Culturable bacteria from plum fruit surfaces and their potential for controlling brown rot after harvest

Authors: Janisiewicz, Wojciech; Jurick, Wayne; VICO, I - University Of Zagreb; Peter, Kari; Buyer, Jeffrey

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2012
Publication Date: 11/7/2012
Citation: Janisiewicz, W.J., Jurick II, W.M., Vico, I., Peter, K.A., Buyer, J.S. 2012. Culturable bacteria from plum fruit surfaces and their potential for controlling brown rot after harvest. Postharvest Biology and Technology. 76:145-151.

Interpretive Summary: Some microorganisms living on surfaces of apple, pear and citrus fruits have ability to protect fruit from decay caused by fungal pathogens. This ability was explored in developing commercial products that contain these microorganisms as an active ingredient for controlling various fruit decays after harvest mainly on apples, pears, and citrus fruit. Little is known about the potential of microorganisms living on stone fruit to control postharvest fruit decays. We isolated and identified bacteria occurring on plum fruit throughout the fruit development and determined their ability to control brown rot of plums after harvest. The plum microflora was dominated by four bacteria genera that accounted for 61.45 percent of all bacteria. We found several bacteria that were very effective in controlling brown rot. These bacteria grew very well in fruit wounds which are the main avenue for infection by fungus causing brown rot. Our results indicate that plum microflora is an excellent source of beneficial bacteria against brown rot decay. Future research will be focused on the compatibility of this bacterium with postharvest conditions and practices in fruit storages and packinghouses.

Technical Abstract: Fruit microflora has been the richest source of antagonists against fruit decays and the active ingredient in all currently available commercial biocontrol products. A comprehensive evaluation of plum bacteria for biocontrol activity against Monilinia fructicola, causing brown rot of stone fruit, would allow us to determine their biocontrol potential. We characterized resident culturable bacterial microflora of plums from early fruit development until maturity. The most dominant genera were Curtobacterium (19.88 percent), Pseudomonas (15.06 percent), Microbacterium (13.86 percent), and Clavibacter (12.65 percent). These genera occurred at all four isolation times and accounted for 61.45 percent of all isolates. Microbacterium and Curtobacterium dominated at the early stage of fruit development, while Pseudomonas and Clavibacter were dominant at the end of the season. Less prevalent genera were Enterobacter (5.42 percent), Chrysomonas (4.82 percent), and Pantoea (4.22 percent). Most frequently isolated species were Microbacterium lacticum, Clavibacter michiganensis, Curtobacterium flaccumfaciens, Enterobacter intermedius, and Chrysomonas luteola. The seasonal succession of genera was observed in both MANOVA and frequency analysis. Primary and secondary screening of plum inhabiting bacteria for control of brown rot on wounded fruit resulted in the selection of several antagonists from which Pantonea agglomerans and Citrobacter freundii were the most effective. These antagonists grew well in plum wounds and increased by four log units during the first three days at 24 degrees C, and two log units after day seven at 4 degrees C. Our results indicate that plum microflora is an excellent source of antagonists against brown rot decay originating from wounds after harvest.