Diversity and species composition of arbuscular mycorrhizal fungi across maize fields in the southern part of Belgium

The Effects of Local Weed Species on Arbuscular Mycorrhizal Fungal Communities in an Organic Winter Wheat (Triticum durum L.) Field in Lebanon

We examined the potential effects of weed species on the arbuscular mycorrhizal fungi (AMF) in an organic winter wheat (Triticum durum) field in Lebanon. In this agroecosystem, the field and its surroundings were covered with spontaneous vegetation corresponding to local weeds. The coexistence between wheat and weeds did not modify AM fungal community diversity and colonization in T. durum but changed their composition. We evidenced 22 operational taxonomic units (OTUs) specifically shared between wheat associated with weeds (Tdw) and weeds, regardless of their localization and 12 OTUs with an abundance of variation between wheat without neighboring weeds (Td) and Tdw. The number of AM propagules and total C and N contents were higher in soil covered with wheat associated with weeds (TdWsoil) vs. wheat without neighboring weeds (Tdsoil). In greenhouse experiments, the shoot biomass and root mycorrhizal intensity of Medicago sativa, used as a trap plant, were higher using TdWsoil vs. Tdsoil as the inoculum. Positive correlations were observed between soil AM propagule numbers and M. sativa shoot biomass, on the one hand and M. sativa mycorrhizal intensity, on the other hand. Weeds seemed to exert significant effects on root AM fungal composition in T. durum and these effects may contribute to enhanced AMF development in the field.

Diversity of Arbuscular Mycorrhizal Fungi in Distinct Ecosystems of the North Caucasus, a Temperate Biodiversity Hotspot

BACKGROUND

Investigations that are focused on arbuscular mycorrhizal fungus (AMF) biodiversity is still limited. The analysis of the AMF taxa in the North Caucasus, a temperate biodiversity hotspot, used to be limited to the genus level. This study aimed to define the AMF biodiversity at the species level in the North Caucasus biotopes.

METHODS

The molecular genetic identification of fungi was carried out with ITS1 and ITS2 regions as barcodes via sequencing using Illumina MiSeq, the analysis of phylogenetic trees for individual genera, and searches for operational taxonomic units (OTUs) with identification at the species level. Sequences from MaarjAM and NCBI GenBank were used as references.

RESULTS

We analyzed >10 million reads in soil samples for three biotopes to estimate fungal biodiversity. Briefly, 50 AMF species belonging to 20 genera were registered. The total number of the AM fungus OTUs for the "Subalpine Meadow" biotope was 171/131, that for "Forest" was 117/60, and that for "River Valley" was 296/221 based on ITS1/ITS2 data. The total number of the AM fungus species (except for virtual taxa) for the "Subalpine Meadow" biotope was 24/19, that for "Forest" was 22/13, and that for "River Valley" was 28/24 based on ITS1/ITS2 data. Greater AMF diversity, as well as number of OTUs and species, in comparison with that of forest biotopes, characterized valley biotopes (disturbed ecosystems; grasslands). The correlation coefficient between "Percentage of annual plants" and "Glomeromycota total reads" r = 0.76 and 0.81 for ITS1 and ITS2, respectively, and the correlation coefficient between "Percentage of annual plants" and "OTUs number (for total species)" was r = 0.67 and 0.77 for ITS1 and ITS2, respectively.

CONCLUSION

High AMF biodiversity for the river valley can be associated with a higher percentage of annual plants in these biotopes and the active development of restorative successional processes.

Anchoring the species Rhizophagus intraradices (formerly Glomus intraradices)

The nomenclatural type material of Rhizophagus intraradices (basionym Glomus intraradices) was originally described from a trap pot culture established with root fragments, subcultures of which later became registered in the INVAM culture collection as FL 208. Subcultures of FL 208 (designated as strain ATT 4) and a new strain, independently isolated from the type location (ATT 1102), were established as both pot cultures with soil-like substrate and in vitro root organ culture. Long-term sampling of these cultures shows spores of the species to have considerable morphological plasticity, not described in the original description. Size, shape and other features of the spores were much more variable than indicated in the protologue. Phylogenetic analyses confirmed earlier published evidence that sequences from all R. intraradices cultures formed a monophyletic clade, well separated from, and not representing a sister clade to, R. irregularis. Moreover, new phylogenetic analyses show that Rhizoglomus venetianum and R. irregularis are synonymous. The morphological characters used to separate these species exemplify the difficulties in species recognition due to the high phenotypic plasticity in the genus Rhizophagus. Rhizophagus intraradices is morphologically re-described, an epitype is designated from a single-spore isolate derived from ATT 4, and R. venetianum is synonymised with R. irregularis.