Food Safety(Aflatoxin-Studies)

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Knowledge, Attitude and Practices (KAP) of Farmers on Postharvest Aflatoxin Contamination of Maize in Makueni and Baringo counties, Kenya
(University Of Nairobi, 2021-07) Kamano, Hannah; Okoth M.W; Kogi-Makau, Wambui; Kuloba, Patrick
Abstract Aflatoxin contaminated home grown maize has been a perennial problem in Kenya especially in the Eastern and North Rift parts of the country. This study focused on investigating the influence of knowledge, attitude and practices of farmers on aflatoxin contamination of maize in Makueni and Baringo counties in Kenya. A convergent mixed method study design combined quantitative and qualitative data collection techniques in maize producing areas of Baringo and Makueni Counties in Kenya. These methods included questionnaire administration, focus group discussions and key informant interviews. Of the 220 farmers who participated in the survey, 67.27% were male and 32.73% female in Baringo County whilst 45.45% male and 54.55% female in Makueni County. Majority of the farmers were in a marital union and were between the ages of 40-54 years. The average KAP score for knowledge was 57.6±11.79 % for both counties. The average knowledge score for Makueni was 37.70±11.36 % and 77.2±12.23 % for Baringo County. The average KAP attitude of the farmers in both counties was 77.1±9.32 %. There was a significant difference in the knowledge of factors contributing to aflatoxin in maize, as to the point where contamination begins, the signs of aflatoxin contamination and the consequences of aflatoxin exposure in both counties (p<0.005) The individual county scores were 76.5±9.24% and 77.7±9.41 % in Makueni and Baringo counties respectively. Socio-economic and demographic factors were linear predictors of knowledge (R2=0.76, p<0.001), whereas they had no effect (R2=0.043, p=0.076) on the attitude of the maize farmers. Farmers from Makueni County (Eastern Region of Kenya) were more likely (OR=1.24) to have higher knowledge scores on aflatoxin contamination than those from Baringo County (Rift Region of Kenya). On the contrary, with increasing age the maize farmers were less likely (OR=0.01) to have higher scores of knowledge. Farmers associated poorly dried maize and poor storage conditions as the maize cause of aflatoxin contamination. The study findings revealed a significant difference in knowledge and attitude between the two counties. This consequently had an effect on the practtices of the farmers. There is need for increased awareness creation on dangers posed by consumption of aflatoxin contaminated maize grain within the communities. Training of farmers on good agricultural and management practices is also of utmost importance. This coupled with regular surveillance and enhancement of laboratory capacities can also significantly reduce the occurrence of aflatoxicosis in Kenya.
Impact of Carrageenan Copolymers from Two Red Seaweed Varieties on Dough and Bread Quality
(JOURNAL OF APPLIED PSYCHOLOGY, 2021) Onyango Calvin; Luvita K.S; Lagat Kibet; Kosambo Linus
Abstract The impact of cottonii (COT, Kappaphycus alvarezii) and spinosum (SPI, Eucheuma denticulatum) flour (1–10% w/w) on rheological properties of wheat (WHE) and quality of bread was investigated. Wheat-COT and WHE-SPI had higher water absorption capacities, dough development times, dough stabilities and farinograph quality numbers than WHE dough. Extensograms of composite dough were largely similar to those of WHE at the same incubation times. Dough energy decreased whereas elasticity ratio (ratio of maximum resistance to extensibility) increased when incubation time was increased from 45 to 135 min. Wheat-COT and WHE-SPI had lower pasting temperatures but higher peak, final, breakdown and setback viscosities than WHE flour. Specific volume of bread containing COT (5% w/w) or SPI (7.5% w/w) was not different (p > 0.05) from that of WHE bread. Crumb texture properties of these composite breads were also largely similar to those of WHE bread. The physical properties of WHE dough and bread were influenced by gluten, whereas those of WHE-COT and WHE-SPI were influenced by gluten in addition to κ-carrageenan in COT and ι-carrageenan in SPI. Protein, ash and dietary fibre contents increased (p < 0.05) whereas carbohydrate content of bread decreased (p < 0.05) when WHE was replaced with COT or SPI (5% w/w).
Genetic Diversity of Kenyan Native Oyster Mushroom (Pleurotus)
(The Mycological Society of America, Lawrence, KS, 2015) Otieno Ojwang D.; Wamalwa Mark; Onguso Justus Mungare; Matasyoh Lexa G.; Wanjala Bramwel W.
