Production In sub-Saharan Africa Research Articles

Unlocking Cassava Brown Streak Disease Resistance in Cassava: Insights from Genetic Variability and Combining Ability

Cassava brown streak disease (CBSD) threatens cassava production in sub-Saharan Africa despite the availability of resistant varieties. Extreme environmental factors weaken plant defenses, reducing CBSD resistance. This study examined CBSD inheritance in cassava populations, assessed genetic variability, and identified superior sources of resistance using F1, S1, and half-sib offspring populations derived from resistant sources. The offspring underwent field evaluation at two distinct sites from 2019 to 2021, and the symptom-free genotypes were analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Resistance to CBSD was categorized as most resistant, resistant, most tolerant, or tolerant based on symptoms and virus titers. The findings indicated that the resistance to CBSD is highly influenced by genotypes, F1/S1 types, and environmental conditions. An analysis of combining abilities revealed significant general combining abilities (GCAs) for CBSD, cassava mosaic disease (CMD), and traits associated with yield. The heritability estimates for resistance to CBSD varied between 43.4% and 63.2% for foliar symptoms and 14.6% and 57.9% for root necrosis across locations. The inheritance pattern involved a combination of additive and recessive genes with selfed (S1) populations displaying stronger and more effective resistance to the disease. The cassava brown streak virus (CBSV) was highly prevalent, and the Ugandan cassava brown streak virus (UCBSV) was not prevalent. Four genotypes were highly resistant to CBSD and could be key sources of resistance to this disease.

Gender differences in rice production participation among smallholder farmers in small-scale irrigation schemes in mbarali district, Tanzania

Smallholder farmers are crucial to agri-food production in sub-Saharan Africa. However, gender disparities in rice production participation persist in Tanzania. Existing research has yet to fully explore how demographic and socioeconomic factors influence gendered participation in rice production. This study assesses gender differences in rice production participation patterns among smallholder farmers and identify gender-related socio-economic and demographic factors influencing differences in participation within small-scale irrigation schemes in Mbarali District. Using cross-sectional approach, data were collected from 397 randomly selected farmers through structured questionnaire and analyzed with descriptive and inferential statistics, including ordered probit regression. The results revealed significant gender differences in rice production participation (p < 0.01). Male farmers had higher participation rates in activities such as land preparation, seedbed preparation, seedling management, irrigation, herbicide, fertilizer, pesticide application, harvesting, transporting, storage, and selling, while female farmers had higher participation rates in transplanting and weeding. The overall level of participation was moderate, with 78 % of male farmers and 49 % of female farmers. However, larger proportion of females (43 %) were at a lower participation levels compared to only 1 % of male farmers, while 21 % of males and 8 % of females were at high participation levels. Factors like household size, farming management, hierarchical position within households, decision-making power, and the ability to access irrigation water positively influenced participation levels, while land size cultivated had a negative impact (p < 0.05). These were gender-related socio-economic and demographic factors that disadvantage female farmers' participation (p < 0.05). While the age of the farmer and inadequacy of irrigation water significantly affected participation levels, farm-hired labour had positive influence, however, these factors were not gender-specific. The study concludes that gender differences in participation in rice production are influenced by demographic and socio-economic factors. To address these, the study recommends for interventions that reduce gender disparities by promoting equality in resource access, enhancing women's decision-making power over resources and ability to access irrigation water, and ensure sufficient water in small-scale irrigation schemes. The government should create an enabling environment that supporting female farmers in small-scale irrigation schemes for broader gender equality in agriculture and rural development.

