Chemotaxonomy of toxigenic Fusarium on the base of DNA homology

植物致病性真菌Fusaria分布在世界各地，已知可产生几种真菌毒素。食用受真菌毒素污染的谷物会导致人类和牲畜出现几种真菌中毒。镰刀菌的分类是基于它们的形态标准。然而，大多数镰刀菌研究人员在鉴定镰刀菌分离株时遇到了困难。这是因为类群内的物种缺乏形态稳定性。本研究采用两种分子生物学方法对9种产毒镰刀菌进行了鉴定和分类。(1) DNA同源性检验：将每个变性基因组DNA与被试菌株的生物素标记DNA探针杂交。9种镰刀菌对3种不同试验菌株的同源性平均在50 ~ 119%之间，同一种间同源性均在90%以上。但不同种间的同源性均在100%以上。需要进一步的研究。(2)应用RFLP图谱：通过Southern blot分析，将一株Fn-2B菌株产生的两个32p标记片段（1.1和1.7kb）与三种不同限制性内切酶酶切的其他镰刀菌dna杂交。1.1kb片段在同一种内表现出相似的模式，而在不同种间表现出相对不同的模式。未获得1.7kb片段的关键数据。综上所述，尽管总DNA与1.1kb片段的杂交模式为区分两个亲缘关系密切的镰刀菌种提供了一种替代方法，但我们不能确定这是否可以明确地识别所有分离株。然而，RFLP模式提供了一个有用的工具来区分重要的有毒镰刀菌种类。

Plant pathogenic fungi, Fusaria, are distributed through the world and known to produce several mycotoxins. The consumption of cereals contaminated with mycotoxins cause several mycotoxicoses in human and livestocks. Classification of Fusarium is based on their morphological criteria. However, most of Fusarium researchers have been encountered difficulties on the identification of Fusarium isolates. This is because of lack of morphological stability of species within the group.In this study, two molecular biological approaches were applied for the identification and classification of 9 toxigenic Fusarium species.(1) DNA homology test : Each denatured genome DNA was hybridized with the biotinlabeled DNA probe of test strain. Homology values of 9 Fusarium species against three different test strains ranged 50 to 119% in average, and more than 90% within the same species. However, over 100% of homology value was shown between different species. Further studies were required.(2) Application RFLP patterns : By Southern blot analysis, two 32p-labeled fragments, 1.1 or 1.7kb, generated from a Fn-2B strain of Fusarium, were hybridized with other Fusaria DNAs digested with three different restriction enzymes. The 1.1kb fragment showed similar patterns within the same species, and relatively different patterns among the different species. No critical data with the 1.7kb fragment was obtained.In conclusion, although the hybridization patterns of total DNA against 1.1kb fragment provides an alternative method to differentiate two closely related species of Fusarium, we could not determine whether this may unequivocally identify all isolates or not. Neverthless, RFLP patterns provide an useful tool to distinguish the important toxgenic Fusarium species.