Suchergebnisse

In many African countries south of the Sahara, farmers depend on the cultivation of vegetatively propagated crops (VPCs) for both consumption and commercial purposes. Yet yields for these crops remain at low levels due, in part, to the persistent use of low-quality planting material. Efforts to improve the quality of planting material exchanged in markets or through other channels are often hampered by the unique biological and economic characteristics of vegetative propagation—characteristics that distinguish VPCs from the major cereal crops that drive and shape the policy and investment choices made in many of these countries. This suggests that continued investment in new technologies and systems to produce, package, and distribute VPC planting materials will require customized policies and policy support if these systems are to supply farmers with quality planting material at any significant and sustained scale. This paper explores these issues in the context of the cassava seed system in Nigeria by drawing on (1) prior research, public policy documents, and government statistics; (2) key informant interviews and focus group discussions with seed system actors; and (3) a unique dataset from the 2015 Cassava Monitoring Survey of Nigeria (CMS). The paper examines the production and supply of cassava planting material, the influence of various quality assurance systems on production and supply, and the implications for smallholder farmers in Nigeria. We describe the market, non-market, and regulatory systems that shape the cassava seed market in Nigeria, focusing on effectiveness, influence, and reach. We then explore the ground realities—how farmers actually acquire and use cassava planting material—given the (weak) state of markets and regulation. This is followed by a discussion of alternative policy and regulatory approaches to managing and expanding the cassava seed system, emphasizing a more decentralized approach that prioritizes investment in innovative capacity at the community and enterprise levels.

Plantain and banana (Musa spp.) are among the most important staple crops for food and income generationfor the rural and urban populations in the humid forest agroecological zone of West Africa. Until recently,Cucumber mosaic virus (genus Cucumovirus) and Banana streak virus (genus Badnavirus) were the onlyviruses reported to occur in Musa spp. in West Africa. In 2011, an outbreak of banana bunchy top disease(BBTD) caused by Banana bunchy top virus (BBTV; genus Babuvirus, family Nanoviridae) was reported inOuémé Département (6°30′N and 2°36′E) in the Republic of Benin (2). BBTV is one of the most economicallyimportant pathogens of Musa spp. It is well established in Central Africa and also in Angola, Malawi, andZambia in Southern Africa (2). Plants infected at early growth stages are severely dwarfed and do not bearfruit. BBTV is transmitted by the banana aphid Pentalonia nigronervosa, which is widespread in Africa (1). Theregions in the Republic of Benin affected by BBTV border Ogun State (7°00′N and 3°35′E) of Nigeria.Epidemiological investigations were conducted during May 2012 at 31 locations in Ogun State to determinethe potential risk of BBTV spreading into Nigeria. Plants with typical symptoms of BBTD (stunting, narrow andshortened leaves, chlorotic streaks on petioles and pseudostem) were observed in four locations: Ilashe,Odan-Itoro, Ido-Ologun, and Igbogila. Total DNA was extracted from 90 leaf samples randomly collected fromsymptomatic and asymptomatic banana and plantain plants in these areas. Samples were tested for BBTV bypolymerase chain reaction (PCR) using primer pairs, mREP-F and mREP-R, which amplifies a 241-bp of BBTVDNA-mRep segment (1), and Scp-F and Scp-R specific for approximately 1075-bp BBTV DNA-S that encodescoat protein gene (1). The amplicons of expected size were obtained from 17 of 90 samples analyzed(18.8%). BBTV in the symptomatic plants was further confirmed by nucleic acid spot hybridization (NASH)assay using DIG-labeled 1,075-bp probe corresponding to coat protein gene and chromogenic detection as perthe previously described protocol (3). The DIG-probe specifically reacted with nucleic acid from thesymptomatic plants, but not with negative controls, providing conclusive evidence for the BBTV. The PCRproducts of DNA-mRep segment amplified from three banana plants infected with BBTV collected in Ilashe(Ipokia Local Government Area) were purified and sequenced in both directions. The sequences of theseisolates were 100% identical with each other (GenBank Accession Nos. JX290301, JX290302, and JX290303).A BLASTn search revealed 100% nucleotide sequence identity with a BBTV isolate from Benin (JQ437548) and99 to 100% identity with DNA-mRep sequences of several other BBTV isolates from Africa, Australia, India,and the South Pacific. Further analysis of the 241-bp mRep gene sequences with Neighbor-Joiningphylogenetic analysis grouped the BBTV isolate with the South Pacific isolates. To our knowledge, this is thefirst report of BBTV in Nigeria. This underscores need for surveys to assess the extent of BBTV spread inNigeria and strict implementation of phytosanitary measures, including restrictions on the movement ofplanting material from disease-affected regions, to prevent further spread of this important disease. ; Peer Review