Members of the genus Pleurotus, also commonly known as oyster mushroom, are well known for their socioeconomic and biotechnological potentials. Despite being one of the most important edible fungi, the scarce information about the genetic diversity of the species in natural populations has limited their sustainable utilization. A total of 71 isolates of Pleurotus species were collected from three natural populations: 25 isolates were obtained from Kakamega forest, 34 isolates from Arabuko Sokoke forest and 12 isolates from Mount Kenya forest. Amplified fragment length polymorphism (AFLP) was applied to thirteen isolates of locally grown Pleurotus species obtained from laboratory samples using five primer pair combinations. AFLP markers and internal transcribed spacer (ITS) sequences of the ribosomal DNA were used to estimate the genetic diversity and evaluate phylogenetic relationships, respectively, among and within populations. The five primer pair combinations generated 293 polymorphic loci across the 84 isolates. The mean genetic diversity among the populations was 0.25 with the population from Arabuko Sokoke having higher (0.27) diversity esti mates compared to Mount Kenya population (0.24). Diversity between the isolates from the natural population (0.25) and commercial cultivars (0.24) did not differ significantly. However, diversity was greater within (89%; P . 0.001) populations than among populations. Homology search analysis against the GenBank database using 16 rDNA ITS sequences randomly selected from the two clades of AFLP dendrogram revealed three mushroom species: P. djamor, P. floridanus and P. sapidus; the three mushrooms form part of the diversity of Pleurotus species in Kenya. The broad diversity within the Kenyan Pleurotus species suggests the possibility of obtaining native strains suitable for commercial cultivation.
Structural And Physicochemical Properties And In Vitro Digestibility of Recrystallized Linear Α-D- (1 → 4) Glucans Derived from Mild-Acid-Modified Cassava Starch
(Food Research Internationa, 2010) Mutungi C.; Onyango C.; Rost F.; Doert T.; Rohm H.; Jaaros D.
Molecular structure and recrystallization method influence the techno-functional behaviour of recrystallized starch as a functional ingredient in foods. The physicochemical properties of debranched and recrystallized mild-acid-modified cassava starch were studied. Cassava starch was treated with 0.14 mol/L hydrochloric acid for 24, 96 and 216 h at 40 °C prior to debranching with pullulanase. The debranched starches (DS) were recrystallized by annealing (ANN-DS), temperature-cycling (TC-DS) or heat-moisture treatment (HMT-DS) and the particle distribution, crystallinity, thermal properties, solubility, water binding and in vitro digestibility were analyzed. Acid treatment increased the fraction of linear α-d-(1 → 4) glucans comprising 13–30 monomers. Particles comprised loosely to firmly coalesced primary elements forming aggregates of mono- or bi-modal size distribution at ⩽5 μm and ⩾20 μm. The relative crystallinities ranged between 31.1–56.1%. Water binding decreased significantly with acid treatment whereas both solubility and water binding were influenced by the recrystallization method and decreased in the order: DS > ANN-DS > TC-DS > HMT-DS. Major thermal transitions occurred at 80– 130 °C and 130–160 °C, and the in vitro digestibility rates of 6.8–62.8% correlated significantly (p < 0.001) with relative crystallinity and melting enthalpy.
Rheological And Textural Properties of Sorghum-Based Formulations Modified with Variable Amounts of Native or Pregelatinised Cassava Starch
(LWT - Food Science and Technology, 2011) Onyango Calvin; Mutungi Christopher; Ubehend Gunter; Lindhauer Meinolf G.
Sorghum bread was made from native or pregelatinised cassava starch and sorghum flour in the ratio 10:90, 20:80, 30:70, 40:60 and 50:50. The other ingredients, measured on flour-weightbasis, were water (100%), sugar (6.7%), egg white (6%), fat (2%), salt (1.7%) and yeast (1.5%). The dynamic oscillatory behaviours of the batters were affected by the amount and type of starch. In the amplitude sweep measurements, increasing concentration of native starch decreased storage modulus, whereas increasing concentration of pregelatinised starch increased the linear viscoelastic range of the batters. In the frequency sweep measurements, the loss factor of batters treated with native starch declined with increasing frequency. Batters treated with 10 or 20% pregelatinised starch showed declining loss factors, whereas batters treated with 40 or 50% pregelatinised starch showed increasing loss factors with increasing frequency. Sorghumbased batters containing native starch gave bread with better crumb properties than batters containing pregelatinised starch. Crumb firmness and chewiness declined with increasing native or pregelatinised starch concentration. Crumb adhesiveness of breads containing pregelatinised starch increased with increasing starch content but was not affected by native starch. Cohesiveness, springiness and resilience increased with increasing native starch content, but were minimally affected by increasing pregelatinised starch content.
