Virtual Plant Pathology Lab CD-ROM:
A Tool to Support Plant Pathology Diagnostics Learning for Distance Education

Victor J. Galea
School of Agronomy and Horticulture, University of Queensland, Gatton,
Australia

Introduction

The development of diagnostics skills in students of plant pathology requires significant practice and presentation of a wide range of cases to ensure that sufficient exposure is gained (5).  This allows students to begin to see and understand the patterns of symptom expression and the variations in disease development which may exist among and between cases.  More often than not, students fail to appreciate that plant disease diagnosis is a process which follows a series of logical paths determined by critical decision points that are supported by a range of diagnostic observations or tests.  Because of the limited possibilities for classroom contact, distance mode students are greatly challenged in their ability to grasp such concepts.  The need to keep accurate records of each case, to apply a systematic approach to the investigation and to follow through with the diagnostics task to reach a conclusion are also essential.  Additional emphasis on this learning experience can be gained by using realistic case studies, providing instruction on basic diagnostic skills, illustrating how to access to supporting information resources and showing examples of the development of client recommendations.

This paper describes the development and use of a software package which supports the learning and understanding of the plant disease diagnostic process.  This approach to plant disease diagnosis centres on the use of a logic flow chart, and is supported by a range of diagnostic resources and procedures which assist the student to more fully appreciate what is required to manage a real diagnostic case for a client.  This approach, although initially developed for use by distance mode students, has proven also to effectively support learning for on-campus students.

The concept

The Virtual Plant Pathology Lab CD-ROM (4) was developed to assist distance mode students appreciate the logical approach and skills required to successfully manage a plant disease diagnostic case.  This tool allows students to review a series of realistic field cases by “shadowing” the fictional case manager and to appreciate the diverse way in which different cases may be handled.   The software package has links to a range of web-based resources to support the diagnostic procedure, along with a case form to manage the process. A series of skills modules demonstrate basic methods, such as the preparation of samples for viewing with dissecting and compound microscopes, and the correct use of such equipment.

This tool is designed to prepare distance mode students for the experience of dealing with real plant disease problems in a laboratory class at a residential school. Collaborative work with educational designers and software developers and designers resulted in a highly functional and professional package.

The case form

A blank case form, which can be printed for student use from the CD-ROM, provides an organisational structure to the diagnostic procedure, as well as a means for recording observations and the recommendations developed for the client.  In the first problem case (silverbeet) provided in this software package, the case form is progressively completed “on screen” to illustrate its correct application to the procedure.  In subsequent cases, the form is not prominent as the scenario progresses; however, a completed case form can be printed upon case conclusion.

The flowchart

Central to the operation of this package is the logic flowchart describing the diagnostic process (Figure 1).  The flowchart can be printed from the CD-ROM, and is also represented as an abbreviated active navigation bar at the base of the screen (Figures 2 & 3).

Figure 1. Logic flowchart of the steps in conducting a diagnostic evaluation of a diseased plant and the eventual conclusion of a case (Stewart & Galea 2006)

Case studies

Five real case studies (powdery mildew on silverbeet, pepper mild mottle virus on capsicums, angular leaf spot on honeydew melons, anthracnose on grapes and root knot nematodes on tomatoes) were used in the development of this software package.  Each case was located on commercial farms, and all stages of the diagnostic procedure in the field and the laboratory were expertly recorded by digital still and movie photography (wide-angle, macro-photography, and micro-photography).   Additionally, methodology associated with the use of dissecting and compound microscopes was also recorded.

Fictional scenarios were scripted around each case to provide varied and interesting contextual situations and to encourage student engagement (Figure 2).  The story lines guide the student though the processes and decision points associated with the development and resolution of each case.

Figure 2.  Screen image of program – Establishment of problem context and fictional case scenario.

The supporting information tools

Links to resource web sites such as APSnet (1), Texas AMU plant disease handbook (6), Digital diagnostics @ OSU (3) and the Crop Protection Compendium (2) are used by the student to research the range of potential pathogens on each crop, and to develop a list of possible causes, which is in essence, a pathogen index listing (Figure 3).  Dynamic possible causes lists were developed for each case, allowing students to explore their content and become familiar with the concept of brief symptom descriptors.

Figure 3.  Screen image of program – Visual examination of problem and development of possible causes list.

Microscopy skills modules

Microscopy skills modules were developed to introduce students to the correct use of dissecting and compound microscopes. Particular attention was given to the appropriate adjustment of the condenser height, iris diaphragm and illumination source of the compound microscope (Figure 4).  Various methods for preparing microscope slides from plant material are also illustrated.

Figure 4.  Screen image of program – Example of skills module, correct use of the compound microscope.

Arriving at the diagnosis

Diagnosis of each problem is achieved by systematically working through the procedure outlined in the logic flowchart (Figure 1) during which unlikely possibilities are removed from the possible causes list.  By this process of systematic elimination, the student begins to appreciate the way in which the range of investigative tools used; the understanding of symptom descriptions and microscopic features associated with each pathogen, and the information inherent in the field case data all come together to resolve the identity of the causal pathogen.

Developing a management solution

Completion of each case is achieved by the development of a management solution for the identified problem.  Each solution was developed with integrated disease management (IDM) in mind, incorporating cultural, physical, chemical and biological options.

Student evaluation

In 2005, this software package was distributed to 38 students enrolled in the course Crop Health & Management (PLNT2011) at the University of Queensland.  Of this group, 18 were enrolled in distance mode.  A questionnaire (Table 1) was distributed to both cohorts of students of which 17 responded.

Table 1.  Questionnaire assessing student perceptions of the use of Virtual Plant Pathology Lab CD-ROM in 2005.

Student ratings for all aspects of the use of this software package that were identified in this survey were high, indicating a significant level of satisfaction with this learning tool.

Acknowledgements

The author wishes to acknowledge the team at the Teaching & Education Development Institute (TEDI) of the University of Queensland for their input into the planning, instructional design, programming and software development for this project.   Funding was provided by the Distance Learning & Enhancement Program (DLEP), an initiative of the Faculty of Natural Resources, Agriculture & Veterinary Science (NRAVS) of the University of Queensland.

References

1. APSnet   (www.apsnet.org/online)
2. Crop Protection Compendium   (www.cabi.org)
3. Digital diagnostics @ OSU   (www.ento.okstate.edu)
4. Galea, V.J. 2006.  Virtual Plant Pathology Lab CD-ROM.  Teaching & Education Development Institute, The University of Queensland Australia.  ISBN 1-8649-9818-0
5. Stewart, T.M. & Galea, V.J. 2006.  Approaches to Training Practitioners in the Art and Science of Plant Disease Diagnosis.  Plant Disease 90:539-547
6. Texas (AMU) plant disease handbook   (www.plantpathology.tamu.edu)

Date: 29th May, 2006 email: v.galea@uq.edu.au

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