Africa Rice Center

Cotonou, Benin

Africa Rice Center

Cotonou, Benin

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Demont M.,Africa Rice Center | Demont M.,International Rice Research Institute
Global Food Security | Year: 2013

Economic development in poor countries is often hampered by urban bias. Partly as a result of historical urban bias, African countries have become heavily dependent on food imports with concomitant risks for food security as witnessed during the 2008 food crisis. African governments now recognize that they should reverse urban bias by investing in agriculture in order to decrease food import dependency. However, they typically focus primarily on supply-shifting investments that may be insufficient to render domestically produced food competitive, particularly in import-biased food markets. We review the national rice development investment strategies of 19 African countries and argue that in order to reverse urban bias in African rice markets, more resources will need to be allocated to value-adding and demand-lifting investments. © 2013 Elsevier B.V.


Rodenburg J.,Africa Rice Center | Bastiaans L.,Wageningen University
Weed Research | Year: 2011

Parasitic weeds of the genus Striga cause high yield losses in cereal crops across Africa. Host-plant defence against Striga spp. can be an effective control strategy. It ideally consists of resistance, to reduce infection, complemented with tolerance, to mitigate the effects of infection. As resistance against Striga spp. can both minimise yield losses and reduce future infestation levels in infested fields, current breeding efforts are mainly directed towards this trait. Because it is nearly impossible to screen for tolerance on highly resistant genetic lines, tolerance is often neglected. Here, we argue reconsidering the role of tolerance, as recent findings regarding the physiological expression of tolerance offer a promising track for identifying the genetic background of tolerance. Identification of quantitative trait loci for tolerance would facilitate the inclusion of this trait in adapted cultivars with high levels of resistance, where its main role would be to function as a safety net in case the genetically highly variable parasite populations overcome host-plant resistance. Because Striga spp. are mainly prevalent in subsistence farming systems, we consider this an important addition and it is for this reason that we make a plea for a more prominent role of tolerance in present-day integrated management of this weed. © 2011 The Authors. Weed Research © 2011 European Weed Research Society.


Improving rice (Oryza spp.) competitiveness against weeds would provide a low-cost and safe tool for an integrated weed management strategy. This paper addresses the underlying causes of tradeoff between yield without weed competition and weed competitiveness. Rice yield or weed biomass under weedy conditions are used as indicators of weed competitiveness. For this analysis, a common database was compiled from the results of 45 concurrent field trials comparing the performance of four to 64 genotypes in weed-free and weedy conditions in Asia, West Africa, North America and Latin America. Cyperus spp., Echinochloa spp. and Eleusine indica were the most frequent dominant weed species, being found in 9, 20 and 7 trials, respectively. Mean relative yield reduction [(yield under weed-free conditions - yield under weedy conditions)/yield under weed-free conditions] across genotypes tested for each trial was defined as weed pressure level. Mean yield without weed competition across genotypes ranged from 1.8 to 11.6 t ha -1 with mean relative yield reduction from almost 0 to 91%. Correlations for rice yield between weed-free and weedy conditions were generally positive, and significant in 27 trials. The correlations were related to weed pressure level and dominant weed species, but not to ecosystem (upland or lowland) or yield level under weed-free conditions. Relative yield reduction had a more pronounced effect than dominant weed species. Correlation decreased as weed pressure level increased, and became negative when relative yield reduction exceeded 80%, suggesting that different morpho-physiological mechanisms are responsible for high yields under weed-free conditions or severe weed competition. Correlations between rice yield under weed-free conditions and weed biomass varied, giving 17 and 19 for positive and negative ones, respectively. These correlations were related neither to weed pressure level, ecosystem and yield level under weed-free conditions, nor to dominant weed species. These results indicate that correlations between rice yields under weed-free and weedy conditions can be strongly affected by weed pressure level, and, unless severe weed competition occurs, there appears to be no tradeoff between them. Association of morpho-physiological mechanisms with weed competitiveness under conditions differing in weed pressure levels and dominant weed species deserves further investigation. © 2010 Elsevier B.V. All rights reserved.


Saito K.,Africa Rice Center | Futakuchi K.,Africa Rice Center
Field Crops Research | Year: 2014