Rheological And Baking Characteristics of Batter and Bread Prepared from Pregelatinised Cassava Starch and Sorghum and Modified Using Microbial Transglutaminase
(Journal of Food Engineering, 2010) Onyango Calvin; Mutungi Christopher; Ubehend Gunter; Lindhauer Meinolf G
The effect of different concentrations (0, 0.5, 1 and 1.5 U/g) of microbial transglutaminase (MTG) on the creep-recovery properties of gluten-free batter prepared from pregelatinised cassava starch, sorghum and egg white was investigated. The test conducted in the rheometer had an instant loading of 80 Pa for 60 s and recovery of 0 Pa for 140 s. Increasing MTG concentration decreased the batters’ resistance to deformation and compliances but increased zero shear viscosity and elastic recovery. Changes in batter rheological properties were insignificant (P > 0.05) at MTG concentrations beyond 0.5 U/g. Crumb properties of gluten-free bread baked from the batter revealed that increasing MTG concentration increased (P < 0.05) crumb firmness and chewiness, whereas increasing incubation time decreased (P < 0.05) crumb cohesiveness, chewiness and resilience. There were no significant interaction effects (P > 0.05) between enzyme concentration and incubation time
Physico-chemical Properties of Flour, Dough and Bread from Wheat and Hydrothermally-treated Finger Millet
(Science Direct, 2020-05) Calvin Onyango; Luvitaa S. K; Guenter Unbehend; Norbert Haase
Abstract Hydrothermally-treated (HTT) finger millet was prepared by tempering the grains twice with water (10:1) followed by incubation at about 25–30°C in a woven polypropylene sack for 10 days. Hydrothermally-treated finger millet was darker and had higher α-amylase activity and lower starch digestibility than native (NAT) grains. The HTT finger millet was composited with wheat flour and used to prepare bread. Composite dough had higher dough stability, dough development time and degree of softening but lower dough energy, extensibility and resistance to extension than WHE dough. The higher specific volume and lower crumb firmness and chewiness of WHE-HTT compared to WHE-NAT bread was attributed to the high α-amylase activity and water absorption capacity of HTT finger millet. Wheat-HTT bread had higher dietary fibre, phytate and phenolic acid content but the same starch and protein digestibility as WHE bread.
Determination of Optimum Conditions for Enzymatic Debranching of Cassava Starch and Synthesis of Resistant Starch Type III using Central Composite Rotatable Design
(WILEY ONLINE LIBRARY, 2009-07-13) Christopher Mutungi; Onyango Calvin; Jaros Doris; Henle Thomas; Rohm Harald
Cassava starch was debranched by treatment with isoamylase and pullulanase and the yield of resistant starch type III (RS III) optimized with respect to starch solids concentration (7.5-15%, w/v), incubation time (8-24 h) and enzyme concentration using central composite rotatable design. Higher concentrations of pullulanase (10-35 U/g starch) compared to isoamylase (30–90 mU/g starch) were required to give a similar degree of starch hydrolysis within the experimental domain. A clear debranching end-point was identifiable by following the reducing value, blue value and β-hydrolysis limit of cassava starches debranched using isoamylase. It was difficult to define a debranching endpoint of pullulanase treatment by these parameters due to contaminating α-D-(1→4) activity. The yield of RS III was significantly higher in isoamylolysates and increased steadily with increasing degree of hydrolysis to peak at 57.3%. Purification of the debranched material further increased the RS III yield to 64.1%. Prolonged (24 h) hydrolysis of cassava starch with high concentration of pullulanase (35 U/g) gave lower RS III contents in the purified (34.2%) and unpurified (36.2%) hydrolysates compared to 49.5 and 62.4%, respectively, at moderate pullulanase concentration (22.5 U/g) and incubation time (16 h).
