Enhancement of plant extracts use for pest control and growth promotion of common bean (Phaseolus vulgaris)

A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and TechnologyFor smallholder farmers, suitable plants for pest management and as foliar feed are obtained with ease, and when successfully exploited, could contribute to local income generation through commercialization. However, with extensive research on their efficacy, toxicity and availability, the use of plant extracts is not widely adopted especially for smallholder farmers in rural settings. This study focused on evaluating factors that can foster extensive use of plant extracts among smallholder farmers. Questionnaires and focus group discussion were used to assess the perception of farmers towards using pesticidal plants, highlighting possible challenges, benefits and future enabling aspects for sustainable bean crop production. Plots of 5m 2 were established by farmers where an evaluation of the efficacy of Tephrosia vogelii, Tithonia diversifolia and Lantana camara was done to ascertain their potential for common bean insect pest management and impacts on beneficial arthropods. Additionally, the study evaluated spatio-temporal variability in bioactive phytochemicals of the most effective plant (T. vogelii), as well as the contribution of T. vogelii and T. diversifolia towards growth promotion and yield of common beans. Results showed that high per cent (99%, n=67) of smallholder farmers had pest challenge and that only (39.7%, n= 27) reported using plant extracts. Likewise, farmers reported a lack of working tools and motivation from researchers and extension officers as a challenge hindering the use of plant extracts. Plant extracts showed efficacy in pest management compared with untreated control whereby T. vogelii significantly reduced abundance of aphids (0.06 ± 0.02) and foliage beetles (0.17±0.03 compared with untreated (0.4 ± 0.05 and 0.5 ± 0.04 respectively). Again, the increased grain yield was recorded on plots treated with T. vogelii (3.8 ± 0.23) and T. diversifolia (3.3 ± 0.23) compared with untreated beans (1.5 ± 0.16), when applied as a foliar spray (2.7 ± 0.20) compared with soil drench (2.1 ± 0.16). Phytochemical variation was noted in T. vogelii where an additional chemotype 3 was first recorded. Hence, under smallholder farming conditions, plant extracts can contribute to sustainable bean crop production if practical implementation that involves smallholder farmers is a priority

Understanding drivers of experimental malaria sub-unit vaccine induced immunity in Tanzania volunteers

Despite being a preventable and treatable disease, Plasmodium falciparum malaria remains a major threat, especially in children and pregnant women in sub-Saharan Africa. Considerable progress has been achieved during the past decade, however, these positive trends have stalled in 2017. Efforts towards better disease control and focal elimination are hindered by development and spread of insecticide and drug resistance, leaving a malaria vaccine as a required tool to complement these approaches. RTS, S a subunit pre-erythrocyte stage vaccine is the only advanced malaria vaccine that has received approval for pilot administration in three countries in sub-Saharan Africa. This vaccine is however challenged by low efficacy and fast waning of protection. There is, therefore, an urgent need for the development of more potent malaria vaccines. WHO targets malaria elimination by 2030 and achieving this goal will depend on stopping malaria transmission. This goal will largely depend on reducing asexual blood stage Plasmodium parasites – which are not only the cause of morbidity and mortality -but also responsible for the development of gametocytes. Induction of parasite growth inhibitory antibodies has been shown to be key for protection following natural exposure and therefore, many vaccine development approaches try to follow this guidance from nature. In order to reach this goal of a highly protective vaccine targeting asexual blood stages with acceptable longevity of duration, more research is needed understand mechanisms of optimal induction of long-lived antibody responses in a population that is also affected from other co-infections like helminths or HIV. Therefore, this thesis aimed to 1) investigate a novel blood stage sub-unit malaria vaccine candidate, P27A, for its potential to induce long-lasting antibody responses when formulated in the novel adjuvant GLA-SE in malaria pre-exposed populations, 2) understanding magnitude and cytokine production of the CD4 T cell responses induced by this novel vaccine formulation and the interaction with ongoing helminth co-infections, 3) shed more light on the mechanism of GLA-SE adjuvant being able to induce high and long-lasting antibody responses by studying follicular helper T cells in peripheral blood, 4) implement lymph node excision biopsy in rural Tanzania for detailed investigation of germinal centre responses which are crucial for production of potent antibody response. The antigen P27A, when formulated with GLA-SE, induced a robust humoral immunity, with enhanced production of cytophilic antibodies, IgG1 and IgG3 and expansion of CD4 Th1 cells producing IL2, TNFa and IFNg, and subsequent memory development. In addition, the adjuvant GLA-SE promoted the expansion of peripheral follicular helper T cells and recruitment of T cells bearing common T cell receptors, which is essential for a vaccine intended for the general population

