Food Crop In sub-Saharan Africa Research Articles

Correlate the cyanogenic potential and dry matter content of cassava roots and leaves grown in different environments

Cassava (Manihot esculenta Crantz) is an essential stable food crop in Sub-Saharan Africa commonly consumed amongst the low-income communities in Africa. Though cassava roots and leaf have vast economic and commercial benefits, it produces cyanogenic glycosides, which are toxic and most often responsible for the bitter taste of some cassava cultivars. The study evaluates the cassava roots and leaves’ cyanogenic potential and dry matter content of the Genetic Gain Assessment trial grown in a different environment. It establishes the association between the cyanogenic potential (CNP) and the roots and leaves dry matter (DM). Genetic Gain Assessment (GGA) cassava genotypes (N = 400) selected for the Uniform Yield Trial (UYT) breeding stage were planted under IVS (Dry season in Inland Valley Hydromorphic area) and Upland (rain-fed conditions) in two locations of IITA Research Farms, namely; Ibadan (IVS and Upland) and Mokwa (Upland) in Nigeria. The CNP content of cassava leaves in IVS, Mokwa, and Upland ranged from 3.39 to 272.16 mg/100 g, 4.28 to 228.72 mg/100 g, and 13.13 to 127.39 mg/100 g, respectively. However, the respective CNP range in root samples across IVS, Mokwa, and Upland was 0.76–76.31 mg/100 g, 0.94–136.53 mg/100 g, and 2.37–47.11 mg/100 g. Also, the mean ± SD of DM content of leaves were 27.97 ± 3.01%, 28.81 ± 4.01%, and 13.65 ± 3.69%, respectively, in IVS, Mokwa, and Upland, while the root samples had mean ± SD of DM content of 38.09 ± 4.80%, 32.69 ± ,5.93% and 24.63 ± 5.07% respectively. Furthermore, location and genotype had a highly significant effect (p < 0.001) on the CNP and DM of roots and leaves. Also, linear regressions were established between CNP and DM of root and leaf with regression equation; DM-Root = 1.1999*DM-Leaf (r = 0.956) and CNP-Root = 0.29006*CNP-Leaf (r = 0.54). The relationship between the DM (root and leaf) and CNP (root and leaf) could serve as a valuable “inter-prediction” tool for these parameters.

Forgotten food crops in sub-Saharan Africa for healthy diets in a changing climate

As climate changes in sub-Saharan Africa (SSA), Africa's "forgotten" food crops offer a wide range of options to diversify major staple production as a key measure toward achieving zero hunger and healthy diets. So far, however, these forgotten food crops have been neglected in SSA's climate-change adaptation strategies. Here, we quantified their capacity to adapt cropping systems of SSA's major staples of maize, rice, cassava, and yams to changing climates for the four subregions of West, Central, East, and Southern Africa. We used climate-niche modeling to explore their potential for crop diversification or the replacement of these major staples by 2070, and assessed the possible effects on micronutrient supply. Our results indicated that approximately 10% of the present production locations of these four major staples in SSA may experience novel climate conditions in 2070, ranging from a high of almost 18% in West Africa to a low of less than 1% in Southern Africa. From an initial candidate panel of 138 African forgotten food crops embracing leafy vegetables, other vegetables, fruits, cereals, pulses, seeds and nuts, and roots and tubers, we selected those that contributed most to covering projected future and contemporary climate conditions of the major staples' production locations. A prioritized shortlist of 58 forgotten food crops, able to complement each other in micronutrient provision, was determined, which covered over 95% of assessed production locations. The integration of these prioritized forgotten food crops in SSA's cropping systems will support the "double-win" of more climate-resilient and nutrient-sensitive food production in the region.

Assessing the Prospects of Remote Sensing Maize Leaf Area Index Using UAV-Derived Multi-Spectral Data in Smallholder Farms across the Growing Season

