| Popis: |
The nuclear DNA content of zoospores ofPhytophthora infestans was determined by Feulgen cytophotometry. Isolates from Mexico, where the sexual stage of the fungus is common, were compared with isolates from the United States and Europe. The mean nuclear DNA content of 23 Mexican isolates was 0.59 arbitrary units (a.u.; range, 0.48–0.79), while that of 18 non-Mexican isolates was 0.92 a.u. (range, 0.56–1.11). Mexican isolates are very likely diploid, as indicated by cytological studies of other workers. The non-Mexican group, by contrast, appears to include isolates that are diploid, triploid, tetraploid, and aneuploid. Of three non-Mexican isolates with DNA contents similar to those of the Mexican isolates (apparent diploids), two originated from Southern California and may be of recent Mexican origin. |
