Aflatoxins are toxic and carcinogenic secondary metabolites, produced byAspergillus flavus andAspergillus parasiticus, which contaminate food and feed and threaten human and animal health. To assess the prevalence of aflatoxins in Tanzania, 180 groundnut and 200 maize samples were collected from 9 and 10 districts, respectively. Aflatoxin contamination was quantified using high performance liquid chromatography. Aflatoxins were detected in samples collected from all districts and prevalence ranged from 92 to 100% for groundnuts and 10 to 80% for maize. The mean aflatoxin level for groundnuts was 6.37 μg/kg and the highly contaminated sample had 40.31 μg/kg. For maize, the mean aflatoxin level was 12.47 μg/kg and the highly contaminated sample had 162.40 μg/kg. The estimated average probable daily intake (APDI) of aflatoxin B1 (AFB1) from groundnuts consumption was 1.88 ng/kg body weight/day, while for maize, it ranged between 151.98-272.89 ng/kg body weight/day. The APDI for both groundnut and maize exceeded the provisional maximum tolerable daily intake (PMTDI) of AFB1 for adults (1 ng/kg body weight/day), bringing about health concerns for populations in Tanzania. Another alarming finding was that 75% of the farmers who provided samples for analysis were not aware of aflatoxins or the negative health impacts from consuming contaminated products. Results reported in this paper show that aflatoxin contaminated staple crops are widely distributed in Tanzania and that the risk of human exposure is high due to diet preferences. Awareness campaigns are required to inform and protect farmers and consumers.

Banana is a staple food and cash crop grown in East and Central Africa (ECA). The main banana varieties grown in ECA are the East African highland bananas (EAHB), although dessert/beer bananas such as Sukari Ndizi, Kayinja (Pisang Awak) and Gros Michel are also produced due to their high value at local markets. The Fusarium wilt fungus Fusarium oxysporum f. sp. cubense (Foc) causes disease of susceptible dessert/beer bananas, which significantly reduces yields. Banana Fusarium wilt is managed by excluding the pathogen from disease-free areas and by planting disease-resistant varieties in infested fields. Six phylogenetically closely-related vegetative compatibility groups (VCGs) of Foc, VCGs 0124, 0125, 0128, 01212, 01220 and 01222 are present in ECA, which all group together in Foc Lineage VI. Rapid and accurate detection of Foc Lineage VI strains is thus important to prevent its spread to disease-free areas. In this study, molecular markers specific to Foc Lineage VI were therefore developed. Primer sets were then combined in a multiplex PCR assay, and validated on a worldwide population of 623 known Foc isolates, other formae speciales and non-pathogenic Fusarium oxysporum isolates. The Foc Lineage VI multiplex PCR was used to identify Foc isolates collected in banana fields at five locations in Uganda and Tanzania. Foc Lineage VI DNA was detected at a concentration as low as 0.1 ng/μl, both in the absence and presence of banana DNA, and can therefore be used as an accurate diagnostic tool for Foc Lineage VI strains.

The geographic pattern of cropland is an important risk factor for invasion and saturation by crop-specific pathogens and arthropods. Understanding cropland networks supports smart pest sampling and mitigation strategies. We evaluate global networks of cropland connectivity for key vegetatively propagated crops (banana and plantain, cassava, potato, sweet potato, and yam) important for food security in the tropics. For each crop, potential movement between geographic location pairs was evaluated using a gravity model, with associated uncertainty quantification. The highly linked hub and bridge locations in cropland connectivity risk maps are likely priorities for surveillance and management, and for tracing intraregion movement of pathogens and pests. Important locations are identified beyond those locations that simply have high crop density. Cropland connectivity risk maps provide a new risk component for integration with other factors-such as climatic suitability, genetic resistance, and global trade routes-to inform pest risk assessment and mitigation.

The development of high value crops for domestic consumption and export is considered a priority for economic development and improved livelihoods for many Pacific Island countries. However, attempts to intensify production without adequate attention to research and development in areas such as identification of well-adapted cultivars may lead to gains being limited and short-lived. The Australian Centre for International Agricultural Research project "Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high value crop production" aims to build and sustain capacity to develop integrated crop management strategies for the sustainable intensification of high value crop production for export and domestic markets. Activities include the introduction and evaluation of performance of improved solanaceous cultivars in each target country, and the testing of integrated technologies for their efficacy to increase and extend vegetable production seasons. Tomato is a high-value crop in Fiji and the Solomon Islands. It is commonly grown by farmers for household consumption and the domestic market. Eleven improved open pollinated tomato cultivars sourced from the World Vegetable Center in Taiwan were evaluated over three cropping seasons. Three cultivars ('CLN3150A-5', 'CLN2585D' and 'CLN2071D') were selected and officially released in Fiji and the Solomon Islands. The released cultivars now locally known as 'Melrose' and 'Rio Gold' in Fiji, and 'Rose's Choice' in the Solomon Islands, performed well under local growing conditions and are high yielding, producing well-shaped fruit with a taste preferred by local consumers. For farmers, these new open pollinated cultivars provide an opportunity to produce for the local market and also to save their own seeds for small-scale planting. This was a milestone achievement for project partners - local agriculture ministries, the Pacific Community, the University of Queensland, and the World Vegetable Center.

Soybean rust, caused by the biotrophic pathogen Phakopsora pachyrhizi, is a highly destructive disease causing substantial yield losses in many soybean producing regions throughout the world. Knowledge about P. pachyrhizi virulence is needed to guide development and deployment of soybean germplasm with durable resistance against all pathogen populations. To assess the virulence diversity of P. pachyrhizi, 25 isolates from eight countries, including 17 isolates from Africa, were characterized on 11 soybean genotypes serving as differentials. All the isolates induced tan lesions with abundant sporulation on genotypes without any known resistance genes and on soybean genotypes with resistance genes Rpp4 and Rpp5b. The most durable gene was Rpp2, where 96% of the isolates induced reddish brown lesions with little or no sporulation. Of the African isolates tested, the South African isolate was the most virulent, whereas those from Kenya, Malawi, and some of the isolates from Tanzania had the lowest virulence. An Argentinian isolate was virulent on most host differentials, including two cultivars carrying multiple resistance genes. Ten distinct pathotypes were identified, four of which comprised the African isolates representing considerable P. pachyrhizi virulence. Soybean genotypes carrying Rpp1b, Rpp2, Rpp3, and Rpp5 resistance genes and cultivars Hyuuga and UG5 were observed to be resistant against most of the African isolates and therefore may be useful for soybean-breeding programs in Africa or elsewhere.

Banana is an important crop in the Kagera region of Tanzania. Banana xanthomonas wilt (BXW) was first reported in Kagera in 2006, and is now an important limiting factor in banana production, because all cultivars are susceptible and infected plants can fail to produce fruit. BXW is caused by Xanthomonas campestris pv. musacearum (Xcm), which is spread by farm tools, infected planting materials, and pollinating insects. Practices that address Xcm dissemination, such as mat removal, debudding and tool sterilization, have not prevented the spread of BXW in the region. Disease surveys were conducted in Kagera from 2007 to 2011 to assess BXW presence, monitor its intensity and evaluate its socioeconomic impacts. Spatiotemporal clusters of BXW were analysed with ArcGIS and sas. The relationship between BXW clusters and environmental variables was examined using bivariate correlations in spss; two modelling approaches, MaxEnt (maximum entropy) and logistic regression, were used to predict the potential distribution of BXW in Tanzania. Disease progress over time was best described with the Gompertz model. Significant clustering of BXW was observed in all years and hotspots were located in the Muleba, Karagwe, Misenyi and Bukoba rural districts. These findings suggest that BXW spreads rapidly over short distances. BXW clusters were positively correlated with rainfall and negatively with temperature and altitude. According to MaxEnt, precipitation was the main factor associated with BXW development. MaxEnt and logistic regression predicted a wide potential distribution of BXW in Tanzania because the climate in all banana‐growing regions is conducive for its establishment.

Soybean is a major source of oil and proteins worldwide. The demand for soybean has increased in Africa, driven by the growing feed industry for poultry, aquaculture and home consumption in the form of processed milk, baked beans and for blending with maize and wheat flour. Soybean, in addition to being a major source of cooking oil, is also used in other industrial processes such as in the production of paints and candle wax. The demand for soybean in Africa so far outweighs the supply, hence the deficit is mainly covered through imports of soybean products such as soybean meal. The area under soybean production has increased in response to the growing demand, a trend that is expected to continue in the coming years. As the production area increases, diseases and insect pests, declining soil fertility and other abiotic factors pose a major challenge. Soybean rust disease, caused by the fungus Phakopsora pachyrhizi, presents one of the major threats to soybean production in Africa due to its rapid spread as a result of the ease by which its spores are dispersed by the wind. Disease control by introducing resistant soybean varieties has been difficult due to the presence of different populations of the fungus that vary in pathogenicity, virulence and genetic composition. Improved understanding of the dynamics of rust ecology, epidemiology and population genetics will enhance the effectiveness of targeted interventions that, in turn, will safeguard soybean productivity.

Management of banana xanthomonas wilt (XW) (caused by Xanthomonas campestris pv. musacearum, Xcm) has been impeded by poor adoption of control options that are complex, cumbersome and costly. To improve XW management, this study investigated Xcm survival and latent infections in subsequent generations, survival of latently infected planting materials (suckers), incidence of latent infections in symptomless plants in mats having diseased plants, and XW status across farms and markets in districts previously devastated but currently endemic. On‐station experiments were protected from new infections. Latent bacteria at low levels were detected in up to 20% of the third generation suckers, with a significant (P < 0·05) reduction (43–20%) in subsequent generations. Only 3–6% of latently infected suckers succumbed to XW. Incidence of Xcm in symptomless suckers from farmers' fields (with up to 70% incidence) was low (3%) while it increased (8–25%) with disease severity in mats in controlled experiments. In the surveyed districts, incidence had significantly declined with yields observed to have recovered relative to earlier reports, although latent infections remained high. This study provides evidence that if new infections are prevented, fields with high XW incidence can be rejuvenated. It showed incomplete systemic movement of Xcm in mats coupled to a gradual decline of bacterial load in subsequent generations to levels that cannot initiate disease. These studies explain the current successes in farms practising single diseased plant removal instead of whole mat rouging, and gives hope to farmers lacking access to clean planting material.

Bacterial spot (BS) is an important disease of tomato in Nigeria (2). Although a xanthomonad was isolated from tomato in Nigeria and characterized using phenotypic and pathogenicity tests, the bacterium was not characterized genetically to confirm the species. To determine the species associated with BS, leaves were collected in fields in northwestern Nigeria from tomato plants showing typical BS symptoms, which consisted of dark, irregular-shaped brown leaf spots that coalesced, resulting in a blighted appearance. Isolations from individual lesions were made on nutrient agar (NA). Yellow, mucoid colonies typical of Xanthomonas were isolated from 14 lesions and all were determined to be amylolytic (3). To determine the races of these strains, bacterial suspensions of the tomato strains, derived from 24-h cultures grown on NA at 28°C, were adjusted to 108 CFU/ml and infiltrated into leaves of tomato and pepper differential genotypes (5). The tomato strains elicited hypersensitive reactions (HRs) on the four pepper differential lines and an HR on the tomato genotype FL 216, which contains the R gene Xv3, but elicited susceptible reactions on the tomato genotypes Hawaii 7998 and Bonny Best. These reactions are typical of X. perforans tomato race 3 strains (5). Multilocus sequence analysis (MLSA) of six housekeeping genes (fusA, lacF, gyrB, gltA, gapA, and lepA) was used to further analyze four representative strains (1) (GenBank Accession Nos. KJ938581 to KJ938584, KJ938588 to KJ938591, KJ938595 to KJ938598, KJ938602 to KJ938605, KJ938629 to KJ938632, and KJ938636 to KJ938639, respectively). A partial sequence of hrpB2 was also made since the four Xanthomonas species associated with BS can be differentiated based on sequence divergence of this gene (3) (KJ938609 to KJ938621 and KJ938628). The housekeeping gene sequences were aligned along with other Xanthomonas sequences imported from the National Center for Biotechnology Information (NCBI) database ( www.ncbi.nlm.nih.gov ) using the MUSCLE tool from MEGA software, 5.2.2. Maximum likelihood phylogenetic trees constructed for the six housekeeping gene sequences individually and in concatenation revealed that the strains grouped most closely with the X. euvesicatoria reference strain 85-10 but more distantly to X. perforans. The hrpB2 sequence, which is highly conserved for each Xanthomonas species pathogenic on tomato (4), was sequenced from the tomato strains. These sequences were identical to the hrpB2 sequence from X. perforans strains but different from X. euvesicatoria. Although BS is common in Nigeria, to our knowledge, this represents a unique group of X. euvesicatoria strains from tomato that are identical to X. perforans based on pathogenic reactions on tomato and pepper and hrpB2 sequence identity but are more closely related to X. euvesicatoria based on the six housekeeping gene sequences. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) E. U. Opara and F. J. Odibo. J. Mol. Genet. 1:35, 2009. (3) J. B. Jones et al. Syst. Appl. Microbiol. 27:755, 2004. (4) A. Obradovic et al. Eur. J. Plant Pathol. 88:736, 2004. (5) R. E. Stall et al. Annu. Rev. Phytopathol. 47:265, 2009.

