CHARACTERIZATION OF A RHIZOCTONIA SOLANI STRAIN CARRYING PLASMIDS

Abstract

A Rhizoctonia solani strain, RI-64, carrying DNA plasmids grew slowly, was weakly pathogenic, produced oxalic acid and was unable to form sclerotia on agar media. But 5 of 205 isolates regenerated from protoplasts of RI-64 grew rapidly and formed sclerotia, yet they carried plasmids and produced a small amount of oxalic acid. Sclerotia were formed in media containing pyruvate or glycerol, but were repressed in media containing large amounts of glucose. Growth and sclerotium formation were repressed in media adjusted to low pH and in media containing oxalic acid. These results suggest that slow growth and inability to form sclerotia in strain RI-64 result from low pH in the media around mycelia, caused by the production of oxalic acid.