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result(s) for
"Mwangi, Maina"
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Farmers’ perceptions on tomato early blight, fungicide use factors and awareness of fungicide resistance: Insights from a field survey in Kenya
by
Runo, Steven
,
Mwangi, Maina
,
Nuwamanya, Andrew M.
in
Agricultural production
,
Agriculture
,
Antifungal agents
2023
Early blight (EB) caused by Alternaria solani is one of the most devastating tomato diseases in Kenya and is most often managed by application of synthetic fungicides. However, there have been reports from farmers about the declining efficacy of some fungicides. These reports suggest that A . solani populations in Kenya could be developing resistance to some of the commonly used fungicides. In this study, we surveyed 175 tomato fields, sampled in 3 major tomato producing counties in Kenya, to determine the status of EB, management practices, and fungicide use factors that could contribute to development of resistance to fungicides among A . solani populations in Kenya. Data was recorded on farm characteristics, EB prevalence, fungicide usage, and farmers’ perceptions on fungicide efficacy. EB was prevalent in 85% of the fields and 90% of the farmers identified it as a major cause of yield loss. Tomato was grown all year round on 60% of the fields with only short fallow periods. All farmers reported that they were relying on fungicides for EB control and none among the cultivars grown was resistant to the disease. A total of 40 fungicide products, representing 20 active compounds with varying FRAC resistance risk levels were in use against EB. Majority (83%) of the farmers were applying fungicides at dosages and frequencies higher than those indicated on labels. Most farmers (81%) indicated that they had observed declines in effectiveness of at least one fungicide, used at EB control. This observation was more with fungicides in the strobilurin and triazole groups. These findings demonstrate that the current tomato production systems in Kenya do not take into account the risk of A . solani developing resistance to fungicides. Enhancing farmers’ knowledge of the disease and their ability to properly select and apply fungicides is therefore crucial for effective control of EB and mitigating the high risk of fungicide resistance build up.
Journal Article
Temperature dependent immunological responses of Spoladea recurvalis exposed to entomopathogenic fungi
2026
Spoladea recurvalis
is a major pest of amaranth, capable of causing up to 100% yield loss if not controlled. Current control measures rely on synthetic chemicals; however, these chemicals are unsafe due to the crop’s short maturity that make pre-harvest intervals observation difficult. A sustainable alternative to synthetic chemicals would be entomopathogenic fungi (EPF) though, a few bottlenecks still exist in the effective use of these biological solutions. Studies show low susceptibility of
S. recurvalis
to
Metarhizium anisopliae
isolates ICIPE 30 and ICIPE 18, with larval mortalities of 58.3 and 6.7%, respectively. Temperature can affect the efficacy of EPF and how the insect’s immunity responds to fungal infections, but the effect of temperature on
S. recurvalis
and their interactions with the EPF is unknown. Therefore, we evaluated immune responses and gut microbiome of
S. recurvalis
when exposed to EPF at 15, 20, 25, 30 and 35 °C. From the results,
S. recurvalis
susceptibility increased at 30 °C, with ICIPE 30 causing the strongest effect. Total hemocyte counts in ICIPE 30-treated larvae reduced from 30.25 × 10
4
/ml on day 3 to 10.75 × 10
4
/ml on day 7. Granulocytes and plasmatocytes also decreased significantly. The dominant bacterial genera were
Enterobacter
,
Enterococcus
, and
Klebsiella
, with microbial diversity highest in ICIPE 30-treated larvae on day 1 and ICIPE 18-treated larvae on day 7, and lowest in ICIPE 30-treated larvae on day 7. The Findings of this study demonstrate that temperature influences this EPF’s efficacy and provide important information on the optimal conditions for this biopesticide in the pest’s management.
Journal Article
Composition, structure, and functional shifts of prokaryotic communities in response to co-composting of various nitrogenous green feedstocks
by
Mwangi, Edwin
,
Tanga, Chrysantus
,
Musyoka, Martha Wangu
in
Abundance
,
Agricultural wastes
,
Algorithms
2023
Background
Thermophilic composting is a promising method of sanitizing pathogens in manure and a source of agriculturally important thermostable enzymes and microorganisms from organic wastes. Despite the extensive studies on compost prokaryotes, shifts in microbial profiles under the influence of various green materials and composting days are still not well understood, considering the complexity of the green material sources. Here, the effect of regimens of green composting material on the diversity, abundance, and metabolic capacity of prokaryotic communities in a thermophilic compost environment was examined.