Maize (Zea mays L.) is a major food and fodder crop cultivated on 1.54 million ha in the Democratic Republic of the Congo (DRC). In December 2013, unusually severe chlorotic mottle symptoms and pale green streaks were observed in local varieties (Mudishi 1 and 2, Bambou, Kasayi, H614, H613, and Mugamba) and exotic varieties (H520, H624, H403, HDK8031, and ZM607) in Beni, Lubero, and Rutshuru territories at 1,015 to 1,748 m elevation in North Kivu Province. Symptoms were prominent on newly emerging leaves that later developed marginal necrosis resembling the symptoms of maize lethal necrosis (MLN), caused by a dual infection of Maize chlorotic mottle virus (MCMV, genus Machlomovirus) and Sugarcane mosaic virus (SCMV, genus Potyvirus). Each of these viruses, but particularly MCMV, is also known to cause severe mosaic and mottling symptoms in maize (4). In January 2014, symptomatic and asymptomatic samples (n = 20) from disease-affected fields in Beni and Lubero provinces were collected for virus testing using Whatman FTA Classic Cards (1) and analyzed for MCMV (2681F: 5?-ATGAGAGCAGTTGGGGAATGCG and 3226R: 5?-CGAATCTACACACACACACTCCAGC) and SCMV (8679F: 5?-GCAATGTCGAAGAAAATGCG and 9595R: 5?-GTCTCTCACCAAGAGACTCGCAGC) by reverse transcription (RT)-PCR (4). Samples were also analyzed for Maize streak virus (MSV, genus Mastrevirus), an endemic virus in DRC, by PCR using MSV specific primers (MSV215-234: CCAAAKDTCAGCTCCTCCG and MSV1770-1792: TTGGVCCGMVGATGTASAG) (3). A DNA product of expected size (~520 bp) resulted only for MCMV in all the symptomatic plant samples. None of the samples tested positive for SCMV or MSV. RT-PCR analyses were performed to ascertain the absence of potyviruses using the degenerate potyvirus primers (CIFor: 5?GGIVVIGTIGGIWSIGGIAARTCIAC and CIRev: 5?ACICCRTTYTCDATDATRTTIGTIGC3?) (2) were also negative. Occurrence of MCMV in symptomatic samples was further confirmed by antigen-coated plate (ACP)-ELISA using anti-MCMV rabbit polyclonal antibodies produced at the Virology Unit, IITA, Ibadan, Nigeria. The RT-PCR product of MCMV was purified and sequenced in both directions (GenBank Accession No. KJ699379). Pairwise comparison of 518 bp nucleotide sequence corresponding to p32 and p37 open reading frames of MCMV by BLASTn search revealed 99.8% nucleotide sequence identity with an MCMV isolate from Kenya (JX286709), 98 to 99% identity with the isolates from China (JQ982468 and KF010583), and 96% identity with the isolates from the United States (X14736 and EU358605). MCMV is a newly emerging virus in Africa, first detected during a severe MLND outbreak in 2011 in Kenya (4). This disease has since become a serious threat to maize production in East Africa. MCMV has been reported in maize from Kenya, Rwanda, Tanzania, and Uganda. To our knowledge, this is the first report of MCMV occurrence in DRC. This finding confirms the further geographic expansion of MCMV and illustrates the need for further studies to identify vectors and also create awareness about the disease and to strengthen surveillance to prevent its further spread in the continent. ; Peer Review

Banana bunchy top virus (BBTV) was first reported from sub-Saharan Africa (SSA) from Democratic Republic of Congo (DRC) in the 1950s, has become invasive and spread into 11 countries in the region. To determine the potential threat of BBTV to the production of bananas and plantains (Musa spp.) in the sub-region, field surveys were conducted for the presence of banana bunchy top disease (BBTD) in the DRC, Angola, Cameroon, Gabon and Malawi. Using the DNA-S and DNA-R segments of the virus genome, the genetic diversity of BBTV isolates was also determined from these countries relative to virus isolates across the banana-growing regions around the world. The results established that BBTD is widely prevalent in all parts of DRC, Malawi, Angola and Gabon, in south and western part of Cameroon. Analysis of the nucleotide sequences of DNA-S and DNA-R indicate that BBTV isolates from these countries are genetically identical forming a unique clade within the 'South Pacific' phylogroup that includes isolates from Australia, Egypt, South Asia and South Pacific. These results imply that farmers' traditional practice of transferring vegetative propagules within and between countries, together with virus spread by the widely prevalent banana aphid vector, Pentalonia nigronervosa, could have contributed to the geographic expansion of BBTV in SSA. The results provided a baseline to explore sanitary measures and other 'clean' plant programs for sustainable management of BBTV and its vector in regions where the disease has already been established and prevent the spread of the virus to as yet unaffected regions in SSA. ; United States Agency for International Development ; Peer Review