Drivers and Consequences of Land Degradation on Livestock Productivity in Sub-Saharan Africa: A Systematic Literature Review

Land degradation is a major threat to sub-Saharan Africa rangelands, which are crucial for livestock farming and the livelihood of millions of people in the region. This systematic review aims to provide a comprehensive understanding of the causes and effects of land degradation, as well as to evaluate the effectiveness of different mitigation strategies. Following the PRISMA guidelines, we identified, screened, and analyzed 25 peer-reviewed articles published before 30 June 2024 using Scopus. The review highlights key factors that drive land degradation, such as soil erosion, drought, deforestation, and climate change, as well as socio-economic factors like poverty, land tenure issues, population pressure, and economic instability. These factors have serious implications, as land degradation can lead to poor quality of forage, an increased incidence of diseases, higher mortality rates among livestock, and a significant decline in livestock productivity. The socio-economic consequences of this degradation are significant, leading to reduced household income, increased poverty, and heightened food insecurity. Furthermore, the review assesses various mitigation strategies and concludes that practices such as rotational grazing and soil conservation techniques demonstrate high effectiveness, while agroforestry practices show only moderate success. An integrated approach that combines environmental, economic, and policy measures is crucial to addressing the complex challenge of land degradation in sub-Saharan Africa. Strengthening land tenure, improving economic stability, and promoting sustainable agricultural practices are essential steps toward improving the health of rangelands, increasing livestock productivity, and supporting the resilience and well-being of rural communities.

Grain yield and nitrogen cycling under conservation agriculture and biochar amendment in agroecosystems of sub-Saharan Africa. A meta-analysis

Soil nitrogen (N) is one of the most limiting factors affecting crop production in sub-Saharan Africa (SSA). Here we conducted a meta-analysis on the effect of climate smart agricultural (CSA) practices (conservation agriculture (CA) and/or biochar (BC)) application on: (1) soil nitrate-N (NO3-N), nitrous oxide (N2O) emission, biological N2-fixation, percent of nitrogen derived from the atmosphere (%Ndfa), grain yield and nitrogen use efficiency (NUE), (2) the role of soil properties and regions on grain yield and N cycling under CA and/or BC biochar application; and (3) the relationship between inorganic N fertilizer and NO3-N, N2O emissions, NUE and grain yield. We synthesized 87 unique papers, from 15 countries in SSA with 1643 paired observations. On average across all studies, CA and/or BC significantly increased grain yield and NUE, compared to conventional practices. Residue retention resulted in a significant increase in soil NO3-N and N2O emission, compared to conventional practices. Our analysis further indicates that BC application significantly increased biological N2-fixation, grain yield and NUE. Auxiliary soil parameters also affected grain yield and N cycling. Grain yield was significantly influenced by total organic carbon classes (TOC), whereby highest grain yield was recorded under CSA in soils with 0.5–1 % TOC, compared to soils with < 0.5 % TOC and > 1 % TOC. In addition, total nitrogen (TN) significantly affected the response ratio of CSA and conventional agriculture on N2O emission and biological N2-fixation. N2O emission increased significantly in soils with < 0.05 % TN, while biological N2-fixation increased significantly in soils with > 0.2 % TN. Increasing N fertilizer use significantly increased the response ratio of CSA and conventional agriculture on N2O and NO3-N while significantly reducing the response ratio of yield and NUE. The gap in yield and NUE between CSA and conventional agriculture practises was more pronounced at lower N rates of 0 kg ha−1 and narrowed as N input increased to 120 kg ha−1; this implies that, CSA offers more benefits compared to conventional agricultural practices under low N rates.

Combining Farmyard Manure with Mineral Nitrogen Fertilizer Boosts Maize Yields and Maintains Soil Health: Insights from Four Long-Term Experiments

Maize productivity in sub-Saharan Africa often falls below its potential due to soil fertility challenges. Researchers assessed the potential to counteract soil organic carbon (SOC) losses and yield declines using different organic resource treatments, with and without mineral nitrogen (N) fertilizer. While all treatments that received mineral N had similar yields in the first year, the application of farmyard manure (FYM) combined with mineral N was the only treatment that did not lose yields over the two decades, eventually outperforming all others. The results suggest that combining FYM with mineral N is the most effective of all tested strategies for simultaneously sustaining maize yields and SOC levels in similar tropical soils.

