Bacterial microflora of nectarines

Authors: Janisiewicz, Wojciech; Buyer, Jeffrey

Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2010
Publication Date: 6/10/2010
Citation: Janisiewicz, W.J., Buyer, J.S. 2010. Bacterial microflora of nectarines. Canadian Journal of Microbiology. 5:480-486.

Interpretive Summary: Alternatives to chemical control are needed in fruit production. The fruit surface is colonized by a variety of micro-organisms that include bacteria and yeasts. Some of these natural colonists (resident microflora) are beneficial organisms, and they have been used to control fruit decays after harvest. We characterized this bacterial resident microflora of nectarine fruit from the early stage of fruit development until harvest. There were bacterial species that may be worth exploring for beneficial activity for the control of nectarine fruit decays, because they have been reported earlier to be beneficial in other host/pathogen systems or had high frequency of occurrence on nectarine fruit. Our work also confirms that natural fruit microflora is a rich source of beneficial micro-organisms that can be used for the control of fruit decays after harvest.

Technical Abstract: Microflora of fruit surfaces has been the best source of antagonists against fungi causing postharvest decays of fruit. However, there is little information on microflora colonizing surfaces of fruits other than grapes, apples, and citrus fruit. We characterized bacterial microflora on nectarine fruit surfaces from the early stage of development until harvest. Identification of bacterial strains was made using MIDI (fatty acid methyl ester analysis) and Biolog systems. Biolog identified 35% and MIDI 53% of the strains; thus, results from MIDI were used to determine the frequency of occurrence of genera and species. Most frequently occurring genera were Curtobacterium (21.31 %), followed by Pseudomonas (19.99 %), Microbacterium (13.57 %), Clavibacter (9.69 %), Pantoea (6.59 %), and Enterobacter (4.26 %). The frequency of isolations of some bacteria e.g. major Pseudomonads, P. syringae, P. putida and P. savastonoi or Pantoea agglomerance tend to decline as fruit developed. As Pseudomonas declined, Curtobacterium became more dominant. The time of isolation was a significant factor in the frequency of occurrence of different bacteria indicating succession of the genera. Nectarine fruit was colonized by species representing some of the best biocontrol agents against postharvest fruit decays, such as P. syringe, P. agglomerans, or Burkholderia cepacia, confirming that resident microflora of fruit is an excellent source of antagonists against fruit decaying fungi.