Rice grains can be attacked by a range of pathogens, including Aspergillus species, which can cause the accumulation of aflatoxins and represent a serious threat to the consumers. Aflatoxins are secondary metabolites synthesized by Aspergillus species and naturally occur in various foodstuffs. In this study, we sought to analyze the prevalence of aflatoxin-producing Aspergillus spp. in rice grains currently sold in Kenyan local markets. We analyzed a total of 98 samples randomly collected and primarily analyzed to observe moisture content and fungal growth. We then isolated Aspergillus species, characterized them morphologically and using the Internal transcribed spacer (ITS) primers. Finally, we screened them for aflatoxin-producing isolates targeting Norsolorinic Acid (nor-1) and Versicolorin (ver-1) specific genes involved in aflatoxin biosynthesis. We observed that all tested samples were contaminated. The highest prevalence of Aspergillus species and aflatoxigenic fungal species, had values of 66% and 36.4% for nor-1 and ver-1, respectively. In total, 66% of all isolates were confirmed to be aflatoxin producers. The occurrence of high contamination levels of Aspergillus species points to the possibility of production of aflatoxins in rice grains. This work provides a baseline for future studies on the occurrence of mycotoxigenic fungal species in rice grains being sold in local markets and strategies to control these aflatoxigenic strains at pre- and post-harvest levels.

Aflatoxigenic fungi are most common filamentous fungi that synthesis aflatoxins and represent the major fungal pathogens to agricultural products. Aflatoxins remain a major threat to global food security, these molecules could be resisted into food during processing and in additional may remain within the food chain. Aflatoxins are carcinogenic, hepatotoxic, mutagenic, teratogenic, can inhibit numerous metabolic systems and immunosuppressive properties. Studies of aflatoxigenic strains can help to enhance strategies control and prevent aflatoxigenic fungi contamination and aflatoxins production in foodstuffs. In this study, isolation of Aspergillus species was based on morphological characteristics including the mycelium growth pattern, color, and properties of fruiting bodies of the fungi. The innovated technique loop-mediated isothermal amplification assay was applied to amplify Norsolorinic Acid gene. The loop-mediated isothermal amplification have been optimized by combination of the rapidity, simplicity and specificity to detect the target genomic DNA in the reactions. The amplification curves monitored by Loopamp realtime Turbidi meter were analyzed in order to distinguish aflatoxigenic and non-aflatoxigenic strains. Overall, the results showed that the loop-mediated isothermal amplification method was effective in detecting aflatoxigenic strains with high specificity of 71.5 % and sensitivity under lower concentrations of DNA. In additional, it was faster than the conventional polymerase chain reaction. The loop-mediated isothermal amplification assay described in this study might be a promising tool for prediction potential threats by aflatoxigenic fungi and aflatoxins risk in food and commodities.

The most important pathogens of global significance in food security are mycotoxigenic fungi. Aflatoxigenic strains contamination in rice grains can lead to a health risk for consumers. Under appropriate conditions, aflatoxigenic fungi can grow and subsequently produce aflatoxins. Aflatoxin poses a real threat to food safety and security and destroys approximately 25 % of the world's food crops and every year 420,000 people die from consuming contaminated food causing an estimated loss of 33 million healthy life years. This study screened Norsoloric Acid gene involved in the biosynthesis pathway, gene expression profile of aflatoxigenic strains characterized from rice grains, and assessed aflatoxin B₁ levels in white rice grains. We combine the use of molecular techniques and Enzyme-Linked Immunosorbent Assay to detect aflatoxin biosynthesis aflD gene and quantify gene expression profile, and analyzed aflatoxin B₁ levels, respectively. The results shown that all aflatoxigenic strains analyzed in this study are clustered within the same clade based on the aflD gene. The targeted aflD gene for expression was amplified in all aflatoxigenic strains with higher relative level in Aspergillus flavus but no relative expression shown in Aspergillus fumigatus. Enzyme-Linked Immunosorbent Assay showed that 43.1 % of the samples were found positive, with15.9 % being local rice and 27.2 % imported rice. Notably, 11.3 % of analyzed samples were above the recommended aflatoxin B₁ in rice grains established by European Union with aflatoxin concentration ranging between 0 μg/kg to 3.2 μg/kg. These results are indicative of exposure of the population to aflatoxin B₁ and possible health hazard. Our study reveals high levels of aflatoxin B₁ contamination in both imported and local rice grains in Kenya. This study highlights the aflatoxigenic strains which are the potential aflatoxins contamination of different types of foodstuffs.

The magnitude of rice grain losses during storage is huge and warrants critical attention. We investigated the diversity of fungi and insect contamination related to losses of domestic and imported rice from local mills and markets, stored under room conditions for 10 weeks in Cameroon. The highest percentage discolored grain was on imported milled white rice (3.5%), 10 weeks after storage. In general, imported rice samples contained the highest fungal load with a proportion of 65.90% compared to 34.3% for domestic samples. Weight loss due to insect damage was up to 19.9% in white milled domestic rice. Among the 67 isolated fungi strains, the genus Aspergillus had the highest prevalence (63.8%). From all the samples, 877 insects were collected with 719 (81.9%) of Sitophilus. It is urgent to develop sustainable and affordable storage methods to limit insect and fungi infestation on rice in Cameroon.