DISAPPEARANCE OF A GENETIC MARKER FROM A CYTOPLASMIC HYBRID PLASMODIUM OF A TRUE SLIME MOLD.

Two strains of the true slime mold Didymium nigripes form distinctive plaques when their spores are plated clonally. Strain C6 gives rise to plaques surrounded by large plasmodia. Plaques of strain A20 at first contain only amoebas, the formation of plasmodia being delayed; and strain A20 is resistant to cycloheximide. Plasmodia of C6 and A20 were fused, and at intervals the fused plasmodia were cut into segments and each segment was permitted to fruit. The resulting spores were plated clonally and the plaques scored as C6-type or A20-type. When equal-sized C6 and A20 plasmodia were fused, the A20 characteristic of delayed plasmodium formation disappeared with time so that after 8 hours few A20 plaques could be recovered even from the A20 side of the fused plasmodium. When the ratio between sizes of C6 and A20 plasmodia to be fused was varied, similar results were obtained. The A20 characteristic did not disappear until fruiting.