Ideal weed-competitive rice (. Oryza sp.) varieties are high yielding under both weed-free and weedy conditions, and have strong weed-suppressive ability (WSA). WSA is the ability to suppress weed growth and reduce weed seed production, benefiting weed management in both the current and the subsequent growing seasons. WSA is determined by assessing weed biomass under weedy conditions. However, natural weed growth in field conditions is heterogeneous, resulting in high experimental error in phenotyping studies. Using crops as substitute weeds is one approach for improving the accuracy of estimation of WSA. Four upland-rice experiments were conducted using 14 diverse varieties in Benin between 2009 and 2011 to examine if the use of substitute weeds can improve estimation of WSA, and help identify varieties with strong WSA. Two rice varieties (Aus 257, which was also included in 14 varieties tested, and IR 1552, a purple-leaved rice) and cowpea (cv. KVx396-18) were tested as substitute weeds, and compared with natural weed infestation. At 50-62 days after rice sowing, weed biomass (weeds, rice or cowpea) were measured as an indicator of WSA. While WSA was more heritable in plots with substitute weeds than with natural weed infestation, there was no large difference in heritability among substitute weeds. In only one of the four experiments was the effect of variety on WSA not consistent between substitute weeds and natural weeds. But in this experiment, Aus 257 consistently showed strong WSA in both plots with substitute weeds and plots with natural weed infestation. Superior WSA of Aus 257 was also observed in the other experiments, and associated with higher biomass accumulation. These results indicate that the use of substitute weeds can offer an efficient selection approach for improving weed-suppressive ability of upland rice. Aus 257 can be used as donor for developing varieties with strong weed-suppressive ability. © 2014.


Demont M.,Africa Rice Center | Rizzotto A.C.,Africa Rice Center
Development Policy Review | Year: 2012

In response to the world food crisis in 2008, Senegal developed a productivist national food self-sufficiency programme. However, the critical question is not whether the programme can meet its ambitious target of self-sufficiency in rice production by 2015, but, if it does, how will domestic rice reach urban markets, where consumers generally prefer imported rice for its superior grain quality. Information collected through interviews and a stakeholder workshop advances the argument that policy sequencing will be crucial in order to upgrade Senegalese rice value chains progressively. Any large-scale investments in productivity will need to be preceded by investments in post-harvest grain-quality infrastructure before sector-wide marketing strategies can be adopted that enhance the chain competitiveness of domestic relative to imported rice. © The Authors 2012. Development Policy Review © 2012 Overseas Development Institute.


Demont M.,Africa Rice Center | Demont M.,International Rice Research Institute | Stein A.J.,International Food Policy Research Institute
New Biotechnology | Year: 2013

Unlike the other major crops, no genetically modified (GM) varieties of rice have been commercialized at a large scale. Within the next 2-3 years new transgenic rice varieties could be ready for regulatory approval and subsequent commercialization, though. Given the importance of rice as staple crop for many of the world's poorest people, this will have implications for the alleviation of poverty, hunger and malnutrition. Thus, policy-makers need to be aware of the potential benefits of GM rice. We provide an overview of the literature and discuss the evidence on expected agronomic and consumer benefits of genetically engineered rice. We find that while GM rice with improved agronomic traits could deliver benefits similar to already commercialized biotechnology crops, expected benefits of consumer traits could be higher by an order of magnitude. By aggregating the expected annual benefits, we estimate the global value of GM rice to be US$64 billion per year. This is only an indicative value, as more GM varieties will become available in future. Nevertheless, such a figure can help guide policy-makers when deciding on the approval or funding of biotechnology crops and it may also raise awareness among consumers about what is at stake for their societies. © 2013 Elsevier B.V..


Saito K.,Africa Rice Center | Azoma K.,Africa Rice Center | Rodenburg J.,Africa Rice Center
Field Crops Research | Year: 2010

Weeds are a major constraint to rice (Oryza spp.) production in West Africa. Superior weed competitive rice genotypes may reduce weed pressure and improve rice productivity. Two upland and two lowland experiments were conducted in southern Benin to examine genotypic variations in weed-suppressive ability and grain yield under weedy conditions, and to identify plant characteristics that could be used as selection criteria for improved weed competitiveness. A total of 19 genotypes, including Oryza sativa and Oryza glaberrima genotypes and interspecific hybrids developed from crossing O. sativa and O. glaberrima, were grown under weed-free and weedy conditions in an upland with supplemental irrigation and in a flooded lowland. In weedy plots, hand weeding was done once or not at all. Mean relative yield loss across all genotypes due to weed competition ranged from almost 0% to 61%. Large genotypic variations in weed biomass and grain yield under weedy conditions were found. Visual growth vigor at 42 and 63 days after sowing (DAS) under weed-free conditions significantly correlated with weed biomass at maturity in both upland and lowland experiments (R2 = 0.26-0.48). Where weed pressure was low to moderate, with mean relative yield loss less than 23%, the multiple regression models using grain yield and plant height at maturity or only grain yield measured under weed-free conditions as independent variables could explain 66-88% of the genotypic variation in grain yield under weedy conditions. At higher weed pressure (mean relative yield loss: 61%), as observed in one of the upland experiments, biomass accumulation of rice at 42 days after sowing was associated with higher grain yield under weedy conditions. Biomass accumulation also significantly correlated with visual growth vigor at the same sampling dates. Therefore, we conclude that grain yield, plant height at maturity and visual growth vigor at 42-63 DAS under weed-free conditions appear to be useful selection criteria for developing superior weed competitive rice genotypes. © 2010 Elsevier B.V. All rights reserved.