Maize (Zea Mays) is one of the most valuable food crops in sub-Saharan Africa and is a critical component of local, national and regional economies. Whereas over 50% of maize production in the region is produced by smallholder farmers, spatially explicit information on smallholder farm maize production, which is necessary for optimizing productivity, remains scarce due to a lack of appropriate technologies. Maize leaf area index (LAI) is closely related to and influences its canopy physiological processes, which closely relate to its productivity. Hence, understanding maize LAI is critical in assessing maize crop productivity. Unmanned Aerial Vehicle (UAV) imagery in concert with vegetation indices (VIs) obtained at high spatial resolution provides appropriate technologies for determining maize LAI at a farm scale. Five DJI Matrice 300 UAV images were acquired during the maize growing season, and 57 vegetation indices (VIs) were generated from the derived images. Maize LAI samples were collected across the growing season, a Random Forest (RF) regression ensemble based on UAV spectral data and the collected maize LAI samples was used to estimate maize LAI. The results showed that the optimal stage for estimating maize LAI using UAV-derived VIs in concert with the RF ensemble was during the vegetative stage (V8–V10) with an RMSE of 0.15 and an R2 of 0.91 (RRMSE = 8%). The findings also showed that UAV-derived traditional, red edge-based and new VIs could reliably predict maize LAI across the growing season with an R2 of 0.89–0.93, an RMSE of 0.15–0.65 m2/m2 and an RRMSE of 8.13–19.61%. The blue, red edge and NIR sections of the electromagnetic spectrum were critical in predicting maize LAI. Furthermore, combining traditional, red edge-based and new VIs was useful in attaining high LAI estimation accuracies. These results are a step towards achieving robust, efficient and spatially explicit monitoring frameworks for sub-Saharan African smallholder farm productivity.

Estimating genetic gains for tolerance to stress combinations in tropical maize hybrids.

Maize is a strategic food crop in sub-Saharan Africa. However, most maize growing tropical savannas particularly in West and Central African experience the occurrence of frequent droughts and Striga infestation, resulting in 30-100% yield losses. This production zones need maize cultivars that combine tolerance to the two stresses. IITA in collaboration with national partners has thus employed a sequential selection scheme to incorporate both drought tolerance and Striga resistance in topical maize hybrids using reliable screening protocols. The main objective of the present study was therefore to use grain yield and other agronomic traits recorded in regional collaborative hybrid trials conducted for 8years under manged stressful and non-stressful conditions and across rainfed field environments to estimate genetic gains in grain yields using mixed model analyses. The results showed significant (p < 0.05) annual yield gains of 11.89kgha-1 under manged drought stress (MDS) and 86.60kgha-1 under Striga infestation (STRIN) with concomitant yield increases of 62.65kgha-1 under full irrigation (WW), 102.44kgha-1 under Striga non-infested (STRNO) conditions and 53.11kgha-1 across rainfed field environments. Grain yield displayed significant but not strong genetic correlation of 0.41 ± 0.07 between MDS and STRIN, indicating that gene expression was not consistent across the two stress conditions. Furthermore, grain yield recorded in MET had significant moderate genetic correlations of 0.58 ± 0.06 and 0.44 ± 0.07It with MDS and STRIN, respectively. These results emphasize the need to screen inbred linens under both stress conditions to further enhance the rate of genetic gain in grain yield in hybrids for areas where the two stresses co-occur. Nonetheless, this study demonstrated that the sequential selection scheme has been successful in generating hybrids with dependable yields that can reduce chronic food deficits in rural communities experiencing simultaneous presence of drought and S. hermonthica infestation in their production fields.

Effects of intercropping sunn hemp into maize at different times and densities on productivity under rainwater harvesting technique

Maize is a major food crop in Sub-Saharan Africa (SSA), and its productivity is affected by climate change-adaptive sustainable management practices. A 2-year field study (2019/20 and 2020/21 growing seasons) was carried out to evaluate the effect of sunn hemp (Crotalaria junceaL.) living mulch management on maize (Zea maysL.) production. Three sunn hemp planting periods were simultaneous with maize planting (P1), V15 maize growth stage (P2), and R1 maize growth stage (P3) and three densities 16.1 plants m−2(D1-low), 32.1 plants m−2(D2-medium), and 48.1 plants m−2(D3-high). The intercrop components were planted in a split-plot treatment arrangement as an additive series with three replications and laid out in a randomized complete block design under the in-field rainwater harvesting (IRWH) technique. The growing season conditions revealed significant differences in rainfall distribution. Therefore, the planting period had highly significant (p&amp;lt; 0.001) effects on sunn hemp biomass, with an LSD value of 610.2 kg ha−1, showing that the highest was obtained in P2 (2636.7 kg ha−1) compared to P3 (811.3 kg ha−1). However, the P3 treatment resulted in maize grain yield penalty, with yields as follows: P3 (2775.2 kg ha−1), sole maize (3263.8 kg ha−1), P2 (3281.9 kg ha−1), and P1 (3287.8 kg ha−1). P2 yielded a significantly (p&amp;lt; 0.05) high-income equivalent ratio of 2.09, indicating a 109% advantage for increasing farmers' income by integrating sunn hemp under the no-till area of IRWH. P1 and P2 sunn hemp planting periods are viable options for smallholder farmers in summer rainfall regions to improve economic benefits.

