DEVELOPMENT OF SPORES AND CHARACTERS OF MYCORRHIZAE

OF THE GENUS PARAGLOMUS

In water
In PVLG+Melzer's reagent
In PVLG

Spores of species of the genus Paraglomus J.B. Morton & D. Redecker origin blastically at the tip of mycorrhizal extraradical hyphae, i. e., identically to those of Glomus spp. (Morton 2002; Morton and Redecker 2001; Renker et al., in press). The spores of the known species of this genus occur singly in the soil. They are globose to irregular and colourless to pale coloured. The subcellular structure of spores of members of the Paraglomus consists of a spore wall comprising two to three layers continuous with those of their subtending hyphae. The outermost spore wall layer deteriorates and partly or completely sloughs with age.

Spores of Paraglomus spp. germinate by germ tubes emerging from both the lumen of the subtending hypha and the spore wall (Morton and Redecker 2001).

At present, the genus Paraglomus in the family Paraglomeraceae J.B. Morton & D. Redecker and the order Paraglomerales C. Walker& Schuessler includes three species, Par. brasilianum (Spain & J. Miranda) J.B. Morton & D. Redecker, Par. laccatum (Blaszk.) C. Renker, Blaszk. & F. Buscot, and Par. occultum (C. Walker) J.B. Morton & D. Redecker (Morton and Redecker 2001), forming spores indistinguishable from those of Glomus spp. All these species have originally been described within the genus Glomus Tul. & C. Tul. (Blaszkowski 1988; Spain and de Miranda 1996; Walker 1982).
In PVLG

The only morphological distinction between Paraglomus spp. and Glomus spp. is in properties of mycorrhizae. Although the arbuscules of Paraglomus spp. are similar to those of Glomus spp., i. e., have cylindrical or slightly flared trunks with branches progressively tapering in width toward tips (Morton 2002; Morton and Redecker 2001; Renker et al., in press), the mycorrhizae of Paraglomus spp. do not contain vesicles and their intraradical hyphae are frequently coiled within and between cortical cells. In contrast, Glomus spp. frequently produce vesicles, and coils in mycorrhizae of these fungi rarely occur, except near entry points. The main visible evidence of mycorrhizae of Paraglomus spp. is their light staining or the lack of any staining reaction in trypan blue or other stains despite the presence of extraradical hyphae.

The most precise method of the disclosure of the species listed above and other candidates of the Paraglomus is the molecular analysis of their spores or mycorrhizal structures (Morton and Redecker 2001; Renker et al., in press; Schüßler et al. 2001).

 

 

REFERENCES

Blaszkowski J. 1988. Three new vesicular-arbuscular mycorrhizal fungi (Endogonaceae) from Poland. Bull. Pol. Acad. Sci. Biol. Sci. 36, 271-275.

Morton J. B. 2002. International Culture Collection of Arbuscular and Vesicular-Arbuscular Mycorrhizal Fungi. Address: West Virginia University. http://invam.caf.wvu.edu.

Morton J. B., Redecker D. 2001. Two new families of Glomales, Archaeosporaceae and Paraglomaceae, with two new genera Archaeospora and Paraglomus, based on concordant molecular and morphological characters. Mycologia 93, 181-195.

Renker C, Blaszkowski J, Buscot F 2007. Paraglomus laccatum comb. nov. - a new member of Paraglomeraceae (Glomeromycota). Nova Hedwigia 84 (3-4), 395-407.

Spain J. L., de Miranda J. C. 1996. Glomus brasilianum: an ornamented species in the Glomaceae. Mycotaxon 60, 137-142.

Walker C. 1982. Species in the Endogonaceae: a new species (Glomus occultum) and a new combination (Glomus geosporum). Mycotaxon 15, 49-61.