Yeast microflora of nectarines and their potential for biocontrol of brown rot

Authors: Janisiewicz, Wojciech; Kurtzman, Cletus; Buyer, Jeffrey

Submitted to: Yeast
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2010
Publication Date: 7/12/2010
Citation: Janisiewicz, W.J., Kurtzman, C.P., Buyer, J.S. 2010. Yeast microflora of nectarines and their potential for biocontrol of brown rot. Yeast. 27: 389-398.

Interpretive Summary: The fruit surface is colonized by a variety of microorganisms that include bacteria and yeasts. Some of these natural colonists (resident microflora) are beneficial organisms and have been used to control fruit decays after harvest. With the exception of grapes, apple and citrus, little is known about natural microflora of fruits, but such information can be very useful in developing biological control of fruit decays using a natural colonist of the fruit. We characterized yeast resident microflora of nectarine fruit from the early stage of fruit development until harvest. Several of the yeasts appear to represent new species. Isolated yeasts include a few species representing the beneficial yeasts used for the control of fruit decays on various fruits and vegetables. Preliminary biocontrol tests against brown rot of nectarine fruit indicated significant decay control potential by some of the identified yeast species. Our work also confirms that the natural fruit microflora is a rich source of beneficial microorganisms that can be used for the control of fruit decays after harvest.

Technical Abstract: Resident fruit microflora has been the source of biocontrol agents for the control of postharvest decays of fruits and the active ingredient in commercialized biocontrol products. With the exception of grapes and apples, information on the resident microflora of other fruits is only fragmentary; however, greater knowledge in this area can be very helpful in developing biocontrol strategies. We characterized the yeast microflora of nectarines (cv. 'Croce del Sud') from the early stages of fruit development until harvest. The fruit samples were collected from trees in an unmanaged orchard block. The resident fruit microflora was separated from the occasionally deposited microorganisms by discarding initial fruit washings before the final wash that was followed by sonication and plating on NYDA medium. The isolated yeasts were identified by BIOLOG and by sequencing the D1/D2 domain of a large subunit of the rRNA gene and where available, the ITS sequence. BIOLOG identified 19 and the genetic analysis 23 species of yeasts. Although the identification by these two systems was not always the same, the predominant yeasts were Rhodotorula spp., Sporodiobolus spp., Cryptococcus spp., Pichia spp., Candida spp., and yeast-like Aureobasidium pullulans. Several of the taxa appear to represent new species. The preliminary biocontrol tests against brown rot of nectarine fruit caused by Monilinia fructicola indicates significant decay control potential of some of the identified yeast species.