Botanical extracts control the fungal pathogen Colletotrichum boninense in smallholder production of common bean

Anthracnose caused by Colletotrichum spp. remains an intractable problem in the most common bean (Phaseolus vulgaris) production areas worldwide and can cause total yield loss. Many smallholder farmers are familiar with using botanical extracts to control insect pests; however, there is less familiarity with their use to control fungal diseases due to a lack of evidence. Here, we demonstrate that anthracnose could be controlled effectively by pesticidal plant species that are used for insect control. In laboratory trials, water extracts from 11 plant species could inhibit fungal growth (100%) and spore germination (75–100%) equally well to two commercially available fungicides, the synthetic Mancolaxyl and biofungicide Bioderma. In screenhouse trials, anthracnose disease was reduced by the extracts of three plant species. Moreover, bean crop growth in these botanical treatments did not differ significantly from that observed in the commercial fungicide treated plants. Field trials in a smallholder community reporting severe problems with anthracnose showed an effect similar to the screenhouse results. Field trials resulted in bean seed yields approximately 350 kg/ha higher in bean plants treated with Azadirachta indica and Lippia javanica at 10% w/v compared to the negative control untreated plants. In all trials, botanical extracts were as effective as commercially available fungicides, suggesting that these botanical extracts could provide dual-purpose pest and disease management for anthracnose and crop pest insects. The outcomes of this research show that prospects for using locally available resources to control anthracnose on common bean are credible and can be combined with controlling insect pests

Epitope mapping and fine specificity of human T and B cell responses for novel candidate blood-stage malaria vaccine P27A

P27A is a novel synthetic malaria vaccine candidate derived from the blood stage Plasmodium falciparum protein Trophozoite Exported Protein 1 (TEX1/PFF0165c). In phase 1a/1b clinical trials in malaria unexposed adults in Switzerland and in malaria pre-exposed adults in Tanzania, P27A formulated with Alhydrogel and GLA-SE adjuvants induced antigen-specific antibodies and T-cell activity. The GLA-SE adjuvant induced significantly stronger humoral responses than the Alhydrogel adjuvant. Groups of pre-exposed and unexposed subjects received identical vaccine formulations, which supported the comparison of the cellular and humoral response to P27A in terms of fine specificity and affinity for populations and adjuvants. Globally, fine specificity of the T and B cell responses exhibited preferred recognized sequences and did not highlight major differences between adjuvants or populations. Affinity of anti-P27A antibodies was around 10−8 M in all groups. Pre-exposed volunteers presented anti-P27A with higher affinity than unexposed volunteers. Increasing the dose of GLA-SE from 2.5 to 5 μg in pre-exposed volunteers improved anti-P27A affinity and decreased the number of recognized epitopes. These results indicate a higher maturation of the humoral response in pre-exposed volunteers, particularly when immunized with P27A formulated with 5 μg GLA-SE

