Production In sub-Saharan Africa Research Articles

User-producer interactions: Policy implications for developing appropriate innovations for small-scale agricultural production in sub-Saharan Africa

The dearth of technological progress in small-scale agricultural activities in sub-Saharan Africa has been majorly attributed to inappropriate innovations. This study employs the user-producer approach to recommend mechanisms to ensure the development of appropriate innovations for the sector. An analytical framework consisting of five types of policy actions which could foster the development appropriate innovations was developed from the approach to execute a qualitative analysis on a series of successful and failed attempts to mechanize small-scale oil palm fruit processing in Nigeria. The study revealed that initial technologies introduced failed because they were made to process other raw materials, were beyond the financial capability of processors and culturally incompatible. More successful innovations were found to be those developed in conjunction with processors. Recommended mechanisms include mandating and supporting research institutions to determine the needs of smallholders before R&D activities commence; funding the adoption and debugging of adopted technologies to further align technologies with smallholder needs; encouraging linkages among research institutions to enhance capabilities for problem solving; and increasing the number and types of research institutions in the sector to reduce the imposition of innovations.

Performance Assessment of Drought Tolerant Maize Hybrids under Combined Drought and Heat Stress.

Drought and high temperature are two major factors limiting maize productivity in sub-Saharan Africa. An increase in temperature above 30 °C reduces yield by 1% under optimal rain-fed condition and by 1.7% under drought stress (DS) and up to 40% under combined drought and heat stress (DSHTS). Approaches that improve performance under the two stresses are essential to sustain productivity. The objectives of this study were to (i) assess the extent of variation in tolerance to DSHTS from among the existing best drought tolerant (DT) hybrids; (ii) examine the response patterns of the hybrids to DSHTS; (iii) identify traits that contributed to better performance under DSHTS; and (iv) select the best hybrids with tolerance to DSHTS stress. We evaluated 40 DT hybrids under DSHTS, DS, and well-watered (WW) conditions for three years. Highly significant (p < 0.001) differences were found among hybrids for grain yield and other traits. Moderately to low repeatability values were detected for grain yield under DS (0.63) and under DSHTS (0.48). Grain yield under DS was not correlated with grain yield under DSHTS (r = 0.29; p = 0.06), but it was correlated with grain yield under WW (r = 0.74; p < 0.001). Grain yield was strongly correlated with ears per plant, ear and pant aspects, days to anthesis and silking under both DS and DSHTS. Tassel blast accounted for 28% of the yield reduction under DSHTS. The top five DT hybrids produced 9 to 26% more grain yields than the best commercial hybrid. Three hybrids produced high grain yields under DTHTS and DS as well as under WW. These hybrids will be tested further in collaboration with partners for possible release.

Influence of Tillage Systems on Diversity and Abundance of Insect and Nematode Pests of Maize in Malete, Kwara State, Nigeria

Pests are major biotic factors causing up to 45% yield reduction in maize production in sub-Saharan Africa. To develop improved methods for maize management, the species and abundance of insects and nematodes associated with ten quality protein maize varieties (QPMVs) were evaluated with two commonly used tillage practices, ‘plough only plots (POP)’ and ‘plough and harrow plots (PAHP)’. The experiment was carried out using QPMVs at the Teaching and Research Farm of the Kwara State University, Malete, Nigeria, and arranged in a randomized complete block design with 11 treatments replicated 3 times, including local check “pambo”. A total of 833.1±4.0 and 799.3±3.4 arthropods specimens were collected from POP and PAHP, respectively, comprising 8 orders and 18 families. Ootheca mutabilis was the most abundant species with 5.47% (POP) and 5.68% (PAHP) and the least abundant was Rhopalosiphum maidis 1.82% (POP) and 1.80% (PAHP). As indicated by Shannon Wiener (3.46±0.023) and Simpson indices (0.97±0.0008) there are even distribution in the tillage practices. Three genera of plant parasitic nematodes (PPNs) were identified, Meloidogyne spp. (POP (78.33±19.65), PAHP (1.33±0.33), Pratylenchus spp. (POP (41.67±9.26), PAHP (5.00±2.31), and Helicotylenchus spp. (POP (58.33±38.35), PAHP (23.33±14.50). The use of PAHP tillage practices is effective in reducing insects and nematodes associated with maize in Nigeria and therefore recommended for the management of both pests in maize production.

