VIEW ARTICLE

Etiology

Isolation, Culture, and Pathogenicity to Sudan Grass of a Corynebacterium Associated with Ratoon Stunting of Sugarcane and with Bermuda Grass. C. H. Liao, Assistant research professor, Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903; T. A. Chen, professor, Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903. Phytopathology 71:1303-1306. Accepted for publication 16 March 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1303.

The small bacterium associated with ratoon stunting disease (RSD) of sugarcane was successfully cultured in a cellfree medium containing Muller-Hinton agar (3.8%) or Muller-Hinton broth (2.2%), hemoglobin (10 μg/ml), Isovitalex (BBL) (1%), asparagine (0.2%), glutamic acid (0.05%), KH₂PO₄ (0.1%), K₂HPO₄ (0.25%), MgSO₄·7H₂O (0.02%), sodium citrate (0.01%), ammonium sulfate (0.05%), CaCl₂ (0.5 μg/ml), ZnSO₄ (0.01 μg/ml), and CuSO₄ (0.01 μg/ml). The same medium was also used to isolate and culture the RSD-like bacterium present in Bermuda grass. The bacterium recovered from either sugarcane or Bermuda grass can infect and multiply in a Sudan grass-sorghum hybrid. Wilting symptoms were observed in some of the inoculated plants. Cultured organisms exhibited lack of motility, absence of endospores, nonacid fastness, and Gram-positive reaction, but often irregular staining, aerobic growth, and a filamentous-rod (0.25–0.35 × 2–5 μm), clublike, or occasionally V-form morphology was observed. Tiny colonies (0.05–0.23 mm in diameter) were observed in agar medium after 8–19 days of incubation at 30 C.