THE FATE OF INTEGRATED DNA IN GAEUMANNOMYCES-GRAMINIS TRANSFORMANTS

The fate of integrated transforming DNA in fungicide (benomyl or phleo mycin)-resistant transformants of Gaeumannomyces graminis was investig ated. Transforming DNA was mitotically and meiotically stable in sever al transformants. However, other transformants of varieties graminis a nd tritici were less resistant to fungicide after meiosis. Hybridizati on analyses indicated that transforming DNA in ascospore progeny had r earrangements and/or deletions, and that similar events could occur du ring a second meiotic cycle, further reducing their levels of resistan ce. Rearrangements and/or deletions were most common in transformants with multiple copies of a benomyl-resistance (Ben(r)) plasmid. Transfo rming sequences were not extensively methylated, even when present in multiple copies.