Effect of landscape diversity and crop management on the control of the millet head miner, Heliocheilus albipunctella (Lepidoptera: Noctuidae) by natural enemies

The pearl millet head miner, Heliocheilus albipunctella, is a major constraint to increasing crop productivity in sub-Saharan Africa. In the absence of any insecticide application by farmers, its control mostly relies on the action of natural enemies.The objective of the present study is to identify crop management and landscape features affecting biocontrol services by natural enemies. A set of 45 millet fields were selected in a 20 ∗ 20 km area in Senegal, from the analysis of high resolution satellite images (Pleiades), and hypotheses on relative abundance of millet fields and semi-natural habitats (mainly trees) in the agricultural landscape. A biocontrol service index (BSI) was computed for each field over two cropping seasons by experimentally excluding natural enemies from naturally egg-infested millet panicles. Information on crop management was collected through farmer’s interviews. An information theoretical approach and model averaging were performed to rank the effect of landscape metrics on BSI at eight spatial scales (from 250 to 2000 m).The BSI was generally high (77%) but highly variable among fields (0–100%), and was greater in compound fields compared to bush fields. The BSI also increased with the abundance of tree patches and the diversity of vegetation in a 1750 m-buffer around millet fields.Results support previous studies stressing the importance of semi-natural areas and vegetation diversity to support pest regulation by natural enemies. Further research is needed to better understand relationships between agroforestry systems and biological control, to promote ecologically-intensive solutions for reducing crop losses.

Editorial: Special Edition on Innovations in Cassava Processing

In 2015 we considered small-scale cassava processing in this journal with interesting results. Since then, cassava production in sub-Saharan Africa has continued to grow by volume, and new uses and value chains are slowly emerging. But many of the founding conditions that hold the sector back remain in place. A tiny fraction of farmers have access to improved cassava planting material and varieties, or farming methods that increase productivity, despite significant investment by major donors. Rural infrastructure remains the key constraint to any leap forward in efficiency in the sector. Policy remains at odds with reality, with new calls for fixed cassava quotas in domestic foods, but very little coordinated action to support these demands.

Got forages? Understanding potential returns on investment in &lt;i&gt;Brachiaria&lt;/i&gt; spp. for dairy producers in Eastern Africa

Production of livestock and dairy products in Sub-Saharan Africa struggles to keep pace with growing demand. The potential exists to close this gap in a climate-friendly way through the introduction of improved forage varieties of the Brachiaria genus. We assess the potential economic impact of the development and release of such varieties in 6 Eastern African countries using an economic surplus model. Results are presented across a range of potential scenarios involving different adoption rates and percentage increases in production. For all but the lowest levels of adoption and production increases, improved forages have the potential for positive return on investment. Using these results, we present formulae that help readers calculate the adoption rate or percentage increase in production necessary to achieve specific desired levels of net benefit. Overall, the model output suggests that investment in a forages research program related to the qualities of the forage itself as well as programs to enhance dissemination and adoption of new materials would be low risk and have high likelihood for positive outcomes, generating discounted net benefits in the order of multiple tens of millions of dollars over a 30-year time horizon.

Genetic Variances and Heritabilities of Traits of an Early Yellow Maize Population after Cycles of Improvement for Striga Resistance and Drought Tolerance.

Drought and Striga are principal constraints to maize (Zea mays L.) production in sub-Saharan Africa. An early yellow maize population, TZE-Y Pop DT STR, which had undergone five cycles of selection for resistance to Striga, followed by three cycles of improvement for drought tolerance, was investigated for yield gains, changes in genetic variance, and interrelationships among traits under drought stress and optimum environments. Two hundred and forty S1 lines comprising 60 each from the base population and subsequent populations from three selection cycles improved for grain yield and drought tolerance were assessed under drought and optimal environments in Nigeria from 2010 to 2012. Genetic improvements in grain yield of 423 and 518 kg ha–1 cycle–1 were achieved under drought stress and optimal environments. Predicted improvements in selection for yield were 348 and 377 kg ha–1 cycle–1 under drought stress and optimum environments, respectively. The highest yield observed in C3 was accompanied by reduced days to silking and anthesis–silking interval, improved plant aspect and ear aspect, and increased plant height and ears per plant across research environments, as well as improved stay-green characteristic under drought. The level of genetic variability for yield and a few other traits were maintained under drought and optimal environments in the population. The presence of residual genetic variability for yield and other assayed traits in C3 indicated that progress could be made from future selection in the population depending on the ability of breeders to identify outstanding genotypes and the precision level of experimentation. Substantial improvement has been made in yield and drought tolerance in C3 of the population.

