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Banana Xanthomonas wilt, caused by the bacterium Xanthomonas campestris pv. musacearum, and banana bunchy top virus disease (BBTD), caused by the banana bunchy top virus (BBTV), are two of the most devastating diseases of banana in East and Central Africa, and cause significant losses in food security and income for millions of farmers, traders and consumers. To prevent the establishment and spread of the diseases across the region, control interventions must be rapidly deployed. A first and critical step towards deployment of appropriate disease management strategies is the rapid and precise diagnosis of the causal agent of disease. The diagnosis of Xanthomonas wilt in the field based on disease symptoms is often confused with another disease that causes wilting that is due to the fungus Fusarium oxysporum f.sp. cubense, so diagnostic tools that are easy to use, cost-effective and reliable are required to help field workers. BBTD symptoms can also be confused with nutrient deficiencies or varietal differences. To this end, three types of portable kits were evaluated for their performance in capturing pathogen DNA from the field for use in precise, molecular-based pathogen diagnostics under controlled laboratory conditions. All three prototypes tested – FTA cards, the PhytoPASS kit and two-minute DNA extraction dipsticks – gave excellent results and methods were optimized for sample collection in the field, DNA extraction and PCRbased diagnostics for X. campestris pv. musacearum and BBTV. The benefits of using DNA capture kits included: collection of pathogen DNA in a cheap and practical manner, safe and fast transfer of high integrity pathogen DNA across country borders, rapid and precise diagnosis using state-of-the-art molecular technologies and direct comparison of results from geographically diverse samples. This is possible because analysis is performed in a uniform manner in terms of method, date, equipment, reagents and technical staff. Technical support was provided to workers in the field to help them differentiate symptoms based on diagnostic results from laboratory analyses; such support could also be provided to regulatory officials at borders to ensure that, for example, planting material is free from disease. Countries involved in testing the DNA capture kits for X. campestris pv. musacearum included Burundi, Democratic Republic of Congo (DR Congo), Kenya, Rwanda, Tanzania and Uganda. The same countries, with Zambia also included, were also tested for BBTV. While no positive results for X. campestris pv. musacearum were obtained from samples originating from surveys in Burundi, subsequent DNA capture kits from samples from Bubanza and Cankuzo provinces did test positive, thus confirming an outbreak of Xanthomonas wilt in this country. BBTV was confirmed in DR Congo, Burundi, Rwanda and Zambia. ; Association for Strengthening Agricultural Research in Eastern and Central Africa ; Food and Agriculture Organization of the United Nations ; Peer Review

The request for this training was initiated by L'Institut des Sciences Agronomiques du Burundi(ISABU), who invited IITA to provide tuition and materials for the production and use of semiselectivemedia for banana Xanthomonas wilt (*see box below). ISABU wanted to create the capacity toindependently diagnose and culture BXW from diseased banana plant samples.IITA were already working on BXW in Burundi under the Crop Crisis Control (C3P) projectmanaged by Catholic Relief Service (CRS). IITA and CRS liaised closely to develop a regionaltraining course, so that participants from Rwanda and DRC could also learn new techniques, whileencouraging greater coordination in the future. The original request for training was broadenedextensively to include new methods for surveillance and vigilance of all banana diseases.The course was attended by 11 participants from extension and research, Universities and IRAZ, aregional organisation. The trainers were Fen Beed and Komi Fiaboe (IITA), Eric Boa of the GlobalPlant Clinic (CABI) and Julian Smith (CSL), combining expertise in research, surveillance, vigilanceand diagnostics for plant diseases. All trainers are closely involved with BXW in East Africa.The training consisted of presentations, group discussions and practical demonstrations.Participants saw how to make the semi-selective medium for BXW and isolate bacteria. Theypracticed field and laboratory diagnostic techniques and carrying out participatory plant diseasesurveys, a new method tried here for the first time. They learnt how to use FTA cards to collectDNA samples from the field for laboratory analysis. FTA cards can be safely transported and sentoutside the country without the risk of spreading the disease. A prototype rapid serologicaldiagnostic test for BXW (lateral flow device or LFD) was demonstrated in the field and lab.Participants discussed how to quantify disease incidence and severity and learnt how to use GPSequipment and characterise field sites. The participatory disease surveys in Rugombo and Gitundahelped to pinpoint areas where more intensive assessments of BXW incidence and severity mightbe carried out. They also revealed how growers interpret symptoms and hence report potential newdiseases.The presentations described current knowledge of BXW and related advances in laboratorydiagnostics. The importance of publishing New Disease Reports was emphasised and the purposeof Pest Risk Analysis (PRA) explained in relation to BXW and other key diseases. Participantsreceived a comprehensive list of reference and lab materials which will assist in detection andcontrol of BXW and other banana diseases. Course feedback was positive and encouraging.Participants were asked to consider how they would use their new knowledge and methods afterthe course had ended and link more closely with national and regional partners.A proposal for further work is included in this report. A follow-on intensive programme oftraining, surveys and clinics seeks to reduce current threats to agricultural productivity through earlydetection of and timely advice on plant diseases. A practical blend of good science, effectivesurveillance and proven advisory services will strengthen the joint contributions of extension andresearch to increase food security, income generation and improved trade. The proposal highlightsfurther support required from national and regional organisations, as well as governments anddonors. These include local training for field and lab diagnostic techniques and expansion of theparticipatory disease surveys and strengthening of disease vigilance through the establishment of(mobile) plant health clinics. ; Catholic Relief Services ; United States Agency for International Development