In West Africa, upland rice (Oryza spp.) is mainly grown in low-input systems by resource-poor farmers. Weeds are one of the major constraints to rice production. Ideal rice varieties are high-yielding with strong weed-suppressive ability (WSA). WSA is the ability to suppress weed growth and reduce weed seed production and is determined by assessing weed biomass under weedy conditions. Development of such varieties requires simple screening protocols based on highly heritable traits, which can be evaluated in small plots under weed-free conditions. Then, in later stages of the breeding program, selected breeding lines could be evaluated with substitute weeds instead of natural weeds, as natural weed growth is heterogeneous. To develop such a protocol, I evaluated agronomic traits of 10 diverse rice varieties grown in plots with different numbers of rows (unbordered 1-row and 2-row, and self-bordered 4-row, in which the middle 2-rows were sampled) without weed competition and evaluated weed biomass of these varieties under competition with rice and cowpea as substitute weeds. I then examined whether agronomic traits in unbordered plots can predict yield and weed biomass in self-bordered plots. Broad-sense heritabilities of agronomic traits measured in weed-free conditions and weed biomass under weedy conditions were estimated. Among agronomic traits in unbordered plots, yield was positively correlated with yield in self-bordered plots (r= 0.88 and 0.96 in 1-row and 2-row plots, respectively, P< 0.01). Weed biomass estimated in competition with two rice varieties was more heritable than weed biomass in competition with cowpea. In 1-row plots, growth vigor at 63 days after sowing (DAS), total aboveground biomass at harvest, and yield were related to weed biomass in competition with cowpea and rice variety Aus 257. Growth vigor at 42 and 63 DAS was a reliable estimator for total aboveground biomass and number of panicles at harvest, as well as integrated information on height and number of stems (height multiplied by number of stems). I suggest that growth vigor at 42-63 DAS in unbordered, 1-row plots appears to be a useful selection criterion for developing high-yielding varieties with superior WSA, and WSA of selected varieties can be validated using rice varieties as substitute weeds. Future research is needed to validate this protocol with breeding populations, a wide range of genetic materials, and other important weed species in West Africa before it can be implemented in breeding programs. © 2014 Elsevier B.V.


Abe S.S.,Africa Rice Center | Wakatsuki T.,Kinki University
Pedobiologia | Year: 2010

There has been less concern about soil mineralogical alteration than about soil physical, chemical and biological changes induced by termite nest-building activity. Furthermore, much less attention has been paid to free sesquioxides than to phyllosilicate minerals. In the present study, we conducted field morphological observations and selective dissolution analysis to characterize free sesquioxides in termite (Macrotermes bellicosus) mounds as compared with surrounding pedons in different toposequence positions, i.e., seasonally flooded valley bottom, hydromorphic fringe and well-drained upland sites. Distinctive redoximorphic features, such as surface yellowish layers on mound structures from the fringe site, indicate possible alteration of iron sesquioxide forms in the mounds due to the transportation of soil from reductive (aquic subsoil) to oxidative (epigeal mound) environments by the nest-building activity of M. bellicosus. On the other hand, the iron-soluble content in the dithionite-citrate-bicarbonate (DCB) system (Fed) was generally higher in the mound structures than at the adjacent sub-surface (Ap2) horizon at each toposequence position, while there was less difference in the content of acid ammonium oxalate (AAO) extractable iron (Feo) as compared to Fed. As a consequence, the iron activity index (Fed/Feo ratio) was found for the most part to be lower in the mound structures than in the neighboring Ap2 horizon. In addition, the content of Fed, AAO-soluble Al (Alo) and DCB-extractable Al (Ald) was significantly correlated with clay content in these soils. These findings suggest that M. bellicosus preferentially collects clay particles, probably from the clay-rich subsoils, such as the argillic horizon, which has been formed by the co-migration of phyllosilicate minerals and relatively crystalline sesquioxides. The species then likely incorporates them into the mounds, which induces an increase in the Fed content relative to that of Feo, resulting in a decreased iron activity index in the mound structures. © 2010 Elsevier GmbH.


