Distribution and diversity of Paraglomus spp. in tilled agricultural soils.

Understanding of the ecology of arbuscular mycorrhizal fungi comes primarily from the order Glomerales, and relatively little is known of the ecology of other orders including the Paraglomerales. We investigated the distribution of the Paraglomerales across the English agricultural landscape under different management systems. Soils were collected from 11 tilled agricultural sites. Presence of Paraglomerales was assessed using PCR amplification of 18S/ITS region ribosomal DNA isolated from trap plants, terminal restriction fragment length polymorphism and cloning. Paraglomus spp. were detected in all samples from one location and sporadically in six more, but not at the other locations. Distribution was not related to soil physiochemical characteristics, but the Paraglomaceae were significantly more common in soils under organic management. Cloning of samples from three sites produced sequences closely related to Paraglomus laccatum but only distantly related to Paraglomus brasilianum and Paraglomus occultum. Individual sites had between 10 and 27 separate terminal restriction fragments (T-RFs). The large number of T-RFs reflected a significant sequence diversity in the ITS region. Paraglomerales were, therefore, widely distributed across the agricultural landscape, though with patchy distribution and low diversity. More intensive agricultural management appeared to impact negatively on Paraglomus spp.