Elements of agroecological pest and disease management

The development of large-scale monocropped agrisystems has facilitated increased problems with pests and diseases, perpetuating the reliance of farmers on synthetic pesticides. The economic success of synthetic inputs has, however, been achieved at a high cost to the environment through the loss of biodiversity, depletion of soil quality, greenhouse gas emissions, and disrupting the ecosystem services that can otherwise help mitigate losses caused by pests and diseases. Environmentally benign alternatives for pest and disease management are urgently needed and are now widely recognized as essential for sustainable food and agriculture. The Food and Agriculture Organization, for example, has published the 10 elements of agroecology as a framework for the transformation of agriculture. Agroecology combines ecological and social concepts and principles to develop sustainable food and agricultural systems by harnessing nature-based solutions that are tailored to farmers’ needs. Plant-based biopesticides, for example, offer an alternative to synthetic pesticides that are less harmful to the environment and nonpersistent, yet effective at managing pests and have a long tradition of use among farmers so are more socially acceptable. Here, we provide a critical assessment of how nature-based approaches to pest and disease management comply with the 10 elements of agroecology and show how they integrate with other ecosystem services through farmer participatory research. We conclude that the adoption of nature-based solutions for pest management addresses all 10 elements of agroecology and provides an entry point to promote sustainable farming practices among farmers more widely

Assessment of resistant Escherichia coli in groundwater sources and sanitary inspection for contamination risk in Bagamoyo, Tanzania

This Research Article was published by the Bulletin of the National Research Centre,2024Background Two billion people globally are using faecal-contaminated water. E. coli poses a health risk due to its potential to cause diseases which highlights the need for understanding its antimicrobial resistance profile and associated factors for contamination. Methods A cross-sectional study was conducted in the Bagamoyo district council that involved 163 groundwater sources with sanitary inspection and isolation of E. coli was conducted using a Membrane filtration method and CHROMagar CCA. In this study, antibiotic susceptibility was carried out according to CLSI guidelines by disk diffusion methods. E. coli strain ATCC 25922 was used as the control strain in isolation and susceptibility tests. Results The current study found that 44.8% of groundwater samples were contaminated with E. coli, with 83.6% of isolates were resistant to antibiotics. High resistance was observed to cefazolin (56.16%), nitrofurantoin (54.79%), amoxicillin-clavulanic acid (45.21%), and ceftriaxone (42.47%). Also, the study reveals that 70% of E. coli isolates had multidrug resistance. On the other hand, sanitary inspection showed that 46.2% of dug wells were at a high sanitary risk level, 32.8% of tube wells with hand pumps were at High and low sanitary risk level, respectively and 73.3% of boreholes were at a low sanitary risk level. However, the study showed a high rate of E. coli contamination in boreholes at a low sanitary risk level. Also, tube wells with hand pumps and dug wells at high sanitary risk levels had a high rate of E. coli contamination. Moreover, resistant E. coli in groundwater across varying contamination risk levels revealed a significant prevalence of contamination

Indigenous vegetables: a sustainable approach to improve micronutrient adequacy in Tanzanian women of childbearing age

This research article was published by Springer Nature in 2021Background/objectives Increasing dietary diversity is a viable strategy for addressing micronutrient malnutrition in women of childbearing age (WCA) from low-income countries. Recently, it has been demonstrated that some indigenous vegetables (IV) with high nutrient density may help to ameliorate micronutrient’s intake. The Minimum Dietary Diversity index for Women (MDD-W) could be considered as a proxy to describe one important dimension of women’s diet quality. This cross-sectional study aimed at exploring aspects contributing to micronutrients adequacy in Tanzanian WCA, with a focus on IV consumption and other socio-demographic factors. Subjects/methods Data collection was conducted among urban and peri-urban women in Arusha city, Tanzania. Socio-demographic factors were collected using a structured interview. Information on IV consumption and MDD-W calculation were obtained using a 24-h recall. Results One-hundred and forty-one women aged 14–49 years were interviewed. Sixteen per cent of the sample consumed at least one portion of IV/day. The total median MDD-W was 4.0 (IQR. 3.0–5.0) and it was adequate in the 44% of the sample. Women who consumed IV had MDD-W 0.66 points (95% CI: 0.02–1.30, p = 0.046) higher than those who did not; consuming IV had an odds ratio of more than three times concerning women not consuming IV (OR: 3.30, 95% CI: 1.24–8.81, p = 0.017). Conclusions The IV consumption is positively associated with micronutrient adequacy and its absence from the diet can be an indicator of micronutrient deficiencies in vulnerable people such as WCA. For that reason, this study suggests that IV consumption may improve micronutrient deficiency in WCA

