Resistance of Tripsacorn to Sitophilus zeamais and Oryzaephilus surinamensis

One strategy that has been used to find germplasm for developing improved plant varieties is to test ancestral germplasm for the desired traits. Although the progenitors of commercial maize are not known, a hybrid (called Tripsacorn) developed from a perennial teosinte, Zea diploperennis, and eastern gamagrass, Tripsacum dactyloides, resembles the earliest known samples of primitive domesticated maize. We tested resistance of whole Tripsacorn to the primary storage pest (primary storage pests can infest intact kernels) the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), and resistance of ground Tripsacorn to the secondary storage pest (secondary pests usually cannot infest intact kernels) the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae). Tripsacorn was immune to attack by S. zeamais. The weevils were unable to lay eggs in the Tripsacorn, and we hypothesized that the hardness of the fruitcase was responsible for lack of weevil oviposition. Oryzaephilus surinamensis were able to complete immature development on ground Tripsacorn, but duration of development was longer and weight of emerged adults was less than for beetles developing on wheat. Hardness of the fruitcase may have been a primitive mechanism of defense against insects and other pests, but probably would not be an acceptable trait in commercial varieties. It remains to be determined whether the possible antibiotic effect demonstrated in ground Tripsacorn would be a useful trait in commercial maize hybrids.     

Synergistic effects of insect-resistant maize and Teretrius nigrescens on the reduction of grain losses caused by Prostephanus truncatus (Horn.)

Prostephanus truncatus is a pest that causes serious losses in stored maize (Zea mays L.) especially in developing countries. This research was conducted to investigate the use of post-harvest insect resistance maize in combination with biological control of P. truncatus by the predator Teretrius nigrescens to reduce maize storage losses. We studied the population dynamics of P. truncatus with and without a predator in combination with susceptible maize and resistant maize to insects under laboratory conditions. This study confirms that P84c3 is a resistant variety against P. truncatus. Maize resistant kernels had a reduction of 30% losses in comparison with susceptible kernels. Significant and favorable interactions were observed between P84c3 maize and presence of T. nigrescens. A dramatic reduction of 80% in progeny number, 81% grain weight loss, and 75% frass production caused by P. truncatus was observed when the predator was used in combination with P84c3. Resistant maize reduced the prey development time and consequently the insect density allowing the predator to control more effectively the population. Prey/predator proportion on resistant maize was significantly higher in comparison with susceptible kernels; thus, giving a more effective pest population control by the predator. These results demonstrated that the combination of post-harvest insect resistance maize with the predator T. nigrescens reduces grain maize losses by P. truncatus.     

Resistance of maize to the maize weevil: III. Grain weight loss assessment and implications for breeding

The maize weevil (Sitophilus zeamais) is a significant pest of stored maize grain in tropical and subtropical regions worldwide. As a further step towards finding maize genotypes with acceptable levels of resistance to the maize weevil, 53 experimental maize hybrids that were generated in a North Carolina design II mating scheme, were evaluated for grain weight loss due to maize weevil damage under ambient temperature and humidity (ATH) conditions, in the on-station stock room at Harare, Zimbabwe. The study indicated that genotypic variation for grain weevil resistance was large (19%–57%) after five months of infestation by the maize weevils. A few F₂ populations with potential for use as sources of breeding new varieties for maize weevil resistance were identified. They displayed consistency of high performance (better than the standard control varieties) and showed a lower rate of grain weight loss due to the maize weevils over the five months in the stock room. The male and female GCA and SCA effects were highly significant (P ≤ 0.01) for maize weevil resistance, especially at two months after infestation, indicating that resistance was controlled by genes with both additive and non-additive effects, respectively. Further, the distribution of grain weight loss data for the hybrids was continuous and almost normal at the four intervals of data collection, clearly supporting that resistance was partial and possibly conditioned by minor genes with cumulative effects. Therefore, resistance could probably be improved by selection among the promising F₂ populations identified in this study. Although resistance was partial, a plot of grain weight loss of hybrids from the different categories demonstrated the advantage to farmers for growing a resistant variety (low percentage loss over time) compared to the susceptible ones that incurred significant grain weight losses. However, grain weight loss data were not significantly correlated with yield (r = 0.14; P > 0.05), suggesting that the traits are not mutually exclusive. Therefore, breeding for maize weevil resistance in these populations would not necessarily compromise grain yield. Our results demonstrate that there is potential in developing maize varieties with acceptable levels of maize weevil resistance through recurrent selection procedures which exploit both GCA and SCA effects with sustainable impact on food security and the environment.     

