title: Cultural characteristics of Sporisorium sorghi and detection of the pathogen in plant tissue by microscopy and PCR.
abstract: Despite the economic importance of covered kernel smut of sorghum (Sporisorium sorghi) in many African states and other parts of the world, only limited information is available on laboratory cultivation methods for this fungus and techniques for its diagnosis in plant tissue. When in the present study spores of S. sorghi were kept as intact sori at 5 degrees C, 80% of the spores germinated even after 24 months of storage. Spore germination on agar medium and production of mycelial dry weight in still culture were highest between 20 and 35 degrees C, with a peak at 30 degrees C. Both showed a steady increase from pH 4.5 to pH 7.5, followed by a decline at pH 8.5 and 9.5. In shake culture in different broth media the addition of 0.3% peptone from soybean caused an increase in fungal growth compared to the media alone. Of the media tested, mycelial production was highest in malt dextrose broth supplemented with peptone. When cultivated on different agar media, the morphology of single spore isolates differed both among isolates and depending on the agar medium. In greenhouse experiments, five short heighted, early maturing sorghum breeding accessions proved to be partially or fully resistant to covered kernel smut. Among the plant material tested, cv. 'Dorado' appeared to be the one best suited for greenhouse experiments with covered kernel smut. By microscopy of hand-cut sections stained with trypan-blue, hyphae of S. sorghi were seen in apical buds and in nodes of young sorghum plants. Diagnostic PCR amplified a 903 bp element comprising the internal region of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) encoding gene and enabled the detection of S. sorghi in both nodes and apical buds of infected sorghum seedlings. Both techniques, i.e. microscopy and diagnostic PCR have the potential to be used in studies for the identification of effective sorghum seed treatments already at the seedling stage.
authors.affiliation: Department of Plant Pathology, Faculty of Agriculture, Sohag University, El-Kawther, 82786 Sohag, Egypt. moharam@hotmail.com
authors.forename: M H A
authors.initials: MH
authors.lastname: Moharam
authors.forename: A
authors.initials: A
authors.lastname: Leclerque
authors.forename: E
authors.initials: E
authors.lastname: Koch
mesh_terms: D001487:Basidiomycota / Q000502:physiology*; D018533:Biomass; D006863:Hydrogen-Ion Concentration; D009172:Mycology / Q000379:methods; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D045868:Sorghum / Q000382:microbiology*; D013048:Specimen Handling; D013172:Spores, Fungal / Q000502:physiology; D013997:Time Factors