Changes in fungal population and aflatoxin levels and assessment of major aflatoxin types in stored peanuts (Arachis hypogaea Linnaeus)

Peanut kernels of Homabay Local, Valencia Red, ICGV-SM 12991 and ICGV-SM 99568 cultivars were storedfor six months in jute, polypropylene and polyethylene bags to assess the effect of storage bags, temperature andR.H. on fungal population and aflatoxin contamination. Moisture content (M.C.), fungal population and aflatoxinlevels were determined before storage and after every 30 days during storage. Isolates of Aspergillus flavus andA. parasiticus were assayed for production of aflatoxin B1, B2, G1 and G2. The correlation between MC,population of A. flavus and A. parasiticus and aflatoxin levels in peanuts was also determined. Six fungalpathogens were commonly isolated from the peanut samples and occurred as follows in decreasing order:Penicillium spp. (106.6 CFU/g), A. flavus L-strain (4.8 CFU/g), A. flavus S-strain (2.9 CFU/g), A. niger (2.6CFU/g), A. parasiticus (1.7 CFU/g) and A. tamarii (0.2 CFU/g). The overall population of A. flavus L-strain was66% higher than that of A. flavus S-strain. Ninety one percent of A. flavus and A. parasiticus isolates produced atleast one of the four aflatoxin types assayed, with 36% producing aflatoxin B1. Total aflatoxin levels rangedfrom 0 - 47.8 μg/kg with samples stored in polyethylene and jute bags being the most and least contaminated,respectively. Eighty nine percent and 97% of the peanut samples met the EU (≤ 4 μg/kg) and Kenyan (≤ 10μg/kg) regulatory standards for total aflatoxin, respectively. Peanuts should be adequately dried to safe moisturelevel and immediately packaged in a container - preferably jute bags - which will not promote critical increasesin fungal population and aflatoxin contamination

Occurrence of Aspergillus species and aflatoxin contamination in raw and roasted peanuts from formal and informal markets in Eldoret and Kericho towns, Kenya

Published Online: August 2013.The population and diversity of fungal species and levels of aflatoxin contamination were investigated in 228 marketed peanut samples; 140 from formal and 88 from informal markets, in Kericho and Eldoret towns of Kenya. Ground pea- nut samples were cultured on Modified Dichloran Rose Bengal (MDRB) agar while aflatoxin level was quantified based on indirect competitive ELISA. Correlation between the incidence of major aflatoxin-producing fungal species and aflatoxin levels was also established. Fungal species commonly isolated from the peanut samples included Asper-gillus flavus L strain, A. flavus S strain, A. parasiticus, A. tamarii, A. caelatus, A. alliaceus (all of Aspergillus section Flavi) and A. niger. Fungi isolated in low frequency included Fusarium spp., Penicillium spp., Mucor spp. and Rhi- zopus spp. Aflatoxin levels in peanut products ranged from 0 to 2345 μg/kg in raw peanuts, 0 to 382 μg/kg in roasted coated peanuts, and 0 to 201 μg/kg in roasted de-coated peanuts. Overall, levels of total aflatoxin were higher in sam- ples from informal (mean = 97.1 μg/kg) than formal (mean = 55.5 μg/kg) market outlets. There was a positive and sig- nificant correlation (R2 = 0.63; p ≤ 0.05) between aflatoxin levels and the major aflatoxin producing fungi in raw pea- nuts from formal markets in Eldoret town. Additionally, total aflatoxin in raw peanut samples from informal markets in Kericho was positively and significantly correlated (R2 = 0.81; p ≤ 0.05) to the population of A. flavus (L and S strains). In roasted coated peanuts sampled from formal market outlets in Eldoret, aflatoxin levels correlated positively and sig- nificantly (R2 = 0.37; p ≤ 0.05) with A. flavus S strain. There is need to create awareness among peanut traders and con- sumers on proper handling of peanuts and health risks associated with consumption of unsafe peanut products

Fungal species isolated from peanuts in major Kenyan markets: Emphasis on Aspergillus section Flavi

