Scutellospora alterata, a new gigasporalean species from the semi-arid Caatinga biome in Northeastern Brazil

Abstract

A new species of Gigasporales (Glomeromycota) was isolated from soils of the semi-arid Caatinga biome in NE Brazil. It produced spores in the rhizospheres of Sorghum sudanense, Zea mays, Panicum maximum, and Helianthus annuus in pot cultures. Spores are triple-walled, roughened, yellow-white to light yellow, and 150–255 μm in diameter. The single germination shield is hyaline, oval to ovoid, and bi-lobed and has the two germ tube initiations (gtis) typical for Scutellospora species. The shields can change shape under light pressure on the cover slide, causing several 'false' lobes to appear that do not bear gtis but inflate from the shield periphery. Molecular analyses of the partial LSU rDNA gene place the fungus in a clade next to Scutellospora calospora, S. dipurpurescens, and S. spinosissima. Further investigations on germ shield morphology showed that several false lobes also form in other Scutellospora species in lactic acid based mountants under pressure on the cover slide. In Racocetraceae more than two 'true' lobes form during spore formation, each potentially bearing one gti.