News Article | December 12, 2016
Site: www.eurekalert.org

Lincoln, Nebraska, Dec. 12, 2016 - Maximizing cereal crops yields in sub-Saharan Africa would still fail to meet the region's skyrocketing grain demand by 2050, according to a new study from the University of Nebraska-Lincoln, Wageningen University and multiple African institutions. Sub-Saharan Africa produces about 80 percent of the grain it now consumes. But that consumption could triple if its population rises an expected 250 percent by 2050. Presently, cereal crops account for about half of sub-Saharan Africa's food and farmland. Even if sub-Saharan yields continue rising at the rate they have over the last quarter-century, the region's existing farmland would still produce only between a third and half of the grain needed in 2050, researchers reported Dec. 12 in Proceedings of the National Academy of Sciences. "The status quo is simply not acceptable," said co-author Ken Cassman, professor emeritus at Nebraska and fellow of the Daugherty Water for Food Global Institute. "Complacency is the enemy. This is a clarion call for action."To maintain even 80 percent of its self-sufficiency in 2050, sub-Saharan Africa must reach the realistic yield thresholds of corn, millet, rice, sorghum and wheat, the study found. The region currently grows about a quarter of the cereal crops it could by optimizing its plant and soil management, the authors said. Closing this gap would require what the study called a "large, abrupt acceleration" in yield trajectories similar to the Green Revolution that transformed North American, European and Asian agriculture in the mid-20th century. "But our analysis shows that even closing the gap between potential yields using modern farming practices and current farm yields, with traditional crop varieties and little fertilizer, still leaves the area at a deficit with regard to cereals," Cassman said. "That's quite eye-opening, because my guess is that most people in the agricultural development community might have thought sub-Saharan Africa could be self-sufficient, or even produce excess cereal, if it were able to close existing yield gaps."The authors analyzed 10 sub-Saharan countries using the Global Yield Gap Atlas, which estimates the disparity between actual and potential yields while accounting for differences in soil types and climate. After assembling location-specific data and assessments from agronomists in each of the 10 countries, the team used a novel upscaling technique to estimate yield gaps at national and sub-continental levels. Meeting future cereal demands could depend on expanding responsible irrigation use to raise yield ceilings and stabilize cereal production, said Kindie Tesfaye, agronomist with the International Maize and Wheat Improvement Centre in Ethiopia. Recent analyses have documented regional aquifers that could become sources of sustainable irrigation, though the authors emphasized the importance of withdrawing only what can be replenished by rainfall and recharge. Tesfaye said irrigation could ramp up yield thresholds by allowing farmers to annually grow a crop multiple times in the same field or introduce new cereals into yearly planting schedules. Patricio Grassini, assistant professor of agronomy and horticulture at Nebraska, stressed that these efforts will require "massive and strategic investments in agricultural development on an unprecedented level." Combining the yield gap findings with socioeconomic and other data, Grassini said, could inform essential upgrades to infrastructure that might include roads and water pipelines; publicly financed research and development; and farmer access to credit, state-of-the-art equipment and pest-management resources. A failure to upgrade could force sub-Saharan Africa to transform savannahs, rainforests or other natural ecosystems into farmland - a process, the study noted, that would produce massive amounts of greenhouse gases while shrinking the habitats of native plant and animal species. If yield growth and cropland distribution remained constant across the 10 countries, seven would lack the land area to accommodate such expansion, said Abdullahi Bala, professor at Nigeria's Federal University of Technology, Minna. And the newly converted land would very likely prove less fertile than the region's current farmland, Cassman said. Though the region might also resort to importing cereal crops, the authors cautioned that many of the developing countries in sub-Saharan Africa could struggle to do so. The price spikes that often accompany drought-driven market shortages could further complicate matters. "If it is true that sub-Saharan Africa will depend more heavily on food imports," Grassini said, "the next question is: What would be the infrastructure networks needed to alleviate food shortages in the most vulnerable areas?" The researchers said several sub-Saharan countries may produce surpluses that could be shared among neighbors. Though the projected surpluses would fall short of compensating for neighboring deficits,this represents one of several opportunities the region might seize to contend with the profound challenges ahead. "To reach those goals is going to take very strategic, careful prioritization and adequate resources to do the job," Cassman said. "Having a strategic vision of what to invest in - to fund those things that can give greatest payoff - is critical. What this work does is allow for a much more surgical look at how to do that, which just wasn't possible before." The Daugherty Water for Food Global Institute, the Bill and Melinda Gates Foundation, USAID and the university supported the development of the Global Yield Gap Atlas, which agronomists at Nebraska and Wageningen created in 2011. The new study was co-authored by agronomists at the International Crops Research Institute for the Semi-Arid Tropics (Kenya); International Food Policy Research Institute; Africa Rice Center (Benin); Jomo Kenyatta University of Agriculture and Technology (Kenya); International Institute of Tropical Agriculture (Ghana); AGRHYMET Regional Centre (Niger); Federal University of Technology, Minna (Nigeria); University of Zimbabwe; National Agricultural Research Laboratories (Uganda); Institute of Rural Economy (Mali); Ministry of Agriculture Food and Cooperatives (Tanzania); Environmental and Agricultural Research Institute (Burkina Faso); and the International Maize and Wheat Improvement Centre (Ethiopia).

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