5 Plant Disease Diagnostic Capabilities and Networks in the Diagnosis of Plant Diseases – The Path to Effective Control Measures

Transcript

Hello!! Welcome to the last talk of the week as well as of the course that is plant disease diagnostic capabilities and networks. We all know that plant disease detection and diagnosis is so vital to save the crop from getting incurring severe losses but at the same time we need to have capable resource persons available to perform the task and networking of resource persons is always a useful tool to provide solutions to the end users that is the small farm holders. So, plant disease diagnostic networks have developed worldwide to address the problems of efficient and effective disease diagnosis and pathogen detection, engendering cooperation of institutions and experts within countries and across national borders. Networking maximizes the impact in the face of shrinking government investments in agriculture and diminishing human resource capacity in diagnostics and applied pathology. New technologies promise to improve the speed and accuracy of disease diagnostic and plant pathogen detection. Widespread adoption and standard operating procedures and diagnostic laboratory accreditation served to build trust and confidence among the institutions.

Why Diagnostics Matter?

It is well recognized that threats in invasive pathogens to plants, whether crops, horticultural commodities, or members of natural communities such as forests and grasslands are increasing as a result of globalization, increased human mobility, climate change and pathogen and vector evolution. Taken in total with damage caused by emerging, re-emerging and chronic or endemic pathogens, the potential for economic loss is significant in plant systems. The food security is threatened in resource-poor countries during these epidemics in stable crops and income generation from opportunities to exploit new and emerging markets is curtailed. Disease diagnosis and pathogen detection are central to our ability to protect crops and natural plant systems and are crucial prelude to undertake prevention and management measures. So, that is why diagnosis of plant pathogen is highly essential and it does matters to us.

Plant Safeguarding and Biosecurity

The responsibility of safeguarding plants against invasive pathogens is held officially by national plant protection organizations (NPPOs). In addition to their regulatory functions, NPPOs conduct pathogen surveillance and pest risk analyses, inspect, treat and certify export products, inspect and, if necessary mitigate risk on imports and share information on pathogens and regulations.

Disease Management Decision Making

So, disease management is a decision-making process and it is very essential to have a decision before we adopt for a particular disease management practice. Diagnostic networks are crucial in conducting large-scale monitoring programs, surveillance may be done by established networks or by networks organized for monitoring a specific pathogen and disbanded after completion of the program. The example of soybean rust illustrates the role of diagnostic networks in pathogen detection diagnosis and surveillance. Phakopsora pachyrhizi, the causal agent of soybean rust was initially listed as a select agent before its recent entry into the United States. It’s an economically devastating disease and their diagnostic network was established to identify the pathogen in new localities in the United States. The diagnostics tests included a real-time PCR assay, an immunofluorescence spore assay and a field-usable lateral flow immunoassay were developed and tested. Surveillance and monitoring well accomplished utilizing a network of sentinel plots and spore traps, tied into web-based reporting and communications. Thousands of farmers and agronomic professionals were trained as the first detectors. This is how the capability of the first detectors were enhanced to check and monitor the progress or occurrence of a newly emerging pathogen in the United States.

Diagnostic Capacity

Diagnostic capacity-building involves training of the human resource and it is common and easily recognized disease are often diagnosed by an astute individual, who may be trained diagnostician, experienced farmer, extension educator or consultant familiar with the crop. However, unlike human and veterinary medicine, trained practitioners in plant pathology are a relatively rare commodity and clinicians with appropriate training and access to necessary infrastructure and technology to diagnose a broad range of pathogens afflicting plants are particularly scarce. So, this is a challenge and that is why we need to increase the base of human resources to enhance their capacity to diagnose possible pathogens that cause diseases in the particular area. Human resource development in plant diagnostics in the developing world has generally lagged behind then that of the developed countries.

Technology

The technologies that are involved during capacity building – capacity for traditional pathogen identification is generally insufficient to meet needs in both developed and developing countries, therefore the certain high-tech tools for pathogen diagnostics have expanded at a rapid rate. Field-ready serological tests such as lateral flow devices are commonly used as diagnostic tools to aid disease management decision-making, to back up diagnosis based on symptoms and as it triage tool to pre-screen plants for specified target diseases. For example, an LFD for Phytophthora species detection has proven to be significant value in the United Kingdom for pre-screening woody plants for the absence of Phytophthora ramorum or Phytophthora kernoviae at the time of inspection. Samples testing positive are then sent to laboratory for follow-up testing with more specific lab tests such as PCR and pathogen culture. So, technologies like (LFDs) are coming in a big way to help in the decision making process. So, in case of United Kingdom it was Phytophthora species that was causing sudden death in the oak plants and initially althoughLFDs has given some indications of the pathogen then based on those indications that samples were sent to the lab for final confirmation and with final confirmation then their appropriate corrective measures were adopted.

