College of Agriculture & Natural Resources (COANRE)

Farmers’ Perceptions, Distribution and Molecular Characterization of Groundnut Rosette Disease in Western Kenya

Thu, 26 Mar 2026 00:00:00 GMT

Farmers’ Perceptions, Distribution and Molecular Characterization of Groundnut Rosette Disease in Western Kenya Were, Eric Osewo Groundnut rosette disease (GRD) is the most important viral disease of groundnuts in sub-Saharan Africa. In Kenya, GRD attack especially before flowering results in 100% loss in pod yield. Surveys were conducted between 2015 and 2017 to determine farmers’ knowledge and perceptions of GRD and its management as well as its distribution in five major groundnut growing Counties of western Kenya. In addition, the molecular diversity of the viruses causing GRD was determined. A structured questionnaire was used to assess GRD incidence and severity as well as farmers’ knowledge and management of GRD. Reverse transcription (RT)-polymerase chain reaction (PCR) was used for the detection of groundnut rosette assistor virus (GRAV), groundnut rosette virus (GRV) and satellite RNA (SatRNA), the causal agents of GRD in symptomatic and asymptomatic samples collected during the survey. The amplified RT-PCR products from the isolates of GRAV, GRV and Sat-RNA from infected groundnut plants were sequenced using the Sanger sequencing method. The sequences were edited, aligned and compared with other published sequences from GenBank using a Basic Local Alignment Search Tool (BLAST) and phylogenetic analysis. A total of 76 purposively selected farmers with groundnut fields were interviewed, and results indicated that pests and diseases are the main production constraints as indicated by 77% of the farmers. Awareness of GRD varied significantly (P < 0.001) among the farmers across the five counties as well as their knowledge on causes and management of GRD (P < 0.001The study findings revealed that 18.4% of groundnuts farmers in western Kenya had some knowledge about GRD. For the management of GRD, more than forty percent (43.58%) of respondents removed infected plants from the fields, 12.34% sprayed plants showing disease symptoms with chemical insecticides, 12.58% carried out crop rotations in their fields while 27.76% did not apply any management strategy on the diseased plants. It was also observed that GRD was prevalent in all the fields surveyed in the five Counties. The highest (35.7%) mean disease incidence was in Busia County while the lowest (23.1%) incidence was in Siaya. The most conspicuous symptoms observed in all the fields inspected were yellow/chlorotic and green rosette. The highest (3.1) mean disease severity was observed in farmers’ fields in Busia County, while the lowest (2.8) was observed in Siaya. Both GRAV and GRV were detected in all symptomatic and asymptomatic samples of groundnut leaves collected from the surveyed region. There was high degree of nucleotide identity among the Kenyan GRAV isolates from the five Counties in western Kenya. In conclusion, groundnut farmers in the sampled regions have limited awareness, knowledge and management of GRD. It is therefore important to build capacity of the farmers on detection, identification of the disease and its management. GRD is widely distributed in all groundnut fields in western Kenya and hence the need to use certified seeds. The disease is caused by presence of GRAV and GRV. It’s therefore important for plant breeders to develop groundnut varieties that are resistance to both GRAV and GRV with farmers’ preferred traits and high yielding. Researchers to perform Next Generation Sequencing to identify other unknown viruses infecting groundnuts in western Kenya MSc in Plant Health Science and Management

Management of Root Knot Nematode, Meloidogyne incognita Using Tithonia diversifolia and Tagetes minuta Through a Slow-Release Technique in Tomato