Mapping of maize storage losses due to insect pests in central Mexico

Postharvest grain storage are a major problem in Mexico, influencing the economy, livelihoods, and food security of most farmers. At present, very limited information is available on postharvest maize losses and the associated insect pests in Mexico. Therefore, the objective of this study was to quantify and map maize storage losses in Central Mexico (State of Mexico) to analyze the effects of major pests in the different regions and to provide useful data to policymakers and local stakeholders. The study was conducted with 120 farmers dispersed across all regions of maize production in the State of Mexico. Storage losses were quantified using standardized maize samples that harvest, stored for a year, and sampled periodically. These data, together with geographic coordinates, were integrated into a geographic information system (GIS) to generate maps of maize storage damage and weight losses. The resulting maps show that in the southern region of the State of Mexico the standardized samples exhibited the highest maize losses after a one-year storage period, with an average of 76% loss and 100% grain damage, followed by the northern region, with an average of 18% loss and 52% damage. The eastern region reported 10% loss and 16% damage, whereas the Central region showed 5% loss and 14% damage. The main storage pests identified displayed localized geographic distributions, with the maize weevil, Sitophilus zeamais, being mainly localized in the South, the larger grain borer, Prostephanus truncatu, in the East and North, and the angoumois grain moth, Sitotroga cerealella, in the Northeast and Central regions. Thus, these maps are robust tools that will help towards improving storage facilities and increasing food security for small-scale farmers.     

On-farm maize storage systems and rodent postharvest losses in six maize growing agro-ecological zones of Kenya

Rodents are one of the major postharvest pests that affect food security by impacting on both food availability and safety. However, knowledge of the impact of rodents in on-farm maize storage systems in Kenya is limited. A survey was conducted in 2014 to assess magnitudes of postharvest losses in on-farm maize storage systems in Kenya, and the contribution of rodents to the losses. A total of 630 farmers spread across six maize growing agro-ecological zones (AEZs) were interviewed. Insects, rodents and moulds were the main storage problems reported by farmers. Storage losses were highest in the moist transitional and moist mid-altitude zones, and lowest in the dry-transitional zone. Overall, rodents represented the second most important cause of storage losses after insects, and were ranked as the main storage problem in the lowland tropical zone, while insects were the main storage problem in the other AEZs. Where maize was stored on cobs, total farmer perceived (farmer estimation) storage weight losses were 11.1 ± 0.7 %, with rodents causing up to 43 % of these losses. Contrastingly, where maize was stored as shelled grain, the losses were 15.5 ± 0.6 % with rodents accounting for up to 30 %. Regression analysis showed that rodents contributed significantly to total storage losses (p < 0.0001), and identified rodent trapping as the main storage practice that significantly (p = 0.001) lowered the losses. Together with insecticides, rodent traps were found to significantly decrease total losses. Improved awareness and application of these practices could mitigate losses in on farm-stored maize.     

Post-harvest food losses in a maize-based farming system of semi-arid savannah area of Tanzania

An assessment of post-harvest handling practices and food losses in a maize-based farming system in semi-arid areas of Central and Northern Tanzania was carried out in 2012. Seventeen crops were mostly cultivated by the farmers in the surveyed areas; maize (32%), sunflower (16%) and pigeon peas (12%) were the most cultivated while maize was the most stored. There are at least 7 months between two harvest seasons of each crop; while farmers sold the crops soon after harvest to cater for household expenditure (54%) and school fees (38%), the market prices increased significantly (P ≤ 0.05) within six months of storage. Most processing activities (winnowing, dehulling, drying, sorting and shelling) were carried out manually, almost entirely by women, but mechanized processing for maize, sunflower, millet, and sorghum were commonly practiced. Quantitative post-harvest losses of economic importance occur in the field (15%); during processing (13–20%), and during storage (15–25%). The main storage pests responsible for the losses are larger grain borers (Prostephanus truncatus), grain weevils (Sitophilus granarius) and, the lesser grain borer (Rhyzopertha dominica). Most of the farmers considered changes in weather (40%), field damage (33%), and storage pests (16%) as the three most important factors causing poor crop yields and aggravating food losses. However, survey results suggest that the farmers' poor knowledge and skills on post-harvest management are largely responsible for the food losses. 77% of the surveyed farmers reported inadequate household foods and 41% received food aid during the previous year. Increasing farmers' technical know-how on adaptation of the farming systems to climate variability, and training on post-harvest management could reduce food losses, and improve poverty and household food security.     

