Servicios eco-sistémicos provistos por hongos formadores de micorrizas y efecto de las prácticas de manejo en cultivos de base agroecológica

Los hongos formadores de micorrizas están ampliamente distribuidos tanto en ambientes naturales como antrópicos. Son un conjunto de especies que establecen simbiosis con la mayoría de los cultivos de importancia económica y se mantienen vivos en el suelo sólo si hay una cubierta vegetal en activo crecimiento. A cambio de fotoasimilados, las micorrizas proveen innumerables beneficios para la planta y para el funcionamiento del ecosistema. Está demostrado que contribuyen en la nutrición, sanidad y balance hídrico vegetal, y que generan una red de micelio en el suelo a través del cual las raíces se comunican entre sí y comparten información, agua y nutrientes. Esta red es una valiosa forma de conservar el carbono y nutrientes del suelo. Además, las micorrizas están implicadas en la producción de una sustancia aglutinante de las partículas del suelo que favorece la formación de agregados y disminuye el riesgo de erosión. Sin embargo, de modo desapercibido, el hombre puede atentar contra los hongos micorrícicos. En este capítulo se presenta información sobre el impacto de prácticas de manejo sobre parámetros relacionados a los hongos formadores de micorrizas. En algunos casos, con resultados obtenidos de experimentación en sistemas de producción agroecológicos de Argentina y una breve reseña basada en experiencias europeas. En la producción agroecológica, las relaciones entre sus componentes deben priorizar los beneficos que la naturaleza brinda. Entonces, esperamos acercarles información concreta y práctica para ser tenida en cuenta al momento de diseñar estrategias que contemplen la biodiversidad

Mycorrhizal fungi – How to produce your own bio-fertilizer (SolACE Practice abstract)

Outcome Application of mycorrhizal fungi is a simple technique for improving the growth as well as tolerance against biotic and abiotic stresses of a wide range of crop plants. In addition, they can help to improve the soil structure and to prevent nutrient leaching. Practical recommendations - Propagation unit: Depending on the required amount of mycorrhizal inocula, different types of propagation units can be established: container, pot or concrete units. Container units consist of a plastic beaker with holes at the bottom (to allow water passage) (figure 1a), concrete units consists of a tank made e.g. from cement or PVC tubes (figure 1b), and pot units of two pots with a garden fleece in between (to prevent inoculate leakage) (figure 1c). Beaker and pot units should be placed on a hard surface (e.g. stone, wood or a saucer) to prevent roots growing through. Units should be placed in a wind and rain protected place. - Propagation substrate: The propagation substrate consists of 1 part sand mixed with 9 parts co-substrate such as Perlite or Vermiculite. Light co-substrate are recommended in order to facilitate the handling and transport. For fertilization urea (100 mg nitrogen per kg substrate) and/or mature, pathogenfree compost (1% of the substrate) is mixed into the substrate. - Host plants: A mixture of at least two plant species is recommended such as sorghum-barley, sorghumflax, maize-barley or leek-flax. Seeds can be soaked in water for several hours before sowing. - Starter inocula: Is added at a rate of 2% of the propagation substrate. It should be purchased from a reliable company. - Set-up and harvest: Units are filled with pre-mixed substrate and irrigated (figure 2a). Starter inocula is added as a layer 5-8 cm below the substrate surface (figure 2b) and covered with another layer of substrate (figure 2c). Host plant seeds (amount dependent on host plant species) are distributed onto the surface (figure 2d), covered with a layer of substrate (figure 2e) and irrigated. Ninety days after sowing, irrigation is stopped to dry the substrate completely. Shoots are removed and roots are cut inside the propagation unit into small pieces of 1- 1.5 cm using scissors and mixed with the substrate. Then the mycorrhizal inoculate is ready. For quality check, root samples can be taken before drying the substrate to measure mycorrhizal colonization (%RLC) and subsamples of the dried inoculants to assess spore abundance and purity (see practice abstract “Mycorrhizal assessments”). - Application: Mycorrhizal inocula can be used for applications at the nursery stage by adding 100 ml inocula to the root system and during field transplantation by spreading 200 ml inocula into the planting hole below the root system

Arbuscular mycorrhizal (AM) fungal diversity of arid lands : from AM fungal species to AM fungal communities