Tue, 24 Feb 2026 00:00:00 GMT

Management of Root Knot Nematode, Meloidogyne incognita Using Tithonia diversifolia and Tagetes minuta Through a Slow-Release Technique in Tomato Macharia, Rachael Muthoni Tomato (Solanum lycopersicum) is an economically important crop in Africa produced largely by small-scale farmers. The root-knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, causes serious constraints in tomato production. Synthetic nematicides have been used in the management of RKN, however, they have adverse effects on users and the environment. Botanical pesticides are a safer alternative since they contain compounds that act as hatching inhibitors, repellents and nematoxicants. These compounds are constituted in leaves, seeds, flowers and roots and are applied through aqeous extracts, essential oils, powder or pellets derived from various plant parts. The use of plant extracts has been effective, however, more than two applications are done for effective RKN management. This study investigated the use of a filter bag as a slow release technique, to ensure the continuous release of the nematotoxic compounds to enhance the management of M. incognita and minimize the number of applications done. Powder and pellet of Mexican sunflower, Tithonia diversifolia Hemsl. and Mexican marigold, Tagetes minuta L. incorporated in a filter bag made of non-woven interfacing fusible fabric, were used in the management of M. incognita in tomato production. The experiment was laid out in a completely randomized design with a Pre-plant and Post-plant application of ammendments. Tomato seedlings were inoculated with about 1500 freshly hatched second-stage juveniles of M. incognita in both trials. Data collected on the nematode population dynamics, changes in tomato fruit qualities, and yield and root phenols and soil chemical properties. Data was subjected to analysis of variance and means separated using the Tukey Studentized Range Test (P = 0.05). Results of this study showed that pellet and powder from respective plant parts significantly (P = ˂0.001) reduced nematode populations relative to the untreated control but compared favorably to the positive control. The filter bag technique significantly improved the management of M. incognita. Pre-plant application of pellets incorporated in the filter bag resulted in plants that had lower egg mass and gall index and soils with lower juvenile populations. The fruit qualities were significantly improved where higher total soluble solids (4.37), total titratable acidity (0.83) and Vitamin C (18.33) content was recorded. The root phenols, N, P, K and organic carbon levels were higher in soils amended with ammendments incorporated in the filter bag. There was however no significant difference between ammendments in the filter bag and those without. The filter bag technique proved to be better in the pre-plant application relative to the post-plant application. These findings indicate that the filter bag technique averts the need for re-application which could help reduce the operation costs. MSc in Plant Health Science and Management

Utilization of Black Soldier Fly Larvae as a Protein Source in Fish Diets for Nile Tilapia (Oreochromis niloticus)

Mon, 16 Feb 2026 00:00:00 GMT

Utilization of Black Soldier Fly Larvae as a Protein Source in Fish Diets for Nile Tilapia (Oreochromis niloticus) Kariuki, Mercy Wangui Insect meals, such as black soldier fly larvae (BSFL), have the potential to be used as a source of protein in animal feeds due to their high nutritional profile and cost effectiveness. The objective of this study was to elucidate the impact of BSFL meal included at different levels in fish diets of Nile Tilapia (Ocreochromis niloticus, L) on the growth performance, survival rate, somatic indexes and economic benefits. Four experimental diets were prepared; three with BSFL meal as a substitute for fish meal at 25% (T25%), 50% (T50%) and 75% (T75%) and a control diet without BSFL meal (T0%, 100% FM). A total of 360 fingerlings weighing about 20 - 30 grams each were assigned to twelve cages built in a 720m2 earthen pond, with 30 fingerlings in each cage in a completely randomized design (CRD) with three replications in each treatment group. The fingerlings were fed the experimental diets for 26 weeks. The results showed that the growth performance parameters were not significant, their levels were comparable in all treatments. BSFL inclusion up to 75% did not affect the growth performance parameters. The final weight, body weight gain, daily body weight gains were similar for all treatments respectively. The final body lengths were also similar they ranged between (15.91cm- 16.50) the final lengths were not significant they were not affected by BSFL inclusion at the different levels. The daily feed intake and FCR were comparably the same (p>0.05) BSFL did not affect these parameters. The survival rate was significantly influenced (P<0.05) by the diet treatment groups, while blood parameters, visceral somatic and Hepatosomatic indexes did not vary significantly (P>0.05) across the treatment diets. Return on investment and the cost-benefit ratio were significantly (p<0.05) affected by the partial replacement of fishmeal with BSFL meal. Diets T25%, T50%, T75% had higher (p<0.05) profit margins when compared with diets T0 %( control). The study found that BSFLM can replace FM in diets for Nile Tilapia without compromising on the growth performance of the fish while also increasing the profitability. Keywords: Animal Feed, Fish, Nutritional composition, Insect-based-meal Master of Science in Animal Nutrition