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. ; Peer Review

Soybean rust (SBR), caused by Phakopsora pachyrhizi, has become established in Africa since the first report in Uganda in 1996 (2). The urediniospores, as windborne propagules, have infested new regions of Africa, initiating SBR in many countries, including Ghana and Democratic Republic of the Congo in 2007 (4) and Tanzania in 2014 (3). No refereed reports have been published about rust in Malawi, but some people have indicated that soybean rust may have been observed as early as 2008. Typical symptoms and signs of SBR, including leaf yellowing and tan, sporulating uredinia, were observed on soybean in May 2014 during field surveys in the major soybean-growing areas of Malawi, including the central (Dowa, Mchinji, and Kasungu) and southern (Thyolo) regions in nine out of 12 sites surveyed. When microscopically examined, urediniospores were elliptical, echinulate, and hyaline to pale yellowish brown. Leaves exhibiting sporuliferous uredinia were sent by APHIS permit to the University of Illinois. To confirm the pathogen, symptomatic soybean leaf tissue of approximately 1 cm2 was excised from each of the samples, and DNA was extracted using the FastDNA Spin Kit (MP Biomedicals, Solon, OH), with further purification using the MicroElute DNA Clean-up Kit (Omega Bio-Tek, Norcross, GA). The resulting DNA was analyzed by quantitative PCR using published Taqman assays for P. pachyrhizi and P. meibomiae, with a multiplexed exogenous internal control reaction to validate negative results (1). P. pachyrhizi DNA was detected in excess of 180,000 genome equivalents/cm2 in all samples, indicating a substantial infection. P. meibomiae DNA was determined to be absent from all samples, within the limit of quantification of ~2 pg DNA/cm2. Urediniospores dislodged from three leaves and inoculated onto susceptible soybean cultivar Williams 82 produced tan lesions after 2 weeks of incubation in a detached-leaf assay. This is the first confirmed report of P. pachyrhizi causing rust on soybean in Malawi, putting at risk 14,000 ha currently under soybean production. The reports of soybean rust in Malawi and adjoining countries will alter soybean production practices and research interests. In some cases, foliar application of fungicides has increased and planting dates have been changed to avoid conditions that are most conducive for rust development. Efforts to understand the virulence and genetic diversity of the pathogen in the region are needed in order to develop and deploy resistant cultivars. ; Peer Review