Mapping Nairobi's dairy food system: An essential analysis for policy, industry and research

Demand for dairy products in sub-Saharan Africa, is expected to triple by 2050, while limited increase in supply is predicted. This poses significant food security risk to low income households. Understanding how the dairy food system operates is essential to identify mitigation measures to food insecurity impact. This study aims to determine the structure and functionality of Nairobi's dairy system using a value chain mapping approach.Primary data were gathered through focus group discussions and key informant interviews with dairy value chain stakeholders in Nairobi to obtain qualitative information on people and products in the chains while describing their interactions and flows. Qualitative thematic analysis combined with flowcharts created by participants enabled identification of key food system segments and the development of chain profiles (or flow-diagrams) which together form Nairobi's dairy system.Seven chain profiles forming Nairobi's dairy value chain were identified. These were found to be dominated by small-scale individuals who operate largely independently. Our profiles for the urban and peri-urban farming systems were structurally similar in their downstream networks, obtaining inputs from similar sources. Upstream, the urban systems were shorter, supplying mostly to immediate neighbours or based on own consumption, while the peri urban systems supplied to a wider network and showed some affiliations to producers' associations. Two distinct profiles characterize the milk flow from traders belonging either to a Dairy Traders Association (DTA) or those not belonging to this association (non-DTA). DTA traders sell mainly to fixed retailers and non-DTA traders to mobile retailers (hawkers or roadside vendors). Profiles associated with medium and large cooperatives were driven by networks of collection centres, but with medium-sized cooperatives selling half of their production to large processing companies, and large cooperatives only to fixed retailers. Large processing companies' profiles indicated distribution of high volumes and value addition processing. They reported strategic milk collection arrangements with suppliers on long, medium - or short - term contracts and with well-established product distribution channels.We have identified numerous inter-linkages across dairy chain profiles in Nairobi's complex system, demonstrating significant interdependency among the stakeholders. Therefore, enhancing the system's efficiency requires a holistic, system-wide approach and any policy interventions should consider every segment of the value chain. This study provides a methodological approach for organizations and policy makers to understand and address structural and functional vulnerabilities within food systems more broadly. The insights from this study are relevant to other rapidly growing cities in the region.

Combining Ability and Heterosis of Tolerance to Low Soil Nitrogen in Tropical Maize Cultivars Derived from Two Breeding Eras

Abstract Low soil nitrogen is one of the principal abiotic stresses affecting maize productivity in Sub-saharan Africa. Field studies were conducted at the International Institute of Tropical Agriculture (IITA), Ibadan during the cropping seasons for three years, from 2010 to 2012, with ten open pollinated maize varieties (OPVs) derived from two breeding eras (1 and 2). The ten OPVs and their crosses were evaluated under high-N and low-N conditions. The aim was to identify superior populations that may be useful sources genes for inbred line extraction and hybrid development for grain yield. Under low-N condition, mid and high parent heterosis for grain yield were low indicating the suitability of the hybrids for cultivation only in environments with high productivity index. Hybrid DMR-LSR-W (Era 1) × TZSR-Y-I (Era 2) had greatest mid and high-parent heterosis for grain yield under high-N and across the other four test environments. Parent AMATZBR-WC2B with higher general combining ability effects and mean values for grain yield, and cross combinations DMR-LSR-W (Era 1) x BR9928DMRSR (Era 2) and BR9922DMRSR (Era 2) x TZBRELD-4C0W (Era 2) with higher specific combining ability for grain yield under low-N environment are promising candidates for the development of nitrogen use efficient varieties for cultivation in low-N environments.

