Plant disease diagnostic capabilities and networks

Emerging, re-emerging and endemic plant pathogens continue to chal-lege our ability to safeguard plant health worldwide. Further, global-ization, climate change, increased human mobility, and pathogen andvector evolution have combined to increase the spread of invasive plantpathogens. Early and accurate diagnoses and pathogen surveillance onlocal, regional, and global scales are necessary to predict outbreaks andallow time for development and application of mitigation strategies.Plant disease diagnostic networks have developed worldwide to addressthe problems of efficient and effective disease diagnosis and pathogendetection, engendering cooperation of institutions and experts withincountries and across national borders. Networking maximizes impact inthe face of shrinking government investments in agriculture and dimin-ishing human resource capacity in diagnostics and applied pathology.New technologies promise to improve the speed and accuracy of diseasediagnostics and pathogen detection. Widespread adoption of standardoperating procedures and diagnostic laboratory accreditation serve tobuild trust and confidence among institutions. Case studies of national,regional, and international diagnostic networks are presented

Surveillance of potential pathogenic fungi associated with water hyacinth in Lake Kainji, Nigeria

The entire Kainji Lake and the riverine areas upstream of Yauri were surveyed monthly between February and May 2002 with a motorboat to make full inspection of fungi-infested water hyacinth plants. Various parts of water hyacinth plant showing symptoms of fungal infection were collected, dried between paper towels, labeled, treated and planted onto growth agar media in petri dishes sealed with parafilm. All isolates were characterised for identification. On some older plants with larger leaves were found sporulating Myrothecium roridum. On the smaller plants with purple flecking lesions were isolates of Alternaria eichhorniae of, which were necrotic patches surrounded by chlorotic halos. The presence of A. eichhorniae in Nigeria indicates a great promise as its choice in most African environment by the International Mycoherbicide Programme for Eichhornia crassipes Control in Africa (IMPECCA) for development into a mycoherbicide. Other fungal pathogens isolated included Rhizoctonia solani, Acremonium zonatum and Cercospora piaropi

Quantitation of multiple mycotoxins and cyanogenic glucosides in cassava samples from Tanzania and Rwanda by an LCMS/MSbased multitoxin method

A multi-mycotoxin method based on liquid chromatography/tandem mass spectrometry (LC-MS/MS) was used for a mycotoxin survey in 627 samples of processed cassava collected from different districts across Tanzania and Rwanda after the method performance for this matrix had been determined. Matrix effects as well as extraction efficiencies were found to be similar to most other previously investigated matrices with the exception of distinct matrix effects in the negative ionisation mode for early eluting compounds. Limits of detection were far below the regulatory limits set in the European Union for other types of commodities. Relative standard deviations were generally lower than 10% as determined by replicates spiked on two concentration levels. The sample-to-sample variation of the apparent recoveries was determined for 15 individually spiked samples during three different analytical sequences. The related standard deviation was found to be lower than 15% for most of the investigated compounds, thus confirming the applicability of the method for quantitative analysis. The occurrence of regulated mycotoxins was lower than 10% (with the exception of zearalenone) and the related limits were exceeded only in few samples, which suggests that cassava is a comparatively safe commodity as regards mycotoxins. The most prevalent fungal metabolites were emodin, kojic acid, beauvericin, tryptophol, 3-nitropropionic acid, equisetin, alternariol methylether, monocerin, brevianamide F, tenuazonic acid, zearalenone, chrysophanol, monilifomin, enniatins, apicidin and macrosporin. The related concentrations exceeded 1 mg kg–1 only in few cases. However, extremely high levels of cyanogenic plant toxins, which had been previously added to the method, were observed in few samples, pointing out the need for improved post-harvest management to decrease the levels of these compounds

Climate change and micro-organism genetic resources for food and agriculture: state of knowledge, risks and opportunities

This technical study focuses on the role of micro-organism genetic resources for agriculture and the influence of a changing climate. Agriculture is defined as crop-based food production for yield and quality. It excludes micro-organism genetic resources associated with livestock, fish and non-food-borne human pathogens. The study encompasses micro-organisms in five functional domains: soil inhabitants, plant and rhizosphere inhabitants, plant pathogens, biological control agents and food production systems. The scope of this study is vast as a consequence of the unrivalled diversity of micro-organism genetic resources for agriculture and the correspondingly huge variety of functions they perform, largely beneficial but also some harmful to agriculture. The study summarizes the role of micro-organism genetic resources for agriculture, provides examples demonstrating the potential influence of changes in climate on their performance, and describes their potential role in adapting agriculture to climate change and in mitigating changes in climate. While this study can only take preliminary steps towards detailing the complexity of the subject, the authors greatly appreciate the opportunity to increase awareness of micro- organism genetic resources for agriculture among the global community of decision-makers

Development of a lateral flow device for infield detection and evaluation of PCR based diagnostic methods for Xanthomonas campestris pathovar musacearum, the causal agent of banana Xanthomonas wilt.

Xanthomonas campestris pathovar musacearum (Xcm) is the causal agent of bananaXanthomonas wilt, a major threat to banana production in eastern and central Africa. Thepathogen is present in very high levels within infected plants and can be transmitted by abroad range of mechanisms; therefore early specific detection is vital for effective diseasemanagement. In this study we have developed a polyclonal antibody (pAb) and deployed thisin a lateral flow device (LFD) format to allow rapid in-field detection of Xcm. We alsoindependently assessed published Xcm PCR assays: only two assays gave specificamplification of Xcm, whilst others cross-reacted with non-target Xanthomonas species. Purecultures of Xcm were used to immunise a rabbit, the IgG antibodies purified from the serumand the resulting polyclonal antibodies tested using ELISA and LFD. Testing against a widerange of bacterial species showed the pAb detected all strains of Xcm, representing isolatesfrom seven countries and the known genetic diversity of Xcm. The pAb also detected theclosely related Xanthomonas axonopodis pathovar vasculorum (Xav), primarily a sugarcanepathogen. Detection was successful in both naturally and experimentally infected bananaplants, and the LFD limit of detection was 105 cells/ml. Whilst the pAb is not fully specificfor Xcm, Xav has never been found in banana. Therefore the LFD can be used as a first linescreening tool to detect Xcm in the field. Testing by LFD requires no equipment, can beperformed by non-scientists and is cost-effective. Therefore this LFD provides a vital tool toaid in the management and control of Xcm