Phytopathology and Diagnosis of Plant Diseases | Universidad Zamorano
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Phytopathology and Diagnosis of Plant Diseases

Author: Cristian F. Quispe, Ph.D. Associate Professor of Phytopathology, ZAMORANO University

Source: Riley, M.B., M.R. Williamson, and O. Maloy. Plant disease diagnosis. The Plant Health Instructor. DOI: 10.1094 / PHI-I-2002-1021-01

Photos: Laboratory of Phytopathology, Diagnosis and Molecular Research of ZAMORANO


The diagnosis of diseases in plants is a hypothesis that must be supported by observable and bibliographical sources. Their complexity and urgency are comparable to a detective’s investigation, all concerns about phytopathological problems come late and it is constantly forgotten that prevention is better than cure.

Diagnosis requires observation and research skills, as multiple factors (biotic and abiotic) can cause problems. Symptoms of the disease are usually insufficient to diagnose, and laboratory testing is often necessary. Diagnostic tests for the isolation and identification of the causative agent are costly, time consuming and require specific means of growth, verification processes and sophisticated equipment. In addition, many biotic agents are difficult or impossible to grow on synthetic media. For example, for the identification of viruses, the most commonly used tools are serological (ELISA), molecular (PCR) and electron microscopy. Similarly, soil quality diagnostic tests, water, pH, nutrients and pesticides analyses are useful for identifying the abiotic factors affecting the crop.

In the field, it is essential to identify the normal appearance of a plant for morphological comparisons. It is helpful to know the scientific name and the variety of crop in order to identify the genetic origin, degree of susceptibility, verify the specificity of the pathogen and avoid confusion with the generic names of the crop. By examining the variability of signs and symptoms, lack or overdevelopment of tissues, organ necrosis, abnormal appearance of the crop, distribution of affected plants (patterns of infection), or by checking for progression of symptoms, one can realize, for example, how to solve problems caused by chemicals or other abiotic agents.

Finally, knowing the cultural practices and environmental changes help to determine a correct diagnosis, since diseases of infectious origin develop over time and it is rare to observe them in full swing.

The Department of Agricultural Science and Production has the diagnostic clinic of ZAMORANO, is a multidisciplinary entity that provides the analysis and diagnosis of problems related to diseases in agricultural crops. It focuses on providing diagnostic and advisory services for the resolution of phytopathological problems. Its vision is to be a catalyst for technology transfer, aimed at promoting the sustainable and environmentally responsible management of crops in the Latin American region.

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