Transformation of Candida oleophila and survival of a transformant on orange fruit under field conditions.

Histidine auxotrophs of wild-type strain I-182 of Candida oleophila, produced using ethyl methanesulfonate, were transformed with plasmids containing the HIS3, HIS4 and HIS5 genes of Saccharomyces cerevisiae. Histidine auxotrophy was complemented by the HIS5 gene of S. cerevisiae. Stability of the transformants under non-selective conditions and DNA gel-blot analysis suggested that the transforming DNA had integrated into the C. oleophila genome. There were no detectable physiological differences between the wild-type and the transformants. The biological control ability of C. oleophila was not affected by the transformation. A genetically marked transformant (with a beta-glucuronidase gene) colonized wounds on oranges, and its population increased under field conditions. The identity of the genetically marked transformant was established by PCR-amplification of a portion of the beta-glucuronidase gene.