 isolates from the United States analyzed during 1994. It was not detected at all in more limited samples from 1996. Thus, ability to infect both potato and tomato apparently did not increase the fitness of this genotype relative to US-8, as predicted previously. US-1, the previously dominant genotype throughout the United States and Canada, made up 8% or less of the samples analyzed during 1994 through 1996. A few additional genotypes were detected, which could indicate the beginnings of sexual reproduction of P. infestans within the United States and Canada. However, clonal reproduction still predominated in all locations sampled; opportunities for sexual reproduction probably were limited, because the A1 and A2 mating types usually were separated geographically. The high sensitivity of the US-1 genotype to the fungicide metalaxyl also could have reduced opportunities for contact between the mating types in fields where this compound was applied. The previous correlation between metalaxyl sensitivity and genotype was confirmed and extended to a new genotype, US-17: all US-1 isolates tested were sensitive; all isolates of the US-7, US-8, and US-17 genotypes tested to date have been resistant. Isolates of P. capsici and P. erythroseptica, two other species often found on tomato and potato, could be easily distinguished from each other and from P. infestans using a simple allozyme assay for the enzyme glucose-6-phosphate isomerase. This technique could be useful for rapid identification of species, in addition to genotype of P. infestans. It generally was not possible to...