Soil Organic Carbon Storage, Nitrous Oxide Emission and Net Climate Benefit of Conservation Agriculture: Insights from Two Long-Term Experiments in Zimbabwe

The slow increase in grain production in sub-Saharan Africa (SSA) is largely the result of cropland expansion rather than an increase in crop yields, which have been stagnantly low (&lt; 1.5 t ha-1). Sustainable intensification of crop production is therefore needed to feed a growing population whilst minimizing negative impacts on the environment, biodiversity, and climate. Full accounting of the net global warming potential (GWP) of management practices can provide a holistic approach for identifying cropping systems that promote sustainable agriculture intensification to ensure food security whilst mitigating climate change.

Performance of tropical and subtropical maize inbred lines under well-watered and drought-stressed environments

Drought is a major constraint for maize production in sub-Saharan Africa. Developing high-yielding drought-tolerant maize germplasm will safeguard maize yields in the ever-increasing fluctuating rainfall conditions. This study aimed to identify high-yielding inbred lines with stable performance for utilization in hybrid production. One hundred eighty-two (182) maize inbred lines were evaluated under well-watered and drought-stressed conditions at Ukulinga, Makhathini, and Cedara research stations in KwaZulu-Natal, South Africa. The experiments were carried out in a 13 × 14 alpha lattice design with two replications. The inbred lines exhibited significant differences (p ≤ 0.001) for grain yield and yield-related traits under well-watered and drought-stressed environments. The GGE biplot identified three mega-environments, clearly separating drought-stressed from well-watered environments. Inbred lines TZISTR1190, TZISTR1231, TZISTR1261 and CML540 were superior under well-watered conditions, while TZISTR1164 and CML390 performed well under drought condition. TZISTR1190 displayed both high average yield and stability across environments. Inbred lines combining stable high yielding performance in optimum and stress conditions such as TZISTR1190 and TZISTR1231, can be incorporated into local maize breeding pipelines to develop stable high yielding resilient hybrids.

Genomic Prediction of The Performance of Tropical Doubled Haploid Maize Lines under Artificial Striga hermonthica (Del.) Benth. Infestation.

Striga hermonthica (Del.) Benth., a parasitic weed, causes substantial yield losses in maize production in sub-Saharan Africa (SSA). Breeding for Striga resistance in maize is constrained by limited genetic diversity for Striga resistance within the elite germplasm and phenotyping capacity under artificial Striga infestation. Genomics-enabled approaches have the potential to accelerate identification of Striga resistant lines for hybrid development. The objectives of this study were to evaluate the accuracy of genomic selection for traits associated with Striga resistance and grain yield (GY) and to predict genetic values of tested and untested doubled haploid (DH) maize lines. We genotyped 606 DH lines with 8,439 rAmpSeq markers. A training set of 116 DH lines crossed to two testers was phenotyped under artificial Striga infestation at three locations in Kenya. Heritability for Striga resistance parameters ranged from 0.38‒0.65 while that for GY was 0.54. The prediction accuracies for Striga resistance-associated traits across locations, as determined by cross validation (CV) were 0.24 to 0.53 for CV0 and from 0.20 to 0.37 for CV2. For GY, the prediction accuracies were 0.59 and 0.56 for CV0 and CV2, respectively. The results revealed 300 DH lines with desirable genomic estimated breeding values (GEBVs) for reduced number of emerged Striga plants (STR) at 8, 10, and 12 weeks after planting. The GEBVs of DH lines for Striga resistance associated traits in the training and testing sets were similar in magnitude. These results highlight the potential application of genomic selection in breeding for Striga resistance in maize. The integration of genomic-assisted strategies and DH technology for line development coupled with forward breeding for major adaptive traits will enhance genetic gains in breeding for Striga resistance in maize.

Assessing homogeneous and heterogeneous economic impacts of fall armyworm management practices on farm performance in Ghana

One of the emerging challenges impinging on sustainable food production in sub-Saharan Africa is the invasion of the fall armyworm (FAW) pest. Data collected from farm households in different agro-ecological zones in Ghana and a Multivalued Treatment Effect (MVTE) model were used to argue that FAW management practices are key to stemming the debilitating effects of FAW infestations on farm performance. Previous studies have analysed homogeneous treatment effects to explain FAW management practices. The present study employs heterogeneous treatment effects to account for the differential effects of FAW management practices such as early planting, application of prescribed pesticides, and a combination of both practices while accounting for socioeconomic characteristics. Findings from the study reveal that distance to extension services exerts negative effects on adoption of early planting only, and adoption of both FAW management practices. Moreover, past FAW infestations tend to exert a positive effect on adoption of pesticide application only and adoption of a combination of the FAW management practices. Adopting the FAW management practices examined in this study assisted the maize producers in raising their farm performance. Socioeconomic characteristics also tend to influence the homogeneous treatment effects of adoption of the FAW management practices on farm performance. This finding indicates that heterogeneity within farm households is crucial for policy regarding adoption of FAW management practices.

