Morphological differences between aerial and submerged sporidia of bio-fongicide Pseudozyma flocculosa CBS 16788

PLoS One. 2018 Aug 1;13(8):e0201677. doi: 10.1371/journal.pone.0201677. eCollection 2018.

Abstract

Pseudozyma flocculosa is a fungus very useful and highly efficient as a biocontrol agent against powdery mildew. The reproduction of this fungus occurs exclusively by asexual production of conidia or sporidia that are the most suitable form for agricultural use and seems to be the most resistant to storage conditions. Despite the advantages offered by P. flocculosa in biological control, the use of this fungus use remains largely limited compared to that of chemical fungicides, at least partly due to the difficulty to obtain sporidia resistant to adverse environmental stresses in submerged culture conditions. Under solid-state and submerged-state cultivation, P. flocculosa strain CBS 16788 produced different types of sporidia. The submerged sporidia (SS) appeared relatively uniform in size, which was 15,4 ± 1,6 μm μm long, and 2,8 ± 0.8 μm wide. The aerial sporidia (AS) varied in shape and size, with a mean length of 8,2 ± 3 μm and width of 2,3 ± 0.6 μm. Under scanning and transmission electron microscopy, the cell wall of submerged sporidia was thinner than that of aerial spores, and the surface was smooth in contrast to the aerial sporidia that had a tendency to have verrucous, brittle surface characteristics. The thickness of the aerial sporidia wall is due to the presence of an outer layer rich in melanin. The sporidia germination was compared on YMPD (yeast extract, malt extract, soy peptone, dextrose and agar) coated coverslips. The aerial sporidia did not show germ tubes until 5 h of incubation, while the submerged sporidia showed many germ tubes after the same time. The resistance against the adverse environmental conditions in relation to the type of sporidia of P. flocculosa is discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Wall / ultrastructure
  • Microscopy, Acoustic
  • Microscopy, Electron, Transmission
  • Plant Leaves / microbiology
  • Spores, Fungal / ultrastructure
  • Ustilaginales / isolation & purification
  • Ustilaginales / physiology*
  • Ustilaginales / ultrastructure

Grants and funding

This study was supported by Région Wallonne; Artechno sa, Isnes, Belgium; and université de liège, faculté de Gembloux agro biotec. Please note that one or more of the authors are employed by Artechno sa, Isnes, a commercial company. Despite this commercial affiliation, the funding organization, Artechno sa, only provided financial support in the form of authors' salaries [OZ, AS and FW] and/or research materials, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘updated author roles’ section.