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Legg J.P.,IITA Tanzania | Jeremiah S.C.,IITA Tanzania | Jeremiah S.C.,Ukiriguru Agricultural Research Institute LZARDI | Obiero H.M.,Kenya Agricultural Research Institute | And 10 more authors.
Virus Research | Year: 2011

The rapid geographical expansion of the cassava mosaic disease (CMD) pandemic, caused by cassava mosaic geminiviruses, has devastated cassava crops in 12 countries of East and Central Africa since the late 1980s. Region-level surveys have revealed a continuing pattern of annual spread westward and southward along a contiguous 'front'. More recently, outbreaks of cassava brown streak disease (CBSD) were reported from Uganda and other parts of East Africa that had been hitherto unaffected by the disease. Recent survey data reveal several significant contrasts between the regional epidemiology of these two pandemics: (i) severe CMD radiates out from an initial centre of origin, whilst CBSD seems to be spreading from independent 'hot-spots'; (ii) the severe CMD pandemic has arisen from recombination and synergy between virus species, whilst the CBSD pandemic seems to be a 'new encounter' situation between host and pathogen; (iii) CMD pandemic spread has been tightly linked with the appearance of super-abundant Bemisia tabaci whitefly vector populations, in contrast to CBSD, where outbreaks have occurred 3-12 years after whitefly population increases; (iv) the CMGs causing CMD are transmitted in a persistent manner, whilst the two cassava brown streak viruses appear to be semi-persistently transmitted; and (v) different patterns of symptom expression mean that phytosanitary measures could be implemented easily for CMD but have limited effectiveness, whereas similar measures are difficult to apply for CBSD but are potentially very effective. An important similarity between the pandemics is that the viruses occurring in pandemic-affected areas are also found elsewhere, indicating that contrary to earlier published conclusions, the viruses per se are unlikely to be the key factors driving the two pandemics. A diagrammatic representation illustrates the temporal relationship between B. tabaci abundance and changing incidences of both CMD and CBSD in the Great Lakes region. This emphasizes the pivotal role played by the vector in both pandemics and the urgent need to identify effective and sustainable strategies for controlling whiteflies on cassava. © 2011 Elsevier B.V.


ST. LOUIS, MO, December 16, 2016 /24-7PressRelease/ -- The Donald Danforth Plant Science Center announces that the Virus Resistant Cassava for Africa Plus (VIRCA Plus) consortium of American, Nigerian, Ugandan, and Kenyan institutions recently received a five-year, $10.46 million grant from the Bill & Melinda Gates Foundation to develop disease-resistant and nutritionally-enhanced cassava varieties to improve the livelihoods and health status of African farm families. Cassava is an important food and cash crop for small-holder farmers in Africa. It is the second most important staple food crop after maize in sub-Saharan Africa. Approximately one-third of the population relies on its starchy tuberous roots for over 50 percent of their daily caloric intake. It grows well in conditions of drought and low soil fertility prevalent in many African countries. However, plant viral diseases can destroy up to 100 percent of a cassava crop yield, threatening livelihoods and leading to hunger. Although it is an excellent source of calories, cassava does not contain significant levels of key nutrients to meet minimum daily requirements, especially for women and children. The VIRCA Plus collaboration will address these challenges by developing and delivering two products. The first will be East African cassava varieties with resistance to both Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD). The second will be a Nigerian cassava variety with elevated levels of iron and zinc for improved nutrition, as well as disease resistance. VIRCA Plus builds on the success of two predecessor projects. The VIRCA project successfully developed strong and stable resistance to CBSD in cassava, validated over four field trials and multiple cropping cycles in Kenya and Uganda. The BioCassava Plus project succeeded in developing and testing cassava plants that accumulated greater than 10 times more iron and zinc than comparable varieties. Both minerals are retained after processing into common foodstuffs at levels that could provide 40-70 percent of the Estimated Average Requirement for vulnerable women and children. "By combining capacities and successes of the two predecessor projects, VIRCA Plus is poised to make important strides in improving agricultural productivity for farmers and enhancing nutrition for smallholder households in East and West Africa," said Nigel Taylor, Ph.D., Dorothy J. King Distinguished Investigator and Senior Research Scientist at the Donald Danforth Plant Science Center, and the principal investigator for VIRCA Plus. Partner institutes: The Donald Danforth Plant Science Center in St. Louis, MO, USA; the National Root Crops Research Institute (NRCRI) in Nigeria; the National Crop Resources Research Institute (NaCRRI)/ National Agricultural Research Organization (NARO) and the Science Foundation for Livelihoods and Development (SCIFODE) in Uganda; the Kenyan Agricultural and Livestock Research Organization (KALRO) and the ISAAA AfriCenter in Kenya; and the International Institute for Tropical Agriculture (IITA)in Nigeria. About The Donald Danforth Plant Science Center Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center's work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations. Follow us on Twitter at @DanforthCenter.


International Collaboration Receives Grant to Advance Improvements in Cassava Harvests and Nutrition for Smallholder Families in Sub-Saharan Africa Virus Resistant Cassava for Africa Plus (VIRCA Plus) consortium received a five-year, $10.46 million grant to develop disease-resistant and nutritionally-enhanced cassava varieties to improve the status of African farm families. St. Louis, MO, December 16, 2016 --( Cassava is an important food and cash crop for small-holder farmers in Africa. It is the second most important staple food crop after maize in sub-Saharan Africa. Approximately one-third of the population relies on its starchy tuberous roots for over 50 percent of their daily caloric intake. It grows well in conditions of drought and low soil fertility prevalent in many African countries. However, plant viral diseases can destroy up to 100 percent of a cassava crop yield, threatening livelihoods and leading to hunger. Although it is an excellent source of calories, cassava does not contain significant levels of key nutrients to meet minimum daily requirements, especially for women and children. The VIRCA Plus collaboration will address these challenges by developing and delivering two products. The first will be East African cassava varieties with resistance to both Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD). The second will be a Nigerian cassava variety with elevated levels of iron and zinc for improved nutrition, as well as disease resistance. VIRCA Plus builds on the success of two predecessor projects. The VIRCA project successfully developed strong and stable resistance to CBSD in cassava, validated over four field trials and multiple cropping cycles in Kenya and Uganda. The BioCassava Plus project succeeded in developing and testing cassava plants that accumulated greater than 10 times more iron and zinc than comparable varieties. Both minerals are retained after processing into common foodstuffs at levels that could provide 40-70 percent of the Estimated Average Requirement for vulnerable women and children. “By combining capacities and successes of the two predecessor projects, VIRCA Plus is poised to make important strides in improving agricultural productivity for farmers and enhancing nutrition for smallholder households in East and West Africa,” said Nigel Taylor, Ph.D., Dorothy J. King Distinguished Investigator and Senior Research Scientist at the Donald Danforth Plant Science Center, and the principal investigator for VIRCA Plus. Partner institutes: The Donald Danforth Plant Science Center in St. Louis, MO, USA; the National Root Crops Research Institute (NRCRI) in Nigeria; the National Crop Resources Research Institute (NaCRRI)/ National Agricultural Research Organization (NARO) and the Science Foundation for Livelihoods and Development (SCIFODE) in Uganda; the Kenyan Agricultural and Livestock Research Organization (KALRO) and the ISAAA AfriCenter in Kenya; and the International Institute for Tropical Agriculture (IITA)in Nigeria. About The Donald Danforth Plant Science Center Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center’s work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations. Follow us on Twitter at @DanforthCenter. St. Louis, MO, December 16, 2016 --( PR.com )-- The Donald Danforth Plant Science Center announces that the Virus Resistant Cassava for Africa Plus (VIRCA Plus) consortium of American, Nigerian, Ugandan, and Kenyan institutions recently received a five-year, $10.46 million grant from the Bill & Melinda Gates Foundation to develop disease-resistant and nutritionally-enhanced cassava varieties to improve the livelihoods and health status of African farm families.Cassava is an important food and cash crop for small-holder farmers in Africa. It is the second most important staple food crop after maize in sub-Saharan Africa. Approximately one-third of the population relies on its starchy tuberous roots for over 50 percent of their daily caloric intake. It grows well in conditions of drought and low soil fertility prevalent in many African countries. However, plant viral diseases can destroy up to 100 percent of a cassava crop yield, threatening livelihoods and leading to hunger. Although it is an excellent source of calories, cassava does not contain significant levels of key nutrients to meet minimum daily requirements, especially for women and children.The VIRCA Plus collaboration will address these challenges by developing and delivering two products. The first will be East African cassava varieties with resistance to both Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD). The second will be a Nigerian cassava variety with elevated levels of iron and zinc for improved nutrition, as well as disease resistance.VIRCA Plus builds on the success of two predecessor projects. The VIRCA project successfully developed strong and stable resistance to CBSD in cassava, validated over four field trials and multiple cropping cycles in Kenya and Uganda. The BioCassava Plus project succeeded in developing and testing cassava plants that accumulated greater than 10 times more iron and zinc than comparable varieties. Both minerals are retained after processing into common foodstuffs at levels that could provide 40-70 percent of the Estimated Average Requirement for vulnerable women and children.“By combining capacities and successes of the two predecessor projects, VIRCA Plus is poised to make important strides in improving agricultural productivity for farmers and enhancing nutrition for smallholder households in East and West Africa,” said Nigel Taylor, Ph.D., Dorothy J. King Distinguished Investigator and Senior Research Scientist at the Donald Danforth Plant Science Center, and the principal investigator for VIRCA Plus.Partner institutes: The Donald Danforth Plant Science Center in St. Louis, MO, USA; the National Root Crops Research Institute (NRCRI) in Nigeria; the National Crop Resources Research Institute (NaCRRI)/ National Agricultural Research Organization (NARO) and the Science Foundation for Livelihoods and Development (SCIFODE) in Uganda; the Kenyan Agricultural and Livestock Research Organization (KALRO) and the ISAAA AfriCenter in Kenya; and the International Institute for Tropical Agriculture (IITA)in Nigeria.About The Donald Danforth Plant Science CenterFounded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center’s work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations. Follow us on Twitter at @DanforthCenter. Click here to view the list of recent Press Releases from Donald Danforth Plant Science Center


ST. LOUIS, MO, December 14, 2016-The Donald Danforth Plant Science Center announces that the Virus Resistant Cassava for Africa Plus (VIRCA Plus) consortium of American, Nigerian, Ugandan, and Kenyan institutions recently received a five-year, $10.46 million grant from the Bill & Melinda Gates Foundation to develop disease-resistant and nutritionally-enhanced cassava varieties to improve the livelihoods and health status of African farm families. Cassava is an important food and cash crop for small-holder farmers in Africa. It is the second most important staple food crop after maize in sub-Saharan Africa. Approximately one-third of the population relies on its starchy tuberous roots for over 50 percent of their daily caloric intake. It grows well in conditions of drought and low soil fertility prevalent in many African countries. However, plant viral diseases can destroy up to 100 percent of a cassava crop yield, threatening livelihoods and leading to hunger. Although it is an excellent source of calories, cassava does not contain significant levels of key nutrients to meet minimum daily requirements, especially for women and children. The VIRCA Plus collaboration will address these challenges by developing and delivering two products. The first will be East African cassava varieties with resistance to both Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD). The second will be a Nigerian cassava variety with elevated levels of iron and zinc for improved nutrition, as well as disease resistance. VIRCA Plus builds on the success of two predecessor projects. The VIRCA project successfully developed strong and stable resistance to CBSD in cassava, validated over four field trials and multiple cropping cycles in Kenya and Uganda. The BioCassava Plus project succeeded in developing and testing cassava plants that accumulated greater than 10 times more iron and zinc than comparable varieties. Both minerals are retained after processing into common foodstuffs at levels that could provide 40-70 percent of the Estimated Average Requirement for vulnerable women and children. "By combining capacities and successes of the two predecessor projects, VIRCA Plus is poised to make important strides in improving agricultural productivity for farmers and enhancing nutrition for smallholder households in East and West Africa," said Nigel Taylor, Ph.D., Dorothy J. King Distinguished Investigator and Senior Research Scientist at the Donald Danforth Plant Science Center, and the principal investigator for VIRCA Plus. Partner institutes: The Donald Danforth Plant Science Center in St. Louis, MO, USA; the National Root Crops Research Institute (NRCRI) in Nigeria; the National Crop Resources Research Institute (NaCRRI)/ National Agricultural Research Organization (NARO) and the Science Foundation for Livelihoods and Development (SCIFODE) in Uganda; the Kenyan Agricultural and Livestock Research Organization (KALRO) and the ISAAA AfriCenter in Kenya; and the International Institute for Tropical Agriculture (IITA)in Nigeria. Founded in 1998, the Donald Danforth Plant Science Center is a not-for-profit research institute with a mission to improve the human condition through plant science. Research aims to feed the hungry and improve human health, preserve and renew the environment and position the St. Louis region as a world center for plant science. The Center's work is funded through competitive grants and contract revenue from many sources, including the National Institutes of Health, U.S. Department of Energy, National Science Foundation, U.S. Department of Agriculture, U.S. Agency for International Development, the Bill & Melinda Gates and Howard G. Buffett Foundations. Follow us on Twitter at @DanforthCenter.


Ghislain M.,International Potato Center | Tovar J.,International Potato Center | Prentice K.,International Potato Center | Ormachea M.,International Potato Center | And 9 more authors.
Acta Horticulturae | Year: 2013

African sweetpotato weevils (SPW), Cylas puncticollis and C. brunneus, pose a major threat to sweetpotato, which plays a vital role in food security and income generation for both the urban and rural poor in Sub-Saharan Africa (SSA). SPW can limit sweetpotato production causing total crop loss. Control methods such as integrated pest management and breeding have not succeeded satisfactorily in curbing out these pests thus opening the door for using biotechnology and genetic engineering to make transgenic sweetpotato that are resistant to weevil infestation. At least three protein samples from Bacillus thuringiensis (Bt) have been found to be toxic to both SPW species at less than 1 ppm (Cry7Aa1, CryET33/CryET34, and Cry3Ca1). Corresponding gene constructs were developed using sporamin and b amylase regulatory sequences to express and accumulate high Cry protein levels in the storage root. Approximately 100 transformed events from sweetpotato cultivars (including one African cultivar), were produced by Agrobacterium tumefaciens transformation of petioles and somatic embryos. Gene expression from leaf tissues using qRT-PCR revealed up to 20X difference among events. Protein accumulation using DAS-ELISA and storage roots exhibited even larger variation between events. However, so far only 18 of the 90 events have produced storage roots which could be bio-assayed. Most events accumulated Cry proteins below the LC50 level, two events accumulated Cry protein at the LC50 level and only one event accumulated Cry protein above the LC50 level (3 times the LC 50 level). Bioassays using transgenic tissues infested with SPW larvae are on-going but preliminary results reflect low toxicity as expected based on Cry protein content in the storage roots. Future steps include the screening of additional events, characterization of competitive binding of these Cry proteins and confined field trials of SPW-resistant events.


Tembo L.,Makerere University | Tembo L.,University of Zambia | Asea G.,National Crop Resources Research Institute | Gibson P.T.,Southern Illinois University Carbondale | Okori P.,Makerere University
Journal of Crop Improvement | Year: 2014

Stenocarpella maydis and Fusarium graminearum are the predominant species causing maize (Zea mays L.) cob rots in the tropics and sub-Saharan Africa. Developing varieties resistant to cob rots is an alternative strategy that is practical and provides better insurance for small-scale farmers. The subjectivity of scoring and the varying virulence responses of these pathogens to environmental conditions make selection for resistance difficult. The objectives of this study were to map quantitative trait loci (QTL) associated with resistance to S. maydis and F. graminearum and to analyze the possibilities of utilizing these QTL for marker-assisted selection (MAS). Stable QTL mapped were Fg_4,2 (r2 = 0.22) and Sm_4,1 (r2 = 0.16) associated with resistance to F. graminearum and S. maydis, respectively, on chromosome 4. Another QTL associated with resistance to F. graminearum was Fg_5 (r2 = 0.30) on chromosome 5. A QTL with pleiotropic effect was detected on chromosome 1, 22 cM from umc1269 marker (r2 values of 13% and 22% for resistance to S. maydis and F. graminearum, respectively). Additive effects ranged from -0.14 to -0.35 for associated QTL of both pathogens, and all mapped QTL were more than 5 cM from the nearest molecular marker utilized in the study. Therefore, there is need to utilize the maize genomic map to identify and test several markers, < 5 cM, near the detected QTL, in order to locate more reliable molecular markers for utilization in MAS. Copyright © Taylor & Francis Group, LLC.


Zawedde B.M.,U.S. National Center for Biotechnology Information | Harris C.,Michigan State University | Alajo A.,National Crop Resources Research Institute | Hancock J.,Michigan State University | Grumet R.,Michigan State University
Economic Botany | Year: 2014

Factors Influencing Diversity of Farmers' Varieties of Sweet Potato in Uganda: Implications for Conservation. There is increasing concern that agricultural intensification is causing loss of crop biodiversity due to displacement of traditional farmers' varieties by a small number of improved cultivars. Using ethnobotanical surveys, we assessed the implication of adoption of new sweet potato (Ipomoea batatas) cultivars on the maintenance of farmers' varieties in Uganda. Other factors influencing varietal diversity were also assessed. A total of 102 farmer households distributed in the top three sweet potato production agro-ecological zones were interviewed. With the exception of released cultivars, very few varieties appeared in more than one region. The majority of the respondents indicated that they continue to plant some of the existing varieties when they adopt new cultivars. Loss of planting materials due to drought was a major constraint to maintaining varietal diversity for this vegetatively propagated crop. Limited land and lack of access to best management practices were also key constraints to maintenance of farmers' varieties. The primary criteria for adopting new cultivars were higher yield, taste, and duration to maturity. Yield stability, tolerance to native biotic and abiotic stresses, and good taste were important for maintenance of currently grown varieties. Overall, criteria for variety selection varied with household characteristics including farmer age and gender, uses of the crop, micro-climatic conditions in the farmers' fields, and level of access to agricultural extension. The observed heterogeneity in selection criteria, influence of social ties, and the role of environment in varietal maintenance have important implications for establishing breeding priorities and preservation of crop diversity. © 2014 The New York Botanical Garden.