Genetic diversity analysis of tropical and sub-tropical maize germplasm for Striga resistance and agronomic traits with SNP markers.

Striga hermonthica (Sh) and S. asiatica (Sa) are major parasitic weeds limiting cereal crop production and productivity in sub-Saharan Africa (SSA). Under severe infestation, Striga causes yield losses of up to 100%. Breeding for Striga-resistant maize varieties is the most effective and economical approach to controlling the parasite. Well-characterized and genetically differentiated maize germplasm is vital to developing inbred lines, hybrids, and synthetic varieties with Striga resistance and desirable product profiles. The objective of this study was to determine the genetic diversity of 130 tropical and sub-tropical maize inbred lines, hybrids, and open-pollinated varieties germplasm using phenotypic traits and single nucleotide polymorphism (SNP) markers to select Striga-resistant and complementary genotypes for breeding. The test genotypes were phenotyped with Sh and Sa infestations using a 13x10 alpha lattice design with two replications. Agro-morphological traits and Striga-resistance damage parameters were recorded under a controlled environment. Further, high-density Diversity Array Technology Sequencing-derived SNP markers were used to profile the test genotypes. Significant phenotypic differences (P<0.001) were detected among the assessed genotypes for the assessed traits. The SNP markers revealed mean gene diversity and polymorphic information content of 0.34 and 0.44, respectively, supporting the phenotypic variation of the test genotypes. Higher significant variation was recorded within populations (85%) than between populations using the analysis of molecular variance. The Structure analysis allocated the test genotypes into eight major clusters (K = 8) in concordance with the principal coordinate analysis (PCoA). The following genetically distant inbred lines were selected, displaying good agronomic performance and Sa and Sh resistance: CML540, TZISTR25, TZISTR1248, CLHP0303, TZISTR1174, TZSTRI113, TZDEEI50, TZSTRI115, CML539, TZISTR1015, CZL99017, CML451, CML566, CLHP0343 and CML440. Genetically diverse and complementary lines were selected among the tropical and sub-tropical maize populations that will facilitate the breeding of maize varieties with Striga resistance and market-preferred traits.

Current Status and Perspective of Rice Production in Sub-Saharan Africa

Current Status and Perspective of Rice Production in Sub-Saharan Africa

Limited growth in smallholder farm productivity in sub-Saharan Africa.

Limited growth in smallholder farm productivity in sub-Saharan Africa.

Sweet Potato Virus Disease and Its Associated Vectors: Farmers’ Knowledge and Management Practices in Uganda

Effective management of sweet potato diseases such as sweet potato virus disease (SPVD) depends to a large extent on farmers&amp;rsquo; knowledge of the disease as well as on the integration of recommended management methods in their farming practices. SPVD has continued to be the most important disease constraining sweet potato (Ipomoea batatas) production in sub-Saharan Africa (SSA). Inadequate information about farmers&amp;rsquo; perception, knowledge and practices are the major impediments in developing countries and has hindered development of effective management of SPVD. This paper addresses the gap by (i) Understanding the socioeconomic characteristics of sweet potato farmers. (ii) Assessing knowledge level of the farmers about SPVD, SPVD vectors and management methods. (iii) Examining the relationship between farmers&amp;rsquo; coping strategies to control SPVD and knowledge. To achieve the study objectives, a cross sectional survey was carried out among 95 sweet potato growing households in central, eastern and western regions of Uganda during 2017. Results showed that sweet potato is valued as the second most important subsistence crop among smallholder farmers. The female farmers (54.7%) were more involved in production than their male counterpart. SPVD was perceived by the majority of farmers (63.6%) as the most important disease and a total of 70.5% of these farmers had experienced the disease in their fields. Despite of SPVD prevalence as perceived by the farmers, close to half (48.4%) of these farmers did not have good knowledge of the SPVD, 67.4% were ignorant about SPVD vectors, 85.8% did not know management methods and hence 68.4% did not use any management method. These knowledge gaps down play stability of the farmers to effectively manage the disease. Nevertheless, it was revealed that the ability to identify SPVD, month of occurrence and education level improves its management. This paper recommends gender tailed support to sweet potato farming, increased awareness and training of farmers to improve their knowledge of SPVD, and development of effective control strategies for SPVD.