Nutritional management and maize variety combination effectively control Striga asiatica in southern Africa

Maize (Zea mays L.) is an important staple food crop in sub-Saharan Africa (SSA) and contributes significantly to food security. Due to Striga, maize yield loss is estimated between 20 and 80% forcing some farmers to abandon their land therefore threatening food security. Many strategies have been applied to combat Striga infested fields to improve maize yields but alternative feasible approaches are still required. This study aimed at determining effects of phosphorus (P) and maize variety on Striga asiatica germination and attachment. A factorial experiment of eight P levels (0, 10, 20, 30, 40, 50, 60 and 70 kg ha−1), six maize varieties and Striga (inoculated and non-inoculated) in a 4 × 24 α-lattice design with three replications was set in a glasshouse at the University of Zimbabwe. A similar experiment was set under laboratory conditions using agar gel plates to determine S. asiatica germination using a complete randomized design with three replications. Adding P (at 40 kg ha−1) to soil infected with Striga, significantly (p < 0.05) reduced Striga counts and haustorial root attachments in all varieties with CV4 and R201 supporting lowest numbers. P also significantly (p < 0.05) improved plant height, chlorophyll content, leaf, cob, total biomasses and grain yield across all maize genotypes. Cultivar CV4 produced the highest grain yield under Striga attack. Furthermore, cultivars CV4 and CV1 had significantly (p < 0.05) lowest Striga seed maximum germination distance and percentages at zero P. Application of P reduced Striga germination, attachments and emergence in all varieties and increased tolerance of maize varieties.

​​Identification of Insect Pests of Maize (Zea mays L.) in Girar Jarso and Hidebu Abote Districts, North Shewa Zone, Oromia, Central Ethiopia

Background: Maize is the most important staple food crops in sub-Saharan Africa, including Ethiopia, predominantly produced and consumed directly by the smallholder farmers. Insect pests are the serious pests causing yield loss of maize in field at different growth stages. Methods: The field survey was carried out during 2019-2020 crop growing season. Purposive sampling technique was used for selecting the districts based on the potential producers of maize and a random sampling technique was used to select the kebeles and the stakeholders. Result: The major identified insect pests of maize in the two districts were grass hopper (Hieroglyphus nigrorepletus), maize leaf hopper (Cicadulin ambila), maize pod borers (Helicoverpa armigera, Etiella), maize stem borers (Chilopartellus Swinhoe), Hairy caterpillar (Amsacta albistriga Walker), Black cut worm (Agrotis ipsilon Hufnagal), Maize leaf Aphid (Rhopalosiphum maidis Fitch), Army worm (Mythimna separata Walker), Fall armyworm (Spodoptera frugiperda), Pink stem borer (Sesamiain ferens Walker), Corn Earworm (Helicoverpa zea Boddias), Chafer beetle (Chiloloba acuta Wiedmann), Shoot bug (Peregrinus maidis Ashamed), White grub (Holotrichia consanguinea) and shoot fly (Atherigona soccata).

Assessing Suitability of Sorghum to Alleviate Sub-Saharan Nutritional Deficiencies through the Nutritional Water Productivity Index in Semi-Arid Regions.

Lack of cereal nutritional water productivity (NWP) information disadvantages linkages of nutrition to water–food nexus as staple food crops in Sub-Saharan Africa (SSA). This study determined the suitability of sorghum (Sorghum bicolor L. Moench) genotypes to alleviate protein, Zn and Fe deficiency under water-scarce dryland conditions through evaluation of NWP. Sorghum genotypes (Macia, Ujiba, PAN8816, IsiZulu) NWP was quantified from three planting seasons for various sorghum seed nutrients under dryland semi-arid conditions. Seasons by genotypes interaction highly and significantly affected NWPStarch, Ca, Cu, Fe, and significantly affected NWPMg, K, Na, P, Zn. Genotypic variations highly and significantly affected sorghum NWPProtein, Mn. Macia exhibited statistically superior NWPprotein (13.2–14.6 kg·m−3) and NWPZn (2.0–2.6 g·m−3) compared to other tested genotypes, while Macia NWPFe (2.6–2.7 g·m−3) was considerably inferior to that of Ujiba and IsiZulu landraces under increased water scarcity. Excellent overall NWPprotein, Fe and Zn under water scarcity make Macia a well-rounded genotype suitable to alleviating food and nutritional insecurity challenges in semi-arid SSA; however, landraces are viable alternatives with limited NWPprotein and Zn penalty under water-limited conditions. These results underline genotype selection as a vital tool in improving “nutrition per drop” in semi-arid regions.