Crops that feed the world 6. Past successes and future challenges to the role played by maize in global food security

Maize is one of the most important food crops in the world and, together with rice and wheat, provides at least 30% of the food calories to more than 4.5 billion people in 94 developing countries. In parts of Africa and Mesoamerica, maize alone contributes over 20% of food calories. Maize is also a key ingredient in animal feed and is used extensively in industrial products, including the production of biofuels. Increasing demand and production shortfalls in global maize supplies have worsened market volatility and contributed to surging global maize prices. Climatic variability and change, and the consequent rise in abiotic and biotic stresses, further confound the problem. Unless concerted and vigorous measures are taken to address these challenges and accelerate yield growth, the outcome will be hunger and food insecurity for millions of poor consumers. We review the research challenges of ensuring global food security in maize, particularly in the context of climate change. The paper summarizes the importance of maize for food, nutrition and livelihood security and details the historical productivity of maize, consumption patterns and future trends. We show how crop breeding to overcome biotic and abiotic stresses will play a key role in meeting future maize demand. Attention needs to be directed at the generation of high yielding, stress-tolerant and widely-adapted maize varieties through judicious combination of conventional and molecular breeding approaches. The use of improved germplasm per se will not, however, be enough to raise yields and enhance adaptation to climate change, and will need to be complemented by improved crop and agronomic practices. Faced with emasculated state extension provision and imperfect markets, new extension approaches and institutional innovations are required that enhance farmers’ access to information, seeds, other inputs, finance and output markets. Over the long-term, large public and private sector investment and sustained political commitment and policy support for technology generation and delivery are needed to overcome hunger, raise the incomes of smallholder farmers and meet the challenges of growing demand for maize at the global level.     

Deleterious effects of Myracrodruon urundeuva leaf extract and lectin on the maize weevil,Sitophilus zeamais (Coleoptera,Curculionidae)

Deterioration and degradation of grains by storage insect pests lead to economic losses of several billion dollars and affect food security. Sitophilus zeamais is responsible for pre- and post-harvest damages to maize. The high toxicity of synthetic insecticides and the development of resistance by insects to the chemicals currently used stimulate the investigation of plant-derived insecticides as new alternatives for pest control. In this study, we report the effects of diets containing Myracrodruon urundeuva leaf extract (10–150 mg/g) and lectin (MuLL; 3–150 mg/g) on the survival, feeding, and nutrition of the storage pest S. zeamais. The digestive enzyme activity in gut extracts from the insects reared on the leaf extract (25 mg/g) or MuLL (15 mg/g) diets was also evaluated. The leaf extract induced mortality (LC₅₀: 72.4 mg/g), while MuLL (30–150 mg/g) exerted strong feeding deterrence. The leaf extract and MuLL promoted the loss of biomass, as reflected in the negative values for relative biomass gain rates and efficiencies in converting ingested food. Protease, trypsin-like, acid phosphatase, and amylase activities in the insects reared on leaf extract or MuLL diets were significantly (P < 0.05) lower than those in the control insects. MuLL ingestion also significantly reduced (P < 0.05) endoglucanase and alkaline phosphatase activities. In conclusion, the leaf extract and MuLL have the potential for S. zeamais control by killing adults and preventing the use of a food source, respectively. The deleterious effects of the extract and lectin on S. zeamais may be linked to enzyme inhibition and consequent suppression of digestive processes.     