Genome-wide association studies reveals new candidate genes associated with resistance to Striga gesneroides in Cowpea [Vigna unguiculata (L.) Walp.] accessions from sub-Saharan Africa

Parasitic plant Striga gesneroides reduces cowpea productivity in sub-Saharan Africa, leading to substantial yield losses. This weed is the major reason for land abandonment by many farmers. While various methods have been proposed for managing Striga invasion and parasitism, host-plant resistance remains the most effective and affordable option for small-scale farmers in the sub-region. This study aims to expedite the improvement of Striga resistance breeding through marker-assisted selection by identifying genomic regions and candidate genes associated with Striga resistance indicator traits using association mapping. A panel of 188 cowpea accessions assembled from five gene banks in West Africa were phenotyped for two years under Striga-infested and non-infested research conditions. These accessions were equally genotyped using the medium-density genotyping of the Diversity Arrays Technology sequencing (DArTseq) platform to obtain marker information. High broad-sense heritability estimates were observed for Striga resistance status (SRS), number of Striga per plot (NSPlot), and Pod weight (PW) while low heritability estimates were observed for fodder weight (FW) and Plant Aspect (PASP). Twenty-four SNP markers were identified across SRS, NSPlot, FW, PASP, and PW under Striga-infested conditions. Under non-infested conditions, 17 SNPs were identified across FW, PASP, and PW. Gene annotation of the significant SNPs revealed candidate genes such as ubiquitin ligase activity, cell wall reinforcement protein, and pathogenesis-related protein. These genes function in plant growth regulation, development, and defense mechanisms. This study offers valuable insights for marker selection, validation, and deployment in cowpea improvement for Striga resistance in SSA.

How do financial inclusion and bank stability explain agricultural productivity in Sub-Saharan Africa?

PurposeThis study aims to examine the impact of financial inclusion and bank stability on agricultural productivity in Sub-Saharan Africa (SSA).Design/methodology/approachThe study used 38 countries in the SSA with data spanning between 2004 and 2021. The data were analyzed using the two-step system generalized method of moments (GMM) and the panel-corrected standard error (PCSE) model.FindingsThe study found a positive effect of financial inclusion and bank stability on agricultural productivity. The study also discovered that while the access component of financial inclusion has a negative influence on agricultural productivity, the usage dimension has a positive impact.Research limitations/implicationsThe study suggests to policymakers that an inclusive and stable financial system improves agricultural productivity. The findings recommend that policymakers should empower farmers to leverage financial inclusion.Originality/valueThis study provides insightful discussion on the impact of financial inclusion and its various dimensions and bank stability on agricultural productivity in SSA.

Evaluation of granular formulated strigolactone analogs for Striga suicidal germination.

