The unusual sclerotium of Rhizopogon roseolus reported from pure cultures

Abstract

Abstract During the assessment of mycelial cords of Rhizopogon roseolus on poor nutrient of Modified Melin-Norkrans (MMN) medium, we found some sclerotia produced on the surface of extraradical mycelia. The sclerotia were 0.27 mm in average of diameter and produced after 2 months of incubation. The current knowledge defined the sclerotium as mass of hyphae and normally having no spores in or on it. However, we found and suspected the small structures like spores (1-1.5 um) inside the sclerotium. These structures were ellipsoid, hyaline, with the smooth surface. We then incubated the sclerotium and these small structures on TM7 detecting medium whether they can produced the secondary mycelia of R. Roseolus, but no germination was observed. Interestingly, the bacterial colonies which connected to hyphae of sclerotium were appeared. The colonies were transferred to Luria agar (LA) medium. The morphological observation of bacterial cells from TM7 and LA confirmed that they were the same as small structures inside the sclerotium. This is the first report on production of unusual sclerotium of R. roseolus in pure cultures. Further study is required to reveal the role of bacteria on production of sclerotium of R. Roseolus.