Traditional maize post-harvest management practices amongst smallholder farmers in Guatemala

Much of the maize that is produced in Guatemala is planted, harvested and handled via subsistence-oriented agricultural practices, strongly connected to Mayan heritage. This post-harvest assessment study was done to characterize the current practices used in the region of Huehuetenango, Guatemala, in order to identify the different grain handling practices in the region as well as possible factors contributing to post-harvest losses of maize. A total of 280 families representing 14 rural communities were surveyed through interviews. Survey revealed that most (88%) of interviewed farmers prefer to dry the maize cobs after harvest by laying them in stacks exposed to direct sunlight. After drying, harvested maize is stored until consumption along with purchased maize kernels from the market. Among storage practices, 62% of surveyed families store the maize as shelled kernels; while 38% store it on cobs. When storing shelled maize, bags are the preferred containers among 81% of farmers, while only 14% use metal silos. Among farmers who stored maize on cobs, 74% use the tapanco as the preferred storage structure. Forty-one percent of farmers indicated storing the maize for at least 4 months. During the storage time, 61% of farmers perform grain quality checks once a week. Moreover, 65% perform pest control during storage; however, in most cases, the control is not preventive but corrective. For 49% of farmers, the main cause of loss between harvest and consumption is the mishandling of grain moisture, leading to insect and fungal infestation. With this data, it was possible to identify diverse maize harvesting, drying, storage and consumption practices within the studied communities. Understanding the traditional post-harvest practices will help better design intervention steps to improve these practices and to increase food security and food safety for smallholder farmers in the Guatemalan Highlands.     

Population dynamics of stored maize insect pests in warehouses in two districts of Ghana

Understanding what insect species are present and their temporal and spatial patterns of distribution is important for developing a successful integrated pest management strategy for food storage in warehouses. Maize is stored in bags in warehouses in many countries in sub-Saharan Africa, but little monitoring information is available on insect activity in those warehouses. We monitored the populations of major post-harvest insect pests of maize at three different warehouses (MiDA, Gundaa and Wienco) in two regions in Ghana (Middle Belt and Northern Belt). The study was conducted from September 2015–July 2016, which represents a common maize harvest and storage period in the two regions. The most abundant insect pest found in the warehouses was Plodia interpunctella (Hübner), but other major pest species were recovered during the study. Sitotroga cerealella (Oliver) and Prostephanus truncatus (Horn) which are major pests on farms, were more likely to be captured in traps outside or at nearby farms than inside the warehouses. When recovered inside they tended to be found in the receiving and cleaning areas. Sitophilus spp. were commonly captured in the warehouses, but were more abundant in the Middle Belt warehouse. Our results identified the major species found during warehouse storage of maize in Ghana and suggest that the specific pest species may be different in warehouses compared to on-farm storage.     

Susceptibility of Ethiopian wheat varieties to granary weevil and rice weevil infestation at optimal and sub-optimal temperatures

Integrating varietal resistance with temperature manipulation during storage may provide a better option for protection of stored grains and may decrease reliance on the use of synthetic chemicals. The current study was conducted to determine the susceptibility of different varieties of wheat seed to the infestation by the granary weevil, Sitophilus granarius (L.), and rice weevil, Sitophilus oryzae (L.), at optimal (30 °C) and sub-optimal (19 °C) temperatures. Kernels of six wheat varieties namely, Danda'a, Digalu, ET-13-A2, Kakaba, Millennium, and Pavon-76 were examined over a period of 90 d. Significant interactions were detected between wheat varieties and storage temperature for progeny emergence, percentage of insect damaged kernels, grain weight loss, and amount of powder produced per gram of wheat. Kernels of Danda'a, infested with S. oryzae at 30 °C exhibited significantly lower mean progeny counts (13.3 live insects), lower percentage of grain weight loss (4.2%) and insect-damaged kernels (6.4%), and powder production (1.5 mg/g). Kernel weight and hardness index were negatively associated with percentage of insect damaged kernels and grain weight loss. Kernel diameter was positively associated with both of percentage of insect damaged kernels and grain weight loss. Wheat varieties with high Zeleny sedimentation values had lower percentage of insect-damaged kernels and grain weight loss. These results indicated that kernel weight, hardness index, and protein content are predominant factors contributing to wheat resistance against S. granarius and S. oryzae. The varieties Millennium and Danda'a can be considered with other integrated pest management approaches to reduce stored grain losses of wheat in Ethiopia.     