Striga hermonthica, an obligate root parasitic weed, poses a significant threat to cereal production in sub-Saharan Africa. Lowering Striga seed bank in infested soils is a promising strategy to mitigate infestation levels. The dependency of Striga seed germination on strigolactones opens up the possibility of a 'suicidal germination' approach, where synthetic germination stimulants induce lethal germination in the absence of a host. Implementing this approach requires active germination stimulants with a suitable formulation for field application. Here, we describe the development of slow-releasing granular formulation of two potent germination stimulants 'Methyl Phenlactonoate 3' and 'Nijmegen-1' and the assessment of their activity under Laboratory, greenhouse, mini-field, and field conditions. Under laboratory conditions, the granular formulation of either of the two germination stimulants (1.25 mg per plate, corresponding to 0.09 mg a.i.) induced Striga seed germination at a rate of up to 43%. With 10 mg granular product (0.75 mg a.i.) per pot, we observed 77-83% reduction in Striga emergence under greenhouse pot conditions. Application of the formulated stimulants under artificially or naturally infested fields resulted in approximately 56%, 60%, and 72% reduction in Striga emergence in maize, sorghum, and millet fields in Kenya and Burkina Faso, respectively. Our findings on the newly designed granular formulation of Methyl Phenlactonoate 3 and Nijmegen-1 reveal encouraging prospects for addressing the Striga problem in Africa. These findings underscore several significant advantages of the formulated stimulants, including suitability for the African agricultural context, and, most importantly, their effectiveness in reducing Striga infection. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluating the Effect of Cowpea Variety on the Insecticidal Response and Antioxidant Enzymes of Callosobruchus Maculatus (Fabricius) Treated with Two Plant Powders

Callosobruchus maculatus (Fabricius), a notorious pest wreaking havoc during the storage phase of cowpea, has remained a serious menace militating against cowpea production in sub-Saharan Africa for years. This study investigated the effects of cowpea varieties [Gombe (GBV) and Sokoto (SKV)] on the insecticidal response and antioxidant enzymes of adult C. maculatus treated with powders of Piper guineense (Schum and Thonn) and Syzygium aromaticum (L.). The study was conducted at an ambient temperature (28 ± 3ºC) and relative humidity (75 ± 6). Bruchids were exposed to dosages ranging from 0.05 to 0.55 g/20 g cowpea. The morphometrics of the cowpea seeds and emerged bruchids were also subjectively determined. GBV generally had significantly longer, wider, and thicker seeds than SKV. Similarly, GBV-reared bruchids were significantly (P 0.001) wider and longer in body size than SKV-reared bruchids. Regardless of cowpea variety, S. aromaticum was generally more toxic to the bruchids than P. guineense. GBV-reared bruchids were more susceptible to both plant powders than SKV-reared bruchids. The specific activities of Superoxide Dismutase, Catalase, and Glutathione also varied with cowpea varieties and plant powders. Cowpea variety, experimental dosage, and their interaction (V*D) significantly (P 0.001) influenced the specific activities of the three enzymes. Hence, the two plant powders, especially S. aromaticum, could be used as effective protectants of cowpea seeds against C. maculatus infestation. The findings in this study could ultimately contribute to ensuring the security and integrity of cowpea seeds, sustaining them as a staple food crop.

Financial Proximity and Agricultural Productivity: New Evidence from Sub-Saharan African Countries

ABSTRACT: Agriculture plays a vital role in driving economic output and employment in Sub-Saharan African (SSA) countries. Despite some progress, agricultural productivity in SSA still lags behind other regions. Limited access to finance remains a significant impediment to improving agricultural productivity in Sub-Saharan Africa. This paper investigates the effect of financial proximity on agricultural productivity in Sub-Saharan African countries. The study primarily employs the system GMM estimator, chosen to address the endogeneity issue typical in macro panel data. This method is also well-suited to our study because it accommodates a high number of cross-sections relative to the number of periods within each cross-section. Additionally, the IV-2SLS method is employed to check the robustness of the findings. The study uses an unbalanced panel for the 36 African countries with data for the period 2004-2019. Our findings show that increasing the financial proximity favors agricultural productivity in SSA countries. Specifically, the number of commercial bank branches (CBB) and the number of automated teller machines (ATM) per 100 000 adults, as indicators of financial proximity, have positive and significant effects on agricultural value added per worker in SSA. Additionally, our findings show that rainfall, arable land, and institutional quality are robust determinants of agricultural productivity. The positive effects of the number of CBB and the number of ATM are even more pronounced on agricultural productivity when coupled with strong institutional quality. Our findings suggest that improving financial services' accessibility in rural areas, coupled with enhanced institutional quality, regular rainfall, ample arable land, and increased access to water and land, are pivotal steps for achieving sustainable enhancements in labor productivity. This, in turn, leads to increased returns through value-added growth and expanded employment in the agricultural sector.

