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United States Department of Agriculture

Agricultural Research Service

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Research Project: Utilizing High Resolution Computed Tomography to Visualize Early Stages of Wood Canker Disease in Resistant and Susceptible Grapevines

Location: Crops Pathology and Genetics Research

2013 Annual Report

1a.Objectives (from AD-416):
Using High Resolution Computed Tomography (a type of CAT scan) to assess the following objectives: 1)Characterize the early stages of wood canker infection with unprecendented resolution on intact and excised woody portions of grapevines; and 2)Examine the influence of drought stress on the progression of early stages of infection.

1b.Approach (from AD-416):
High Resolution Computed Tomography (HRCT-a type of CAT scan) technology and custom software has recently been developed and used in the McElrone lab to analyze fine scale details of xylem that contribute to drought resistance in stems. We will pair HRCT with scanning electron and light microscopy to characterize the early stages of infection at unprecedented resolution. This work will involve culturing of wood canker pathogens at discrete points after inoculation to determine the extent of spread within the grapevine xylem.

3.Progress Report:

This agreement was established in support of objective 3 of the in-house project, which is to develop sustainable water management practices for vineyards. The goal of this project is to examine the influence of drought stress on the progression of early stages of wood canker infection of grapevines.

This agreement was recently established. We will utilize High Resolution Computed Tomography (HRCT), a type of CAT scan, to characterize the early stages of wood canker infection with unprecedented resolution on intact and excised woody portions of grapevines. By accomplishing these objectives, we will establish the foundation needed to develop detection techniques that utilize asymptomatic green tissues to confirm the presence of an infection within the woody portions of the vine. The pathogen does not reside in green tissues, but they are connected to the infected, woody tissue via a common vascular system and, thus, exhibit ‘signals’ of infection at the biochemical and molecular levels. Green tissues are much more convenient and less destructive samples to gather from the field compared to woody tissues. Also, green tissues are processed more rapidly in the diagnostic lab, as they do not contain as many inhibitory compounds (e.g., phenolics) as are found in wood, which necessitate lengthy extractions and confound nucleic acid-based detection tools. In essence, the non-colonized green tissues will serve as a bio-indicator of canker infection that is present lower in the woody portions of a grapevine.

Personnel were hired in order to assist in completing this work. Scans for the full experiment of inoculated and control vines were completed in winter 2012/2013 using high resolution computed tomography (HRCT) scans at the Advanced Light Source at Lawrence Berkeley National Lab. Data generated from these scans are still being analyzed by a research assistant using AVISO software. Output of HRCT scan data is being compared against light microscopy and tissue culture analyzes used to detect the extent of spread of the fungi within the test material. HRCT data is functioning primarily for assessing vessel functionality to determine if spread of the fungi induces changes in water conducting capacity of the xylem, but is also being used to evaluate the extent of tylose development. We expect data analysis and results to be completely compiled by early 2014 followed by publication of a manuscript in Spring 2014.

Last Modified: 4/17/2014
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