Utilization of Indigenous Plant-Based Treatments and Nixtamalization for Mitigating Mycotoxin Contamination in Maize in Eastern Democratic Republic of Congo

Tue, 02 Dec 2025 00:00:00 GMT

Utilization of Indigenous Plant-Based Treatments and Nixtamalization for Mitigating Mycotoxin Contamination in Maize in Eastern Democratic Republic of Congo Matendo, Esther Rehema Food security considerations have shifted in recent years with the recognition that available food should also be nutritious and safe. Mycotoxins, which are secondary metabolites produced by a number of mycotoxigenic molds are a major food safety concern, especially aflatoxin and fumonisin contamination of maize, a major staple food crop in the Democratic Republic of Congo. To ensure food safety regarding maize, mitigation measures to prevent mold contamination and subsequent mycotoxin contamination need to be considered and put in place. The purpose of this study was to assess the levels of contamination of maize with aflatoxin and fumonisin and to determine the potential use of plant extract and nixtamalization techniques to mitigate the production of these secondary fungal metabolites along the supply chain in South Kivu. A total of 335 maize samples (grains and flour) were randomly collected for mycotoxin analysis. Total aflatoxins and total fumonisins were determined by a single-step lateral flow immunochromatographic assay. A survey of 335 stakeholders (farmers, processors, and traders) in two counties (Ruzizi Plain and Kabare) and one town (Bukavu) was carried out using a structured questionnaire. Focus group discussion, face-to-face interviews, and observation were used to assess the knowledge and awareness of mycotoxin contamination among different actors along the value chain. AFB1 and FB1 were determined by enzyme-linked immunosorbent assay method. Mycotoxigenic fungi were characterized according to gene sequencing data. Standard techniques were used to determine the phytochemical composition of the moringa, cloves, and ginger extracts; while the antimicrobial activity of extracts of moringa, cloves, and ginger was investigated using the agar-well diffusion method. Atomic absorption spectrophotometry determined the concentrations of minerals in composite flour while high-performance liquid chromatography determined phytate, and UV-VIS spectrophotometry determined tannins in composite flour. Aflatoxin was found in all maize samples, with freshly harvested dry maize having the lowest content with a mean and range of 3.2±0.3 µg/kg, and 0.3-18.5 µg/kg respectively. Aflatoxin levels were high in the market, with a range of 1 - 823.2 µg/kg of flour. At the market level, nearly all maize flour collected from the three areas had a high contamination level that exceeded the maximum tolerable limit of 10 µg/kg. At the processor level, there were significant differences (p<0.05) in aflatoxin contamination between flour and grain. The flour had the highest aflatoxin contamination with a mean of 148.9±164.5 μg/kg. The overall maximum concentration of aflatoxin in maize grain at the processor level was 97.9±182 μg/kg with levels ranging from 1.16 to 841.5 μg/kg. The high value for aflatoxin contamination was found in samples collected in Bukavu town. Fumonisin was found in all samples at varying concentrations. Almost all maize samples (80%) collected from the three areas had a degree of contamination that did not exceed the maximum tolerable limit of 4 µg/g. According to the interview, the majority of respondents were unaware of the mycotoxin contamination of maize. According to the interview, most of the respondents were aware of the mycotoxin contamination in maize: 63.7% and 69.3% of the farmers and processors, respectively. Most of the traders were unaware of the mycotoxin contamination. Contamination of both FB1 and AFB1 in flour was higher at the market level than at processor and farmer levels. At the market level, AFB 1 in flour was 12.3 ± 02.9 μg/kg, while in