Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/1999
Publication Date: N/A
Interpretive Summary: Strains of the biological control fungus Trichoderma virens can be separate into "P" and "Q" groups based on the production of the antifungal antibiotics gliovirin and gliotoxin, respectively. Previously this required extraction of fungus cultures and chromatography of the extracts. Recent results, however, indicate that "P" and "Q" strains may be identified by culture on media that contain fungicides to which the two groups are differentially susceptible or resistant. "Q" strains grow on media containing gliotoxin or fluidioxinil, while "P" strains will not. "P" strains grow on thiabendazole or chlorothalonil containing media, while "Q" strains will not. Strains of both groups can be selectively isolated from natural soil on media containing the above components along with the antibiotic rifampicin. Since "P" and "Q" group strains differ in their efficacy as control agents of different diseases, isolation from natural soil and separation into groups on agar media simplifies and accelerates screening procedures for the discovery of effective biocontrol agents.
Technical Abstract: Strains of the biocontrol fungus Trichoderma virens may be separated into P (gliovirin producing) or Q (gliotoxin producing) groups by culture of conidial inoculum on agar media containing selective amendments. Strains of the P group will grow on PDA amended with chlorothalonil or thiabendazole, but not on PDA amended with gliotoxin or fludioxonil, and they do not inhibit the growth of Bacillus subtilis in culture. Strains o the Q group will grow on gliotoxin and fludioxonil, but not on chlorothalonil or thiabendazole, and they inhibit the growth of B. subtilis in culture. Strains of T. virens can also be isolated from natural soil with selective media. A PDA medium containing Rifampicin (50 ug ml-1), chlorothalonil (1.25 ug ml-1) and thiabendazole (0.6 ug ml-1) can be used to selectively isolate P strains from soil. PDA containing Rifampicin (50 ug ml-1), gliotoxin (50 ug ml-1) and low chlorothalonil (0.75 ug ml-1) will selectively isolate Q strains from soil. Since P and Q strains of T. virens are known to differ in their biocontol efficacy toward different soil-borne diseases, their separation into groups and isolation from soil on selective agar media should allow the development of more focused and efficient screening procedures.