Diversity and efficacy of arbuscular mycorrhizal (AM) fungi isolated from soils of soybean fields

A field survey evaluated the population composition of AM fungal species in Clarion (a well drained fine-loamy, mixed, mesic Typic Hapludoll) and Webster (a poorly drained fine-loamy, mixed, mesic Typic Endoaquoll) soils of four Iowa soybean (Glycine max, L.) fields. Spores from six species of Glomus and from the genera Acaulospora, Gigaspora , and Paragomus were found in the original field soils. G. claroideum, G. etunicatum, G. mosseae, G. viscosum, and Paraglomus occultum-like spores were prevalent in both Clarion and Webster soils of all four fields. Minor species included G. geosporum and G. intraradices. Trap cultures led to detection of several additional AM fungal species, including G. clarum, G. constrictum, G. fasciculatum, and Entrophospora infrequens;The selectivity of four soybean cultivars, BSR201, Iowa2052, Mandarin, and Peking, for AM fungi was assessed in pots inoculated with composite soil samples from Clarion and Webster soils. A total of 12 morphotypes of AM fungal species were identified. Pots of Iowa2052 soybean cultivar harbored all 12 AM fungal species. Spores of E. infrequens were found uniquely in Iowa2052 pots. Peking had only 8 different types of AM fungi. G. claroideum produced a high proportion of the spore population in pots of BSR201 (up to 75%), but this species was low in Peking (2 to 12%) when the inocula were derived from Webster soils;Soybean cultivars BSR201, Iowa2052, and Peking inoculated with five strains of G. claroideum, two strains of G. etunicatum, and one strain of G. mosseae obtained from Clarion and Webster soils of two Iowa fields produced significantly higher shoot dry weights and seed numbers per pot than those that were nonmycorrhizal. The efficacy of the isolates on the growth of inoculated 10-wk-old plants depended on both the host cultivar and the infecting AM fungal strain. Isolates of G. claroideum and G. etunicatum originally from Clarion soils typically increased shoot dry weight more than did the isolates of either G. etunicatum or G. mosseae from Webster soil. Isolates of G. claroideum and G. etunicatum generated higher dry weight in Peking plants than in the plants of the other two cultivars

Atmospheric nitrogen assimilation in Ustilago maydis.

Nitrogen is an essential nutrient for all living creatures. Ammonium is one of the most efficiently used and thus preferred, sources of nitrogen. As with other dimorphic fungi, yeast-like cells of Ustilago maydis, a fungal pathogen of maize, switches to filamentous growth when starved for nitrogen/ammonium. U. maydis carries two genes, ump1 and ump2, encoding ammonium transporters that facilitate both uptake of ammonium and the filamentous response to its absence. While no obvious phenotype is observed when ump1 is deleted, cells without ump2 are unable to filament in response to low ammonium, although they can still grow. Surprisingly, ump1ump2 double mutants can also grow on low ammonium. More amazing still, both wild-type and mutant cells continue to grow, even after strenuous efforts were made to remove all nitrogen sources from their growth media. To further investigate these unusual observations, we examined the growth character of cells in various low and no-ammonium conditions with variable glucose concentrations, examined isotopic enrichment employing 15N2 gas as a tracer and D-[U-13C]Glucose, conducted PCR screenings and evaluated the possibility of an endosymbiont. The Dump1Dump2 mutant appeared to produce longer cells than the wild-type and achieved higher titers under 50 mM glucose with no ammonium. That mutant also incorporated more 15N than the wild-type in liquid culture under low and no-ammonium conditions. Cells passed through serial treatments of high levels of antibacterial compounds persisted in growth and 15N accumulation. PCR results indicated there was neither prokaryotic 16S rDNA nor the gene for dinitrogenase reductase, typical of prokaryotic diazotrophs. Overall our studies indicate the novel discovery of an unknown nitrogen fixation system in U. maydis. While the molecular mechanism remains unresolved a metabolic capacity to convert dinitrogen into nitrogen that is bioavailable natively in a eukaryotic system holds the potential to change our understanding of the biogeochemical cycling of nitrogen. Moreover, these findings also present a potential way to reduce the anthropogenic contribution of organic nitrogen that is a large contributor to the accretion of eutrophication, “dead zones”, in our coastal waters and large lake system

