Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/12/1999
Publication Date: N/A
Technical Abstract: The ability to produce stipitate sclerotia and synnemata by a mutant culture derived from Aspergillus flavus NRRL 3357 is reported for the first time. Stipitate sclerotia were observed on Czapek agar (CZA) while synnemata formed on Murashige-Skoog agar (MSA) and on oats agar. Incubation at 30-32 C hastened the initiation and maturation of the sclerotia and the formation of synnemata. Sclerotia were abundant when the carbon source in CZA were replaced with dextrose, fructose, melibiose, or xylose; whereas MSA amended with fructose, mannitol, and sorbitol produced numerous 6-12 mm long synnemata but no sclerotia. Glycine, asparagine, or proline-amended CZA supported abundant production of sclerotia, comparable to those obtained when the nitrogen source is NaNO3, while cultures grown on media containing lysine, serine, or threonine produced only synnemata. Using sucrose and NaNO3, the highest number of sclerotia were produced at 3:33:1 C:N ratio; higher C:N ratios decreased synnemata and sclerotia formation. The development of synnemata or sclerotia may originate from the same immature conidioma; their differentiation into either sclerotia or synnemata was influenced by environmental and nutritional conditions. The ability of this mutant to produce synnemata and stipitate sclerotia substantiates the view for an evolutionary link between A. flavus and Stilbothamnium togoense, a tropical fungus that produces these same structures. A single weak band was detected when the genomic DNA of S. togoense was fingerprinted using the DNA probe pAF28 derived from A. flavus, suggesting some degree of relationship between these two fungi.