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Applied and Environmental Microbiology, August 2003, p. 4892-4900, Vol. 69, No. 8
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.8.4892-4900.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Single-Leaf Resolution of the Temporal Population Dynamics of Aureobasidium pullulans on Apple Leaves

Scott T. Woody,¹ Russell N. Spear,¹ Erik V. Nordheim,^2,3 Anthony R. Ives,⁴ and John H. Andrews^1*

Department of Plant Pathology,¹ Department of Forest Ecology and Management,² Department of Statistics,³ Department of Zoology, University of Wisconsin—Madison, Madison, Wisconsin 53706⁴

Received 19 February 2003/ Accepted 12 May 2003

The abundance of phylloplane microorganisms typically varies over several orders of magnitude among leaves sampled concurrently. Because the methods traditionally used to sample leaves are destructive, it has remained unclear whether this high variability is due to fixed differences in habitat quality among leaves or to asynchronous temporal variation in the microbial population density on individual leaves. We developed a novel semidestructive assay to repeatedly sample the same apple leaves from orchard trees over time by removing progressively more proximal 1-cm-wide transverse segments. Aureobasidium pullulans densities were determined by standard leaf homogenization and plating procedures and were expressed as CFU per square centimeter of segment. The A. pullulans population densities among leaves were lognormally distributed. The variability in A. pullulans population densities among subsections of a given leaf was one-third to one-ninth the variability among whole leaves harvested concurrently. Sequential harvesting of leaf segments did not result in detectable changes in A. pullulans density on residual leaf surfaces. These findings implied that we could infer whole-leaf A. pullulans densities over time by using partial leaves. When this successive sampling regimen was applied over the course of multiple 7- to 8-day experiments, the among-leaf effects were virtually always the predominant source of variance in A. pullulans density estimates. Changes in A. pullulans density tended to be synchronous among leaves, such that the rank order of leaves arrayed with respect to A. pullulans density was largely maintained through time. Occasional periods of asynchrony were observed, but idiosyncratic changes in A. pullulans density did not contribute appreciably to variation in the distribution of populations among leaves. This suggests that persistent differences in habitat (leaf) quality are primarily responsible for the variation in A. pullulans density among leaves in nature.

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* Corresponding author. Mailing address: Department of Plant Pathology, 1630 Linden Dr., University of Wisconsin—Madison, Madison, WI 53706-1598. Phone: (608) 262-0928. Fax: (608) 263-2626. E-mail: jha{at}plantpath.wisc.edu.

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Applied and Environmental Microbiology, August 2003, p. 4892-4900, Vol. 69, No. 8
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.8.4892-4900.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• McGrath, M. J., Andrews, J. H. (2007). Role of Microbial Immigration in the Colonization of Apple Leaves by Aureobasidium pullulans. Appl. Environ. Microbiol. 73: 1277-1286 [Abstract] [Full Text]