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Oyo, Nigeria

Karasev A.V.,University of Idaho | Nikolaeva O.V.,University of Idaho | Hu X.,University of Idaho | Sielaff Z.,University of Idaho | And 3 more authors.
American Journal of Potato Research

In the course of a multi-year survey of Potato virus Y (PVY) incidence and diversity in the U. S. seed potato crop, an unusual PVY variant was identified in low but significant levels in multiple states. This variant, PVYO-O5, was initially detected by a commercially available PVYN-specific monoclonal antibody, 1F5. This antibody is widely used by U. S. Seed Certification programs to test for PVYN and is one of two antibodies designated by the North American Plant Protection Organization (NAPPO) for pre-shipment testing of tuber lots that are to be transported between countries. Consequently, PVYN positives identified by the 1F5 antibody have triggered quarantine actions, prevented cross-border shipments and impacted trade. Here, we demonstrate by a variety of methods that the PVYO-O5 is a variant within the ordinary PVY strain (PVYO). Specifically, the PVYO-O5 variant likely arose due to a single amino acid substitution within the capsid protein. This variant does not induce vein necrosis in tobacco or tuber necrosis in susceptible varieties of potato. Furthermore, it is identified by RT-PCR based diagnostics as PVYO and it has a typical PVYO genome sequence. We demonstrate that another PVYN specific monoclonal antibody, SASA-N, recognizes an epitope distinct from that recognized by 1F5, and correctly identifies the PVYO-O5 variants as belonging to the PVYO serotype. Since the PVYO-O5 variant is present in many seed producing states and misidentification of PVYO-O5 as PVYN/NTN has clear quarantine implications for export shipments of potato, the limitations of the commercially available monoclonal antibodies should be considered in any certification or phytosanitary testing program. © Potato Association of America 2009. Source

Kumar P.L.,International Institute Of Tropical Agriculture | Selvarajan R.,National Research Center for Banana | Iskra-Caruana M.-L.,CIRAD - Agricultural Research for Development | Chabannes M.,CIRAD - Agricultural Research for Development | Hanna R.,IITA
Advances in Virus Research

Banana and plantain (Musa spp.), produced in 10.3 million ha in the tropics, are among the world's top 10 food crops. They are vegetatively propagated using suckers or tissue culture plants and grown almost as perennial plantations. These are prone to the accumulation of pests and pathogens, especially viruses which contribute to yield reduction and are also barriers to the international exchange of germplasm. The most economically important viruses of banana and plantain are Banana bunchy top virus (BBTV), a complex of banana streak viruses (BSVs) and Banana bract mosaic virus (BBrMV). BBTV is known to cause the most serious economic losses in the "Old World," contributing to a yield reduction of up to 100% and responsible for a dramatic reduction in cropping area. The BSVs exist as episomal and endogenous forms are known to be worldwide in distribution. In India and the Philippines, BBrMV is known to be economically important but recently the virus was discovered in Colombia and Costa Rica, thus signaling its spread into the "New World." Banana and plantain are also known to be susceptible to five other viruses of minor significance, such as Abaca mosaic virus, Abaca bunchy top virus, Banana mild mosaic virus, Banana virus X, and Cucumber mosaic virus. Studies over the past 100 years have contributed to important knowledge on disease biology, distribution, and spread. Research during the last 25 years have led to a better understanding of the virus-vector-host interactions, virus diversity, disease etiology, and epidemiology. In addition, new diagnostic tools were developed which were used for surveillance and the certification of planting material. Due to a lack of durable host resistance in the Musa spp., phytosanitary measures and the use of virus-free planting material are the major methods of virus control. The state of knowledge on BBTV, BBrMV, and BSVs, and other minor viruses, disease spread, and control are summarized in this review. © 2015 Elsevier Inc. Source

Lambrecht I.,Ghana Food Research Institute | Vanlauwe B.,IITA | Maertens M.,Catholic University of Leuven
International Journal of Agricultural Sustainability

Many paradigms on sustainable agricultural intensification promote a combination of different agricultural technologies. Whether such a paradigm survives in practice depends on how farmers combine these technologies on their fields. We focus on integrated soil fertility management (ISFM) and investigate how the concept is put into practice in South-Kivu, Eastern DR Congo. ISFM includes the use of improved germplasm, organic inputs and mineral fertilizer, and emphasizes the complementarities and synergies that arise when technologies are jointly applied. We investigate whether different ISFM components are applied jointly, sequentially or independently, and whether that matters for the long-term use of the technology. We use original survey data from 420 farms, and combine a descriptive statistical analysis and a factor analysis. We find that few farmers in the area have reached ‘full ISFM’, and technology application occurs sequentially rather than simultaneously. Two technology subsets can be distinguished: more resource-intensive and less resource-intensive technologies. These subsets behave as supplements rather than as complements, and adoption within and among each subset is more sequential than simultaneous. Our results imply that there is a disconnect between the theoretical arguments in the agronomic ISFM literature, and the actual patterns of ISFM application on farmers’ fields. © 2015 Taylor & Francis. Source

