Characterization of an epiphytic yeast population of grapefruit capable ofsuppression of green mold decay caused by Penicillium digitatum

An epiphytic yeast population of grapefruit able to grow under high osmotic conditions and a wide range of temperatures was isolated and characterized for its biocontrol activity against green mold decay caused by Penicillium digitatum. Techniques based on random amplified polymorphic DNA (RAPD) and arbitrary primed polymerase chain reaction (ap-PCR), as well, as homologie s between sequences of the rDNA internal transcribed spacers (ITS) and 5.8S gene, were used to characterize the composition of the yeast population an d to determine the genetic relationships among predominant yeast species. E piphytic yeasts exhibiting the highest biocontrol activity against P. digit atum on grapefruit were identified as Candida guilliermondii, C. oleophila, C. sake, and Debaryomyces hansenii, while C. guilliermondii was the most p redominant species. RAPD and ap-PCR analyses of the osmotolerant yeast popu lation showed two different, major groups. The sequences of the ITS regions and the 5.8S gene of the yeast isolates, previously identified as belongin g to different species, were found to be identical. (C) 1999 Academic Press .