Hermetic storage with plastic sealing to reduce insect infestation and secure paddy seed quality: A powerful strategy for rice farmers in Mozambique

Rice is the world's most important staple food and the basis of the diet of the majority of the population. In small farm agriculture, the yields obtained in cereal production are usually low and losses, both in the field and during storage, are dramatically high, particularly in developing countries. In Mozambique, these aspects, together with an increased frequency of floods, are hindering advances in rice production. Aimed at contributing to the reduction of losses in stored rice, trials were carried out to compare the effectiveness of traditional raffia bags and of hermetic storage using single and double plastic bags concerning quantitative losses and seed quality, including germination potential, after three and six months of storage. Pest identification, insect populations estimates, percentage of weight loss, germination power and seedling vigor were evaluated. The results showed that, in descending order of density, Angoumois grain moth (Sitotroga cerealella Olivier), lesser grain borer (Rhyzopertha dominica F.), rice/maize weevil (Sitophilus zeamais Mostch. and Sitophilus oryzae L.) and red flour beetle [Tribolium castaneum (Herbst)] were the main insects infesting the rice. When compared to hermetic storage with both single and duplicate airtight bags, traditional storage presented statistically significant higher mean infestation density (30.63–53.94 individuals/kg in traditional and 0.71–3.50 individuals/kg in hermetic storage) and percentage of weight loss (3.03–3.44% in traditional contrasting with 0.27–0.47% in hermetic conditions). In traditional storage a significant 38.25% drop in the germination potential was also observed, attaining values below the established minimum tolerated in Mozambique (80%), while under hermetic storage, that reduction remained within the acceptable values of 13.9–17.5%. The distinct storage methods did not produce significant differences on the moisture content of the grain. These results demonstrate that the use of hermetic storage has resulted in a safe, pesticide-free, and sustainable storage method, suitable for rice seeds, with advantages over traditional bagging. The results presented here lead to propose hermetic storage to be adopted by paddy small farmers, in order to lever food security and income generation in the country.     

The importance of plant health to food security

Rapid food price rises have highlighted serious concerns about food security globally and have had a huge impact on achieving Millennium Development Goal 1. Since 2007, an estimated 100 million more people have fallen into absolute poverty. Most live in developing countries where low incomes (less than $1 per day) make it difficult to access food. Access to sufficient food for dietary needs and food preferences defines food security. However, whilst price rises have brought food security into sharp focus, underlying problems need to be addressed. Over the last three to four decades, there has been chronic under-investment in agriculture at all levels. Development aid to agriculture has declined and often in-country policies do not support the sector. Low crop yields are common in many developing countries and improved productivity is vital to reducing rural poverty and increasing food security. Whilst the causes of low productivity are complex, one major contributory factor is crop losses due to plant health problems. Often accurate information on the extent of these losses is missing but estimates of 30–40% loss annually from “field to fork” are common. Any future solution regarding improved global food security must address these losses and that means improving plant health. Two trans-boundary diseases, wheat stem rust race Ug99 and Coffee Wilt Disease of Coffea are highlighted. CABI has a number of plant health initiatives and one radical approach (Global Plant Clinic) involves partnership with in-country services to deliver plant health advice to farmers at the point of demand. Such innovations are entirely consistent with a proposed new “Green Revolution” which would need to be “knowledge intensive”.     

Efficacy of combining varietal resistance with harvest time and planting date for the management of Sitophilus zeamais Motschulsky infestation in stored maize

The combination of varietal resistance with three harvest times and planting dates for efficient storage of maize against Sitophilus zeamais infestation was evaluated in the Niger Delta region of Nigeria for two seasons. Seven maize varieties made up of three susceptible local maize cultivars (Akparike, Bende and Ogbia muno) and four improved resistant varieties (ACR.97 TZL COMP.1-W, TZL COMP.4C2, ADV.NCRE-STR and BG 97 TZE COMP.3XL) were used. There were significant differences in the number of teneral adults among harvest times in all the planting dates in both years. Maize harvested when the cobs were completely dry at the latest harvest time (HVT 3) suffered significantly higher weight losses. In 2009, the highest susceptibility was apparent in a local variety Akparike planted on 17 October (PD 1) and harvested at HVT 3 by which time the cobs had completely turned yellow. Combining early planting and early harvest with resistant varieties could be an appropriate tactic for resource-poor farmers to effectively manage maize weevils in the store in the Niger Delta agro-ecological zone.     

