A number of 21Aspergillus sp. strains isolated from cowpeas from Benin (Africa) were characterized by RAPD methodology. Seven of these strains grouped withA. flavus in the dendrogram generated with the RAPD data. Only three were able to produce aflatoxin in significant amounts. Twelve other isolates grouped withA. parasiticus. All of these strains except 3 produced aflatoxin. Two additional strains neither fit with theA. flavus group, nor theA. parasiticus group according to their RAPD pattern. Both did not produce aflatoxin in measurable amounts.Generally the aflatoxin positive strains produced high amounts of aflatoxin after growth on YES medium. However after growth on cowpea based medium aflatoxin biosynthesis was strongly ceased, albeit the growth of the colony was only partly reduced. This was true for media made either with the whole cowpea seed or with cowpea seed without seed coat. Interestingly when the cowpea medium was heat sterilized the fungus was able to produce high amounts of aflatoxin. This, however, was not the case after the use of gamma irradiation as sterilization method for the medium. The expression of thenor- 1 gene, which is one of the early genes involved in aflatoxin biosynthesis, was significantly repressed after growth on gamma irradiated cowpea medium in contrast to YES medium.

中文翻译：

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豇豆作为生长底物不支持曲霉菌产生黄曲霉毒素。

许多 21Aspergillus sp. 从贝宁（非洲）豇豆中分离的菌株通过 RAPD 方法进行表征。这些菌株中的七个与 A 分组。使用 RAPD 数据生成的树状图中的 flavus。只有三个能够产生大量黄曲霉毒素。与 A 分组的其他 12 个分离株。寄生虫。除 3 种外，所有这些菌株均产生黄曲霉毒素。两个额外的菌株都不符合 A。flavus 组，也不是 theA。寄生虫组根据他们的 RAPD 模式。两者均未产生可测量量的黄曲霉毒素。通常，黄曲霉毒素阳性菌株在YES培养基上生长后产生大量黄曲霉毒素。然而，在基于豇豆的培养基黄曲霉毒素生物合成的生长强烈停止后，尽管菌落的生长仅部分减少。这对于用整个豇豆种子或用没有种皮的豇豆种子制成的培养基都是正确的。有趣的是，当豇豆培养基被加热灭菌时，真菌能够产生大量的黄曲霉毒素。然而，在使用伽马辐射作为培养基的灭菌方法后，情况并非如此。与 YES 培养基相比，thenor-1 基因是参与黄曲霉毒素生物合成的早期基因之一，在经过伽马辐照的豇豆培养基上生长后，其表达受到显着抑制。