Development of Intraspora

DEVELOPMENT OF SPORES AND CHARACTERS OF MYCORRHIZAE

OF THE GENUS INTRASPORA


In PVLG			In PVLG+Melzer's

Spores of Intraspora schenckii (Sieverd. & S. Toro) Oehl & Sieverd., the so far only member of the genus Intraspora, occur singly in the soil or in roots. The spores develop inside the neck of a sporiferous saccule at a some distance from the saccule. The sporiferous saccule originates terminally from or intercalary in mycorrhizal extra- and intraradical hyphae. The spores are globose to subglobose and frequently pyriform. Their subcellular structure consists of two walls, a spore wall and an inner germination wall. The spore wall is composed of two layers, of which the outer layer sloughs with age and is continuous with the wall of the neck of the sporiferous saccule. The inner layer of this wall is persistent, semi-flexible, and closes two opposite pores of spores formed at the beginning of their development. The inner germination wall is semi-flexible and finely laminate. According to Sieverding and Oehl (2006), three layers form this wall, of which the outer layer and the innermost one are very thin, rarely separate from the much thicker middle layer and, hence, are exceptionally difficult to observe.

The mycorrhizae of I. schenckii comprise arbuscules, vesicles, as well as intra- and extraradical hyphae. According to Sieverding and Oehl (2006), vesicles form rarely and all the mycorrhizal structures stain faintly in trypan blue. The faint staining of mycorrhizae and the subcellular structure of I. schenckii spores are identical to those of Archaeospora trappei (R.N. Ames & Linderman) J.B. Morton & D. Redecker emend. Spain, a sister species according to Sieverding and Oehl (2006). Hence, the same authors considered Intraspora a sister genus to Archaeospora J.B. Morton & D. Redecker and, thereby, keyed Intraspora into the family Archaeosporaceae J.B. Morton & D. Redecker. Results of molecular analyses of different isolates of I. schenckii are needed to confirm Sieverding and Oehl's (2006) conclusions, because an isolate of I. schenckii found by Blaszkowski (2003; 2005) formed mycorrhizae intensively staining in trypan blue.

Intraspora schenckii has originally been described as Entrophospora schenckii Sieverd. & S. Toro (Sieverding and Toro 1987). The main arguments used to exclude this fungus from the genus Entrophospora were (1) the simple structure of its spore wall relative to E. infrequens (I.R. Hall) R.N. Ames & R.W. Schneid. emend. Oehl & Sieverd., the type species, and E. baltica Blaszk., Madej & Tadych, the only other species remained in the revised genus Entrophospora (Sieverding and Oehl 2006), (2) the formation of spores at a some distance from the sporiferous saccule, and not directly at it as in Entrophospora spp., and (3) the faint staining of mycorrhizal structures of I. schenckii in contrast to the intensively staining mycorrhizae of E. infrequens, the only species of Entrophospora propagated in one-species cultures (Blaszkowski et al. 1998; Sieverding and Oehl 2006).

REFERENCES

Blaszkowski J. 2003. Arbuscular mycorrhizal fungi (Glomeromycota), Endogone, and Complexipes species deposited in the Department of Plant Pathology, University of Agriculture in Szczecin, Poland. http://www.agro.ar.szczecin.pl/~jblaszkowski/.

Blaszkowski J., Madej T., Tadych M. 1998. Entrophospora baltica sp. nov. and Glomus fuegianum, two species in the Glomales from Poland. Mycotaxon 68, 165-184.

Blaszkowski J., Czerniawska B. 2005. Entrophospora schenckii and Pacispora franciscana, arbuscular mycorrhizal fungi (Glomeromycota) new for Europe and Poland, respectively. Acta Mycol. 40(1), 11-18.

Sieverding E., Oehl F. 2006. Revision of Entrophospora and description of Kuklospora and Intraspora, two new genera in the arbuscular mycorrhizal Glomeromycetes. J. Appl. Bot. Food Qual. 80, 69-81.

Sieverding E., Toro S. T. 1987. Entrophospora schenckii: a new species in the Endogonaceae from Colombia. Mycotaxon 28, 209-214.