One of the widespread constituents of soil communities are the symbiotic arbuscular mycorrhizal (AM) fungi which associate in a mutualistic symbiosis with 80% of all land plants. They were shown to positively influence plant nutrition, plant productivity and improve their host plants’ tolerance to biotic and abiotic stresses. It was shown that AM fungal communities vary among broadly defined habitat types and further, that differences in AM fungal communities occur between different continents and climatic zones. This thesis highlights, for the first time, the particularity of the AM fungal communities in one location including four different habitat types of Southern Arabia. Using morphological and molecular methods, three AM fungal species new-to-science were described. These are Diversispora omaniana, Septoglomus nakheelum and Rhizophagus arabicus. In addition, four previously described AM fungal species were detected and isolated from the Arabian Peninsula for the first time. These are Claroideoglomus drummondii, Diversispora aurantia, Diversispora spurca and Funneliformis africanum. The isolated and characterized AM fungal species were then used in two different research approaches. The first approach was to gain basic knowledge on physiological aspects of the isolated species through two experiments. The first experiment was conducted in experimental microcosms with sorghum as host plant to evaluate the interacting effects of water regime and the presence of a potentially invasive AM fungal species, Rhizophagus irrigularis, in an assemblage of our AM fungal species (called native AM fungal assemblage). The community structure of the AM fungi colonizing the roots was assessed by determining the transcript abundance of the large ribosomal subunit (rLSU) of each individual AM fungus, using real-time PCR and species-specific primers. Our results showed that both water regime and the introduction of an invasive AM fungal species strongly altered the structure of the native AM fungal assemblage accompanied by a reduction of the plants’ drought tolerance as reflected by a lower accumulation of plant biomass and reduced amount of extraradical mycelium. Especially in arid environments, where the occurring AM fungal species are adapted to the environmental conditions, such changes can have a great impact on ecosystem functioning. In a second experiment, we wanted to investigate functional characteristics of R. arabicus, one of our newly discovered AM fungal species endemic to the desert ecosystem, in comparison to R. irregularis, a well-studied and established lab AM fungus isolated from an agricultural field in Switzerland. As the plants’ drought tolerance is highly dependent on the associated AM fungal species we tested the two closely related AM fungi of contrasting climates for their ability to promote drought tolerance of sorghum by comparing transpiration rates, growth and nutrition of sorghum plants. Additionally, we estimated their ability to produce extraradical hyphae and their efficiency to extract nutrients from moist and dry soil to reveal their performance under contrasting conditions. Functional traits as extraradical hyphal formation and nutrient uptake efficiency, which were affected by the applied stress conditions, we observed huge differences between the two AM fungi where Rhizophagus arabicus seems to improve the plants’ drought tolerance more than R. irregularis. These differences might have resulted from specific adaptations to environmental conditions prevalent at the place where the AM fungal species originated from. R. arabicus was isolated from a hyper-arid environment and therefore might be better adapted to dry conditions. In a second part of this experiment, the aquaporin (AQPs) genes of Sorghum bicolor, our model plant were investigated. AQPs are pore-forming integral membrane proteins, located in various membranes of plant cells, and were recognized to play an important role in root water transport. First, we identified and characterized all AQP encoding genes in the fully-sequenced genome of sorghum. Additionally, the regulation of AQP transcript expression of mycorrhizal and non-mycorrhizal sorghum under well-watered and drought condition was assessed. Bioinformatic analyses of the S. bicolor genome revealed 35 genes coding for AQPs. Gene expression studies showed that the selected AQP genes were differentially regulated, either by mycorrhization, by water regime or by their interaction. The last part of this thesis describes experiments that have been conducted to evaluate the abilities of some of the propagated AM fungal strains in promoting the seedling growth of two important plant species: Phoenix dactylifera (Nakhal) and Prosopis cineraria (Ghaf). The application of AM fungal inocula in horticulture, agriculture and revegetation programs became more prominent within the last decades as the number of studies demonstrating improved plant growth after inoculation has steadily increased. Especially in arid and semiarid ecosystems, the use of AM fungal inocula is of particular interest due to additional challenges the plants have to face in these climates such as drought, soil salinity and low nutrient availability. Furthermore, it was shown that the mycorrhizal potential in those soils is comparatively low and the additional application of AM fungi may lead to an improved establishment and functionality of the symbiosis. In our experiments some of the isolated AM fungal species or combinations of species were able to enhance the plants’ growth under nursery conditions. The plants have been transplanted to a desert field site in Oman for continuous long term observations. This PhD thesis displays a full circle of isolation of AM fungi from nature, over their identification and propagation, with their subsequent application in basic and applied experiments. Further experiments assessing functional traits and characteristics of those particular AM fungi would be of high interest. Furthermore, the isolated AM fungi can open new doors in the field of conservation and revegetation in that unique and fascinating part of the world

A new genus, Desertispora, and a new species, Diversispora sabulosa, in the family Diversisporaceae (order Diversisporales, subphylum Glomeromycotina)

Phylogenetic analyses of sequences of the SSU-ITS-LSU nrDNA segment and the RPB1 gene showed that the arbuscular mycorrhizal fungus originally described as Diversispora omaniana does not belong to the genus Diversispora, but represents a separate clade at the rank of genus in the family Diversisporaceae of the order Diversisporales. The closest natural relatives of the fungus proved to be species of the genera Corymbiglomus and Redeckera. Consequently, the new genus was named Desertispora, and Di. omaniana was renamed De. omaniana comb. nov. In addition, the morphological and histochemical features of spores and mycorrhizal structures of a new Diversispora sp., Di. sabulosa, were described and the closest relatives of the species were determined based on phylogenetic analyses of sequences of the two loci mentioned above. The new fungus was grown in single-species cultures established from spores extracted from a trap culture inoculated with a mixture of the rhizosphere soil and root fragments of Ammophila arenaria that had colonized maritime sand dunes of the Curonian Spit located in the north of Lithuania. Diversispora sabulosa was never found before in many different sites of the world which were sampled during the last 34 years by the last author of the paper. Also, the lack of molecular sequences in public databases of identity ≥ 97% to sequences of Di. sabulosa suggests that the fungus is rare on the Earth

