A Semi-selective Medium to Isolate Rhizoctonia solani from Soil and Tissue
W. A. Gutierrez,  H. D. Shew, and T. A. Melton 

A  semi-selective medium was developed to isolate Rhizoctonia solani fron soil samples and infected tissue. This medium allow a faster growth of R. solani colonies compared to the standard water agar medium. 

The medium contains:

  • Water Agar (Difco) 18g/L
  • * Streptomycin sulfate (100 mg/L)
  • * Penicillin-G sodium salt (100 mg/L)
  • * Sodium hydroxide (800 microliters/L)
 (*) Antibiotics and sodium hydoxide are added to the medium after sterilization (121 C at 15 psi for 30 min.).
After isolation, dishes are incubated in the dark at 21 to 23 C.  After 24 hours of incubation, dishes are evaluated to assess the number of R. solani colonies present. 

Colonies of R. solani have a characteristic growth morphology and grow very fast on this selective medium. Colonies can be easily identify after 12 to 24 hour of incubation in the dark. The alkalinity of the medium allow a faster grow of R. solani colonies compared to other fungi, which are more or less inhibited.  This medium is effective to isolate and to clean colonies of most of the anastomosis groups of Rhizoctonia solani.


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Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Reformatted Sept. 2001