Assessment of storage losses and comparison of underground and aboveground storage for better stability and quality of maize (zea mays l.) and sorghum (sorghum bicolor l.) grains in selected districts of jimma zone,Ethiopia

Production and marketing of cereal grains is one of main activities in low income countries farming system. However, yields are very low due to several factors associated with traditional practices. Despite low productivity, the postharvest loss (PHL) of grains mainly during storage is high due to storage pests. The study was conducted to assess storage related losses of grains (maize and sorghum) and compare aboveground and underground storage methods to minimize losses associated with traditional storage structures. In first phase of the study, base line data were collected using focus group discussion, key informants interview and semi-structured questioners. In the second phase, underground and aboveground storage methods were investigated along with their control for better stability of stored maize and sorghum. The survey result showed that, storage related losses (due to different factors) of maize and sorghum were 14.2 and 11.5% respectively. The major identified causes of losses were storage pests and losses due to seepage. In the second phase, from studied storage structures, grains stored in pit storage with PVC layer showed superior stability and quality in terms of prevention of pest attacks and proximate composition, respectively. The study demonstrated that, underground storage method supported with PVC lining was efficient in terms of enhancing storage stability of grains with required quality for consumption or marketing.     

Field effectiveness of improved hermetic storage technologies on maize grain quality in Central Mexico

Maize is the main crop cultivated by small scale farmers (SSF) in Mexico, and its production represents an important goal for local food security. However, SSF very often face severe post-harvest losses in maize, mainly because of insect pests and the lack of suitable storage technology. This study was conducted to compare the field effectiveness in terms of maize quality under on-field conditions of SSF of two improved hermetic storage technologies with the traditional storage. The field experiment was performed on-farm in the highlands of Central Mexico. Maize grains were stored in three storage devices: hermetic plastic bag (sBag), hermetic plastic silo (Bioxilo), or traditional polypropylene sacks. The study considered the quantitative evaluation of storage, physical, nutritional, and industrial qualities of maize after 4, 8 and 12 months of storage. Environmental conditions of storage such as oxygen levels, temperature and humidity were monitored. After 1 year of field storage, compared with traditional sacks, sBag and Bioxilo showed a significant lower losses in storage due to insects. When controlled infested maize by artificial insect infestation methods was used, the improved technologies were also effective in reducing grain losses. Furthermore, both sBag and Bioxilo prevented grain quality detriment in terms of physical, nutritional and industrial (for tortilla and seed) properties (p < 0.01). Additionally, compared with traditional storage, sBag and Bioxilo showed efficient control of the hermetic conditions in terms of oxygen, temperature and humidity, but no significant differences were detected between the two improved technologies. In summary, under on-farm conditions, the successful preservation of maize grain quality was achieved by the improved sBag and Bioxilo in the highlands of Mexico. In the future, positive effects of this storage system will need to be validated under tropical conditions.     

Quantitative and quality losses caused by rodents in on-farm stored maize: a case study in the low land tropical zone of Kenya

Rodents are one of the major storage pests in on-farm maize storage in the tropics. However, information on actual magnitude of weight and quality losses caused by rodents in maize stores and species of rodent associated with the losses is scarce and if available would help to improve maize postharvest management. Maize stores of small-scale farmers in the lowland tropical zone of Kenya were monitored for actual weight losses caused by rodents and rodent trapping was conducted to determine species and estimate population of the rodents associated with the losses. Moulds and total aflatoxin contamination and nutritional value of rodent-damaged grain and non-damaged grain samples were also compared to evaluate the impact of rodent infestation on grain quality. In a sample of 20 farmers, we found that cumulative weight losses due to rodents ranged from 2.2 to 6.9% in shelled maize grain and from 5.2 to 18.3% in dehusked cobs after storage for 3 months. Rattus rattus was the only rodent species captured over the whole trapping period with a trap success rate of 0.6–10.0%. Total mould count, Fusarium spp. incidence and total aflatoxin contamination were significantly higher in rodent-damaged grains than in the non-damaged ones whereas no significant differences were observed for the incidence of Aspergillus spp. There were also significant decreases in dry-matter, fat, crude protein and fatty acid content in rodent-damaged grain compared to non-damaged grain. These findings show that rodents are a significant cause of postharvest losses in on-farm maize storage and impact negatively on food nutrition and safety. Mitigation strategies for postharvest losses should therefore include rodent control.     