Methods
Total community 16S rRNA was recovered from triplicate compost samples of Lantana-based, Tithonia-based, Grass-based, and mixed (Lantana + Tithonia + Grass)- based at 21, 42, 63, and 84 days of composting. The 16S rRNA was sequenced using the Illumina Miseq platform. Bioinformatics analysis was done using Divisive Amplicon Denoising Algorithm version 2 (DADA2) R version 4.1 and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States version 2 (PICRUSt2) pipelines for community structure and metabolic profiles, respectively. In DADA2, prokaryotic classification was done using the Refseq-ribosomal database project (RDP) and SILVA version 138 databases.
Results
Our results showed apparent differences in prokaryotic community structure for total diversity and abundance within the four compost regimens and composting days. The study showed that the most prevalent phyla during composting included
Acidobacteriota
,
Actinobacteriota
,
Bacteroidota
,
Chloroflexi
, and
Proteobacteria
. Additionally, there were differences in the overall diversity of metabolic pathways but no significant differences among the various compost treatments on major metabolic pathways like carbohydrate biosynthesis, carbohydrate degradation, and nitrogen biosynthesis.
Conclusion
Various sources of green material affect the succession of compost nutrients and prokaryotic communities. The similarity of amounts of nutrients, such as total Nitrogen, at the end of the composting process, despite differences in feedstock material, indicates a significant influence of composting days on the stability of nutrients during composting.
Journal Article
Evolution of fungal and non-fungal eukaryotic communities in response to thermophilic co-composting of various nitrogen-rich green feedstocks
2023
Thermophilic composting is a promising soil and waste management approach involving diverse micro and macro-organisms, including eukaryotes. Due to sub-optimal amounts of nutrients in manure, supplemental feedstock materials such as Lantana camara, and Tithonia diversifolia twigs are used in composting. These materials have, however, been reported to have antimicrobial activity in in-vitro experiments. Furthermore, the phytochemical analysis has shown differences in their complexities, thus possibly requiring various periods to break down. Therefore, it is necessary to understand these materials’ influence on the biological and physical-chemical stability of compost. Most compost microbiome studies have been bacterial-centric, leaving out eukaryotes despite their critical role in the environment. Here, the influence of different green feedstock on the fungal and non-fungal eukaryotic community structure in a thermophilic compost environment was examined. Total community fungal and non-fungal eukaryotic DNA was recovered from triplicate compost samples of four experimental regimes. Sequencing for fungal ITS and non-fungal eukaryotes; 18S rDNA was done under the Illumina Miseq platform, and bioinformatics analysis was done using Divisive Amplicon Denoising Algorithm version 2 workflow in R version 4.1. Samples of mixed compost and composting day 84 recorded significantly (P<0.05) higher overall fungal populations, while Lantana-based compost and composting day 84 revealed the highest fungal community diversity. Non-fungal eukaryotic richness was significantly (P< 0.05) more abundant in Tithonia-based compost and composting day 21. The most diverse non-fungal eukaryotic biome was in the Tithonia-based compost and composting day 84. Sordariomycetes and Holozoa were the most contributors to the fungal and non-fungal community interactions in the compost environment, respectively. The findings of this study unravel the inherent influence of diverse composting materials and days on the eukaryotic community structure and compost’s biological and chemical stability.
Journal Article
Bacillus amyloliquefaciens D203 ameliorates rice growth and resistance to rice blast disease
by
Mwangi, Maina
,
Mirara, Francis
,
Dzidzienyo, Daniel Kwadjo
in
Agriculture
,
Agriculture & Environmental Sciences
,
Agriculture and Food
2024
This study evaluated the effects of Bacillus amyloliquefaciens D203 encapsulated in alginate-bentonite coating enriched with titanium nanoparticles on rice germination and Magnaporthe oryzae infection. Seed coating was achieved using the ionic gelation/extrusion method with modifications. The study investigated various concentrations of strain D203 on biomass and bacterial release from the beads, along with its influence on detached leaves. Results showed that treatment with a strain D203 cell suspension (2 × 10
7
CFU/ml) significantly enhanced root and shoot lengths, despite a slightly lower germination rate (90%) compared to the control. Treatment with a concentration of 1 × 10
7
proved to be optimum for growth because it maintained germination at 100% and boosted biomass growth of shoot and root by 49.57% and 16.44%, respectively. Colonization by strain D203, explored through seed coating and subsequent resuspension from roots and media, peaked in roots, indicating preferential root zone inhabitation. In vitro studies demonstrated strain D203's efficacy against M. oryzae at 21 and 40 days, with the 1 × 10
7
CFU/ml spray significantly reducing disease symptoms. Strain D203 exhibited a preventive effect, especially in early growth stages. The encapsulated form of strain D203 had a control effect comparable to 40% Hexaconazole but less effective than 75% Tricyclazole. Uncoated and encapsulated B. amyloliquefaciens treatments significantly improved sterile rice plant growth over 21 days, with the encapsulated bead treatment surpassing both controls and free cell treatments by days 14 and 21, despite slower initial growth. Encapsulation presents a promising alternative, potentially matching the effectiveness of chemical fungicides, emphasizing the importance of environmentally friendly alternatives in sustainable disease management strategies.