A survey was conducted in Nairobi, Nyanza and Western provinces in Kenya between March and July 2009 with 1263 peanut products sampled out of which 705 samples underwent microbial analysis. The study aimed at determining the incidence of fungal species e emphasis on Aspergillus section Flavi e associated with peanut products. A 0.5 kg representative sample was obtained from each surveyed vendor and the colony forming units (CFU) of fungal species determined. The samples were also analyzed for total aflatoxin level while isolates of Aspergillus flavus and Aspergillus parasiticus were screened for production of aflatoxin B1, B2, G1 and G2. Eight fungal species were detected in the samples and were in decreasing order of CFU/g of sample: A. flavus S-strain (467), A. flavus L-strain (341), Penicillium spp. (326), Aspergillus niger (156), Aspergillus tamari (27), Aspergillus alliaceus (21), A. parasiticus (10), and Aspergillus caelatus (5). The overall incidence of A. flavus S-strain in samples from Nairobi was 92 and 1425% higher than samples from Nyanza and Western regions, respectively. The combined incidence of A. flavus and A. parasiticus was varied significantly (p ≤ 0.05) with peanut product: peanut flour (69%), shelled raw peanuts (53%), spoilt peanuts (49%), boiled podded peanuts (45%), podded peanuts (39%), peanut butter (31%), fried peanuts (22%) and roasted peanuts (20%). Seventy three percent of A. flavus and A. parasiticus isolates produced at least one of the aflatoxin types, with 66% producing aflatoxin B1. The total aflatoxin level among peanut products ranged from 0 to 1629 mg/g; and there was a positive correlation (r ¼ 0.2711) between the incidence of A. flavus and A. parasiticus, and total aflatoxin level. The high incidence of aflatoxin producing fungi in peanuts traded in Kenyan markets implies a risk of aflatoxin contamination, highlighting the need for stakeholders to promote sound practices at all stages of the peanut value chain in order to minimize market access by non-complying products

Effect of storage conditions on quality and aflatoxin contamination of peanuts (Arachis hypogaea L.)

Peanuts are prone to various types of deterioration during storage which renders them unsuitable for consumption and trade resulting in large economic losses. Peanut kernels of Homabay Local, Valencia Red, ICGV-SM 12991 and ICGV-SM 99568 varieties were stored for six months in jute, polypropylene and polyethylene bags to assess the effect of the storage bags, temperature and relative humidity (R.H.) on quality and aflatoxin contamination. Moisture content (M.C.), physical damage, rancidity and aflatoxin levels were determined before storage and after every 30 days during storage. Moisture content of the peanuts varied significantly (p ≤ 0.05) from 3.3 to 6.9% with samples stored in different bag types recording mean values of: 5.1% - polypropylene, 5.2% - polyethylene, and 5.3% - jute. Physical damage – which ranged from 0.1 to 9.8% - was significantly influenced by storage temperature and R.H., and the type of storage bag. Rancidity ranged from 0.8 to 5.3 and increased with storage duration from a mean of 1.5 before storage to a peak of 2.5 after 5 months of storage. There was a significant variation in the total aflatoxin levels ranging from 0 – 47.8 μg/kg, where peanuts stored in polyethylene bags were 7.3 and 13.4% more contaminated than samples stored in polypropylene and jute bags, respectively. Dried peanuts should be packaged in a container that will impede critical increases in M.C. and aflatoxin contamination and stored in a well-ventilated dry room with adequate air circulation

Changes in Fungal Population and Aflatoxin Levels and Assessment of Major Aflatoxin Types in Stored Peanuts (Arachis hypogaea Linnaeus)

Peanut kernels of Homabay Local, Valencia Red, ICGV-SM 12991 and ICGV-SM 99568 cultivars were stored for six months in jute, polypropylene and polyethylene bags to assess the effect of storage bags, temperature and R.H. on fungal population and aflatoxin contamination. Moisture content (M.C.), fungal population and aflatoxin levels were determined before storage and after every 30 days during storage. Isolates of Aspergillus flavus and A. parasiticus were assayed for production of aflatoxin B1, B2, G1 and G2. The correlation between MC, population of A. flavus and A. parasiticus and aflatoxin levels in peanuts was also determined. Six fungal pathogens were commonly isolated from the peanut samples and occurred as follows in decreasing order: Penicillium spp. (106.6 CFU/g), A. flavus L-strain (4.8 CFU/g), A. flavus S-strain (2.9 CFU/g), A. niger (2.6 CFU/g), A. parasiticus (1.7 CFU/g) and A. tamarii (0.2 CFU/g). The overall population of A. flavus L-strain was 66% higher than that of A. flavus S-strain. Ninety one percent of A. flavus and A. parasiticus isolates produced at least one of the four aflatoxin types assayed, with 36% producing aflatoxin B1. Total aflatoxin levels ranged from 0 - 47.8 μg/kg with samples stored in polyethylene and jute bags being the most and least contaminated, respectively. Eighty nine percent and 97% of the peanut samples met the EU (≤ 4 μg/kg) and Kenyan (≤ 10 μg/kg) regulatory standards for total aflatoxin, respectively. Peanuts should be adequately dried to safe moisture level and immediately packaged in a container - preferably jute bags - which will not promote critical increases in fungal population and aflatoxin contamination