Infrastructure

Then infrastructure is also equally important just like technology and human resources. Visual examination, microscopy, culturing, a few simple biochemical tests and ELISA are the mainstays for most routine diagnosis. When coupled with diagnostic references such as disease compendia, pathogen-specific manuals, image databases, these techniques in the hands of trained diagnosticians and specialists are sufficient to provide answers in a reasonable amount of time at a manageable cost. So, simply in the involvement of simple or sophisticated equipment may not lead to an answer at times so that has to be supported with other information such as availability of disease compendia, pathogen specific manuals and image databases which greatly helped the are diagnosed stations to go for specific diagnostic tests. Many diagnostic networks build and maintain expertise database within their communication system to facilitate knowledge sharing. For example, European plant protection organizations supports a searchable database on its website containing a list of laboratories by country and an expertise list by pathogen. Experts can be contacted via email by network members upon entry to and access code. So, diagnostic networks can again help the diagnosticians in other part of the world. If these diagnostic platforms are made available to each and every worker then they can get access to even experts and get a proper feedback on their queries.

Plant Disease Diagnostic Networks

So, plant disease diagnostic networks in the United States they have National Plant Disease Diagnostic Networks. In the Mediterranean and European Plant Protection Organization (EPPO) has expanded from 15 to 50 member countries because of its usability and usefulness. Then Global Plant Clinic (GPC) are also coming up and the global plant clinic it is a consortium of CABI Bioscience, Rothamsted Research, States resource and Central Science Laboratory, United Kingdom. The Global Plant Clinic provides a cost-free diagnostic and advisory services for NPPO’s in developing countries that provide diseased plants samples. The GPC initiated the establishment of mobile plant health clinics in several developing countries. So plant health clinics fulfill an advisory role in a cost-efficient and locally operated manner. They occur in public places such as market on a regular basis where growers routinely arrive with disease plant samples. The clinics offer reliable advice on routine plant health problems affecting any crop and differentiate symptoms due to a biotic and biotic stresses. So, global plant clinic is a bigger platform, a bigger network led by CABI bioscience, United Kingdom and it is also providing assistance in the form of mobile clinics where a grower can bring their samples to the plant doctors and they can be given proper advice looking into the symptoms that is another characteristics of the disease plants.

International Plant Diagnostic Network

The International Plant Diagnostic Network (IPDN) was initiated in 2005 with a goal of fostering development of local capacity for diagnostics through establishment of communication and data sharing networks, training in classical and modern diagnostics and research into new diagnostic methods. The IPDN model after the United States and NPDN, and as with that network is comprised of regional hub, local satellite diagnostic laboratories. Three regional programs have been established to date; in Central America, it is the hub lab in Guatemala coordinated by a private company; Agroexpertos, East Africa a hub in Kenya coordinate by that Kenya Agricultural Research Institute and in West Africa the hub in established in Benin and is coordinated by IITA.

The important objective of IPDN is training diagnosticians in basic and advanced diagnostic methodologies. Reporting new disease through International outlet is highly encouraged and the same was done in West Africa regional program where they have reported the occurrence of Ralstonia solanaceraum, the causal agent of devastating wilt disease of tomato through the Benin. So, this is how the International plant diagnostic network is working and it’s coming up and people are taking help of these diagnostic networks and that is how the emphasis has been given that more number of resource persons are available at various levels through capacity building and training for them for proper diagnosis and followed by support by a international database of global plant clinic database which supports them with necessary information and images and the plant doctors can very well take help of this necessary information from this international networks and then they can help the local growers through either advisor mode or through the mobile clinics. So, with this we have come to an end of the week six and with end of the course ‘Detection Diagnosis and Plant Disease Management’. I am sure you all have gained comprehensive understanding on the methodologies that are used to detect and diagnose plant pathogens and how this detection and diagnosis is helping us to take a decision on management aspects of plant pathogens and thereby, it is preventing entry of quarantine pathogens, as well as it is also preventing loss during the international trade, and it is also preventing loss to the growers at their own farm. So, I am sure you have enjoyed this course thoroughly and I wish you good luck with your future endeavors.

Thank you so much for being with me for this last six weeks.