Use and Efficiency Of Low Temoerature Plasma In Foods: Promising Intervention On Aflatoxin Control In Maize In Kenya – A Reviewg
(Najfand, 2021-10) Kamano HM; Okoth M; Wambui-Kogi M; Kuloba P
ABSTRACT Maize (Zea mays var. indentata L.) is the most important food security crop in Kenya and plays an important role in human nutrition. Mycotoxins (MTs) are fungal toxic metabolites which naturally contaminate food and feed. When ingested, inhaled or adsorbed through the skin, even in very small concentrations, are associated with various cancers, retarded growth, suppressed immunity and mutations among other complications. Aflatoxins especially aflatoxin B1, are considered the most lethal in the group of more than three hundred known mycotoxins. In Kenya, aflatoxin contamination in maize leads to huge losses in the country’s breadbasket and also in the grain reserves. One of the possible methods for control of the aflatoxin menace in maize would be through the use of plasma technology. Plasma, an electrically energized matter in form of a gas that is generated at different atmospheric pressures, has several uses. At low temperature, it makes the process of decontamination practical, inexpensive and suitable for products whereby use of heat is not desired. Non thermal plasma, a new discipline in food processing has been shown to destroy microorganisms including spores to undetectable levels. Over the years, there has been increased concern over the rising cases of aflatoxin poisoning in Kenya due to contaminated maize. The presence of aflatoxins is promoted by various factors, among them poor storage conditions, soil type, insect activity and drought conditions before harvest. Several measures including use of hermetic storage types such as pics (Purdue Improved Cowpea Storage) bags to store maize and proper drying of maize to the right moisture content to discourage mould growth have been suggested and used to tackle the aflatoxin menace. In Mexico and Caribbean countries, nixtamalization is widely practised and has been used to reduce aflatoxin in tortilla. Nixtamilization involves cooking the maize in an alkaline solution resulting in detoxification. The traditional nixtamalization and extrusion cooking processes have been combined in making of the dough (masa) for corn tortillas and have shown better success in elimination of aflatoxin. The main challenge with the use of this method of detoxification is acidification of aflatoxin extracts, which occurs during digestion and can lead to a rebuilding of the aflatoxin molecule leading to poisoning. The application of low temperature plasma technology can bring much needed reprieve in tackling the aflatoxin menace in maize and other foods both in Kenya and even worldwide.
Fungi and Aflatoxin Levels in Traditionally Processed Cassava (Manihot esculenta Crantz) Products in Homa Bay County, Kenya
(International Journal of Microbiology, 2020-08-26) Obong’o, Boniface Oure; Ayodo, George; Kawaka, Fanuel; Adalla, Morelly Kathy
Cassava (Manihot esculenta Crantz) is a major source of carbohydrates, calcium, vitamins (B and C), and essential minerals and is the third most important source of calories in the tropics. However, it is not clear if the traditional processing methods expose the products to microbial contamination. This study assessed the levels of fungi and aflatoxin contamination in traditionally processed cassava products (Akuoga and Abeta). A total of 38 samples were collected from the local markets in 7 subcounties in Homa Bay County, Kenya. The levels of aflatoxin were determined using an indirect competitive ELISA protocol. Yeast and mould contamination was determined using ISO 21527-2 method. Mean aflatoxin levels in chopped, fermented, and sun-dried cassava (Akuoga) were 0.36 μg/kg compared to 0.25 μg/kg in chopped and sun-dried (Abeta) products. Aflatoxin contamination was detected in 55% of the samples and ranged from 0–5.33 μg/kg. These levels are within 10 μg/kg recommended by the CODEX STAN 193-1995. Yeast and mould counts in fermented and chopped sun-dried products were 3.16 log Cfu/g and 2.92 log Cfu/g, respectively. The yeast and mould counts were above standards set by East African Standard 739:2010 in 62% (Akuoga) and 58% (Abeta). The most prevalent fungal species were Saccharomyces cerevisiae (68.4%) and Candida rugosa (68%) followed by Candida parapsilosis (18.4%), Candida tropicalis (15.8%), Candida humilis (15.8%), and Aspergillus spp. (5.3%). Aspergillus spp. was the only mycotoxigenic mould isolated from the samples. The study shows that cassava consumers are exposed to the risk of aflatoxin poisoning. The study, therefore, recommends appropriate surveillance to ensure safety standards.
