Diversity of arbuscular mycorrhizal fungi in no-till and conventionally tilled vineyards

The use of a permanent vegetation cover or frequent tillage in vineyards may affect soil water budget, nutrient availability, soil compaction, soil erosion and soil microbe biodiversity, and through all these and other factors also yield and wine quality parameters. The abundance and diversity of arbuscular mycorrhizal fungi (AMF) might also be influenced, but so far effects on AMF by permanent vege-tation cover (= no-tillage systems) or repeated chiseling and rotary-tillaging have rarely been compared in vineyards. The objective of this on-farm study was to determine AMF species richness and diversity in two adjacent vineyards in Palatinate (SW Germany). In both vineyards, grown on fertile Luvisols, the var. “Pinot Gris” was grown for 39 years, but with different soil cultivation and different fertilization strategies. In one vineyard, soil was maintained periodically without vegetation by passing rotatory cultivator and chiseling between the grapevine rows (‘inter-rows’) several times per year, preferably during spring and summer and in dependency of rainfall and ‘weed’ growth, and fertilization was mainly by organic fertilizers in the last ten years before soil sampling. In the other vineyard, a permanent vegetation has been established since planting, dominated by Lolium perenne, and mineral fertilizers were exclusively applied. Despite of similar high nutrient availability in both soils, in particular of phosphorus, astonishing high AMF species richness and diversity were found in both vineyards. In the no-tillage inter-rows, 34 AMF species were found, with a species composition typically for Central European permanent grasslands (Shannon diversity index 2.45). In the tillage system 24 AMF species were found with a composition as known for extensively used, cultivated Central European croplands (diversity index 2.26). We conclude that above all soil cultivation has affected AMF diversity in these Central European vineyards, while the level and type of fertilization affected the AMF communities only on a minor level

Rhizoglomus venetianum, a new arbuscular mycorrhizal fungal species from a heavy metal-contaminated site, downtown Venice in Italy

Rhizoglomus venetianum, a new arbuscular mycorrhizal fungal species, has been isolated and propagated from a heavy metal-contaminated site in Sacca San Biagio island, downtown Venice, Italy. Interestingly, under the high levels of heavy metals occurring in the site, the new fungus was able to grow only intraradically. In greenhouse trap and single species cultures under low heavy metal levels, the fungus produced innumerous spores, clusters, and sporocarps extraradically, which were formed terminally on subtending hyphae either singly, in small spore clusters, or, preferably, in loose to compact non-organized sporocarps up to 2500 × 2000 × 2000 μm. Spores are golden-yellow to bright yellow brown, globose to subglobose to rarely oblong, 75–145 × 72–140 μm in diameter, and have four spore wall layers. Morphologically, the new fungus is similar to R. intraradices, and phylogenetically, it forms a monophyletic clade next to R. irregulare, which generally forms irregular spores and lacks, like R. intraradices, the flexible innermost wall layer beneath the structural/persistent third wall layer. A key for the species identification is presented comprising all 18 Rhizoglomus species, so far described or newly combined

Ambispora reticulata

A new glomeromycotean fungus,Ambispora reticulata, was found in the Swiss Alps and in the Chilean Andes. Only acauloambisporoid spores were detected so far, 87-131 x 125-150 μm in diameter and having a three-layered, yellow-brown to brown outer wall, a bi-layered, hyaline middle wall and a generally three-layered, hyaline inner wall. The middle wall has a characteristic reticulate outer surface with irregular triagonal to octagonal (usually tetrato hexagonal) pits that are surrounded by ridges. As known for all Ambispora species with acaulo-ambisporoid spore formation, the middle wall is a substantial part of the pedicel which connects the spore with the mycelium. The new species is a frequent member of arbuscular mycorrhizal fungal communities in mountainous and subalpine grasslands of the Swiss Alps at 1000-2100 m above sea level. It occurred less frequent in high alpine grasslands and at altitudes below 1000 m, where the fungus was found in a conservation tillage and a low-input tillage system. It was also detected in evergreen and in deciduous forests in the Andes of Southern Chile at elevations of 550-1600 m