Seroprevalence and risk factors associated with Theileria parva infection among calves in Narok County, Kenya

Background and Aim: East Coast fever (ECF), caused by Theileria parva, is a devastating disease that causes significant economic losses to cattle production in sub-Saharan Africa. Prevention and control of ECF are challenging in pastoral settings due to inadequate epidemiological information. This study aimed to estimate the seroprevalence and risk factors associated with T. parva infection among calves in different production systems to help design appropriate control interventions. Materials and Methods: Blood samples were collected from 318 calves and tested using an indirect enzyme-linked immunosorbent assay targeting antibodies against polymorphic immunodominant molecules found on the surface of T. parva. Information on calf characteristics and management practices was also collected during sampling. Descriptive statistics and logistic regression were used to analyze potential risk factors, such as age and acaricide application, where p &lt; 0.05 was considered significant Results: Of the 318 calves sampled, 41 (12.89%) were positive for T. parva, with a higher proportion in pastoral systems (36.58%) than in mixed farming systems (34.10%) and agropastoral systems (29.27%). From univariate analysis, calf age (p = 0.002), body weight (p = 0.001), suckling status (p = 0.026), rectal temperature (p = 0.06), calves on pasture (p = 0.022), other feeds (p = 0.004), feed grown within the farm (p = 0.004), acaricide application (p = 0.001), and acaricide application frequency (p = 0.001) were significantly associated with seropositivity. However, calf age (odds ratio [OR], 0.96; 95% confidence interval [CI], 0.91-0.99; p = 0.04), other feeds (OR, 8.82; 95% CI, 1.74-44.63; p = 0.009), and suckling status (OR, 0.38; 95% CI, 0.15-0.99; p = 0.05) were significantly associated with T. parva infection in the multivariable mixed logistic model. Conclusion: T. parva is circulating in young calves in the study area (and possibly in cattle populations due to maternal transfer of antibodies to the calves). There is a need for molecular surveillance to determine the presence and burden of T. parva infection. Keywords: calves, risk factors, seroprevalence, Theileria parva.

In silico prediction of candidate gene targets for the management of African cassava whitefly (Bemisia tabaci, SSA1-SG1), a key vector of viruses causing cassava brown streak disease.

Whiteflies (Bemisia tabaci sensu lato) have a wide host range and are globally important agricultural pests. In Sub-Saharan Africa, they vector viruses that cause two ongoing disease epidemics: cassava brown streak disease and cassava mosaic virus disease. These two diseases threaten food security for more than 800 million people in Sub-Saharan Africa. Efforts are ongoing to identify target genes for the development of novel management options against the whitefly populations that vector these devastating viral diseases affecting cassava production in Sub-Saharan Africa. This study aimed to identify genes that mediate osmoregulation and symbiosis functions within cassava whitefly gut and bacteriocytes and evaluate their potential as key gene targets for novel whitefly control strategies. The gene expression profiles of dissected guts, bacteriocytes and whole bodies were compared by RNAseq analysis to identify genes with significantly enriched expression in the gut and bacteriocytes. Phylogenetic analyses identified three candidate osmoregulation gene targets: two α-glucosidases, SUC 1 and SUC 2 with predicted function in sugar transformations that reduce osmotic pressure in the gut; and a water-specific aquaporin (AQP1) mediating water cycling from the distal to the proximal end of the gut. Expression of the genes in the gut was enriched 23.67-, 26.54- and 22.30-fold, respectively. Genome-wide metabolic reconstruction coupled with constraint-based modeling revealed four genes (argH, lysA, BCAT & dapB) within the bacteriocytes as potential targets for the management of cassava whiteflies. These genes were selected based on their role and essentiality within the different essential amino acid biosynthesis pathways. A demonstration of candidate osmoregulation and symbiosis gene targets in other species of the Bemisia tabaci species complex that are orthologs of the empirically validated osmoregulation genes highlights the latter as promising gene targets for the control of cassava whitefly pests by in planta RNA interference.