Efficacy of Plasma Technology in Eliminating Fungi and Aflatoxins in Maize in Makueni and Baringo Counties, Kenya
(University Of Nairobi, 2022) Hannah Mugure Kamano
Maize (Zea mays var. indentata L.) is the most important food security crop in Kenya and plays an important role in human nutrition. Over the years, there has been increased concern over the rising cases of aflatoxin poisoning in Kenya due to contaminated maize especially in Eastern and North Rift parts of the country. This has led to huge losses not only in the country’s breadbasket areas but also in the national grain reserves. Aflatoxins are fungal toxic metabolites that naturally contaminate food and feed. Exposure to aflatoxins is associated with various cancers, suppressed immunity, retarded growth, mutations, and aggravation of other existing conditions such as HIV among others. Plasma technology presents a possible solution. Plasma is electrically energized matter in gaseous form that is generated at different conditions of temperature, pressure and ionization power. Low temperature plasma is an emerging technology that is finding space in the food industry particularly in decontamination processes. Use of plasma at low temperature makes the decontamination process practical, inexpensive and suitable for products where high temperatures are not desired. The main objective of this study was to determine the efficacy of plasma technology in destroying fungi and aflatoxins in maize in Makueni and Baringo counties in Kenya. The specific objectives were: to determine the influence of knowledge, attitude and practices of farmers on aflatoxin contamination of maize in Makueni and Baringo counties in Kenya, to determine the influence of postharvest practices and storage conditions on aflatoxin contamination in maize in the two counties, to isolate and characterize the fungi responsible for contamination in both counties and finally to determine the efficacy of plasma technology in destroying fungi and aflatoxin in maize. A convergent mixed method study design that combined quantitative and qualitative data collection techniques was used for the knowledge, attitude and practices study. The data collection methods included interviewing, using a pretested questionnaire, focus group discussions and key informant interviews. To screen the aflatoxin levels in the maize samples from both counties, 144 samples were randomly collected and subjected to the ELISA technique for quantitative detection of aflatoxin B1, B2, G1 and G2. Confirmatory test for the ELISA positive samples was carried out using HPLC analysis. Isolation of fungal strains was done using rose bengal selective media which contained chloramphenicol thereby suppressing bacterial growth. Isolated strains were characterised based on their phenotypic characteristics on the plate and microscopic techniques. Finally, the efficacy of Low temperature nitrogen plasma (LTNP) in destroying fungi and aflatoxin was studied using an experimental design generated using Response Surface Methodology (RSM) of the Box Benken Design (BBD) of the Design Expert software (StatEase, 2020). Independent factors were exposure time, pressure and ionization power whilst percent reduction in both the fungal load and aflatoxin level were the response variables. The results of the knowledge, attitude and practices (KAP) study revealed a significant difference in the knowledge of factors contributing to aflatoxin contamination in maize. Socio-economic and demographic factors were linear predictors of knowledge (R2=0.76, p<0.001), whereas they had no effect (R2=0.043, p=0.076) on the attitude of the maize farmers. Farmers indicated poorly dried maize and poor storage conditions as the main causes of aflatoxin contamination. The aflatoxin analysis on the maize showed that Makueni County had the highest percentage of aflatoxin positive samples with up to 174 ppb. The type of storage condition had a significant effect on the extent of contamination and accounted for 11% of the variation (R2 =0.11). Gunny bags were the most common type of storage condition and had the highest level of contamination in both counties whilst metallic bins had the lowest contamination. Strains of Aspergillus flavus, Aspergillus terreus and Aspergillus parasitucus were positively identified after characterization of the isolated strains. Finally the RSM linear model predicted the reduction in fungal load and aflatoxin content with F-values of 7.22 and 15.89 respectively (P ≤ 0.01). An increase in exposure time and pressure lead to a corresponding decrease in the fungal load and aflatoxin content. Ionization power did not have a significant effect on both response variables. For optimisation of the detoxification process, the RSM model supported process settings of time at 153.58 seconds, pressure of 0.98 Pascals and ionization power of 194.82 Watts. The findings lead to the conclusion that more awareness creation, training of farmers on good agricultural practices, enhanced market surveillance and laboratory services are needed to educate farmers and the general public on dangers related to exposure to aflatoxins. The type of storage condition significantly affects the aflatoxin level in stored maize, proper drying of maize and storage in hermetic structures offers the best method to prevent aflatoxin contamination. Finally, plasma is efficacious in destroying aflatoxins and fungi in the maize to a reduction of 68.78% and 33.89 log (cfu/g) for aflatoxin content and fungal load, respectively. Further the research recommends encompassing temperature as an independent variable in the RSM model to fine tune optimisation parameters.