Grössere Biomassen und aktivere mikrobielle Gemeinschaften in Böden unter biologischer Bewirtschaftung eine globale Meta-Analyse

Population growth, climate change and other impacts challenge our food and farming system and provide arguments for further intensification in agriculture. One option is eco-functional intensification through organic farming, an approach based on exploiting internal natural resources and processes for securing and improving agricultural productivity whilst minimizing negative environmental impacts. In this concept an active soil microbiota plays a crucial role. Thus, we conducted a literature search followed by meta-analysis to quantify possible differences in key indicators for soil microbial abundance and activity in organic and conventional farming systems. We integrated data from 57 studies including 148 pairwise comparisons and found significant differences for almost all investigated effect sizes. Microbial biomass carbon and nitrogen, total phospholipid fatty acids, basal respiration, dehydrogenase, urease and protease activity were increased up to 84% in organic systems. The metabolic quotient remained unaffected with regard to the overall effect. Summarizing, this study shows that long-term organic farming enhances microbial abundance and activities in agricultural soils

Engrais phosphatés de recyclage - Ce que le secteur bio en pense

Le phosphore contenu dans les eaux usées devra être récupéré dès 2026. Qu’en pensent agriculteurs et experts

Quantification of arbuscular mycorrhizal fungi by quantitative polymerase chain reaction (SolACE Practice abstract)

Method to quantify arbuscular mycorrhizal fungal (AMF) in plant roots

Rezyklierte Phosphordünger - was die Branche davon hält

Phosphor in Abwässern muss ab 2026 rückgewonnen werden. Was halten Landwirte und andere Düngeexperten davon

Quantification of arbuscular mycorrhizal fungi root colonization in wheat, tomato, and leek using absolute qPCR

Arbuscular mycorrhizal fungi (AMF) form symbioses with most terrestrial plants and are known to have a positive effect on plant growth and health. Different methodologies have been developed to assess the AMF-plant symbiosis. The most applied method, which involves staining of roots and microscopic observation of the AMF structures, is tedious and time consuming and the results are highly dependent on the observer. Using quantitative polymerase chain reaction (qPCR) to quantify AMF root colonization represents a reliable, high-throughput technique that allows the assessment of numerous samples. Quantification with qPCR can be performed through two methods: relative quantification and absolute quantification. In relative quantification, the target gene is normalized with a reference gene. On the other hand, absolute quantification involves the use of a standard curve, for which template DNA is serially diluted. In a previous paper, we validated the primer pair AMG1F and AM1 for a relative quantification approach to assess AMF root colonization in Petunia. Here, we tested the same primers with an absolute quantification approach and compared the results with the traditional microscopy method. We evaluated the qPCR method with three different crops, namely, wheat (cv. Colmetta and Wiwa), tomato, and leek. We observed a strong correlation between microscopy and qPCR for Colmetta (r = 0.90, p < 0.001), Wiwa (r = 0.94, p < 0.001), and tomato (r = 0.93, p < 0.001), but no correlation for leek (r = 0.27, p = 0.268). This highlights the importance of testing the primer pair for each specific crop

Organic farming enhances soil microbial abundance and activity - A meta-analysis and meta-regression

Population growth and climate change challenge our food and farming systems and provide arguments for an increased intensification of agriculture. A promising option is eco functional intensification through organic farming, an approach based on using and enhancing internal natural resources and processes to secure and improve agricultural productivity, while minimizing negative environmental impacts. In this concept an active soil microbiota plays an important role for various soil based ecosystem services such as nutrient cycling, erosion control and pest and disease regulation. Several studies have reported a positive effect of organic farming on soil health and quality including microbial community traits. However, so far no systematic quantification of whether organic farming systems comprise larger and more active soil microbial communities compared to conventional farming systems was performed on a global scale. Therefore, we conducted a meta-analysis on current literature to quantify possible differences in key indicators for soil microbial abundance and activity in organic and conventional cropping systems. All together we integrated data from 56 mainly peer-reviewed papers into our analysis, including 149 pairwise comparisons originating from different climatic zones and experimental duration ranging from 3 to more than 100 years. Overall, we found that organic systems had 32% to 84% greater microbial biomass carbon, microbial biomass nitrogen, total phospholipid fatty-acids, and dehydrogenase, urease and protease activities than conventional systems. Exclusively the metabolic quotient as an indicator for stresses on microbial communities remained unaffected by the farming systems. Categorical subgroup analysis revealed that crop rotation, the inclusion of legumes in the crop rotation and organic inputs are important farming practices affecting soil microbial community size and activity. Furthermore, we show that differences in microbial size and activity between organic and conventional farming systems vary as a function of land use (arable, orchards, and grassland), plant life cycle (annual and perennial) and climatic zone. In summary, this study shows that overall organic farming enhances total microbial abundance and activity in agricultural soils on a global scale