Yeasts associated with plums and their potential for controlling brown rot after harvest

Authors: Janisiewicz, Wojciech; Jurick, Wayne; Peter, Kari; Kurtzman, Cletus; Buyer, Jeffrey

Submitted to: Yeast
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2014
Publication Date: 4/23/2014
Citation: Janisiewicz, W.J., Jurick II, W.M., Peter, K.A., Kurtzman, C.P., Buyer, J.S. 2014. Yeasts associated with plums and their potential for controlling brown rot after harvest. Yeast. 31:207-218.

Interpretive Summary: Fruit surfaces are naturally colonized by variety of microbes including bacteria and yeast. Some of those native microorganisms have been shown to have a beneficial effect on reducing fruit decay after harvest and have been developed into commercial biological control products that can replace fungicides. Unfortunately, with the exception of grapes and apples, our knowledge of the natural (resident) fruit microflora is rudimentary and the extent of its potential for biological control of fruit decays remains largely unknown. We identified yeasts naturally colonizing plums from early fruit development until harvest and explored their potential for controlling brown rot after harvest, the most destructive disease of stone fruits. Three yeast genera were dominant and occurred throughout fruit development. They constituted 79 percent of all isolated yeasts (Aureobasidium 24.7 percent, Rhodotorula 29.5 percent and Sporidiobolus 24.7 percent). Several other genera occurred only on more mature fruit. A few species from dominant and less dominant genera controlled brown rot development on stone fruits after harvest in the preliminary tests. Our results indicate that the plum surface harbors several yeast species with excellent potential for use in biological control of brown rot of stone fruits.

Technical Abstract: Bacterial and yeast antagonists isolated from fruit surfaces have been effective in controlling various postharvest diseases and several have been developed into commercial products. Our knowledge of the fruit microflora with the exception of grapes, apples and some citrus fruit is rudimentary, and the potential of the resident yeasts for biocontrol remains largely unknown. We determined the occurrence of yeasts on plum surfaces during fruit development from the pre-hardening stage until harvest during two years. A total of 16 species from 13 genera were isolated. The dominant yeast genera were Aureobasidium (24.7 percent), Rhodotorula (29.5 percent) and Sporidiobolus (24.7 percent) accounting for 78.77 percent of all isolations; Cryptococcus constituted only 6.2 percent, and all of them occurred throughout the fruit development. The yeast community in the final sampling was significantly different from the first three samplings, reflecting a rapidly changing fruit habitat during the maturation of fruit. Screening of the yeasts for antagonistic activity against Monilinia fructicola, a fungus causing brown rot, revealed a range of biocontrol activities, including several isolates providing complete control of the decay on plums challenged with a pathogen suspension of 10E3conidia/mL, and more than 90 percent of control on fruit inoculated with the pathogen at a concentration 10 times higher. Some of the best antagonists included A. pullulans and R. phylloplana. Populations of both of these antagonists increased rapidly by several orders of magnitude in wounds of plums incubated at 24 degrees C and 4 degrees C. Our results indicate that the plum surface harbors several yeast species with excellent potential for use in biological control of brown rot of stone fruits.