Modulation of Aflatoxin Production by Interaction of Aspergillus Species from Eastern Kenya
(IOSR Journal of Environmental Science, 2019-04-13) Lagat Micah Kipkemboi; Toroitich Faith Jebet; Obonyo Meshack Amos; Makonde Huxley Mae
Aflatoxin contamination of grain has continued to pose a significant threat to sustainable food security and trade worldwide. In the field, there are incidences of varying contamination levels in grain within the same niche. We hypothesize that the variation could be due to fungal species interaction at the kernel level. Seventeen isolates (14 Aspergillus flavus and 3 Aspergillus parasiticus) from Eastern Kenya were selected and confirmed for toxigenicity using Dichlorvos-Ammonia method, then cultured based on their isolation frequencies and co-existence in nature. The fungi were co-cultured using maize kernels as growth substrate, which was then used to estimate aflatoxin produced in a competitive ELISA. A one-sample two-tailed t-test was carried out to determine the degree of significance in aflatoxin production. Eight isolates were non-toxigenic, while nine were toxigenic. When co-cultured with some non-toxigenic isolates such as A. parasiticus (2EM0601), the most toxigenic A. flavus isolate (1EM1901) significantly increased aflatoxin production, while it reduced with others. These observations warrant investigation on the interaction of Aspergillus species in culture especially given their diverse toxigenic potential. We concluded that colony-mediated aflatoxin production could explain the variations of toxin levels observed in freshly collected field samples.
Occurrence of Fusarium Head Blight of Wheat and Associated Mycotoxins in Narok and Nakuru Counties, Kenya
(Science and Education Publishing, 2016) Wagacha, John Maina; Njeru, Nancy Karimi; Okumu, Oliver Otieno; Muthomi, James Wanjohi; Mutegi, Charity Kawira
Fusarium head blight (FHB) is an important disease of small grain cereals. This study assessed the incidence and severity of FHB of wheat at hard dough stage, and levels of deoxynivalenol and T2-toxin at harvest by direct competitive enzyme linked immuno-sorbent assay. Wheat ears were randomly sampled from 51 farms in Narok County and 51 farms in Nakuru County at hard dough stage while wheat kernels were sampled at harvest. Prevalence of FHB in both Counties was 100%. The mean incidence of FHB was 28.4% and 20.5% in Narok and Nakuru Counties, respectively with 16.9% and 11.7% corresponding severity. Over 14 Fusarium spp. were isolated from wheat ears and kernels with F. avenaceum, F. poae and F. graminearum being isolated in the highest incidence. Levels of DON in the kernels ranged from below limit of detection (
Effect of Cropping Systems on Accumulation of Fusarium Head Blight of Wheat Inocula in Crop Residues and Soils
(Academic Journals Inc., 2016-12-21) Njeru, N.K.; Muthomi, J.W.; Mutegi, C.K.; Wagacha, J.M.
Fusarium head blight (FHB) is an economically important disease of wheat, which causes reduction in grain yield both quantitatively through reduced seed weight and qualitatively by contaminating grains with mycotoxins. The effect of cropping systems on accumulation of FHB inocula in crop residues and soil was assessed at hard dough stage of wheat during the 2013 cropping season in three agro-ecological zones in Narok County, Kenya. A semi structured questionnaire was used to obtain information on wheat production practices. Fusarium spp. were isolated from crop residues and top soil, while incidence and severity of FHB were assessed at mid-anthesis. Majority of the wheat farmers were small scale producers who rotated wheat with maize, grew the two crops in adjacent fields, grew wheat in consecutive years, left wheat residues as standing hay for livestock and practiced simple land preparation methods. Prevalence of FHB was 100%, while mean incidence and severity were 20.7 and 28.4%, respectively. The most frequently isolated Fusarium spp. were F. chlamydosporum and F. graminearum in crop residues and F. oxysporum and F. proliferatum in soil. The incidence of Fusarium spp. in soil and crop residues was highly correlated to FHB incidence but not to severity of the disease. Wheat production practices affect the survival of Fusarium spp. in soil and crop residues between cropping seasons. It is therefore, recommended that after harvesting, wheat straw and maize stover should be removed from the field or be incorporated into the soil through tillage to allow faster decomposition. Inclusion of maize as a rotation crop in wheat production should also be avoided.