Genetic diversity and SNP's from the chloroplast coding regions of virus-infected cassava.

Cassava is a staple food crop in sub-Saharan Africa; it is a rich source of carbohydrates and proteins which currently supports livelihoods of more than 800 million people worldwide. However, its continued production is at stake due to vector-transmitted diseases such as Cassava mosaic disease and Cassava brown streak disease. Currently, the management and control of viral diseases in cassava relies mainly on virus-resistant cultivars of cassava. Thus, the discovery of new target genes for plant virus resistance is essential for the development of more cassava varieties by conventional breeding or genetic engineering. The chloroplast is a common target for plant viruses propagation and is also a potential source for discovering new resistant genes for plant breeding. Non-infected and infected cassava leaf samples were obtained from different locations of East Africa in Tanzania, Kenya and Mozambique. RNA extraction followed by cDNA library preparation and Illumina sequencing was performed. Assembling and mapping of the reads were carried out and 33 partial chloroplast genomes were obtained. Bayesian phylogenetic analysis from 55 chloroplast protein-coding genes of a dataset with 39 taxa was performed and the single nucleotide polymorphisms for the chloroplast dataset were identified. Phylogenetic analysis revealed considerable genetic diversity present in chloroplast partial genome among cultivated cassava of East Africa. The results obtained may supplement data of previously selected resistant materials and aid breeding programs to find diversity and achieve resistance for new cassava varieties.

Improving rapid multiplication of sweetpotato (Ipomoea batatas L. (Lam) pre-basic seed using sandponics technology in East Africa

AbstractSweetpotato (Ipomoea batatas, Convolvulaceae) is an important food crop in Sub-Saharan Africa (SSA). Lack of access to quality sweetpotato planting material after sweetpotato limits utilization of market oriented improved clones and new varieties. Obtaining clean planting material in the right quantity and quality is a challenge in the SSA region. Farmers often obtain planting materials from their own sources with multiple rooting, drawn from a previous crop or neighbors and face the risk of it being infected with sweetpotato viruses. The objective of this study was to examine the economic and physical yield performance of sandponics multiplication method by comparing with conventional soil method using optimal N-nutrient inputs. The performance of five sweetpotato cultivars (Irene, Delvia, Tanzania, Gweri, and Kabode) in the modified prototype sweetpotato nutrient media was evaluated. Vine production utilizing modified sandponics nutrient media with trellised plants was compared to the conventionally used soil media. Analysis of variance indicated that the main effects of cultivar and substrate were highly significant (p &lt; 0.0001) for nodes produced, vine multiplication rate (VMR), number of cuttings produced, and vine length. In addition, cultivar by substrate interaction was highly significant at 0.01 probability level for nodes produced, VMR, and vine length. Vine multiplication rate was 33% higher in the sandponics system compared to the conventional soil method of multiplying sweetpotato vines. Among the cultivars studied, Irene was the most favorable cultivar with a VMR of 65.2 in sand and 45.5 in soil. The cost-effectiveness analysis indicates that the cost per cutting (i.e., 3–4 nodes) produced from sandponics method was 4.6 KSH (US$ 0.046) as compared to 3.1 KSH (US$ 0.031) per cutting produced from conventional method. Sandponics system is competitive due to its capability of increased VMRs. However, the optimal number of ratooning needs to be investigated to understand the economies of scale in future research.