HomePlant DiseaseVol. 99, No. 6First Report of 16SrII-C Subgroup Phytoplasma Causing Phyllody and Witches’-broom Disease in Soybean in Tanzania PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of 16SrII-C Subgroup Phytoplasma Causing Phyllody and Witches’-broom Disease in Soybean in TanzaniaH. Murithi, A. Owati, C. S. Madata, M. Joosten, F. Beed, and P. Lava KumarH. MurithiSearch for more papers by this author, A. OwatiSearch for more papers by this author, C. S. MadataSearch for more papers by this author, M. JoostenSearch for more papers by this author, F. BeedSearch for more papers by this author, and P. Lava KumarSearch for more papers by this authorAffiliationsAuthors and Affiliations H. Murithi , International Institute of Tropical Agriculture (IITA), P.O. Box 34441, Dar es Salaam, Tanzania, and Laboratory of Phytopathology, Wageningen-UR (WUR), 6700 AA Wageningen, the Netherlands A. Owati , IITA, PMB5320, Oyo Road, Ibadan, Nigeria C. S. Madata , Agricultural Research Institute-Uyole, Mbeya, P.O. Box 400, Tanzania M. Joosten , WUR, Wageningen, the Netherlands F. Beed , IITA, Dar es Saalam, Tanzania, and AVRDC, Bangkhen, Bangkok 10900, Thailand P. Lava Kumar , IITA, Ibadan, Nigeria. Published Online:18 May 2015https://doi.org/10.1094/PDIS-11-14-1225-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Soybean production in Tanzania is steadily increasing, driven by growing demand from feed and livestock producers and also for human consumption. Soybean production area has increased from 795 ha in 2003 to 4,100 ha in 2013 (FAO 2014). Major soybean production is in the Morogro, Ruvuma, Iringa, and Mbeya regions. During a soybean rust disease survey conducted in May 2014 in Morogoro in the southern highlands of Tanzania, soybean plants with phyllody and witches’-broom disorder typical of phytoplasma infection was observed on cultivar, Uyole Soya#1 in a farmer’s field at Msufini village (6°17′0.099″ S; 37°28.791″ E). Symptoms consisted of shoot proliferation, reduced size of the leaflets and petiole, proliferation of axillary shoots with shortened internodes, phyllody, and viriscence. About 50% of the plants assessed (n = 20) from one plot in a farmer’s field were infected. Symptomatic and asymptomatic leaves were collected for total genomic DNA extraction and PCR amplification using Candidatus phytoplasma universal primer pair P1 and P7 for 16S-23S ribosomal RNA encoding region (Sharmila et al. 2004). PCR amplicons of expected size (∼1,700 bp) resulted from the templates of the symptomatic samples only. They were directly sequenced in both orientations and the nucleotide sequence was submitted to GenBank (Accession No. KP205526). A BLASTn search revealed that the phytoplasma sequences had a nucleotide sequence identity of 99% with those of 16SrII group phytoplasma associated with phyllody and witches’-broom disease of soybean in Malawi (HQ845208) and Mozambique (HQ840717). Phylogenetic analysis revealed