In vitro antifungal activity of Desmodium intortum and D. uncinatum root extracts against growth of toxigenic Fusarium verticillioides and Aspergillus flavus
(AJCS, 2020) Njeru, Nancy Karimi; Midega, Charles Aura Odhiambo; Muthomi, James Wanjohi; Wagacha, John Maina; Khan, Zeyaur Rahman
Maize grown under push-pull cropping system has been reported to contain lower concentrations of fumonisin and aflatoxin than maize monocrop. This study determined the inhibitory effect of desmodium root extracts on spore germination and radial growth of toxigenic Aspergillus flavus and Fusarium verticillioides. Aspergillus flavus and F. verticillioides were isolated from maize and soil and tested for ability to produce aflatoxin and fumonisin by inoculation on mycotoxin-free maize. Aflatoxin and fuminisin were detected and quantified by direct competitive ELISA. Desmodium roots were dried, ground to fine powder and extracted with methanol and dichloromethane and evaluated for anti-fungal activity by inhibition of spores of A. flavus and F. verticillioides potato dextrose agar (PDA) medium. Isolates of F. verticillioides produced up to 599,741 µg/kg fumonisin while isolates of A. flavus produced up to 199,184 µg/kg aflatoxin. Desmodium root extracts reduced germination of A. flavus spores and F. verticillioides by 9.6% and 43.8%, respectively and reduced their respective colony radial growth by 15% and 57%. The results suggested that desmodium roots contain chemical compounds that inhibit growth of A. flavus and F. verticillioides. This may explain the reduction in infection of maize with mycotoxin-producing fungi before harvest in push-pull cropping systems by reducing the pathogen inoculum in the soils. Determination of the active compounds in the root exudates is recommended.
Influence of socio‐economic and agronomic factors on aflatoxin and fumonisin contamination of maize in western Kenya
(Wiley Periodicals, Inc., 2019-05-08) Njeru, Nancy Karimi; Midega, Charles Aura Odhiambo; Muthomi, James Wanjohi; Wagacha, John Maina; Khan, Zeyaur Rahman
Consumption of maize contaminated with mycotoxins has been associated with detrimental health effects. A farm survey covering 116 push‐pull and 139 non‐push‐pull cropping systems was conducted to determine the socio‐economic and agronomic factors that influence farmers’ knowledge on incidence and contamination of maize by ear rots and associated mycotoxins in western Kenya. All the respondents were smallholder farmers between the ages of 23 and 80 years, with 50% of them being female. Maize samples were collected from the standing crop in the field of each interviewed farmer and analyzed for aflatoxin and fumonisin. Only a small proportion of farmers had knowledge of aflatoxin and ear rots in maize. Overall, less than 20% of maize samples were contaminated with both aflatoxin and fumonisin, and more maize samples were contaminated with fumonisin as compared to aflatoxin. Proportions of maize samples containing higher than the acceptable Kenyan regulatory threshold (10 µg/kg) for aflatoxin and European Commission regulatory threshold (1,000) µg/ kg for fumonisin were lower in maize samples from push‐pull cropping system. Age of farmer and county of residence were significantly and positively associated with knowledge of aflatoxin, while cropping system, county of residence, and level of education were positively associated with knowledge of maize ear rots. There was strong correlation between knowledge of maize ear rots and knowledge of aflatoxin. Levels of both aflatoxin and fumonisin were significantly and positively associated with the use of diammonium phosphate (DAP) fertilizer at planting. Aflatoxin levels were also positively associated with stemborer damage. Agronomic practices were not significantly different between push‐pull and non‐push‐pull farmers. However, use of DAP fertilizer was the most important agronomic factor since it was associated with both aflatoxin and fumonisin contamination of maize. These results imply that creating awareness is key to mitigation of ear rots and mycotoxin contamination of maize. The results also suggest that the levels of aflatoxin and fumonisin in maize in western Kenya were influenced both by pre‐harvest agronomic practices and by the cropping system adopted, push‐pull or not.
Impact of push–pull cropping system on pest management and occurrence of ear rots and mycotoxin contamination of maize in western Kenya
(2020-08-18) Njeru, Nancy K.; Midega, Charles A. O.; Muthomi, James W.; Wagacha, John M.; Khan, Zeyaur R.
Push–pull involves intercropping of cereals with Desmodium as a “push” crop and planting Napier grass/Brachiaria as the “pull” crop at the border. The technology has been reported to effectively control stemborers, striga weed, and fall armyworm (FAW), and to improve soil nutrition, resulting in increased grain yield. This study evaluated the impact of stemborer and FAW management using this technology on incidence of maize ear rots and preharvest contamination of grains with aflatoxin and fumonisin in western Kenya. The study was conducted during three cropping seasons on maize grown under the push–pull system and as a monocrop. Incidence of stemborer and FAW damage was determined as percentage of damaged plants, while incidence of ear rots was determined as percentage of ears with symptoms. At harvest, fungi were isolated from kernels and aflatoxin and fumonisin were quantified using enzyme-linked immunosorbent assay. Stemborer and FAW damage was significantly (p = .001) reduced by over 50% under the push–pull system. There was also a significant (p < .001) reduction in the incidence of Fusarium verticillioides (60%) and Aspergillus flavus (86%), which was reflected in a reduced incidence of ear rots (50%) with the push–pull system (p = .001). Fumonisin in maize from push-pull farms was significantly (p = .048) reduced (39%) but the technology had no significant (p > .05) effect on aflatoxin. The study showed that push–pull is an effective strategy for managing maize ear rots and fumonisins, and therefore could play a role in improving food safety among smallholder maize farmers in the region.