Threats to cassava production: known and potential geographic distribution of four key biotic constraints

Insect pests and plant diseases reduce cassava yields substantially, posing a threat to food security throughout the developing world. While agricultural scientists have recognized these threats, few assessments of the geographic distribution of cassava pests and diseases have been made at the global scale. The goal of this study is to make such an evaluation for four key biotic constraints to cassava production in developing countries: whiteflies, cassava green mites, cassava mosaic disease and cassava brown streak disease. Occurrence records were obtained from laboratory and biodiversity databases and from the scientific literature. These records were then used in ecological niche models to predict the potential distribution of cassava pests and diseases. The distribution maps were cross validated by holding back 20% of the occurrence records. Potential distribution maps were developed by combining the results of the best ecological niche models. Hotspots for potential cassava pest and disease outbreaks include the Mato Grosso in Brazil, northern South America, the African rift valley, the southern tip of India and much of Southeast Asia, where all four biotic constraints show high potential suitability. Our work highlights how potential geographical shifts in infestation hotspots for several cassava biotic constraints will require intensified monitoring, evaluation and research to prevent yield losses and ensure food security.     

Crops that feed the world 8: Potato: are the trends of increased global production sustainable?

Potato is produced on all continents except Antarctica and is the world??s third most important food crop. Potato production has increased dramatically in developing countries in the past two decades, and has now overtaken that in the developed world, underlining the growing importance of potato as a staple food crop to meet the demands of increasing human populations. Potato is also an important source of starch. It has been adapted for cultivation in a wide range of environments and, with the availability of significant germplasm resources, the potential to further exploit its natural biodiversity is considerable. Potato yields vary considerably across the world, with the lowest being in Sub-Saharan Africa; <75?% of the global average and <30?% of the top producing regions. Many factors contribute to this variation, providing targets for improved agronomic practice and a stimulus to improve varieties to increase production in the poorest-yielding countries. The ability to adapt potato to withstand multiple biotic and abiotic stresses is critical to its future growth as a major food source. In current breeding efforts, strong emphasis is being placed on these traits in attempts to better equip the potato crop in a changing climate. The genomics era is accelerating our understanding of the key genes and mechanisms underlying potato development, physiology, water and nutrient use efficiency and resistance to biotic and abiotic stresses. Genomics technologies provide the potential for more rapid, marker-assisted breeding strategies, and afford the opportunity for biotechnological approaches, particularly in the case of major gene resistance to pests and diseases. Continued review of GM policies and regulations, and associated social and political opinions, are needed to guide and determine the safest and most productive routes to potato improvement.     

Maize: A Paramount Staple Crop in the Context of Global Nutrition

Abstract: The maize plant (Zea mays), characterized by an erect green stalk, is one of the 3 great grain crops of the world. Its kernels, like other seeds, are storage organs that contain essential components for plant growth and reproduction. Many of these kernel constituents, including starch, protein, and some micronutrients, are also required for human health. For this reason, and others, maize has become highly integrated into global agriculture, human diet, and cultural traditions. The nutritional quality and integrity of maize kernels are influenced by many factors including genetic background, environment, and kernel processing. Cooking procedures, including nixtamalization and fermentation, can increase accessibility of micronutrients such as niacin. However, man cannot live on maize alone. For one‐third of the world's population, namely in sub‐Saharan Africa, Southeast Asia, and Latin America, humans subsist on maize as a staple food but malnutrition pervades. Strategies to further improve kernel macronutrient and micronutrient quality and quantities are under intense investigation. The 2 most common routes to enhance grain nutritional value are exogenous and endogenous fortification. Although exogenous fortification, such as addition of multivitamin premixes to maize flour, has been successful, endogenous fortification, also known as “biofortification,” may provide a more sustainable and practical solution for chronically undernourished communities. Recent accomplishments, such as low‐phytate, high‐lysine, and multivitamin maize varieties, have been created using novel genetic and agronomic approaches. Investigational studies related to biofortified maize are currently underway to determine nutrient absorption and efficacy related to human health improvement.