grain it was 9.2 ± 4.2 μg/kg. The farmer levels showed the least contamination, with concentrations of 0.15 ± 0.12 μg/g and 6.64 ± 3.79 μg/kg, respectively. Microscopic and molecular characterization was investigated on thirty isolates of fungi producing aflatoxin and thirty isolates producing fumonisin. Results have shown that 90% of Aspergillus isolates were categorized as yellow-dark green colonies, and all the isolates had conidia that were rough, while Fusarium isolates had whitish to purplish colonies on Potato Dextrose Agar. Molecular characterization was used to confirm their identities using a PCR-sequence analysis of the internal transcribed spacer (ITS) region of rDNA, which revealed that all the isolates from South Kivu that produce aflatoxin were A. flavus and F. verticillioides that produce fumonisin. Based on the seven target genes (aflR, aflM, aflP, aflD, aflQ, aflS, and aflO) producing aflatoxin, A. flavus was classified into five different groups: group I (9 isolates), characterized by the presence of the seven genes; group II (3 isolates), with the presence of aflR, aflM, aflP, and aflD; group III (three isolates), showing three (AflM, aflS, and aflQ); group IV (two isolates), with only two amplicons (aflR and aflD); and finally, group V (13 isolates), with none target gene. For Fusarium isolates, the target gene was Fumarate hydratase 1, mitochondrial (FUM1); only two groups were found: 15 isolates that amplify for the gene FUM1 and 15 that didn’t amplify. Different plants, namely moringa, clove, and ginger, were screened to see their potential to be used as natural products in the mitigation of aflatoxin and fumonisin. After screening the different phytochemicals, the clove methanolic extract had all three types of phytochemicals namely saponins, alkaloids, and terpenoids. The cloves extracts made with methanol and ethanol had a lot of flavonoids (78.3 ± 6.9 mg QE/g and 72.7 ± 1.25 mg QE/g), as well as total phenol (360.4 ± 3.6 mg GAE /g and 470.6 ± 2.4 mg GAE /g). The moringa extract had a high content of tannins (35.4±4.1 mg/g for ethanol and 31.2±2.3 mg/g for methanol). Ginger, clove, and moringa extracts in water and organic solvents had different antimicrobial effects that depended on the concentration. Each microorganism had a very different inhibition zone at 25 mg/mL. It had inhibition zones that were 20.9 ±1.3 mm for Fusarium verticillioides and 18.8 ±1.2 mm for A. flavus when the clove was extracted with ethanol. The minimum inhibitory concentration ranged from 2.5–10 mg/mL in clove extracts. Maize was subjected to nixtamalization and the flour was used to prepare some composite flour with soybean. Results show that the pH value varied with the nixtamalization process, from 6.8 ± 0.7 to 9.3 ± 0.4. The energy content of the composite flour was in the range of 354.77 ± 3.2 to 429.5 ± 4 kcal, meeting the minimum standard set for a cereal-based composite flour which is 400 Kcal. The protein values of the CFs (9.4 ± 0.3 to 13.9 ± 1.9%) on a dry weight basis were slightly below 15% of the recommended levels set by Codex. In conclusion, the composite flour made with 25% hydrothermal treated soybean and 75% nixtamalized maize can be considered the best composite flour concerning its nutritional properties, mineral, antinutrient, and mycotoxin content. Aflatoxin and fumonisin contamination in maize, a staple food in South Kivu, presents a significant public health risk due to its potential adverse effects on consumers. To address this issue, there is an urgent need to implement targeted awareness programs and capacity-building initiatives for key stakeholders along the maize value chain, including farmers, traders, and consumers. Furthermore, this study identifies plant extracts and the nixtamalization process as effective mitigation strategies for reducing contamination levels, highlighting their potential for improving food safety and protecting public health. Doctor of Philosophy in Food Science and Nutrition