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Cashew nuts are among the main cash crops in coastal Kenya, due in large part to their high nutritional value. Unfortunately, they also make them highly susceptible to mold contamination, resulting in biodeterioration of the nutritional value and potential contamination with toxic secondary metabolites, such as aflatoxins, that cause them to be rejected for sale at the market. We determined the population diversity of the Aspergillus species and their role in aflatoxin contamination in cashew nuts in selected coastal regions of Kenya. Fifty raw cashew nut samples were collected from post-harvest storage facilities across three counties in Kenya’s coastal region and examined for moisture content and the presence of Aspergillus fungi. About 63 presumptive isolates were recovered from the cashew nuts. ITS and 28S rDNA regions were sequenced. The aflD, aflM and aflR genes were amplified to identify the potentially aflatoxigenic from the Aspergillus isolates. The Aflatoxins’ presence on the isolates was screened using UV and the ammonia vapour test on coconut milk agar and validated using ELISA assay. A comparison of cashew moisture content between the three counties sampled revealed a significant difference. Sixty-three isolates were recovered and identified to section based on morphological characters and their respective ITS regions were used to obtain species identifications. Three sections from the genus were represented, Flavi and Nigri, and Terrei with isolates from the section Nigri having slightly greater abundance (n = 35). The aflD, aflM and aflR genes were amplified for all isolates to assess the presence of the aflatoxin biosynthesis pathway, indicating the potential for aflatoxin production. Less than half of the Aspergillus isolates (39.68%) contained the aflatoxin pathway genes, while 22.22% isolates were aflatoxigenic, which included only the section Flavi isolates. Section Flavi isolates identification was confirmed by calmodulin gene. The presence of species from Aspergillus section Flavi and section Nigri indicate the potential for aflatoxin or ochratoxin in the cashew nuts. The study established a foundation for future investigations of the fungi and mycotoxins contaminating cashew nuts in Kenya, which necessitates developing strategies to prevent infection by mycotoxigenic fungi, especially during the storage and processing phases.

腰果是肯尼亚沿海地区的主要经济作物之一，这在很大程度上源于其极高的营养价值。然而，这一特性也使其极易遭受霉菌污染，不仅导致营养价值发生生物降解，还可能被有毒次生代谢产物（如黄曲霉毒素（aflatoxins））污染，最终使得腰果在市场销售时遭到拒收。本研究针对肯尼亚沿海部分区域的腰果展开调查，旨在明确曲霉菌（Aspergillus）的种群多样性及其在腰果黄曲霉毒素污染过程中的作用。研究人员从肯尼亚沿海三个郡的收获后存储设施中采集了50份未加工腰果样品，对其含水量以及曲霉菌的存在情况进行了检测，共分离得到约63株疑似曲霉菌株。对ITS（内转录间隔区）与28S rDNA区域进行测序，同时通过扩增aflD、aflM和aflR基因，以从曲霉菌分离株中鉴别出潜在产毒菌株。采用紫外照射法及椰奶琼脂平板上的氨蒸气试验对分离株的黄曲霉毒素产生情况进行初筛，并通过ELISA（酶联免疫吸附测定）法完成验证。对三个采样郡的腰果含水量进行对比分析，结果显示存在显著差异。本次研究共获得63株分离株，依据形态特征将其划分至相应类群，并通过各自的ITS序列完成物种鉴定。该曲霉菌属菌株涵盖三个类群：Flavi（黄曲霉群）、Nigri（黑曲霉群）与Terrei（土曲霉群），其中黑曲霉群分离株的丰度略高（n=35）。对所有分离株扩增aflD、aflM和aflR基因，以评估其黄曲霉毒素生物合成通路的存在情况，进而判断其产生黄曲霉毒素的潜在能力。仅有不到半数的曲霉菌分离株（39.68%）携带黄曲霉毒素通路基因，其中22.22%的分离株具备产黄曲霉毒素能力，且均属于黄曲霉群菌株。通过钙调蛋白基因（calmodulin gene）进一步确认了黄曲霉群分离株的物种鉴定结果。曲霉菌黄曲霉群与黑曲霉群物种的存在，表明腰果存在被黄曲霉毒素或赭曲霉毒素（ochratoxin）污染的潜在风险。本研究为肯尼亚境内腰果污染真菌及真菌毒素的后续研究奠定了基础，同时也凸显出制定相关防控策略的必要性，尤其是在存储与加工阶段，以防止产毒真菌的侵染。