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首页> 外文期刊>British Biotechnology Journal >Prevalence of Aflatoxin Biosynthesis Genes According to Aflatoxin Levels in Maize of Different Varieties in Kenya
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Prevalence of Aflatoxin Biosynthesis Genes According to Aflatoxin Levels in Maize of Different Varieties in Kenya

机译：肯尼亚不同品种玉米中黄曲霉毒素生物合成基因的流行状况

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Aims: To determine aflatoxin biosynthetic genes in fungal isolates in relation to aflatoxin levels in maize grain varieties from epidemiologically aflatoxicosis hot spots and non-aflatoxin hot spots agro-ecological zones in Kenya. Study Design: Purposeful sampling technique was applied targeting regions of variable aflatoxicoses susceptibilities. Place and Duration of Study: Samples were sourced from Kitui/Kibwezi counties, an aflatoxin hot spot, during 2008-2010 Maize growing seasons. Comparative samples were from Uasin-Gishu county and Perkerra irrigation scheme in Baringo County, both with no previous acute aflatoxicosis and practicing commercial cultivation under rain-fed and irrigation farming systems, respectively. Methodology: Maize samples (n=295) and fungal isolates (n=61) were analyzed for aflatoxin contamination and presence of aflatoxin biosynthetic genes, respectively. Total aflatoxin quantification was by a commercial Enzyme Linked Immunosorbent Assay (ELISA) kits, Boratest?, while molecular characterization of Aspergillus flavus (n=40) and A. parasiticus (n=21) isolates applied Quadruplex Multiplex PCR technique encompassing four aflatoxin biosynthetic genes: nor-1, ver-1, omt-A and aflR. Findings from the study variables were analyzed according to maize variety, agro-ecological origin of maize samples and fungal species besides type of farming system. Results: Uasin-Gishu maize samples (n=158) assayed for aflatoxins belonged to six maize commercial varieties; H614, H629, H6213, H6210, H613 and H628 alongside an indigenous variety, Kipkaa. All Perkerra samples (n=61) also belonged to a commercial variety, H513. Contrastingly, all Kitui/Kibwezi samples (n=76) belonged to an indigenous variety, Kikamba (Kinyanya) . The varieties H613, H628 and Kipkaa all had the samples (100%) within the Kenyan statutory safe total aflatoxin limit (≤10.0 ppb) whereas Kikamba and H513 varieties had 82.9% and 83.6% samples within safety limits, respectively. Similarly, the mean aflatoxin content for all the seven Uasin-Gishu varieties was only 1.62 ppb while Kikamba and H513 had means of 14.6 ppb and 15.6 ppb, respectively (P=0.05) . Positive PCR amplification results were obtained in 96.3%, 84.2% and 80% for Kitui/Kibwezi, Perkerra and Uasin-Gishu isolates, respectively whereas regional distribution of amplicon spectrum was 6, 3 and 2 out of 8, respectively. A similar regional pattern was established regarding prevalence of PCR positive isolates and whose maize samples of origin also tested ELISA-aflatoxin positive, having been 81.5%, 52.6% and 26.7% for Kitui/Kibwezi, Perkerra and Uasin-Gishu. Interestingly, the only isolate PCR positive for all the four genes under assay and whose maize sample of origin had aflatoxins was coincidentally from Kitui/Kibwezi, an epidemiologically aflatoxicosis hot spot agro-ecological zone.
机译：目的：确定与肯尼亚流行病学上的黄曲霉病热点和非黄曲霉毒素热点农业生态区的玉米谷物品种相比，真菌分离物中黄曲霉毒素的生物合成基因。研究设计：有针对性的采样技术被应用于针对不同的黄曲霉毒素敏感性的区域。研究的地点和持续时间：样品取自2008-2010年玉米生长期的黄曲霉毒素热点Kitui / Kibwezi县。比较样本来自Uasin-Gishu县和Baringo县的Perkerra灌溉计划，既没有以前的急性黄曲霉病，又分别在雨养和灌溉耕作制度下进行商业化种植。方法：分别分析了玉米样品（n = 295）和真菌分离物（n = 61）的黄曲霉毒素污染和黄曲霉毒素生物合成基因的存在。通过商业酶联免疫吸附测定试剂盒（Boratest ？）进行总黄曲霉毒素定量分析，同时使用Quadruplex Multiplex对黄曲霉（n = 40）和寄生曲霉（n = 21）分离物进行分子鉴定。 PCR技术涵盖了四个黄曲霉毒素生物合成基因：nor-1，ver-1，omt-A和aflR。除耕作系统类型外，还根据玉米品种，玉米样品的农业生态起源和真菌种类分析了研究变量的发现。结果：Uasin-Gishu玉米样品（n = 158）的黄曲霉毒素含量测定属于六个玉米商业品种。 H614，H629，H6213，H6210，H613和H628，以及本地品种Kipkaa。所有Perkerra样品（n = 61）也属于商业品种H513。相反，所有Kitui / Kibwezi样本（n = 76）均属于土著品种Kikamba（Kinyanya）。 H613，H628和Kipkaa品种的样品（100％）均在肯尼亚法定安全黄曲霉毒素总限量（≤10.0 ppb）内，而Kikamba和H513品种的样品分别在安全范围内，分别为82.9％和83.6％。同样，所有七个Uasin-Gishu品种的平均黄曲霉毒素含量仅为1.62 ppb，而Kikamba和H513的平均值分别为14.6 ppb和15.6 ppb（P = 0.05）。 Kitui / Kibwezi，Perkerra和Uasin-Gishu分离株分别以96.3％，84.2％和80％获得阳性PCR扩增结果，而扩增子谱的区域分布分别为8、6、3和2。在PCR阳性分离物的流行方面建立了类似的区域模式，其来源的玉米样品也检测了ELISA-黄曲霉毒素阳性，Kitui / Kibwezi，Perkerra和Uasin-Gishu分别为81.5％，52.6％和26.7％。有趣的是，对所有四个被测基因均呈阳性且其玉米样品中含有黄曲霉毒素的唯一分离PCR，恰好来自Kitui / Kibwezi，这是一种流行病学上的黄曲霉病热点农业生态区。

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