the clustering of these strains with members of 16SrII group. The virtual restriction fragment length polymorphism (RFLP) pattern derived from these sequences using iPhyClassifier software (Zhao et al. 2009) was similar to the reference pattern of the 16SrII subgroup C (cactus phytoplasma, AJ293216), with a pattern similarity coefficient of 0.99. Previous reports of phytoplasma occurrence in Tanzania were related to coconut lethal decline disease caused by 16SrIV-C subgroup phytoplasma (Bila et al. 2014). To our knowledge, this is the first report of the occurrence of 16SrII-C subgroup phytoplasma causing phyllody and witches’-broom disease in soybean in Tanzania. The occurrence of phyllody and witches’-broom disease was first recognized in soybean in Malawi and Mozambique in 2010 (Kumar et al. 2011). Detection of the same pathogen in the diseased soybean plants in Tanzania suggest either spread of 16SrII phytoplasma from neighboring countries or 16SrII phytoplasma may be widespread in asymptomatic wild or weed hosts in southern Africa, spreading to crop hosts like soybean because of intensive cultivation. Nonetheless, this finding underscores the need for better understanding of epidemiology of 16SrII phytoplasma, especially its natural hosts and vectors, to prevent its adverse impacts on soybean production in Eastern and Southern Africa. Further surveys in soybean production areas in Tanzania are necessary to estimate the extent of spread and economic importance.References:Bila, J., et al. 2014. Plant Pathol. Online. https://doi.org/10.1111/ppa.12306. Google ScholarFAO. 2014. Online: http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID=567#ancor, retrieved 7 Oct 2014. Google ScholarKumar, P. L., et al. 2011. Plant Dis. 95:492. https://doi.org/10.1094/PDIS-01-11-0016 Link, ISI, Google ScholarSharmila, L. B., et al. 2004. J. Plant Biochem. Biotechnol. 13:1. https://doi.org/10.1007/BF03263182 Crossref, ISI, Google ScholarZhao, Y., et al. 2009. Int. J. Syst. Evol. Microbiol. 59:2582. https://doi.org/10.1099/ijs.0.010249-0 Crossref, ISI, Google ScholarDetailsFiguresLiterature CitedRelated Vol. 99, No. 6 June 2015SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 23 Jun 2015Published: 18 May 2015First Look: 5 Jan 2015Accepted: 1 Jan 2015 Pages: 886-886 Information© 2015 The American Phytopathological SocietyCited byPest categorisation of the non‐EU phytoplasmas of Cydonia Mill., Fragaria L., Malus Mill., Prunus L., Pyrus L., Ribes L., Rubus L. and Vitis L.EFSA Journal, Vol. 18, No. 1Phytoplasmas Infecting Vegetable, Pulse and Oil Crops5 September 2018Molecular characterization, vector identification and partial host range determination of phytoplasmas associated with faba bean phyllody in IranCrop Protection, Vol. 89First Report of Tomato Big Bud Caused by a 16SrII-C Phytoplasma in TanzaniaA. L. Testen, F. Baysal-Gurel, D. P. Mamiro, and S. A. Miller5 October 2015 | Plant Disease, Vol. 99, No. 12

