Genetic and phenotypic diversity of geographically different isolates of Glomus mosseae

In this work we combined morphological taxonomy and molecular methods to investigate intraspecific diversity of Glomus mosseae, whose global distribution has been reviewed by a survey of scientific literature and web-available records from international germplasm collections (INVAM and IBG). We surveyed 186 publications reporting the occurrence of G. mosseae from at least 474 different sites from 55 countries throughout all continents, producing a geographic map of their distribution. The relationships among G. mosseae isolates originating from Europe (UK), USA (Arizona, Florida, Indiana), Africa (Namibia) and West Asia (Syria) were analysed. The level of resolution of ITS sequences strongly supports the morphological species definition of G. mosseae. An ITS-RFLP assay with the enzyme HinfI yielded a unique profile for all G. mosseae isolates, allowing a straightforward identification of this morphospecies. Genetic variability among G. mosseae isolates was revealed by ISSR-PCR: the magnitude of genetic divergence shown by the investigated geographic isolates was higher than 50%, consistently with previous data on vegetative compatibility and functional diversity. The variability of ISSR patterns suggests that intraspecific diversity is much higher than foreseen by morphology and rDNA regions, and should be further investigated by using other genes, such as those related to functional diversity.