Article purchased; Published online: 28 Feb 2010 ; Xanthomonas campestris pv. musacearum (Xcm) causes a disease onbanana (Musa spp.) and enset (Ensete spp.) known as banana xanthomonaswilt (BXW). Recent studies have shown that Xcm is a strain of X. vasicola(Aritua et al., 2008). However, the status of pathovars within thespecies remains unclear. Prior to its discovery in Uganda in October 2001,the disease had been limited to Ethiopia (first reported 1968). Since thenthe disease has spread to the Democratic Republic of Congo and Rwanda(observed in May 2004 and September 2005 respectively). BXW cancause high yield losses and is a high priority concern within the GreatLakes region. A comprehensive review of the pathogen and diseasewas recently published by Smith et al. (2008). Thus far, outbreaks inTanzania, Kenya and Burundi have only been referred to in symposiumproceedings and on various websites. These new records are thus officiallyreported here for the first time.In Tanzania, the disease was first reported in the Kagera region of northwest Tanzania, bordering Lake Victoria, Uganda, Rwanda and Burundi,in September 2005 (Mgenzi et al., 2006). Spread has continued, but not toother major banana growing areas. In Kenya, the disease was firstreported in September 2006 in the Teso District, of western Kenya,bordering Uganda (Anon, 2006). Spread has since been reported as slow.In Burundi the disease was first observed during October 2006 (Anon.,2006). The current status of BXW in Burundi is unclear with no recentsubstantiated reports.Bacterial cultures were isolated from diseased racemes from Tanzaniaand Burundi at CABI, UK and from Kenya at KARI (NARL). All cultureswere identified to species level at FERA by fatty acid profiling (MIDI system)and DNA analysis using X. vasicola specific primers (Aritua et al.,unpublished data) and partial sequencing of the gyrase B gene (Parkinsonet al., 2007). Koch's postulates were fulfilled for all strains at FERA bystem inoculation of banana plants (height approximately 30 cm) with abacterial suspension (200 lL with ~107 cfu ⁄ mL) under controlled environmentalconditions (minimum temperature 27ºC). Identification ofXcm isolates from Burundi and Kenya was further supported by OhioState University and KARI, respectively, using X. vasicola specific primers(Lewis-Levy Miller, unpublished data) that have a different target site tothose of Aritua et al. (unpublished data).Reference cultures are held by the UK National Collection of PlantPathogenic Bacteria, Accession Nos. NCPPB 4392-5 (Tanzania), 4434(Kenya) and 4433 (Burundi). ; Peer Review

Crop diseases do not respect country borders and yet preventive measures to curtail the introduction, establishment and spread of diseases are often coordinated on a country-by-country basis. This is because each country has its own mandate to safeguard food security and trade relations. However, knowledge held by researchers and regulatory officials within each country for any given disease can benefit those in neighbouring countries, and this can be reciprocated for other diseases, depending on aggregated disease distribution and experience of methods for effective diagnosis and management. Based on an appreciation of this common goal, national research and regulatory officials from seven countries networked to prioritize which diseases of banana (Musa spp.) were of critical importance and where to undertake spatially designed surveillance exercises around the Great Lakes region of sub-Saharan Africa. Surveys for banana Xanthomonas wilt and banana bunchy top disease were targeted to zones where outbreaks had been reported but not confirmed, and where invasion risk was high as a consequence of proximity to areas or countries known to contain either disease. To ensure that disease diagnoses were precise, field based visual assessments of symptoms were supported by molecular based diagnostics performed under laboratory conditions. Samples were transferred from plants in the field to the laboratory using pathogen DNA capture kits that could be swiftly and safely moved across country borders for analysis at a centralized laboratory to ensure that results from different surveys could be compared. The accuracy of global positioning system (GPS) coordinates recorded as the origin of samples from surveys was validated by comparing the altitude given by the GPS with altitude data provided by digital elevation models. Geographical information system (GIS) maps could then be generated to clearly show the prevalence of banana Xanthomonas wilt and banana bunchy top disease for the zones surveyed. Furthermore, the GIS maps can be used to interpolate different GPS-linked data sets to highlight factors driving disease establishment and spread, such as conducive environmental conditions, and to determine where to prioritize management strategies based on food insecurity measures. The need to prioritize investments across a region is of particular importance in developing countries where capacities for disease surveillance and diagnostics are limited, resulting in inaccurate pest lists and, as a consequence, limited prospects for sustained agricultural trade. If there is political will for regional communication, harmonized diagnostics and reporting mechanisms, the current scenario of fighting fully blown epidemics with exorbitant funds can be averted by coordinated, pre-emptive and thus cost efficient management interventions. ; Food and Agriculture Organization of the United Nations ; United States Agency for International Development ; Peer Review