Nowakunda K.,National Crop Resources Research Institute | Ngambeki D.,National Crop Resources Research Institute | Tushemereirwe W.,National Crop Resources Research Institute
Acta Horticulturae | Year: 2010

Smallholder farming, characteristic of banana (Musa spp.) production systems in Uganda presents significant challenges with regard to market access. Small-scale farmers are scattered in villages and not organized. Often, they are unable to meet requirements of larger players in the value chain due to the incompatibility of used production and marketing methods. Small-scale and scattered farmers are unable to engage in formal trade which often requires the use of invoices and receipts, assured variety, quantity and quality of products. As a result, smallholder farmers have been locked out of organized lucrative markets, while conditioning them to selling their produce through an exploitative chain of agents. This has further led to very low farm-gate prices, yet, consumer prices are very high. However, it is hypothesized that opportunities exist to transform Ugandan small-scale banana production into a profitable business if farmers were facilitated to organize themselves into networked groups/associations through which they could link to other organizations and institutions for a variety of services and collectively market their produce. In this study, working through networked groups and a consortium of other private and public organizations/institutions, the farmers were able to: develop and maintain a market-information system; access wholesale markets which offer better prices than middlemen; inputs via bulk purchase; access extension services; improve crop management including pest disease management; and in-field fruit-quality control to obtain market-quality bananas. Similar agronomic practices within groups and selling directly to bulk buyers resulted in better products and facilitated collective marketing which has resulted in farmers margins rising from 20 to 50%.


Zawedde B.M.,Michigan State University | Zawedde B.M.,UBIC | Harris C.,Michigan State University | Alajo A.,National Crop Resources Research Institute | And 2 more authors.
Economic Botany | Year: 2014

Factors Influencing Diversity of Farmers’ Varieties of Sweet Potato in Uganda: Implications for Conservation. There is increasing concern that agricultural intensification is causing loss of crop biodiversity due to displacement of traditional farmers’ varieties by a small number of improved cultivars. Using ethnobotanical surveys, we assessed the implication of adoption of new sweet potato (Ipomoea batatas) cultivars on the maintenance of farmers’ varieties in Uganda. Other factors influencing varietal diversity were also assessed. A total of 102 farmer households distributed in the top three sweet potato production agro-ecological zones were interviewed. With the exception of released cultivars, very few varieties appeared in more than one region. The majority of the respondents indicated that they continue to plant some of the existing varieties when they adopt new cultivars. Loss of planting materials due to drought was a major constraint to maintaining varietal diversity for this vegetatively propagated crop. Limited land and lack of access to best management practices were also key constraints to maintenance of farmers’ varieties. The primary criteria for adopting new cultivars were higher yield, taste, and duration to maturity. Yield stability, tolerance to native biotic and abiotic stresses, and good taste were important for maintenance of currently grown varieties. Overall, criteria for variety selection varied with household characteristics including farmer age and gender, uses of the crop, micro-climatic conditions in the farmers’ fields, and level of access to agricultural extension. The observed heterogeneity in selection criteria, influence of social ties, and the role of environment in varietal maintenance have important implications for establishing breeding priorities and preservation of crop diversity. © 2014, The New York Botanical Garden.


Tembo L.,Makerere University | Tembo L.,University of Zambia | Asea G.,National Crop Resources Research Institute | Gibson P.T.,Makerere University | And 2 more authors.
Plant Breeding | Year: 2013

Maize cob rot caused by Fusarium graminearum and Stenocarpella maydis affects grain yield and quality. The objective of this study was to investigate the appropriateness of multiple infection as a selection and breeding strategy for multiple resistance to F. graminearum and S. maydis. Twelve tropical inbred lines with varying resistance to either or both pathogens were mated in a full diallel and the progeny and their parents evaluated for reaction to single or multiple infection. Under multiple inoculation, S. maydis suppressed colonization of cobs by F. graminearum. General combining ability (GCA) effects indicated that inbred WL 118-10 effectively transmitted resistance to both diseases. Hybrids' resistant to S. maydis was also resistant to F. graminearum, but the reverse was not true. Therefore, efficient screening should initially involve screening for S. maydis followed by F. graminearum. Overall, the suppression of F. graminearum by S. maydis shows that multiple infection cannot be used as an appropriate breeding strategy to obtain multiple resistance. The use of F. graminearum and S. maydis separately is, therefore, the best breeding strategy. © 2012 Blackwell Verlag GmbH.

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