Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 8/26/2001
Publication Date: N/A
Technical Abstract: Reproductive isolation is the first step in species formation. Detecting when this has occurred can be difficult, because morphological differentiation usually is not evident during the early stages of species formation. Gene flow analysis estimates the number of migrants between populations per generation. Populations exchanging fewer than one migrant every other generation are reproductively isolated and may be beginning the speciation process. Gene flow analysis can be used with any type of discrete genetic marker, including those commonly employed by plant pathologists and mycologists (e.g., isozymes, RAPDs, AFLPs). Gene flow analysis of the oomycetes Phytophthora infestans and P. mirabilis indicated that these taxa were reproductively isolated and clearly represent two species, even though their ITS sequences are identical and would not have been separated by sequence analysis of that region. Analysis of the rice blast pathogen Magnaporthe grisea indicated that most host-associated forms are reproductively isolated from the others and probably represent different species. This technique can be a powerful tool for testing the level of gene flow among closely related, morphologically similar taxa.