Studies on cell number and nuclei in spores and on ploidy level in ascochyta rabiei isolates

Isolates of the phytopathogenic ascomycete Ascochyta rabiei (Pass.) Labr. were stained with the DNA-specific fluorochrome 4',6-diamidino-2-phenylindole (DAPI) and compared for differences in number of nuclei per pycnidiospore and the ploidy level. Microscopic analyses revealed that within the examined isolates five different combinations of cell number and number of nuclei in spores exist. A one-celled spore may contain one, two and four nuclei, respectively, and in the case of two-celled spores there exist types with one and two nuclei in one cell. Microfluorometric analyses of wild types and benomyl-treated isolates revealed differences in ploidy level among the wild types.