Occurrence of Fusarium Head Blight of Wheat and Associated Mycotoxins in Narok and Nakuru Counties, Kenya
(Science and Eduacation Publishing, 2016) Wagacha John Maina; Njeru Nancy Karimi; Okumu Oliver Otieno; Muthomi James Wanjohi; Mutegi Charity Kawira
Fusarium head blight (FHB) is an important disease of small grain cereals. This study assessed the incidence and severity of FHB of wheat at hard dough stage, and levels of deoxynivalenol and T2-toxin at harvest by direct competitive enzyme linked immuno-sorbent assay. Wheat ears were randomly sampled from 51 farms in Narok County and 51 farms in Nakuru County at hard dough stage while wheat kernels were sampled at harvest. Prevalence of FHB in both Counties was 100%. The mean incidence of FHB was 28.4% and 20.5% in Narok and Nakuru Counties, respectively with 16.9% and 11.7% corresponding severity. Over 14 Fusarium spp. were isolated from wheat ears and kernels with F. avenaceum, F. poae and F. graminearum being isolated in the highest incidence. Levels of DON in the kernels ranged from below limit of detection n (
Effect of Cropping Systems on Accumulation of Fusarium Head Blight of Wheat Inocula in Crop Residues and Soils
(Journal of Plant Sciences, 2016-04-15) Njeru N.K.; Muthomi J.W.; Mutegi C.K.; Wagacha J.M.
Fusarium head blight (FHB) is an economically important disease of wheat, which causes reduction in grain yield both quantitatively through reduced seed weight and qualitatively by contaminating grains with mycotoxins. The effect of cropping systems on accumulation of FHB inocula in crop residues and soil was assessed at hard dough stage of wheat during the 2013 cropping season in three agro-ecological zones in Narok County, Kenya. A semi structured questionnaire was used to obtain information on wheat production practices. Fusarium spp. were isolated from crop residues and top soil, while incidence and severity of FHB were assessed at mid-anthesis. Majority of the wheat farmers were small scale producers who rotated wheat with maize, grew the two crops in adjacent fields, grew wheat in consecutive years, left wheat residues as standing hay for livestock and practiced simple land preparation methods. Prevalence of FHB was 100%, while mean incidence and severity were 20.7 and 28.4%, respectively. The most frequently isolated Fusarium spp. were F. chlamydosporum and F. graminearum in crop residues and F. oxysporum and F. proliferatum in soil. The incidence of Fusarium spp. in soil and crop residues was highly correlated to FHB incidence but not to severity of the disease. Wheat production practices affect the survival of Fusarium spp. in soil and crop residues between cropping seasons. It is therefore, recommended that after harvesting, wheat straw and maize stover should be removed from the field or be incorporated into the soil through tillage to allow faster decomposition. Inclusion of maize as a rotation crop in wheat production should also be avoided.
Screening of Warburgia Ugandensis Crude Extracts Obtained from Different Organic Solvents against Tomato Phytophthora Infestans and Alternaria Solani
(European Academic Research, 2019-03) Kamau Esther Waithira; G.E Mworia; J.M Maingi; P.W Masinde
Alternaria solani and Phytophthora infestans are causative agents of early and late blight of tomatoes respectively which are currently controlled using fungicides. Overuse of fungicides poses safety concerns. The research objective was to investigate the invitro efficacy of Warburgia organic solvent crude extracts on blight pathogens. Warburgia ugandensis stem bark sample was air dried at room temperature then ground. The powdered material was weighed and soaked in organic solvent then filtered and the solvent recovered using a rotary evaporator. Multiple extraction method was used with four organic solvents. Well diffusion method was used to screen Warburgia extracts against A. solani and P. infestans. All assays were performed in triplicate. Statistical analysis on inhibition zone was carried out using analysis of variance (ANOVA). Warburgia ugandensis hexane crude extract had the highest inhibition zone in A. solani while methanol crude extract gave the highest mean inhibition zone in P. infestans. All the extracts were inhibitive against P. infestans and A. solani. Further studies are required for invivo studies and to analyze the bioactive compounds in the extracts.

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