A method for studying the population dynamics of Candida oleophila on oranges in the grove, using a selective...

Populations of the biological control agent Candida oleophila on fruit in an 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 colonies on a selective medium that suppressed the development of 99% of the filamentous fungi and the indigenous yeasts, Aureobasium (a yeast-like fungus) and Rhodotorula. Only 6-8 indigenous yeasts/cm2 fruit surface gave rise to colonies that resembled C. oleophila on the selective medium. The identity 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 beta-glucuronidase gene primers, confirmed the identity of C. oleophila transformant ADGus-10. Colony-forming units of C. oleophila were recovered efficiently from fortified washes of the fruit surface and from homogenates of wounds excised from fruit sprayed in the grove with C. oleophila.