iGrow Wheat: Best Management Practices for Wheat Production

https://openprairie.sdstate.edu/plant_book/1000/thumbnail.jp

Mycorrhizal symbioses of Salix repens : diversity and functional significance

This thesis investigates the significance of different mycorrhizal fungi, belonging to different functional types (arbuscular mycorrhiza-AM and ectomycorrhiza-EcM), in Salix repens . A comparison between above-ground and below-ground observations on ectomycorrhizal fungi (EcMF) indicated that neither diversity nor abundance above-ground can be used to estimate below-ground diversity or abundance. In all habitats S. repens was highly EcM and slightly AM. Low colonization by arbuscular mycorrhizal fungi (AMF) reflects plant control over mycorrhizal colonization. Arbuscular mycorrhizal colonization was higher in spring than in other seasons, coinciding with higher above-ground P concentration. In sequential inoculations, in the short term AMF interfered with EcMF but the reverse was not observed, whereas in simultaneous inoculations no mutual suppression was observed. Mobilization of plant defence reactions by AMF was transient and led to co-existence between AMF and EcMF. Plant response to AMF, but not of EcMF, depended on internal shoot phosphorus concentration. None of the eleven EcMF investigated exerted the full range of mycorrhizal benefits. Two strategies of EcM were recognized, viz. root manipulation and root replacement. Magnitude of plant response and amount of mycorrhizal colonization were not correlated. Mycorrhizal benefits showed conditionality with regard to pH and nitrogen-to-phosphorus ratio.Genetic variation of S. repens had a large effect on the symbiosis; there was also a large plant origin x soil type interaction. Fungal species origin had only a minor effect on symbiotic effectiveness. After waterlogging intensity of AM colonization was increased and EcMF colonization was decreased. Both changes reflect the differential expression of survival strategies. High mycorrhizal fungal diversity, both in taxonomic and in functional terms is both determining and determined by the wide ecological amplitude of S. repens .</p

Comparative analysis of the Maize Smut Fungi Ustilago maydis and Sporisorium reilianum

The maize plant (Zea mays) is host to two closely related phytopathogenic fungi Ustilago maydis and Sporisorium reilianum. U. maydis infects all aerial parts of the plant, rapidly forming galls or tumours filled with spores. S. reilianum infects young seedlings, remains asymptomatic and grows systemically until it replaces the inflorescence with a mass of sooty spores. The identification of the factors responsible for the difference in infection specificity was the main aim of this work. As S. reilianum is known to be dimorphic it was important to characterise the mating type loci that are fundamental for the morphological changes. S. reilianum, like U. maydis, has a tetrapolar mating system. Molecular characterisation revealed that S. reilianum is an exceptional smut fungus that has three a loci: these were termed a1, a2, and a3. The a loci were found to each contain one receptor gene but two pheromone genes. Functional analysis proved that the native receptor does not recognise the two native pheromones. Instead it can only be stimulated by one pheromone, which is carried by each of the alternate a alleles. S. reilianum, similar to U. maydis, has multiple b mating type loci of which five were isolated and characterised. The b loci of S. reilianum contain two divergently transcribed open reading frames that each contains a homeobox motif. This is as is found in the b loci of U. maydis, which encode proteins that function as a transcription factor. Microscopic comparison of the early stages of infection caused by U. maydis and S. reilianum in maize demonstrated that the two fungi differ remarkably during the colonisation of the host tissue. U. maydis’ proliferative capacity is initiated as early as three dasy post infection (dpi) while S. reilianum shows only sustained hyphal growth at the same time point. Thus, the gene expression profiles produced by U. maydis and by S. reilianum infected maize using amplified fragment length polymorphism on cDNA (cDNA-AFLP) were compared. Interestingly, a nitrilase gene was identified as being differentially expressed in U. maydis tissue three dpi. As a nitrilase may be involved in the final stages of auxin biosynthesis, the auxin generating capability of the U. maydis triple deletion strains missing the nitrilase and the two indole acetaldehyde dehydrogenase genes iad1 and iad2 was investigated. Although auxin production was reduced in the mutants, plant infection assays revealed that tumour formation was unaffected. Consequently, the ability of U. maydis to produce auxin may not be directly related with its ability to produce tumours

Handbook for the analysis of micro-particles in archaeological samples

Horizon 2020(H2020)677576Bioarchaeolog