Morphological and Ultrastructural Characteristics of Dumontinia tuberosa (Bull.) L.M. Kohn from Ranunculus ficaria L.

Abstract

Dumontinia tuberosa fungus was observed in different stages of development growing on the roots of Ranunculus ficaria in Cluj-Napoca (Romania), over the course of several years. It is not frequently encountered, therefore, we decided that will be interesting to cultivate it on nutritive medium, and to use the morphological data and the colony’s characteristics to identify the fungus. The identity of the fungus was reaffirmed through a molecular analysis of sclerotium DNA sequences. A new favourable nutritive medium for the growth and development of the fungus is proposed. The morphology and ultrastructure of the fungus were examined by light and electron microscopy, and micrographs of the relevant details are provided. Differences between the ultrastructural characteristics of sclerotium, apothecium stipe, ascospores, asci and paraphyses are presented and discussed. Intercellular spaces were identified in sclerotium and apothecium stipe and the paraphyses. Asci and ascospores were found to be covered by a sticky mucilage. The ultrastructural characteristics of the aforementioned tissues are presented for different developmental stages. Additionally, the main food stores of the fungus, represented by glycogen, lipids and proteins, are located and described along with other characteristic compounds, such as melanin pigment and a glucan extracellular matrix. The present study complements prior information on the worldwide distribution of this rare species in nature and contributes new findings regarding its morphological and ultrastructural characteristics.