Chemotaxonomy of toxigenic Fusarium on the base of DNA homology

镰刀菌属是一种广泛分布于世界各地的植物病原真菌，能产生多种真菌毒素。食用被霉菌毒素污染的谷物会导致人类和牲畜的几种霉菌中毒。镰刀菌的分类是基于它们的形态标准。然而，大多数镰刀菌研究者在镰刀菌分离物的鉴定上遇到了困难。本研究应用两种分子生物学方法对9种镰刀菌进行了鉴定和分类。(1)DNA同源性试验：将变性的基因组DNA与试验菌株的生物素标记DNA探针杂交。9种镰刀菌与3个供试菌株的同源性平均在50 ~ 119%之间，同一种镰刀菌的同源性在90%以上。不同物种间的同源性均超过100%。需要进一步研究。(2)应用RFLP模式：用Southern杂交分析，从镰刀菌Fn-2B菌株中扩增出1.1kb和1.7kb的~（32）P标记片段，与其它镰刀菌DNA经三种限制性内切酶酶切后进行杂交。1.1kb的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。1.7kb片段的杂交结果没有得到关键性的数据，尽管总DNA与1.1kb片段的杂交模式提供了一种区分两个密切相关的镰刀菌属物种的替代方法，但我们不能确定这是否可以明确地识别所有分离物。尽管如此，RFLP模式提供了一个有用的工具来区分重要的毒素镰刀菌物种。

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.