INDUCTION OF PRECOCIOUS FRUITING BY A DIFFUSIBLE FACTOR IN THE POLYPORE PHELLINUS-CONTIGUUS

Malt extract agar in diffusion contact with growing colonies of Phellinus contiguus developed the capacity to induce precocious fruiting in new colonies of the same fungus. Spent agar from beneath colonies of P. contiguus growing on top of Cellophane, when incorporated into 1% malt extract agar, significantly enhanced the extent of macroscopically visible poroid hymenophore tissue on 10 mm assay discs after incubation for approximately 14 d. The factor was heat stable and its activity increased with increasing concentration, over the range x 0.125 to x 0.5 of the in situ concentration. The factor was produced by both dark- and light-incubated colonies but light was required for expression of the fruiting response. The significantly lower activity present in diffusates from 6-d-old than 21-d-old colonies suggests that this factor is responsible for the minimum colony size required for competence to fruit.