Phenotypic screening of cowpea (Vigna unguiculata (L.) walp) genotypes for resistance to cowpea viral diseases

Viruses are a major constraint to cowpea production in sub-Saharan Africa. Host plant resistance is the most effective and reliable method of managing viral diseases. In order to identify the source of resistance or tolerance, 38 cowpea genotypes were screened for virus infection under field conditions during the 2016 wet and dry seasons. The experiment was laid out in a randomized complete block design with four replications in both seasons. Disease severity was assessed fortnightly based on disease symptom using 1-5 visual scale (1=symptomless, and 5= very severe symptom). The cowpea genotypes exhibited varying reactions to viral infections with mean disease incidence ranging from 17.7% in the fourth week to 29.2% in the eighth week for the wet season and from 34.4% to 53.1% for the fourth and eighth week, respectively in the dry season. Symptoms observed were leaf mosaic (86.7%), leaf mottling (86.7%), chlorotic spots (34.2%), vein clearing (28.9%), leaf curl (26.3%), necrotic lesions (15.8%) and stunting (10.5%). Symptom severity in the rainy season ranged from symptomless (severity score of 1) in IT10K-819-4 and IT07K-297-13 to moderate symptom (severity score of 2.9) in Apagbaala. However, in the dry season, the symptom severity score ranged from 1.11 (mild symptom) in Marfo Tuya to a score of 2.4 (moderate symptom) in IT07K-298-9, thus demonstrating a significant genotype x season interaction effect. Incidence and severity were significantly higher in the dry season than in the rainy season. There was a strong positive correlation between the disease incidence and disease severity as well as AUDPC and no correlation between the cowpea incidence and the seed yield and plant height in the wet season. There was a negative correlation between the incidence and plant height in the dry season. Six genotypes (IT07-210-1-1, IT07K-297-13, IT08K-193- 14, IT09-456, IT10K-817-3 and IT10K-819-4) exhibited mild symptoms and gave high yields in both seasons, thus demonstrating a stable G x E interaction effect. These disease resistant genotypes could be evaluated further before release to farmers. Keywords: Area Under Disease Progress Curve, Host resistance, Vigna unguiculata, Viral diseases

English

Viral infections are a major challenge to sustainable cowpea production in sub-Saharan Africa (SSA). Nine cowpea (Vigna unguiculata L. Walp) genotypes were evaluated for resistance against viral infection in a field trial involving randomized complete block design with 4 replications. Viral disease severity was assessed at 2, 4 and 6 weeks after planting (WAP) based on disease symptoms. Double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) using antisera raised against cucumber mosaic virus (CMV), cowpea severe mottle virus (CPSMV), cowpea mosaic virus (CPMV) and southern bean mosaic virus (SBMV) was used to detect the viruses associated with diseased leaf samples collected from the field. Biometric and yield data were also taken. The mean disease incidence and area under disease progress curve (AUDPC) varied significantly (P < 0.05) among the cowpea genotypes, with 7 (Apagbaala, UCC-366, UCC-489, UCC-490, UCC-497, UCC-514 and UCC-523) out of 9 cowpea genotypes showing field resistance whilst the other two (UCC-473 and UCC-484) exhibited moderate resistance. ELISA showed that all the 9 cowpea genotypes were infected with at least one of the three viruses namely CMV, CPMV and CPSMV, whereas SBMV was not detected. Co-infection by CMV, CPMV and CPSMV was observed in UCC-366. Mean plant height, canopy diameter and seed yield differed significantly (P < 0.05) among the cowpeas. UCC-473, UCC-316, and UCC-523 had high mean seed yields of 6.690, 4.922 and 4.144 t ha-1 respectively, above the overall mean seed yield of 3.63 t ha-1, emphasizing their resilient to viruses. Key words: Vigna unguiculata, viral infection, disease incidence and severity, resistance screening.