A novel clade of sporocarp-forming species of glomeromycotan fungi in the Diversisporales lineage

In the early times of taxonomy of arbuscular mycorrhizal fungi (Glomeromycota), exclusively sporocarpic species were described. Since then the focus has mainly shifted to species forming spores singly. For many of the sporocarpic species, no molecular data have been made available, and their phylogenetic position has remained unclear. We obtained small subunit ribosomal rDNA and internal transcribed spacer data from specimens of glomeromycotan sporocarps from tropical areas that were assigned to three morphospecies. The complete sequence of the 18S small rDNA subunit sequence, internal transcribed spacers (ITS) 1 and 2 and 5.8S rDNA subunit, was determined from a sporocarp of Glomus fulvum. Partial sequences of the small subunit and the other regions were obtained from Glomus pulvinatum and the newly described species Glomus megalocarpum. Molecular phylogenetic analyses placed all species analyzed as a monophyletic sister group to the Diversispora spurca/Glomus versiforme clade group ("Glomus group C”) within the Diversisporales. The phylogenetic divergence from other known species suggests that this clade may constitute a new genus. These findings will have important consequences for taxon definition in the Diversisporales. They will facilitate identification of these fungi using rDNA sequences within colonized roots or the environmen

Bioackerbau fördert Bodenbiodiversität: Artenvielfalt von nützlichen Mykorrhizapilzen in landwirtschaftlichen Böden

The effects of organic and conventional arable farming on the species richness of beneficial soil fungi (arbuscular mycorrhizal fungi) was assessed in 26 arable fields on sandy soil in the Netherlands and in 2 arable fields on a loamy soil in Switzerland. Organically managed fields contained on average 42% more mycorrhizal fungal species than their conventional counterparts. This study shows that organic arable farming has a positive impact on the species richness of these beneficial soil fung

Arbuscular mycorrhizal fungal communities in sub-Saharan Savannas of Benin, West Africa, as affected by agricultural land use intensity and ecological zone

The rapid decline of soil fertility of cultivated lands in the sub-Saharan savannas of West Africa is considered to be the main cause of the increasingly severe constraints of food production. The soils in this tropical area are highly fragile, and crop yields are limited by characteristically low levels of available phosphorus. Under such preconditions, the multiple benefits of the arbuscular mycorrhizal (AM) symbiosis are likely to play a pivotal role for maintaining natural soil fertility by enhancing plant nutrient use efficiency, plant health, and stabilization of a favorable soil structure. Thus, it is important to explore the impact of the commonly applied farming practices on the native AM fungal community. In the present study, we determined the AM fungal species composition in three ecological zones differing by an increasingly prolonged dry season from South to North, from the Southern Guinea Savanna (SG), to the Northern Guinea Savanna (NG), to the Sudan Savanna (SU). In each zone, four "natural” and four "cultivated” sites were selected. "Natural” sites were three natural forest savannas (at least 25-30years old) and a long-term fallow (6-7years old). "Cultivated” sites comprised a field with yam (Dioscorea spp.) established during the first year after forest clearance, a field under mixed cropping with maize (Zea mays) and peanut (Arachis hypogaea), a field under peanut, and a field under cotton (Gossypium hirsutum) which was the most intensively managed crop. Soil samples were collected towards the end of the wet season in each zone. AM fungal spores were extracted and morphologically identified. Soil subsamples were used to inoculate AM fungal trap cultures using Stylosanthes guianensis and Brachiaria humidicola as host plants to monitor AM root colonization and spore formation over 10 and 24months, respectively. A total of 60 AM fungal species were detected, with only seven species sporulating in the trap cultures. Spore density and species richness were generally higher in the natural savannas and under yam than at the other cultivated sites and lowest under the intensively managed cotton. In the fallows, species richness was intermediate, indicating that the high richness of the natural savannas was not restored. Surprisingly, higher species richness was observed in the SU than in the SG and NG, mainly due to a high proportion of species in the Gigasporaceae, Acaulosporaceae, and Glomeraceae. We conclude that the West African savannas contain a high natural AM fungal species richness, but that this natural richness is significantly affected by the common agricultural land use practices and appears not to be quickly restored by fallo

