A method for studying the population dynamics of Candida oleophila on oranges in the grove, using a selective isolation medium and PCR technique

Populations of the biological control agent Candida oleophila on fruit in a n orange grove were monitored by plating fruit washes and peel homogenates on a selective medium, followed by PCR analysis of DNA from yeast colonies resembling C. oleophila. The C, oleophila transformant ADGus-10 formed colo nies on a selective medium that suppressed the development of 99% of the fi lamentous fungi and the indigenous yeasts, Aureobasium (a yeast-like fungus ) and Rhodotorula. Only 6-8 indigenous yeasts/cm(2) fruit surface gave rise to colonies that resembled C. oleophila on the selective medium. The ident ity of the C. oleophila transformant colonies was verified by PCR analysis of yeast DNA. The presence of a 599-bp band in the PCR product primed by B- glucuronidase gene primers, confirmed the identity of C. oleophila transfor mant ADGus-10. Colony-forming units of C. oleophila were recovered efficien tly from fortified washes of the fruit surface and from homogenates of woun ds excised from fruit sprayed in the grove with C. oleophila.