English

Soil degradation and desertification pose a major threat to agricultural production in sub-Saharan Africa. The influence of cropping systems which had been established on selected physical and chemical properties of soil were investigated in Akinyode-Okinni community in Egbedore Local Government Area (LGA) of Osun State, Nigeria. The cropping systems included agri-silviculture (SCM), silvi-pasture (SPC), agri-horti-silviculture (PAH) and agroforestry (AFT) selected from existing farms in the community. The selected plots had cocoa (Theobroma cacao), oil palm (Elais guineensis) and kola-nut (Kola nitida) as permanent crops; coco-yam (Coco nucifera), guinea grass (Panicum maximum), plantain (Musa spp), maize (Zea mays), and cassava (Manihot utilissima) were the annual crops. The experiment was carried out for two cropping seasons. Results showed that in the AFT system bulk density (BD) decreased slightly from 1.22 to 1.16 g/cm3 in the top soil and from 1.18 to 1.09 g/cm3 in the subsoil after two seasons of crop growth. The pH varied between 6.40 and 7.05 in the first season and between 7.05 and 7.29 after two seasons. On average, the topsoil contained more organic carbon (OC) in the SPC (38 g kg-1) and SCM (36 g kg-1) systems than in the PAH and AFT systems. Similarly, the total phosphorus content was higher in the topsoil of SPC and SCM systems than in the other systems. There was a slight reduction in soil acidity and no significant changes occurred in the concentrations of exchangeable bases after two cropping seasons. Conclusively, these cropping systems have the potential to reduce soil deterioration and thus, further studies to develop appropriate management strategies are necessary. Key words: Cropping systems, exchangeable bases, organic carbon, silviculture, soil degradation. &nbsp

Effectiveness of imazaquin seed treatment on Striga gesnerioides control and growth traits of seven cowpea genotypes

Cultural and biological control measures have failed to provide satisfactory management of Striga gesnerioides, a major biotic constraint to cowpea production in sub-Saharan Africa. Field trials were conducted to evaluate the efficacy of imazaquin seed treatment (at 0.00, 0.06, and 0.24 kg a.i. ha−1) on Striga gesnerioides control and the growth of seven cowpea genotypes (Achishiru, IT97K-1263, IT97K-390-2, IT98K-133-1-1, TVU-1283, TVU-1542, and TVU-1908) at the Teaching and Research Farm of the Faculty of Agriculture of Bayero University, Kano, Nigeria, during the rainy seasons of 2010 and 2011. Treating the seeds with imazaquin at 0.24 kg a.i. ha−1 produced the lowest number of striga stand−1. Across herbicide rates, Achishiru had most S. gesnerioides; IT97K-1263 had the fewest. The results indicated that the untreated control recorded the highest number. The untreated TVU-1283 produced the fewest branches; Achishiru produced the least dry matter while IT97K-1263 had the most branches and dry matter in 2010 and 2011 rainy seasons. Application of 0.24 kg a.i. ha−1 to IT97K-390-2 consistently produced the highest branches and dry matter; Achishiru produced the fewest branches and least dry matter in 2010 and 2011 seasons. Treating IT97K-390-2, IT98K-133-1-1, and TVU-1542 with imazaquin at 0.24 kg a.i. ha−1 provided an effective means of managing striga in cowpea and enhanced the growth characters of these genotypes.

KSTP 94, an Open-pollinated Maize Variety Has Postattachment Resistance to Purple Witchweed (Striga hermonthica)

AbstractStriga spp. are obligate root hemiparasites that constrain cereal production in sub-Saharan Africa. Although purple witchweed [Striga hermonthica (Delile) Benth.] and Asiatic witchweed [Striga asiatica (L.) Kuntze] infect all cereal crops, maize (Zea mays L.) is particularly vulnerable to their infestations. A sustainable control strategy for Striga would be to breed crops with host-based resistance as part of an integrated management plan. In maize, the open-pollinated variety Kakamega Striga-tolerant population of the year 1994 (‘KSTP 94’) has been popularized as a Striga-tolerant/resistant variety. This resistance was earlier reported to result from production of low amounts of sorgomol, a less potent strigolactone. To determine whether KSTP 94 harbors postattachment resistance, we used a soil-free assay based on observation chambers called rhizotrons. We found that the size of Striga seedlings attached to ‘CML 144’ (a susceptible maize inbred line) were 2.5-fold longer than those on KSTP 94. In addition, KSTP 94 had significantly fewer Striga attachments, which corresponded to significantly lower biomass (2.6-fold) compared with CML 144. Histological analysis revealed that the low Striga growth and development while infecting KSTP 94 was due the parasite’s inability to penetrate the host’s endodermis and make effective xylem–xylem connections. We therefore conclude that in addition to preattachment resistance, KSTP 94 exhibits postattachment resistance to S. hermonthica and could therefore be a good genetic source for postattachment resistance breeding.