Agro-Economic Implications of Combined Application of Organic and Mineral Fertilizers on Maize

Continuous cultivation without adequate fertilizer application is responsible for plant nutrient depletion and yield decline of major food crops in sub-Saharan Africa. Field experiments were conducted on umbric Cambisol in Babungo and ustic Oxisol in Bansoa in the Western Highlands of Cameroon over two years to evaluate the effects of combined application of leaf biomass of agroforestry species and mineral fertilizers with their economic returns on maize yield performance. Ten treatments encompassing sole mineral fertilizer, sole leaf biomass of Calliandra, Leucaena, Acacia and Cassia, leaf biomasses combined with mineral fertilizer and absolute control were laid in a randomized complete block design and replicated three times. Data collected on maize grain yield was subjected to analysis of variance using XLSTAT version 2014 statistical software. In addition, an economic analysis was performed to evaluate the profitability of the different treatment combinations. The results showed significant differences (P ≤ 0.05) amongst the different treatments on maize yield on both soil types. The highest maize yields which stood at 5.93 t/ha and 6.01 t/ha were recorded in plots treated with Acacia and Cassia plus half recommended mineral fertilizer on umbric Cambisol and ustic Oxisol respectively. Economic analyses showed that Acacia and Cassia plus half recommended mineral fertilizer gave the highest net benefit and return to labor of 286500 FCFA and 5.1 on umbric Cambisol and 296051 FCFA and 5.3 on ustic Oxisol respectively. On both soils, all the treatments except Calliandra with half recommended mineral fertilizers were economically profitable with benefit to cost ratios that ranged from 2.02 to 2.92. Combined application of agroforestry tree species leaf biomass and mineral fertilizers is an appropriate technology to enhance maize grain yield and is economically profitable except Calliandra with half recommended mineral fertilizers and is therefore recommended for degraded Calliandra and Oxisols in the Western Highlands of Cameroon.

Effective Control of Aflatoxin Contamination in Staple Maize Food Crop in Sub-Saharan Africa: A Review of Current Pre- and Postharvest Low-Cost Technologies and Perspectives

Effective Control of Aflatoxin Contamination in Staple Maize Food Crop in Sub-Saharan Africa: A Review of Current Pre- and Postharvest Low-Cost Technologies and Perspectives

Efficacy of fecal fertilizers on growth, nutrient uptake and yield of maize

Maize ( Zea mays L.) is the most widely cultivated staple food crop in sub-Saharan Africa. However, its production is severely constrained by abiotic and biotic factors of which declining soil fertility is a major contributor. A study was conducted to evaluate the efficacy of fecal matter based organic fertilizers on growth, nutrient uptake, yield and yield components of maize, in two distinct agro-ecological zones. Five fertilizer treatments (control, Diammonium Phosphate (DAP), cow manure, struvite, compost from fecal matter) were tested in a randomized complete block design (RCBD) with four replications per site. Data were collected on crop emergence (%), plant height, number of leaves per plant, leaf area index (LAI), tasseling (%), nutrient uptake and grain yield and yield components. Data were subjected to analysis of variance and treatment means separated using Tukey’s HSD test. Results showed that crop emergence in the control treatment, except for struvite, was significantly higher than DAP and fecal matter based organic fertilizer plots in Bahati and Lanet sites. The end-point plant height (9 WAP), LAI and tasseling were significantly (P<0.05) influenced by location and organic fertilizer treatments. At the Lanet site, DAP and struvite treatments equally had the tallest maize plants (163 cm) followed by fecal compost (128 cm), manure (121 cm), and the control (79 cm). Similar result trends were recorded in Bahati where struvite (193 cm) had the tallest plants followed by fecal compost (166 cm), DAP (155 cm), manure (151 cm) and the control (98 cm), respectively. A contrasting result was observed at the Egerton University site in which cow manure and the control plots equally had the tallest plants (117-121 cm), followed by DAP and fecal compost (98-99 cm), and struvite (91 cm). The LAI, tasseling and grain yield were significantly influenced by location with struvite and fecal compost treatments producing the highest grain yield (≈8 t/ha) and one thousand (1000)-seed weights (480-560 g) at the Egerton University and Bahati experimental sites. Nitrogen uptake by maize for organic fertilizer treatments was higher than the control at all three locations. However, there was no difference in uptake of phosphorous and potassium between control and organic fertilizer treatments. These findings have demonstrated the potential of fecal matter based organic fertilizers as alternatives to inorganic fertilizers in smallholder agriculture. Key words: Zea mays , fecal compost, struvite, nutrient uptake, manure, Nitrogen, Phosphorus, Potassium

The Vulnerability of Rice Value Chains in Sub-Saharan Africa: A Review

Rice is one of the most important food crops in sub-Saharan Africa. Climate change, variability, and economic globalization threatens to disrupt rice value chains across the subcontinent, undermining their important role in economic development, food security, and poverty reduction. This paper maps existing research on the vulnerability of rice value chains, synthesizes the evidence and the risks posed by climate change and economic globalization, and discusses agriculture and rural development policies and their relevance for the vulnerability of rice value chains in sub-Saharan Africa. Important avenues for future research are identified. These include the impacts of multiple, simultaneous pressures on rice value chains, the effects of climate change and variability on parts of the value chain other than production, and the forms and extent to which different development policies hinder or enhance the resilience of rice value chains in the face of climatic and other pressures.

