Open AccessVariation in the patterns of virulence and the relative fitness of virulence phenotypes in Swedish populations of Bremia lactucae
Author(s) -
GUSTAFSSON M.,
LARSSON C.
Publication year - 1984
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.1984.tb00443.x
Subject(s) - virulence , biology , obligate parasite , gene , pathogen , obligate , genetics , host (biology) , selection (genetic algorithm) , phenotype , parasite hosting , population , ecology , demography , artificial intelligence , sociology , world wide web , computer science
Pathogenic variation in Bremia lactucae, an obligate parasite on lettuce (Lactuca sativa), was investigated in Sweden between 1971 and 1982. The host‐pathogen interaction conforms to a gene‐for‐gene model, where eleven virulence factors in the host are matched by eleven virulence factors in the parasite. Variation in the pathogen population is characterized by an increase in virulence factor frequencies with time, accumulation of virulence genes with time, and the presence of “unnecessary” virulence. The accumulation of virulence genes and evolution of super‐races have great evolutionary significance. This is particularly the case in host‐pathogen systems exposed to drastic changes in selection pressures caused by the successive introduction of resistance genes. The concept of stabilizing selection has dominated discussions about race specific interactions. However, the influence of directional and disruptive selection on gene frequencies is equally important.