Towards a Knowledge Specialisation Index for Sub-Saharan Africa: an Informetrics Study

The study examines the publications produced in selected sub-Saharan African countries with the aim of assessing research intensity or prioritisation for purposes of developing a knowledge specialisation index in sub-Saharan Africa. The study used data obtained from the Thomson Reuters’ Incites™ Essential Science IndicatorsSM (ESI) database. The specialisation index for each country in sub-Saharan Africa was calculated as country X’s papers in field Y as a proportion of sub-Saharan Africa’s publications in field Y. The study found that knowledge specialisation in sub-Saharan Africa varies from country to country. Sub-Saharan Africa’s intensity is in the fields of microbiology, immunology, agriculture and clinical medicine. The least prioritised knowledge fields are chemistry, engineering, mathematics, physics, material science, computer science and space science. South Africa specialises in the largest number of knowledge fields while such countries as Guinea-Bissau, Seychelles and Mauritius are strongly represented in one knowledge field each. The most common fields of knowledge specialisation, among the 30 countries investigated in the study, were immunology, microbiology and agriculture. It was observed that knowledge production in sub-Saharan Africa addresses areas or sectors that have been considered as key to economic development in the region, namely health and agriculture. We however recommend further research to investigate the factors that may be influencing the knowledge specialisation patterns reported in the study.

Allocation and Valuation of Smallholder Maize Residues in Western Kenya

Crop residues, one of smallholder farmers' most common but overlooked resources, serve multiple purposes in many rural households: they are a source of fuel, animal feed, and soil amendments. They are key to maintaining soil fertility, depletion of which is widely considered to be one of the major causes of low food production in Sub-Saharan Africa. Using household survey data from western Kenya, we investigate the contribution of maize residues to smallholders' agricultural production and estimate their shadow value to be 5.94 Kenyan shillings (US$0.07) per kilogram. Valuing crop residue benefits contributes to multiple social goals, including improved economic evaluation of alternative agricultural practices and environmental conservation efforts.

Land Consolidation for Sub-Saharan Africa’s Customary Lands: The Need for Responsible Approaches

This paper explores the potential of land consolidation for dealing with land fragmentation in Sub-Saharan Africa’s (SSA) rural customary lands – where the intention is to increase food productivity. In SSA’s customary lands, the use of mechanized farming technology and intensive farming techniques have largely failed to increase food productivity. This is despite foreign investment and the interest of the farmers to do so. In many cases, neither the farm parcel structure nor the land tenure arrangements support the use of, or investment in, mechanized equipment. This implies a strong need to deal with the land fragmentation situation. Although land consolidation is argued as an effective response to land fragmentation; its application in SSA’s customary lands has either not been successful, or it has ended up breaking down the customary land tenure arrangements. We argue that past attempts at land consolidation in SSA’s customary lands have failed mainly due to the transfer of European strategies without adequate consideration for the local factors in the planning and implementation, as well as inadequate land information. Land consolidation strategies in Europe have shown that responsible approaches continually considered the changing local factors. There has been a recent push for more responsible approaches to land reform and planning activities that consider social, cultural, and economic factors that were previously not considered. In this paper, the nature and causes of land fragmentation in customary lands will first be explored, then current approaches seeking to increase farm productivity are reviewed. Analysing the problems of land fragmentation in customary lands, the failure to adapt land consolidation approaches in customary lands in the past, and the potential of participatory land administration as an enabling tool, we conclude that responsible approaches are an important component of increasing food productivity in sub-Saharan Africa.

Genetic diversity and virulence of Striga hermonthica from Kenya and Uganda on selected sorghum varieties