Fusarium oxysporum f.sp. strigae was reported to be effective in the control of Striga hermonthica (Del.). The most effective (pathogenic to Striga) isolates were PSM197 and FOXY2 obtained from Nigeria and Ghana, respectively. To make application easier, the organisms were encapsulated in a pesta as carriers. In order to determine the applicability of these bio-control agents, there is the need to evaluate its host range on cultivated crops. Therefore, 26 economically important crops in Nigeria were used in a screen house host range study using the two isolates as a granular formulation (pesta) applied in the planting holes before sowing/planting. Data on plant vigour, plant height, plant fresh and dry weight were taken and analysed using analysis of variance and means were separated using least significance difference. The result showed that 10 crops out of the 26 used in the study statistically differed with respect to plant height; eight crops statistically differed from the other crops in terms of plant vigour while five crops and seven crops differed statistically from the others in terms of fresh and dry weight, respectively. Some of the crops also showed symptoms of infection and this lead to further analysis in the laboratory.

Phakopsora pachyrhizi Syd. was reported on legume hosts other than soybean in Tanzania as early as 1979 (1). Soybean rust (SBR), caused by P. pachyrhizi, was first reported on soybean in Africa in Uganda in 1996 (3), and its introduction into Africa was proposed to occur through urediniospores blowing from western India to the African east coastal areas by moist northeast monsoon winds (4). The fungus rapidly spread and was reported on soybean in South Africa in 2001, in western Cameroon in 2003, and in Ghana and the Democratic Republic of the Congo in 2007 (5). A second species causing SBR on soybean, P. meibomiae, has not been reported in Africa or elsewhere, outside of the Americas. From 2012 to 2014, symptomatic leaf samples were collected in the major soybean growing areas of the Tanzanian Southern Highlands (Iringa, Mbeya, and Ruvuma regions). Symptoms of SBR included yellowing of leaves and tan sporulating lesions. These symptoms were observed at flowering through seed maturity. From fields surveyed in 2012, 2013, and 2014, SBR was observed in 5 of 14, 7 of 11, and 14 of 31 fields, respectively. Some of the leaves sampled had up to 80% of the leaf area affected. When microscopically examined, urediniospores were elliptical, echinulate, and hyaline to pale yellowish brown. In 2014, sporuliferous uredinia were observed on leaf material collected from the Iringa and Ruvuma regions of Tanzania, and a subset of these samples was 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 DNA was subjected to quantitative PCR using published Taqman assays for P. pachyrhizi, P. meibomiae, and a multiplexed exogenous internal control reaction to validate negative results (2). P. pachyrhizi DNA was detected in excess of 66,000 genome equivalents/cm2 in all samples, and P. meibomiae DNA was determined to be absent from all samples (limit of quantification ~2 pg DNA/cm2). Free surviving urediniospores were dislodged from 12 samples and inoculated onto susceptible soybean cultivar Williams 82, which produced sporulating SBR lesions after 2 weeks of incubation in a detached-leaf assay. Thus, Koch's postulates were completed. This is the first report of P. pachyrhizi causing rust on soybean in Tanzania. In vivo cultures have been established from most of these samples, and ongoing research includes an evaluation of the P. pachyrizi virulence on a differential set, and characterization of the genetic diversity. References: (1) D. L. Ebbels and D. J. Allen. Phytopath. Pap. 22:1-89. (2) J. S. Haudenshield and G. L. Hartman. Plant Dis. 95:343, 2011. (3) R. Kawuki et al. Afr. Crop Sci. J. 11:301, 2003. (4) C. Levy. Plant Dis. 89:669, 2005. (5) P. S. Ojiambo et al. Plant Dis. 91:1204, 2007.

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.

Xanthomonas campestris pv. musacearum (Xcm) is the causal agent of banana xanthomonas wilt, a major threat to banana production in eastern and central Africa. The pathogen is present in very high levels within infected plants and can be transmitted by a broad range of mechanisms; therefore early specific detection is vital for effective disease management. In this study, a polyclonal antibody (pAb) was developed and deployed in a lateral flow device (LFD) format to allow rapid in‐field detection of Xcm. Published Xcm PCR assays were also independently assessed: only two assays gave specific amplification of Xcm, whilst others cross‐reacted with non‐target Xanthomonas species. Pure cultures of Xcm were used to immunize a rabbit, the IgG antibodies purified from the serum and the resulting polyclonal antibodies tested using ELISA and LFD. Testing against a wide range of bacterial species showed the pAb detected all strains of Xcm, representing isolates from seven countries and the known genetic diversity of Xcm. The pAb also detected the closely related Xanthomonas axonopodis pv. vasculorum (Xav), primarily a sugarcane pathogen. Detection was successful in both naturally and experimentally infected banana plants, and the LFD limit of detection was 105 cells mL−1. Whilst the pAb is not fully specific for Xcm, Xav has never been found in banana. Therefore the LFD can be used as a first‐line screening tool to detect Xcm in the field. Testing by LFD requires no equipment, can be performed by non‐scientists and is cost‐effective. Therefore this LFD provides a vital tool to aid in the management and control of Xcm.

