DEVELOPMENT OF SPORES AND CHARACTERS OF MYCORRHIZAE

OF THE GENUS DIVERSISPORA

In PVLG
In PVLG+Melzer's reagent

Spores of Diversispora spurca, the only member of the genus Diversispora, develop blastically at the tip of cylindrical to slightly flared sporogenous hyphae continuous with extraradical hyphae of arbuscular mycorrhizae. Although the ontogenesis of spores of this species was not recognized, their components probably origin and differentiate identical to those of spores of the genus Glomus, in which this fungus has originally been accommodated as Gl. spurcum (Pfeiffer et al. 1996). Thus, spores of D. spurca morphologically are as those of Glomus spp. The only structures suggested to separate D. spurca and Glomus spp. are their mycorrhizae. The mycorrhizae of most Glomus spp. consist of arbuscules, vesicles, and hyphae staining intensively in trypan blue, whereas those of D. spurca lack vesicles and stain variably, from almost no staining to intensive staining (Morton 2002). So, these differences are weak.

However, D. spurca and Glomus spp. markedly differ in their molecular properties. The family Diversisporaceae in the order Diversisporales with the genus Diversispora, and the type species D. spurca (Walker and Schüßler 2004) is monophyletic with the families Acaulosporaceae, Gigasporaceae, and Pacisporaceae (Schüßler et al. 2001; Walker and Schüßler 2004) and has specific SSU rRNA gene sequence signatures, for example GGCTCATTYGRRTYTS, ACYCATTRYCAGGCTTAAT, and TTGGCATTTAGYCA, corresponding to homologous positions 487, 648, and 1389, respectively, of the Saccharomyces cerevisieae SSU rRNA sequence J01353.

Apart from molecular properties, D. spurca differs from members the other families of the order Diversisporales in germination of spores not accompanied by formation of a germination shield (Gigasporaceae, Pacisporaceae) or a germination orb (Acaulosporaceae; Walker and Schüßler 2004).

REFERENCES

Morton J. B. 2002. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. West Virginia University.

Pfeiffer C. M., Walker C., Bloss H. E. 1996. Glomus spurcum: a new endomycorrhizal fungus from Arizona. Mycotaxon 59, 373-382.

Schüßler A., Schwarzott D., Walker C. 2001. A new fungal phylum, the Glomeromycota: phylogeny and evolution. Myc. Res. 105, 1413-1421.

Walker C., Schüßler A. 2004. Nomenclatural clarifications and new taxa in the Glomeromycota. Mycol. Res. 108, 979-982.