The nonheterothallic life cycle of Japanese Armillaria mellea

Abstract

The life cycle of Japanese Armillaria mellea was studied with regard to basidiomata formation from monosporous cultures, the nuclear behavior during basidiospore formation and germination, and DNA content per nucleus at different developmental stages. The nuclear behavior during basidiospore formation of A. gallica and Nagasawa's E group (Nag. E) was studied for comparison. Monosporous isolates of Japanese A. mellea formed mature basidiomata. Young basidia of Japanese A. mellea were clampless and each contained one nucleus. DNA content of the nucleus was 2C. After a meiotic division, four nuclei (each 1C) appeared in the basidia. As the basidiospores formed, the meiotic nuclei fused in pairs to form two 2C nuclei. Each of these nuclei migrated into a basidiospore, leaving two spores anucleate. A mitotic division then occurred in the spores; and in some cases, one of the spore nuclei migrated back into the basidium. Thus, anucleate, uninucleate and binucleate spores were formed. Nuclei in the uniand binucleate spores were 2C. All results in this study provided the evidence for nonheterothallic life cycle of Japanese A. mellea with the transient haploid stage limited to the postmeiosisin basidia. The life cycles of A. gallica and Nag. E were same as that of heterothallic species of Armillaria spp. with dikaryotic subhymenium reportedly.