Phylogenetic position of an arbuscular mycorrhizal fungus, Acaulospora gerdemannii, and its synanamorph Glomus leptotichum, based upon 18S rRNA gene sequence

We examined the phylogenetic position of an arbuscular mycorrhizal fungus which produces two types of spore, Acaulospora gerdemannii and Glomus leptotichum , based upon the DNA sequence of the 18S rRNA gene. DNA was extracted separately from both Glomus -like or Acaulospora -like spores and partial 5’-terminus segments of 18S rRNA gene were amplified by the PCR method. Several clones derived from each spore type were sequenced and compared. The sequences from both spore types agreed well, confirming that these morphologically different spores were formed by the same fungus. Nucleotide substitutions were found among several clones, suggesting polymorphism of the rRNA gene in glomalean fungi. Further phylogenetic analysis based upon the whole sequence of the 18S rRNA gene showed that A. gerdemannii may be within the order Glomales but is far from the fungi that have been analyzed and probably should be in a new family.