Journal Article
A Review on Barrier Properties of Cellulose/Clay Nanocomposite Polymers for Packaging Applications
2023
Packaging materials are used to protect consumer goods, such as food, drinks, cosmetics, healthcare items, and more, from harmful gases and physical and chemical damage during storage, distribution, and handling. Synthetic plastics are commonly used because they exhibit sufficient characteristics for packaging requirements, but their end lives result in environmental pollution, the depletion of landfill space, rising sea pollution, and more. These exist because of their poor biodegradability, limited recyclability, etc. There has been an increasing demand for replacing these polymers with bio-based biodegradable materials for a sustainable environment. Cellulosic nanomaterials have been proposed as a potential substitute in the preparation of packaging films. Nevertheless, their application is limited due to their poor properties, such as their barrier, thermal, and mechanical properties, to name a few. The barrier properties of materials play a pivotal role in extending and determining the shelf lives of packaged foods. Nanofillers have been used to enhance the barrier properties. This article reviews the literature on the barrier properties of cellulose/clay nanocomposite polymers. Cellulose extraction stages such as pretreatment, bleaching, and nanoparticle isolation are outlined, followed by cellulose modification methods. Finally, a brief discussion on nanofillers is provided, followed by an extensive literature review on the barrier properties of cellulose/clay nanocomposite polymers. Although similar reviews have been presented, the use of modification processes applied to cellulose, clay, and final nanocomposites to enhance the barrier properties has not been reviewed. Therefore, this article focuses on this scope.
Journal Article
Evaluation of Blast Resistance in Zinc-Biofortified Rice
by
Musila, Ruth
,
Mutiga, Samuel K.
,
Nunu, Anita
in
Agricultural production
,
Agronomy
,
Anthocyanin
2025
Rice is a staple food for over half of the world’s population, and it is grown in over 100 countries. Rice blast disease can cause 10% to 30% crop loss, enough to feed 60 million people. Breeding for resistance can help farmers avoid costly fungicides. This study assessed the relationship between rice blast disease and zinc or anthocyanin content in biofortified rice. Susceptibility to foliar and panicle blast was assessed in a rice panel which differed on grain zinc content and pigmentation. A rice panel (n = 23) was challenged with inoculum of two isolates of Magnaporthe oryzae in a screenhouse-based assay. The zinc content with foliar blast severity was analyzed in the leaves and grain of a subset of non-inoculated rice plants. The effect of foliar zinc supplementation on seedlings was assessed by varying levels of zinc fertilizer solution on four blast susceptible cultivars at 14 days after planting (DAP), followed by inoculation with the blast pathogen at 21 DAP. Foliar blast severity was scored on a 0–9 scale at 7 days after inoculation. The rice panel was scored for anthocyanin content, and the data were correlated with foliar blast severity. The panel was grown in the field, and panicle blast, grain yield and yield-related agronomic traits were measured. Significant differences were observed in foliar blast severity among the rice genotypes, with IRBLK-KA and IR96248-16-2-3-3-B having mean scores greater than 4, as well as BASMATI 370 (a popular aromatic variety), while the rest of the genotypes were resistant. Supplementation with foliar zinc led to a significant decrease in susceptibility. A positive correlation was observed between foliar and panicle blast. The Zn in the leaves was negatively correlated with foliar blast severity, and had a marginally positive correlation with panicle blast. There was no relationship between foliar blast severity and anthocyanin content. Grain yield had a negative correlation with panicle blast, but no correlation was observed between Zn in the grain and grain yield. This study shows that Zn biofortification in the grain may not enhance resistance to foliar and panicle blast. Furthermore, the zinc-biofortified genotypes were not agronomically superior to the contemporary rice varieties. There is a need to apply genomic selection to combine promising alleles into adapted rice genetic backgrounds.
