Palaeospora spainii, a new arbuscular mycorrhizal fungus from Swiss agricultural soils
Oehl, Fritz; Sánchez-Castro, Iván; Palenzuela, Javier; da Silva, Gladstone Alves
A new fungus in the Archaeosporomycetes, Palaeospora spainii, was isolated from six agricultural systems of the Canton Bern in Switzerland. These sites were either permanent or temporary grasslands, or subjected to low-input organic, or medium to high-input conventional notillage and tillage farming systems. The sites had been exposed to very different levels of phosphorus fertilization in the past as suggested by quite diverging levels of soil P availability at sampling time. The fungus has been maintained in monosporal pot cultures on Hieracium pilosella for two cycles. It is bimorphic, sensu lato forming acaulosporoid and glomoid spores. It can easily be identified by spore morphology from all other Archaeosporomycetes species by its small, triple-walled acaulosporoid spores (52–80 × 51–77 μm in diameter) formed laterally on the neck of sporiferous saccules without pedicel formation and surface ornamentation. The mono-walled, hyaline, glomoid spores (22–33 × 22–37 μm) resemble glomoid spores of other Archaeosporaceae, and of many Glomeraceae species with similar spore sizes and colors, and thus they do not serve for species identification. Phylogenetically, P. spainii forms a separate clade close to Archaeospora trappei and Intraspora schenckii. The different P availability and soil cultivation strategies at the isolation sites suggest that the fungus is not much affected by these parameters in grasslands or arable lands as long as almost permanent plant cover is guaranteed in crop rotations throughout the year. Remarkably, within the Archaeosporomycetes, P. spainii and A. trappei, are both frequently found in Swiss low-input to high-input farming systems, while Ambispora species are usually absent under high fertilization input or intensified soil cultivation.