American Potato Journal

, 68:717 | Cite as

Occurrence of the A2 mating type ofPhytophthora infestans in potato fields in the United States and Canada

  • K. L. Deahl
  • R. W. Goth
  • R. Young
  • S. L. Sinden
  • M. E. Gallegly


Ten isolates ofP. infestans collected from blighted potato fields in the U.S. and Canada during the years 1983–1989 were examined for mating type on lima bean, oatmeal, and rye grain media. Two of the ten isolates produced oospores in less than 15 days when cultured in the presence of known A1 mating types from the USA, Mexico, and Europe, indicating they are A2 mating types. When the two A2 isolates (one from Pennsylvania and one from Vancouver, B.C.) were cultured singly or with known A2 isolates, no oospores formed after 6 weeks of culture. Pathogenicity tests showed that both isolates produced typical late blight symptoms on potato foliage and stems, and there appeared to be no difference in virulence between these two A2 and the eight A1 isolates. Inoculations with a mixture of A1 + A2 sporangia also produced oospores in host tissues. This is the first report of the presence of the A2 mating type ofP. infestans in the U.S. and Canada.

Additional Key Words

Potato late blight oospore Solanum tuberosum 


Diez aislamientos deP. infestans obtenidos de campos de papa infectados en los EE.UU. y el Canadá durante los años 1983–1989, fueron examinados para determinar el tipo presente en el apareamiento sobre medios de habas, avena y granos de arroz. Dos de los diez aislamientos produjeron oosporas en menos de 15 días cuando se les cultivó en presencia de los ya conocidos tipos A1 de apareamiento de los EE.UU., México y Europa, indicando que ellos son tipos de apareamiento A2. Cuando los dos aislamientos A2 (uno de Pennsylvania y uno de Vancouver, B.C.) fueron cultivados independientemente o con aislamientos A2, no se formaron oosporas después de seis semanas de cultivo. Las pruebas de patogenicidad mostraron que ambos aislamientos producían síntomas típicos de tizón tardío sobre el follaje y tallos y pareció no existir diferencias en virulencia entre estos dos A2 y los ocho aislamientos A1. Inoculaciones con una mezcla de esporangios A1 + A2 produjeron también oosporas en los tejidos del hospedante. Este es el primer informe de la presencia del tipo A2 de apareamiento deP. infestans en los EE.UU y el Canadá.

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Copyright information

© Springer 1991

Authors and Affiliations

  • K. L. Deahl
    • 1
  • R. W. Goth
    • 1
  • R. Young
    • 2
  • S. L. Sinden
    • 1
  • M. E. Gallegly
    • 2
  1. 1.U.S. Department of Agriculture, Agricultural Research ServiceVegetable LaboratoryBeltsville
  2. 2.West Virginia UniversityMorgantown

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