Joel KA, Runo S, Muchugi A. 2018. Genetic diversity and virulence study of Striga hermonthica from Kenya and Uganda on selected sorghum varieties. Nusantara Bioscience 10: 111-120. Parasitic weeds pose a severe problem in agricultural production, causing massive crop losses in many regions of the world and especially Africa. One example to be considered the most significant biological constraint to food production in sub-Saharan Africa (SSA) is Striga hermonthica, the most widespread among the Striga species in the semi-arid tropical African zones. The wide geographical distribution set conditions for genetically structured populations. The genetic variations among the weed populations allow for the quick breakdown of resistance in crops hence making control of the weed difficult. Efficient and effective control of S. hermonthica demands knowledge on inherent genetic variability within local and regional races of the weed. However, the genetic diversity and virulence of S. hermonthica ecotypes in Kenya and Uganda on selected sorghum varieties remain unknown. This study aimed at evaluating the genetic diversity among seven S. hermonthica populations from locations in Kenya and Uganda using 5 primer sets of Expressed Sequence Tags-Simple Sequence Repeats (EST-SSR). The genetic diversity was moderate as shown by the Nei’s genetic distance values. AMOVA measured low genetic differentiation among the populations. This study also investigated twelve sorghum varieties for their response to S. hermonthica infection. The result demonstrated that the varieties resistance responses to S. hermonthica varied widely. The phenotype of resistant interaction was characterized by the inability of the weeds haustoria to penetrate the sorghums root endodermis due to severe necrosis and in rare cases the parasites radicle growing away from the host root. The resistant sorghum varieties were the Asareca W2, Asareca AG3, N13 and the Wild-type which had low mean number of S. hermonthica plantlets growing on their roots, while the most susceptible varieties were Sap 027, Epurpur which had the highest mean number of S. hermonthica plantlets growing on their roots. There was a highly significant difference in the means of the number of Striga growing on the roots of sorghum varieties, Striga dry biomass and S. hermonthica length between the susceptible and resistant ones. This knowledge holds unique potentiality since resistant sorghum germplasm tested will be sourced and targeted to the seven specific geographical areas where virulence of the particular S. hermonthica populations was characterized.

Assessment of Management Options on Striga Infestation and Maize Grain Yield in Kenya.

The parasitic purple witchweed [Striga hermonthica (Del.) Benth.] is a serious constraint to maize production in sub-Saharan Africa, especially in poor soils. Various Striga spp. control measures have been developed, but these have not been assessed in an integrated system. This study was conducted to evaluate a set of promising technologies for S. hermonthica management in western Kenya. We evaluated three maize genotypes either intercropped with peanut (Arachis hypogaea L.), soybean [Glycine max (L.) Merr.], or silverleaf desmodium [Desmodium uncinatum (Jacq.) DC] or as a sole crop at two locations under artificial S. hermonthica infestation and at three locations under natural S. hermonthica infestation between 2011 and 2013. Combined ANOVA showed significant (P < 0.05) cropping system and cropping system by environment interactions for most traits measured. Grain yield was highest for maize grown in soybean rotation (3,672 kg ha−1) under artificial infestation and in D. uncinatum and peanut cropping systems (3,203 kg ha−1 and 3,193 kg ha−1) under natural infestation. Grain yield was highest for the Striga spp.-resistant hybrid under both methods of infestation. A lower number of emerged S. hermonthica plants per square meter were recorded at 10 and 12 wk after planting on maize grown under D. uncinatum in the artificial S. hermonthica infestation. A combination of herbicide-resistant maize varieties intercropped with legumes was a more effective method for S. hermonthica control than individual component technologies. Herbicide-resistant and Striga spp.-resistant maize integrated with legumes would help reduce the Striga spp. seedbank in the soil. Farmers should be encouraged to adopt an integrated approach to control Striga spp. for better maize yields.

Impacts of climate change on cropping patterns in a tropical, sub-humid watershed.

In recent decades, there have been substantial increases in crop production in sub-Saharan Africa (SSA) as a result of higher yields, increased cropping intensity, expansion of irrigated cropping systems, and rainfed cropland expansion. Yet, to date much of the research focus of the impact of climate change on crop production in the coming decades has been on crop yield responses. In this study, we analyse the impact of climate change on the potential for increasing rainfed cropping intensity through sequential cropping and irrigation expansion in central Benin. Our approach combines hydrological modelling and scenario analysis involving two Representative Concentration Pathways (RCPs), two water-use scenarios for the watershed based on the Shared Socioeconomic Pathways (SSPs), and environmental water requirements leading to sustained streamflow. Our analyses show that in Benin, warmer temperatures will severely limit crop production increases achieved through the expansion of sequential cropping. Depending on the climate change scenario, between 50% and 95% of cultivated areas that can currently support sequential cropping or will need to revert to single cropping. The results also show that the irrigation potential of the watershed will be at least halved by mid-century in all scenario combinations. Given the urgent need to increase crop production to meet the demands of a growing population in SSA, our study outlines challenges and the need for planned development that need to be overcome to improve food security in the coming decades.