Confrontation assay with S. rolfsii . T. virens was coinoculated with S. rolfsii by placing mycelial discs at the opposite sides of PDA plates. Overgrowth of S. rolfsii by the different T. virens strains is evident from the production of green conidia; S. rolfsii does not sporulate and appears white. The picture was taken after 15 days of growth. Ellipses are magnified in the lower images in order to show sclerotia. Arrows in the wt image point to sclerotia which are nearly invisible because they are overgrown with sporulating T. virens. The indicator Phenol Red was incorporated into the media, showing acidic (yellow) to basic (red) pH. A, photos from above showing colony morphology and conidiation; B, photos from below showing pH gradients formed by the growing colonies.