ABSTRACT
Strains of Gliocladium virens can be divided into groups on the basis of their growth and sporulation on differential agar media. On PDA containing 0.5 µg/ml benlate, P strains (gliovirin producers) grow well, whereas the growth of Q strains (gliotoxin producers) is restricted. On PDA containing 50 µg/ml of bliotoxin, Q strains grow well and sporulate profusely, whereas the growth of P strains is reduced and sporulation is severely restricted. Strains within the P group can be further segregated on PDA containing 1 µg/ml flusilazol, which restricts the growth of some strains more than others. Assays of 22 strains of G. virens isolated from 8 cotton growing states showed an absolute correlation between antibiotic production and growth response to inhibitors, indicating that it is feasible to screen soil for strains from a particular group by adding the appropriate inhibitor to the growth medium. Growth responses to inhibitors may also be used as phenotypic markers to detect recombinant strains resulting from crosses between P and Q strains that will grow on media containing both benlate and gliotoxin.
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