Small-Molecule inhibitors: Weed-control measures.

A high-throughput screen in the model plant Arabidopsis unveils leads for potential agents to combat Striga, a devastating root parasitic weed that affects food crops in Sub-Saharan Africa.

Environmental impacts and constraints associated with the production of major food crops in Sub-Saharan Africa and South Asia

Many environmental factors constrain the production of major food crops in Sub-Saharan Africa and South Asia. At the same time, these food production systems themselves have a range of negative impacts on the environment. In this paper we review the published literature and assess the depth of recent research (since 2000) on crop x environment interactions for rice, maize, sorghum/millets, sweetpotato/yam and cassava in these two regions. We summarize current understandings of the environmental impacts of crop production systems prior to crop production, during production and post-production, and emphasize how those initial environmental impacts become new and more severe environmental constraints to crop yields. Pre-production environmental interactions relate to agricultural expansion or intensification, and include soil degradation and erosion, the loss of wild biodiversity, loss of food crop genetic diversity and climate change. Those during crop production include soil nutrient depletion, water depletion, soil and water contamination, and pest resistance/outbreaks and the emergence of new pests and diseases. Post-harvest environmental interactions relate to the effects of crop residue disposal, as well as crop storage and processing. We find the depth of recent publications on environmental impacts is very uneven across crops and regions. Most information is available for rice in South Asia and maize in Sub-Saharan Africa where these crops are widely grown and have large environmental impacts, often relating to soil nutrient and water management. Relatively few new studies have been reported for sorghum/millets, sweetpotato/yam or cassava, despite their importance for food security on large areas of marginal farmland in Sub-Saharan Africa – however, there is mounting evidence that even these low-input crops, once thought to be environmentally benign, are contributing to cycles of environmental degradation that threaten current and future food production. A concluding overview of the emerging range of published good practices for smallholder farmers highlights many opportunities to better manage crop x environment interactions and reduce environmental impacts from these crops in developing countries.

Fusarium oxysporum f. sp. strigae strain Foxy 2 did not achieve biological control of Striga hermonthica parasitizing maize in Western Kenya

The production of maize, a major staple food crop in sub-Saharan Africa is being constrained by the parasitic weed Striga hermonthica. The fungus Fusarium oxysporum f. sp. strigae (Foxy 2) that causes fusarium wilt of Striga in Ghana, West Africa, is being considered for biological control of the weed in Western Kenya. The present study investigated the efficacy of F. oxysporum f. sp. strigae (Foxy 2) for S. hermonthica management in Western Kenya. Research was conducted in post-entry quarantine (PEQ) facilities at Alupe, Busia, Homabay, Kibos and Siaya field stations for two seasons. Each PEQ was a split-plot, with 4main blocks each having 6 treatment subplots. The treatments included seeds of two S. hermonthica-susceptible maize varieties, either coated with Foxy 2 using gum Arabic, gum Arabic alone, or left untreated. Data was collected over seven sampling periods on S. hermonthica population per plant, percentage of those that were wilting, and the severity of wilting. Maize plant growth parameters assessed included duration to 50% anthesis and 50% silking, plant height, number of leaves, stover and cob weights, and maize yield per hectare. Statistical analysis was done using SAS 9.1 software. Data on S. hermonthica population were analyzed by χ2-test using Proc Genmod (Poisson); while the other parameters were analyzed by Proc Mixed using study location, season and blocks as random effects, and the sampling periods as repeated effects. All the assessed parameters were similar between plants grown from seeds inoculated with F. oxysporum f. sp. strigae (Foxy 2), those coated with gum Arabic, and the ones without any coating. These parameters were also not different between the maize varieties. There are varying reasons for the disparities between results on F. oxysporum f. sp. strigae (Foxy 2) obtained in this Kenyan study, and those from researches outside this country. In conclusion, F. oxysporum f. sp. strigae strain Foxy 2 is predominantly safe on maize growth, but its efficacy in controlling S. hermonthica was not evident on the tested Kenyan soils.