Occurrence of Aspergillus Species and Aflatoxin Contamination in Raw and Roasted Peanuts from Formal and Informal Markets in Eldoret and Kericho Towns, Kenya

The population and diversity of fungal species and levels of aflatoxin contamination were investigated in 228 marketed peanut samples; 140 from formal and 88 from informal markets, in Kericho and Eldoret towns of Kenya. Ground peanut samples were cultured on Modified Dichloran Rose Bengal (MDRB) agar while aflatoxin level was quantified based on indirect competitive ELISA. Correlation between the incidence of major aflatoxin-producing fungal species and aflatoxin levels was also established. Fungal species commonly isolated from the peanut samples included Aspergillus flavus L strain, A. flavus S strain, A. parasiticus, A. tamarii, A. caelatus, A. alliaceus (all of Aspergillus section Flavi) and A. niger. Fungi isolated in low frequency included Fusarium spp., Penicillium spp., Mucor spp. and Rhizopus spp. Aflatoxin levels in peanut products ranged from 0 to 2345 μg/kg in raw peanuts, 0 to 382 μg/kg in roasted coated peanuts, and 0 to 201 μg/kg in roasted de-coated peanuts. Overall, levels of total aflatoxin were higher in samples from informal (mean = 97.1 μg/kg) than formal (mean = 55.5 μg/kg) market outlets. There was a positive and significant correlation (R2 = 0.63; p ≤ 0.05) between aflatoxin levels and the major aflatoxin producing fungi in raw peanuts from formal markets in Eldoret town. Additionally, total aflatoxin in raw peanut samples from informal markets in Kericho was positively and significantly correlated (R2 = 0.81; p ≤ 0.05) to the population of A. flavus (L and S strains). In roasted coated peanuts sampled from formal market outlets in Eldoret, aflatoxin levels correlated positively and significantly (R2 = 0.37; p ≤ 0.05) with A. flavus S strain. There is need to create awareness among peanut traders and consumers on proper handling of peanuts and health risks associated with consumption of unsafe peanut products

Genetic structure and relationships within and between cultivated and wild sorghum ( Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers

Understanding the extent and partitioning of diversity within and among crop landraces and their wild/weedy relatives constitutes the first step in conserving and unlocking their genetic potential. This study aimed to characterize the genetic structure and relationships within and between cultivated and wild sorghum at country scale in Kenya, and to elucidate some of the underlying evolutionary mechanisms. We analyzed at total of 439 individuals comprising 329 cultivated and 110 wild sorghums using 24 microsatellite markers. We observed a total of 295 alleles across all loci and individuals, with 257 different alleles being detected in the cultivated sorghum gene pool and 238 alleles in the wild sorghum gene pool. We found that the wild sorghum gene pool harbored significantly more genetic diversity than its domesticated counterpart, a reflection that domestication of sorghum was accompanied by a genetic bottleneck. Overall, our study found close genetic proximity between cultivated sorghum and its wild progenitor, with the extent of crop-wild divergence varying among cultivation regions. The observed genetic proximity may have arisen primarily due to historical and/or contemporary gene flow between the two congeners, with differences in farmers' practices explaining inter-regional gene flow differences. This suggests that deployment of transgenic sorghum in Kenya may lead to escape of transgenes into wild-weedy sorghum relatives. In both cultivated and wild sorghum, genetic diversity was found to be structured more along geographical level than agro-climatic level. This indicated that gene flow and genetic drift contributed to shaping the contemporary genetic structure in the two congeners. Spatial autocorrelation analysis revealed a strong spatial genetic structure in both cultivated and wild sorghums at the country scale, which could be explained by medium- to long-distance seed movemen

Assessment of the 2006 Abuja fertilizer declaration with emphasis on nitrogen use efficiency to reduce yield gaps in maize production