Valbuena D.,Systemwide Livestock Programme | Erenstein O.,CIMMYT | Homann-Kee Tui S.,ICRISAT | Abdoulaye T.,IITA | And 9 more authors.
Field Crops Research

Conservation Agriculture (CA) is being advocated to enhance soil health and sustain long term crop productivity in the developing world. One of CA's key principles is the maintenance of soil cover often by retaining a proportion of crop residues on the field as mulch. Yet smallholder crop-livestock systems across Africa and Asia face trade-offs among various options for crop residue use. Knowledge of the potential trade-offs of leaving more residues as mulch is only partial and the objective of this research is to address some of these knowledge gaps by assessing the trade-offs in contrasting settings with mixed crop-livestock systems. The paper draws from village surveys in 12 sites in 9 different countries across Sub-Sahara Africa and South Asia. Sites were clustered into 3 groups along the combined population and livestock density gradients to assess current crop residue management practices and explore potential challenges to adopting mulching practices in different circumstances. Results show that although high-density sites face higher potential pressure on resources on an area basis, biomass production tends to be more substantial in these sites covering demands for livestock feed and allowing part of the residues to be used as mulch. In medium-density sites, although population and livestock densities are relatively lower, biomass is scarce and pressure on land and feed are high, increasing the pressure on crop residues and their opportunity cost as mulch. In low-density areas, population and livestock densities are relatively low and communal feed and fuel resources exist, resulting in lower potential pressure on residues on an area basis. Yet, biomass production is low and farmers largely rely on crop residues to feed livestock during the long dry season, implying substantial opportunity costs to their use as mulch. Despite its potential benefit for smallholder farmers across the density gradient, the introduction of CA-based mulching practices appears potentially easier in sites where biomass production is high enough to fulfil existing demands for feed and fuel. In sites with relatively high feed and fuel pressure, the eventual introduction of CA needs complementary research and development efforts to increase biomass production and/or develop alternative sources to alleviate the opportunity costs of leaving some crop residues as mulch. © 2012 Elsevier B.V. Source

Chikoye D.,International Institute Of Tropical Agriculture | Abaidoo R.,IITA | Fontem L.A.,University of Buea
Crop Protection

Herbicides applied to combat weeds and increase crop yields may also have undesired effects on beneficial soil microorganisms. Field studies were conducted in 2005 and 2006 in Zaria, Nigeria, to evaluate the response of weeds and soil microorganisms to imazaquin applied at 0.05, 0.10, 0.20 and 0.40kga.i./ha and pendimethalin applied at 1.0, 2.0, 4.0, and 8.0kga.i./ha in cowpea and soybean. Hoe-weeded and unweeded (no herbicide) plots were controls. Both herbicides significantly reduced weed biomass in both crops, when compared to the unweeded control, which had the highest weed biomass at all sampling dates. Treatments with 0.40kga.i./ha of imazaquin, 2.0 and 4.0kga.i./ha of pendimethalin, and the hoe-weeded control, had the highest cowpea grain yield. The unweeded control had the lowest grain yield which was comparable to that in all other herbicide treatments. All treatments except 4.0 and 8.0kga.i./ha of pendimethalin had higher soybean grain yield than the unweeded control. Soybean yield was lowest in the unweeded control, and treatments that received 4.0 and 8.0kga.i./ha of pendimethalin. All rates of imazaquin gave similar soybean grain yields that were 29-41% higher than that from pendimethalin. The hoe-weeded control had the highest yield, which was 79% more than that in the unweeded control. Higher rates of imazaquin and pendimethalin reduced nodulation, nitrogen fixation, and vesicular arbuscular mycorrhizal (VAM) fungi colonisation in both crops. VAM fungi species diversity and species richness in cowpea rhizosphere soil and species diversity in soybean rhizosphere soil were reduced relative to the controls due to application of both herbicides with the rates of 0.10, 0.20, and 0.40kga.i./ha of imazaquin and 8.0kga.i./ha of pendimethalin being significantly effective. © 2014 Elsevier Ltd. Source

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