Qualitative cost-benefit analysis of using pesticidal plants in smallholder crop protection

Assessing the potential drivers of farmers using pesticidal plants for crop protection is essential for wider adoption. However, few studies have focused on collaborative assessments of the underlying trade-offs when using pesticidal plant extracts for pest control. Smallholder farmers in northern Tanzania involved in farmer driven research assessing pesticidal plants evaluated the costs, benefits, trade-offs and areas for future investment. A questionnaire was used to collect demographic information from 77 farmers and their views on pest problems and crop protection in common bean production. This was followed by small focus group discussions (n = 9) using a participatory framework to elucidate the costs and benefits of adopting pesticidal plant technology. A multiple correspondence analysis showed that pesticidal plant use was associated with men greater than 50 years old, and synthetic pesticide use was associated with younger aged farmers and women. Farmers who used synthetics generally did not report the presence of common pest species found in common bean production, whereas farmers who used pesticidal plants were associated with more frequent reports of pest species. This participatory cost–benefit analysis highlighted that tools and processing challenges were the main costs to using pesticidal plants. The main benefit reported when using pesticidal plants was a general improvement to family health. Farmers expressed overall a positive outcome when using pesticidal plants for crop protection and recommended that future investments focus on improving access to tools and education regarding plant processing and extraction to improve uptake of the technology by smallholder farmers

The long and challenging road to capitalize on plant-based extracts from the lab to the field.

Negative impacts of chemical pesticide, social demand (healthier food), organic farming organization, rising costs of inputs linked to oil market and their importation (in Africa), and the circular economy approach are a few arguments/opportunities that underlie the roll-out of alternative solutions, including botanicals

Understanding farmer knowledge and site factors in relation to soil-borne pests and pathogens to support agroecological intensification of smallholder bean production systems

Introduction: Pests and diseases limit common bean (Phaseolus vulgaris) production in intensifying smallholder farming systems of sub-Saharan Africa. Soil-borne pests and diseases (SPD) are particularly challenging for farmers to distinguish and manage in cropping systems that vary in terms of soils, farmer knowledge, and management factors. Few studies have examined soil drivers of SPD in smallholder systems, integrated with farmers’ perceptions and management practices. Methods: In Kilimanjaro, Tanzania, we assessed farmer knowledge and SPD management for common bean alongside soil type and soil quality. Focus group discussions and field survey findings including farmer observations and soil nutrient balances were integrated with soil analyses of farmers’ fields. Multiple correspondence analysis (MCA) and principal component analysis (PCA) assessed relationships among farmer demographics, pests and diseases, soil characteristics, and management practices. Results and discussion: Surveys revealed that 100% of farmers knew of the bean foliage beetle (Ootheca bennigseni) but few recognized the soilborne pest Ophiomyia spp. or bean fly despite it being more destructive. About a third of farmers knew of root rot diseases caused by Pythium spp. and Fusarium spp. Synthetic pesticides were used by 72% of farmers to control pests, while about half that (37%) used pesticidal plants, particularly Tephrosia vogelii extracts sprayed on foliage. Regarding SPD, 90% of farmers reported that their management practices were ineffective. Meanwhile, synthetic fertilizers were used by nearly all farmers in beans intercropped with maize (Zea mays), whilst very few farmers used manure or compost. Soil available phosphorus was low but showed a balance between inputs and outputs regardless of whether fields were owned. Field nitrogen balances were more negative when fields were owned by farmers. An MCA showed that older farmers employed a greater number of pest control practices. The PCA showed that field variability was dominated by soil organic matter, elevation, and soil pH. Higher organic matter levels were also associated with less stunting and wilting of beans observed by farmers. Our results suggest that research and farmer learning about SPD ecology are key gaps, alongside recycling of organic residues to soils. Cost-effective and sustainable practices to manage bean SPDs for smallholders are also needed