Journal Article
The Overlooked Decomposers: Effects of Composting Materials and Duration on the Mesofauna Mediating Humification
by
Kambura, AnneKelly
,
Tanga, Chrysantus
,
Runo, Steven
in
Biological products
,
Composting
,
Decomposition
2024
Compost fauna act by releasing various enzymes that break down organic matter into a stable, agriculturally useful products. Mesofauna are the least studied compared to micro- and macrofauna, with the existing studies relying on classical methods such as morphological identification, essentially leaving out cryptic taxa. We sought to evaluate the ecological response of the mesofauna community to different composting materials and durations. Total mesofauna community 18S rRNA was purified in triplicate from lantana-based, tithonia-based, grass-based, and mixed (lantana + tithonia + grass)-based compost heaps after 21, 42, 63, and 84 days of composting and sequenced using the Illumina Miseq platform. Before performing statistical data analysis, we used the Divisive Amplicon Denoising Algorithm version 2 workflow for bioinformatic analyses. The composting duration, but not the composting materials, significantly influenced the total population and composition of the mesofauna communities. The composting materials and duration significantly affected the dispersion and uniqueness of the compost mesofauna communities. Canonical correspondence analysis of the compost’s physical–chemical and biological states showed a significant influence of the materials on the mesofauna community colonization capacity. The mesofauna communities had a significant response to the composting duration. This, therefore, presents them as valuable tools for understanding the temporal evolution of compost.
Journal Article
Assessment of Coastal Governance for Climate Change Adaptation in Kenya
2017
The coastline of Kenya already experiences effects of climate change, adding to existing pressures such as urbanization. Integrated coastal management (ICM) is increasingly recognized as a key policy response to deal with the multiple challenges facing coastal zones, including climate change. It can create an enabling governance environment for effective local action on climate change by facilitating a structured approach to dealing with coastal issues. It encompasses the actions of a wide range of actors, including local governments close to people and their activities affected by climate change. Functioning ICM also offers opportunities for reducing risks and building resilience. This article applied a modified capitals approach framework (CAF), consisting of five “capitals,” to assess the status of county government capacity to respond to climate change within the context of coastal governance in three county governments in Kenya. The baseline was defined in terms of governance relating to the implementation of the interrelated policy systems of ICM and coastal climate change adaptation (CCA). The CAF framework provided a systematic approach to building a governance baseline against which to assess the progress of county governments in responding to climate change. It identified gaps in human capacity, financial resource allocation to adaptation and access to climate change information. Furthermore, it showed that having well‐developed institutions, including regulatory frameworks at the national level can facilitate but does not automatically enable adaptation at the county level. Key Points The capitals assessment framework provided a systematic approach to building a governance baseline for responding to climate change Existence of national frameworks designed explicitly to enable adaptation is a major strength but require complementary local capacities A more comprehensive use of evidence in decision making can help in defining adaptation pathways
Journal Article
Mechanical Behaviour of Glass Fibre-Reinforced Polymer/Polyvinyl Chloride Foam Cored Sandwich Structures
by
Kanny, Krishnan
,
Kosgey, Edwin Cheruiyot
,
Mwangi, Festus Maina
in
Bearing strength
,
Buckling
,
Compression tests
2024
This study focuses on the fabrication and analysis of the mechanical behaviour of unidirectional (UD) glass fibre-reinforced polymer (GFRP) facesheet and polyvinyl chloride (PVC) foam core sandwich structures fabricated by a vacuum-assisted resin infusion method (VARIM). These sandwich structures are commonly used in marine and wind turbine blade applications. To date, relatively little knowledge about the functional behaviour of UD GFRP compared to composites reinforced with bidirectional mats is available for day-to-day applications. The effects of the facesheet orientation, facesheet thickness, and core thickness on the mechanical behaviour of the specimens were examined. The UD fibres were oriented in cross-ply (0/90), angle-ply (+45/−45), and quasi-isotropic orientations. Various mechanical properties such as tensile, flexural, flatwise compression, and edgewise compression tests were examined. Characterization of the tensile properties of the facesheet showed that the cross-ply orientation had a higher strength than the angle-ply and quasi-isotropic orientations. The flexural load-carrying capacity of the cross-ply facesheet orientation was superior to the other orientations. The increase in the core thickness changed the flexural failure mode from face yield and core shear to core indentation. Flatwise compression (FWC) was tested to determine the core characteristics of the sandwich structure, and the peak loads of 4.90, 1.81, and 3.90 kN were obtained for 10-, 15-, and 20 mm core thicknesses, respectively. Edgewise compression (EWC) exhibited stable end crushing for thinner facesheet, whereas thicker facesheet showed core crushing and buckling. When the facesheet thickness was increased from 1.5 mm to 3 mm in the EWC, the buckling load increase ranged from 2.53% to 44.83% for core thicknesses 10-, 15-, and 20 mm, respectively.
Journal Article