Open Access Journal; Published online: 01 Feb 2022The Abuja Fertilizer Declaration in 2006 recommended the increase of fertilizer use from the current practice for Sub-Saharan Africa (SSA) to achieve food sufficiency and improve soil fertility status. However, the current recommended rates of fertilizer have not been evaluated for specific crops on their potential to reduce the yield gap and optimize nitrogen use efficiency (NUE). In this study, with nitrogen (N) being a significant yield-determinant nutrient, four N use scenarios were drawn from existing recommendations and were evaluated under field conditions for maize crops in two catchments of the Lake Victoria basin. The scenarios included Business as Usual (BAU, 0 kg N ha−1), 25% of the Abuja declaration (ADS 12.5 kg N ha−1), 50% of the Abuja declaration (ADS 25 kg N ha−1), and Abuja declaration–Abuja scenario (ADS, 50 kg N ha−1). The results revealed that increasing N input levels significantly influenced the growth and yield of maize crops. The ADS scenario recorded the highest grain yield increase (167.39%) in Nyando and 103.25% in Rangwe catchments compared to the BAU scenario. N deficits were observed in all the N use scenarios with a range of −66.6 to −125.7 kg N ha−1 in Nyando and −62.5 to −105.4 kg N ha−1 in Rangwe catchments with the 50% ADS scenario having the highest deficits. The deficits imply that the added N input is insufficient to create an N balance for optimal NUE with consequent high risks of soil N mining. In both catchments, all N use scenarios were within the recommended agro-physiological N efficiency (APEN) level of between 40 and 60 kg kg−1 N. The partial N balance obtained at Nyando (1.56–3.11) and Rangwe (1.10–4.64) was higher than the optimal values, a sign of insufficiency of N inputs and possible risk of soil N depletion in all the scenarios. Our findings conclude that the proposed N rates in the region are still very low for food sufficiency and optimized NUE. Therefore, there is a need to explore other sources of N such as biological N fixation and organic manure and inform policy- and decision-makers to recommend higher rates beyond the “Abuja declaration” with the prospect of reaching target yield and optimizing NUE values based on specific crop recommendations

Incidence of aflatoxin in peanuts (Arachis hypogaea Linnaeus) from markets in Western, Nyanza and Nairobi Provinces of Kenya and related market traits

Fungal contaminants in major food staples in Kenya have negatively impacted food security. The study sought to investigate peanut market characteristics and their association with levels of aflatoxin in peanuts from Western, Nyanza and Nairobi Provinces of Kenya. Data were collected from 1263 vendors in various market outlets using a structured questionnaire, and peanuts and peanut products from each vendor were sampled and analyzed for aflatoxin levels. Thirty seven per cent of the samples exceeded the 10 μg/kg regulatory limit for aflatoxin levels set by the Kenya Bureau of Standards (KEBS). Raw podded peanuts had the lowest (χ2 = 167.78; P 10 μg/kg of aflatoxin. Over 70% of all storage structures were poorly ventilated and dusty. Sorting comprised 53% of the various crop protection measures used by traders post-harvest. To reduce aflatoxin exposure to consumers, set standards need to be complemented by strict monitoring systems and education of producers, processors and consumers in crop commodities other than maize, which has received the most attention in Kenya. Alternative uses of contaminated produce need to be explored

Nitrogen budgets and nitrogen use efficiency as agricultural performance indicators in Lake Victoria basin

Open Access JournalToo little nitrogen (N) is a threat to crop productivity and soil fertility in subSaharan Africa (SSA). Nitrogen budgets (NB) and nitrogen use e ciency (NUE) are critical tools for assessing N dynamics in agriculture and have received little or no attention in the region. Data were collected from smallholder farmers clustered into two categories, farmers applying and farmers not applying N fertilizers. NB were calculated using the Coupled Human and Natural Systems (CHANS) model approach for field and farm spatial scales. The results showed spatial variabilities in NB and NUE at the field level (maize and rice) across all the catchments. At the field level, N balances were negative for the two crops in all the catchments. Similarly, at the farm gate, a deficit of −78.37 kg N ha−1 was observed, an indicator of soil N mining. NUE values at the field scale varied across the catchments for both crops, with values for maize grown without N ranging from 25.76 to 140.18%. Even with the application of mineral N at higher levels in rice fields compared to maize fields, NUE values ranged between 81.92 and 224.6%. Our study revealed that the Lake Victoria region suers from ine cient N cycling due to depleted soil N pools and low synchrony between N input and N removal. Therefore, a challenge lies in exploiting more sustainable N sources for farmers in the region for sustainable farming systems. The NB and NUE provide critical information to agriculture stakeholders to develop environmental, agronomic, and economically viable N management solutions