Langzeitversuch Burgrain: Ertrag und Qualität von biologisch und integriert angebauten Ackerkulturen im Vergleich

The effect of integrated and organic farming on crop yield as well as on environmental and economic performance was investigated in a large scale field experiment near Lucerne (Switzerland), which was running for 18 years. Crop yield in organically managed fields was, depending on crop species, between 3% and 36% lower compared to conventionally managed fields. Only slight variations in crop quality were observed between the farming systems, probably as a result of the high nitrogen mineralization potential of the soils in this experiment. Our results show that organic farming on fertile soils provides good yields and is – under the given Swiss agricultural policy – economically beneficial

Welche landwirtschaftlichen Anbausysteme fördern das Bodenleben?

In einem weltweit einmaligen Langzeit-Feldexperiment in der Nähe von Basel werden seit 1978 biologische und konventionelle Anbauweisen in einer 7-jährigen Fruchtfolge miteinander verglichen. Die Landbausysteme wirken sich unterschiedlich auf das Bodenleben aus. Vor allem die biologischen Verfahren fördern die Menge, die Aktivität und die Diversität von Bodenlebewesen. Mit der Entwicklung neuer Methoden sind weitere Erkenntnisgewinne möglich geworden

Impact of long-term conventional and organic farming on the diversity of arbuscular mycorrhizal fungi

Previous work has shown considerably enhanced soil fertility in agroecosystems managed by organic farming as compared to conventional farming. Arbuscular mycorrhizal fungi (AMF) play a crucial role in nutrient acquisition and soil fertility. The objective of this study was to investigate the diversity of AMF in the context of a long-term study in which replicated field plots, at a single site in Central Europe, had been cultivated for 22years according to two "organic” and two "conventional” farming systems. In the 23rd year, the field plots, carrying an 18-month-old grass-clover stand, were examined in two ways with respect to AMF diversity. Firstly, AMF spores were isolated and morphologically identified from soil samples. The study revealed that the AMF spore abundance and species diversity was significantly higher in the organic than in the conventional systems. Furthermore, the AMF community differed in the conventional and organic systems: Glomus species were similarly abundant in all systems but spores of Acaulospora and Scutellospora species were more abundant in the organic systems. Secondly, the soils were used to establish AMF-trap cultures using a consortium of Plantago lanceolata, Trifolium pratense and Lolium perenne as host plants. The AMF spore community developing in the trap cultures differed: after 12months, two species of the Acaulosporaceae (A. paulinae and A. longula) were consistently found to account for a large part of the spore community in the trap cultures from the organic systems but were found rarely in the ones from the conventional systems. The findings show that some AMF species present in natural ecosystems are maintained under organic farming but severely depressed under conventional farming, indicating a potentially severe loss of ecosystem function under conventional farmin

Arbuscular mycorrhizal assemblages along contrasting andean forests of Southern Chile

Southern Chilean pristine temperate rainforests have been floristically stable during the Holocene, thus representing a pre-industrial baseline of forest ecology. Given this and its edaphic limitations, it is imperative to better understand these forests ecological patterns of mycorrhizal symbiosis. Therefore, here we compare the arbuscular mycorrhizal (AM) communities in three treeline Nothofagus pumilio contrasting plots of Chilean Andes (a volcano crater, pristine forest, and disturbed forest). The AM community assemblages were determined by morphological identification and spore counting, in three A horizon soil samples by plot. In the same nine soil samples, standard chemical analysis was performed. Eighteen AM species were described; Acaulospora was the most abundant genus. The forest plot had the highest AM species richness compared to the disturbed and crater plots. Interestingly, soils Olsen P (plant available phosphorus), pH, and Al+++ saturation similarly affected the AM assemblages. We suggest that some AM species could be specially adapted to extremely high Al saturation and extremely low plant available P conditions, as those experienced on Andean Nothofagus forests. These species may help initiate biological succession on highly disturbed ecosystems. We suggest that mycorrhizal fungi play a key role in seedling colonization of extreme environments such as the Andean treeline.CONICYT/21150047FONDECYT/1141060FONDECYT/315017