First published: 11 March 2009 ; Cassava mosaic disease (CMD) is the major production constraint oncassava (Manihot esculenta) in Angola. Previous reports derived fromsingle samples recorded the presence of African cassava mosaic virus(ACMV) and East African cassava mosaic virus (EACMV) in Angola.Regional CMD monitoring initiatives have predicted the spread intonorthern Angola of EACMV-Uganda (-UG), the unusually virulent(aggressive) recombinant strain associated with the African CMDpandemic (Legg et al., 2006). In view of this threat, an assessment surveywas conducted in north and central Angola in April 2008.Eighteen cassava fields were sampled in Bengo, Cuanza Norte, Malanjeand Uige Provinces. Moderate to severe CMD symptoms were observed inmost fields. Sixty-three of 65 samples obtained from these fields testedpositive in TAS-ELISA using monoclonal antibody SCR 20. PCR wasperformed using primer pairs previously described for the specificidentification of ACMV, EACMV, EACMV-UG, East African cassavamosaic Cameroon virus (EACMCV) and Indian cassava mosaic virus(ICMV) (Ogbe et al., 2003), East African cassava mosaic Malawi virus(EACMMV) (Zhou et al., 1998), East African cassava mosaic Zanzibarvirus (EACMZV) (Were et al., 2004) and South African cassava mosaicvirus (SACMV) in mixed infections. This revealed the occurrence ofACMV, EACMV and EACMV-UG, but not EACMZV, EACMMV,SACMV or ICMV. Single infections of ACMV and EACMV were detectedin 32·3 and 9% of samples, respectively. Mixed infections of ACMV withEACMV, EACMV with EACMV-UG and all three viruses were detectedin 35·3, 1·5 and 16·9% of samples, respectively. ACMV, detected in 84·6%of samples, was the predominant species, followed by EACMV (63%) andEACMV-UG (18·5%). Significantly, EACMV-UG occurred mostfrequently in the northernmost part of the surveyed area (Uige Province)immediately to the south of the Bas Congo region of the DemocraticRepublic of Congo, already known to be affected by the pandemic. Thesefindings significantly broaden the known geographical extent of the CMDpandemic and draw attention to the urgent need for the large-scale deploy-ment of resistant cassava varieties, which have been used to reduce lossesin pandemic-affected regions of East Africa. ; Peer Review

Open Access Article; Published online: 27 Sep 2021 ; Banana (including plantain; Musa spp.) is an important vegetatively propagated food staple grown as a semi-perennial crop in fields and backyard gardens in Tanzania. Banana bunchy top disease (BBTD), caused by the banana bunchy top virus (BBTV, genus Babuvirus), is the most economically important viral disease of banana, infection of which results in severe stunting and reduction in fruit production by 90-100% within two seasons. The virus is spread by the banana aphid, Pentalonia nigronervosa, and through vegetative propagation of infected sources. BBTV is an introduced virus first reported in sub-Saharan Africa (SSA) in the 1960s in the Democratic Republic of Congo. Since then, BBTV spread was confirmed in 15 countries in Central, Southern, and Western African regions but was not detected in any previous surveys in the East African sub-region. During banana pests and disease surveys conducted in December 2020 – January 2021 in Buhigwe District in the Kigoma Region of Tanzania revealed banana plants with typical BBTV symptoms (severe stunting, leaves with shortened petioles, chlorotic streaks, and yellow leaf margins) in several banana fields in Muhinda (lon. 29.78662, lat. -4.53672) and Mwayaya (lon. 29.8218, lat. -4.49203) villages. Most of the affected plantations were 5 to 15 years old. Leaf samples (N=21) from symptomatic (N=6) and asymptomatic (N=15) banana plants were collected and used for total DNA extraction and BBTV detection by polymerase chain reaction (PCR) using the primer pair BBTV-1 and BBTV-2 to amplify ~240 bp sequence of DNA-R encoding for core master replication initiator protein gene. All samples from symptomatic plants tested positive and asymptomatic plants were negative. To further confirm the virus identity, four samples, each from symptomatic (PCR positive) and asymptomatic (PCR negative) plants from Muhinda and Mwayaya villages, were tested by Triple Antibody Sandwich-Enzyme-linked Immunosorbent Assay (TAS-ELISA) using BBTV ELISA reagent set (Cat. # SRA24700-1000, Agdia, France) following the manufacturer's protocol. Samples from symptomatic plants reacted positively in TAS-ELISA, and asymptomatic plants were negative. The 240-bp PCR product of two isolates was purified, and both strands were sequenced. A BLAST search of the nucleotide sequences (NCBI GenBank Acc.# MW711671 and MW711672) revealed 99% identity with DNA-R sequences of several other BBTV isolates from Africa (Acc. No# JF755994). Further analysis of the 240-bp nucleotide sequences with Maximum-likelihood phylogenetic analysis using MEGA-X software has grouped the two BBTV sequence isolates with the SSA sub-clade of the South-Pacific group. To our knowledge, this is the first report of BBTV infecting bananas in Tanzania, and East Africa endowed with rich banana diversity and popular East African Highland banana clone. BBTV presents a new threat to banana production in this sub-region due to the high risk of further spread through vegetative propagation, traditional planting material exchange practices, and the ubiquitous banana aphid vector. This study warrants delimitation surveys to assess the extent of spread, with simultaneous efforts to raise awareness about BBTD recognition and control measures among banana growers, including eradicating infected mats and replanting with healthy planting material to recover banana production.