Mycological and aflatoxin contamination of peanuts sold at markets in Kinshasa, Democratic Republic of Congo, and Pretoria, South Africa

Peanut (Arachis hypogaea L.) is an important food crop in sub-Saharan Africa. In this survey, the mycological and aflatoxin contamination of peanuts collected from Kinshasa, Democratic Republic of Congo, and Pretoria, South Africa, was assessed. Twenty peanut samples were purchased randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (AFB1, AFB2, AFG1 and AFG2) using standard methods. The results indicated that 95% of the Kinshasa samples and 100% of the Pretoria samples were contaminated with aflatoxigenic fungi in the ranges 20–49,000 and 40–21,000 CFU/g, respectively. Seventy-five per cent of the Kinshasa samples and 35% of the Pretoria samples exceeded the maximum limits of AFB1 as set by The Joint FAO/WHO Expert Committee on Food Additives. Residents of both cities are at a high risk of aflatoxin exposure despite their apparent cultural, socio-economic, geographic and climatic differences. Further work needs to be done to understand the supply chains of peanut trade in informal markets of the two countries so that interventions are well targeted on a regional rather than a national level.

English

Wheat is an important staple food crop in sub-Saharan Africa. However, the current wheat consumption of 900 000 tons in Kenya outweighs the wheat production of 350 000 tons given the high population growth and inflation. The stem rust currently poses the greatest threat to wheat production due to the emergence of the virulent race of thePuccinia graminis&nbsp;f. sp&nbsp;tritici,&nbsp;Ug99&nbsp;(TTKS) and its variants&nbsp;Ug99 + Sr24&nbsp;(TTKSK) andUg99 + Sr36&nbsp;(TTKST) leading to about 70 to 100% yield losses. This study aimed at evaluating twenty-five wheat genotypes for both field and seedling resistance to stem rust. The genotypes were grown in an alpha lattice design and in two replicates both in the greenhouse and in the field at Kenya Agricultural Research Institute (KARI), Njoro.&nbsp; The seedling stage infection types were scored based on Stakman et al. (1962) scale. At the adult plant stages, the stem rust disease severity was based on modified Cobb&rsquo;s scale. The genotypes showed diverse seedling and adult plant resistance responses. The most resistant entries, KSL-2, KSL-3 and KSL-20 also exhibited the pseudo black chaff (PBC) trait implying they contain the&nbsp;Sr2&nbsp;gene in their background; the basis of breeding for durable resistance to stem rust in wheat. These lines with high stem rust resistance could be backcrossed to the adapted and high yielding but susceptible Kenyan wheat varieties to avert further wheat yield declines. &nbsp; Key words:&nbsp;Stem rust, wheat,&nbsp;Ug99, resistance, disease severity.

Isolation and characterization of resistant gene analogs in cassava, wild Manihot species, and castor bean (Ricinus communis)

Cassava, Manihot esculenta , is one of the major food crops in sub-Saharan Africa (SSA) providing the bulk of dietary calories to hundreds of millions of households. Two viral diseases, namely cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) pose a serious threat to cassava production. The emergence of new virus species and strains that overcome the existing resistant/tolerant cultivars entails identification and pyramiding of new sources of resistance using marker-aided selection. The isolation of resistance gene analogues (RGAs) using a homology-based approach can provide useful resources towards this goal. Degenerate primers based on the conserved motif of the nucleotide binding site (NBS) domain from resistance (R) genes were used to isolate RGAs from genomic DNA and cDNA in cassava, wild Manihot species, and castor bean ( Ricinus communis ). A total of 552 RGAs sequences were identified and deposited in GenBank. Conserved motifs such as P-loop, Kinase-2a and GLPL were present in the NBS domain. This study sheds light on the nature of NBS- leucine-rich repeat (LRR) R genes in cassava and closely related taxa in the family Euphorbiaceae. These candidate sequences mapped to the draft cassava genome with high sequence similarity to predicted NBS-LRR genes. These novel sequences may serve as a stepping stone for further characterization and experimental validation of predicted R genes in the draft cassava genome, ultimately leading to the development of functional gene-targeted markers that can be used in molecular resistance breeding aimed at combating CBSD and CMD. Key words: Cassava, resistance, Manihot , castor bean, resistance gene analog, nucleotide binding site.