Bacterial spot (BS) has been reported as an important disease on pepper in Nigeria (4). Xanthomonas campestris pv. vesicatoria was identified as the causal agent using phenotypic and pathogenicity tests; however, X. campestris pv. vesicatoria is a synonym for two genetically distinct groups that have been elevated to the species X. euvesicatoria and X. vesicatoria (2). Furthermore, the latter two species and X. gardneri cause similar diseases on pepper (2). In order to determine the species associated with BS on pepper, leaves with irregular, dark brown lesions were collected from pepper plants in fields from northwestern Nigeria, and isolations were made on nutrient agar (NA). Yellow, mucoid colonies typical of Xanthomonas were isolated. Six strains isolated from pepper were determined to be non-amylolytic. For race determinations, bacterial suspensions of the pepper strains, derived from 24-h cultures grown on NA at 28°C, were adjusted to 108 CFU/ml and infiltrated into leaves of tomato and pepper differential genotypes (5). The six pepper strains elicited HRs on the tomato differential genotypes. The strains produced a susceptible reaction on all pepper differentials and were designated as pepper race 6 (5). Multilocus sequence analysis (MLSA) using six housekeeping genes (fusA, lacF, gyrB, gltA, gapA, and lepA) was used to further analyze the strains (1) (GenBank Accession Nos. KJ938585 to KJ938587, KJ938592 to KJ938594, KJ938599 to KJ938601, KJ938606 to KJ938608, KJ938633 to KJ938635, and KJ938640 to KJ938642). A partial sequence of hrpB2 was also sequenced since the four Xanthomonas species associated with BS can be differentiated based on sequence divergence (3) (KJ938622 to KJ938627). The housekeeping gene sequences were aligned along with other Xanthomonas sequences imported from the NCBI database using muscle tool from MEGA software, 5.2.2. Maximum likelihood phylogenetic trees constructed for the six housekeeping gene sequences individually and in concatenation revealed that the Nigerian pepper strains were identical to the X. euvesicatoria reference strain 85-10. Although BS is common in Nigeria, to our knowledge, this represents the first report for this pepper pathogen in Nigeria. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (3) J. B. Jones et al. System Appl. Microbiol. 27:755, 2004. (4) A. Obradovic et al. Eur. J. Plant Pathol. 88:736, 2004. (2) E. U. Opara and F. J. Odibo. J. Mol. Gen. 1:35, 2009. (5) R. E. Stall et al. Ann. Rev. Phytopathol. 47:265, 2009.

Banana Xanthomonas wilt (XW), caused by Xanthomonas campestris pv. musacearum (Xcm), results in up to 100% yield loss. The efficiency of XW infection through the corm, pseudostem inoculation at bunch harvest, leaf, female and male bud bracts was evaluated in banana plants. The male and female bud bract inoculations caused the highest incidence (81% and 93%) compared with 0-44% for harvest and corm inoculations. Naturally mediated insect transmission in 'Pisang Awak' resulted in up to 99% disease incidence. Floral inoculations and natural insect-mediated infections only resulted in floral symptoms. Symptom development in insect-transmitted infections simulated artificial male bud inoculations, confirming the male bud bract wounds as the main entry points for insect vector-mediated infections, thus reaffirming the importance of continuous and timely debudding to limit insect spread. Leaf and harvest inoculations resulted only in leaf symptoms, while corm inoculations resulted in late floral symptoms. Floral inoculations were the main mode of infection. Single leaf inoculations resulted in 30% plant mortality despite 100% incidence, with 70% of plants recovering and bearing visibly healthy bunches and suckers. Thus, detection of a diseased plant in a mat shouldn't warrant the destruction of the whole mat. A significant difference in Xcm cfu g(-1) was observed between symptomatic and symptomless leaves, suggesting that practices that keep the bacterial load below the disease-causing threshold could benefit the plant. This could explain the observed success of XW control through removal of single diseased stems in farms.

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.

Rabbit polyclonal antibodies (PAbs) were produced against a pure isolate of Xanthomonas campestris pv. musacearum (Xcm), which is the causal organism of banana Xanthomonas wilt (BXW) disease of banana (Musa spp.) in the Great Lakes region of Africa. Anti-Xcm PAbs were used to develop a direct antigen coating enzyme-linked immunosorbent assay (DAC-ELISA) for the detection of Xcm in leaf and pseudostem tissues of infected banana and plantain (Musa spp.). The anti-Xcm PAbs in DAC-ELISA specifically reacted with Xcm but not with Escherichia coli, X. vasicola pv. vasculorum of maize and sugarcane or X. vasicola pv. holcicola of sorghum. Results of the DAC-ELISA detection of Xcm are comparable with the results of PCR and culture-based detection assays for the same pathogen.