Banana bunchy top disease (BBTD), an invasive and devastating viral disease, is widespread in banana-producing areas in Sub-Saharan Africa. Recovery of banana production in BBTD-affected areas was undertaken in a research project through the CGIAR Research Program on Roots, Tubers and Bananas (CRP-RTB) in eight countries. Understanding household and community dynamics is vital to recovery because decision-making on banana production and resource allocation occur at household level, while opportunity structures for men and women to engage in such work are influenced by social norms expressed both at household and community levels. Studies were undertaken to understand gender norms, practices and experiences in intra- and inter household and community dynamics related to banana farming in BBTD-affected areas. A standardized methodology was applied in all sites including household survey, gender seasonal calendar, daily activity schedule and a community profile. Results from analysis of four cases studies from Burundi, Gabon, Democratic Republic of Congo (DRC) and Nigeria indicated that banana is an important crop for both female and male farmers in all pilot sites and considered as both a staple food and a source of income. Men, women and male and female children are all involved in different banana production activities at household level; some mostly done by men assisted by male children (land preparation in DRC (95%), Nigeria (83%), Gabon (82.5%) and Burundi (64%)) while others are mostly done by women assisted by female children (watering, weeding in Kisangani (87%)). Men and women have differential use, control and ownership rights to different types of productive resources within the household which have implications for effective BBTD control and the benefits derived. Insights from the study will be used to develop guidelines for the incorporation of gender-responsive strategies into the design and implementation of BBTD control strategies. ; Peer Review

Published online: 07 Apr 2022 ; Cassava is an important crop in sub-Saharan Africa for food security, income generation, and industrial development. Business-oriented production systems require reliable supplies of high-quality seed. Major initiatives in Nigeria and Tanzania have sought to establish sustainable cassava seed systems. These include the deployment of new technologies for early generation seed (EGS) production; the promotion of new high-yielding and disease-resistant varieties; the updating of government seed policy to facilitate enabling certification guidelines; the application of ICT tools, Seed Tracker and Nuru AI, to simplify seed system management; and the establishment of networks of cassava seed entrepreneurs (CSEs). CSEs have been able to make profits in both Nigeria (US$ 551–988/ha) and Tanzania (US$1,000 1,500/ha). In Nigeria, the critical demand driver for cassava seed businesses is the provision of new varieties. Contrastingly, in Tanzania, high incidences of cassava brown streak disease mean that there is a strong demand for the provision of healthy seed that has been certified by regulators. These models for sustainable cassava seed system development offer great promise for scaling to other cassava-producing countries in Africa where there is strong government support for the commercialization of the cassava sector.

Published Online:17 Aug 2021 ; Cassava plays a key role in ensuring food security and generating income for smallholder farmers throughout Central Africa, particularly in the Democratic Republic of Congo (DRC). This status is threatened, however, by cassava brown streak disease (CBSD), which has expanded its incidence and range in eastern DRC. The study described here comprises the first extensive assessment of temporal change in the occurrence of CBSD and its causal viruses in DRC, based on surveys conducted during 2016 and 2018. Cassava fields were inspected in Ituri, Nord-Kivu, Sud-Kivu, Tanganyika, and Haut-Katanga provinces within eastern DRC to record foliar incidence and severity of CBSD. Leaf samples were collected for virus detection and species-level identification. New occurrences of CBSD, confirmed by virus diagnostic tests, were recorded in two provinces (Haut-Katanga and Sud-Kivu) and nine previously unaffected territories, covering an area of >62,000 km2, and at up to 900 km from locations of previously published reports of CBSD in DRC. Overall, average CBSD incidence within fields was 13.2% in 2016 and 16.1% in 2018. In the new spread zone of Haut-Katanga, incidence increased from 1.7 to 15.9%. CBSD is now present in provinces covering 321,000 km2, which is approximately 14% of the total area of DRC. This represents a major expansion of the CBSD epidemic, which was only recorded from one province (Nord-Kivu) in 2012. Both Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus were detected in Ituri, Nord-Kivu, and Sud-Kivu, but only CBSV was detected in Haut-Katanga. Overall, these results confirm the increasing threat that CBSD poses to cassava production in DRC and describe an important expansion in the African pandemic of CBSD.