Sporulation and dsRNA Viral Molecules in Penicillium citrinum

Abstract

Viral distribution and sporulation seemed to be characters related to each other in a strain of Penicillium citrinum. While the sporulating isolate exhibited 10 dsRNA molecules whose molecular weights were respectively: 3.98, 2.66, 2.48, 2.10, 1.97, 1.84, 1.78, 1.40, 1.26, and 1.10 × 10⁶ daltons, the nonsporulating one contained only 3 dsRNA molecule species with the following molecular weights: 3.98, 1.26 and 1.10 × 10⁶ daltons. We supposed that only these two last dsRNA molecules were responsible for the nonsporulation of the isolate. In order to show better the correlation between sporulation and the presence of particular viral molecules, we treated the nonsporulating isolate with several salts at various concentrations. Initially we used only MnCl₂ to induce sporulation. It was known to induce morphological variations in strains of Aspergillus nidulans, that appeared very close to those described in Aspergillus glaucus and could be explained as probably due to a mycoviral infection. After the first encouraging results we extended our experiments to other salts. We found that NiCl, FeCl₃, MnCl₂, RbCl, and BaCl₂ were good inducers of sporulation. The experiments of induction were made on Czapek Dox medium plus the substances under test. Fragments of nonsporulating mycelium were placed in the middle of petri dishes. After 15–20 days of incubation at 24°C, we selected the green sporulating sectors. These were used to inoculate flasks containing potato dextrose broth, pH = 7.0. After t days of fermentation at 24°C, the mycelia were harvested and virus extracted.