Soil biochemistry and microbial activity in vineyards under conventional and organic management at Northeast Brazil.

The São Francisco Submedium Valley is located at the Brazilian semiarid region and is an important center for irrigated fruit growing. This region is responsible for 97% of the national exportation of table grapes, including seedless grapes. Based on the fact that orgThe São Francisco Submedium Valley is located at the Brazilian semiarid region and is an important center for irrigated fruit growing. This region is responsible for 97% of the national exportation of table grapes, including seedless grapes. Based on the fact that organic fertilization can improve soil quality, we compared the effects of conventional and organic soil management on microbial activity and mycorrhization of seedless grape crops. We measured glomerospores number, most probable number (MPN) of propagules, richness of arbuscular mycorrhizal fungi (AMF) species, AMF root colonization, EE-BRSP production, carbon microbial biomass (C-MB), microbial respiration, fluorescein diacetate hydrolytic activity (FDA) and metabolic coefficient (qCO2). The organic management led to an increase in all variables with the exception of EE-BRSP and qCO2. Mycorrhizal colonization increased from 4.7% in conventional crops to 15.9% in organic crops. Spore number ranged from 4.1 to 12.4 per 50 g-1 soil in both management systems. The most probable number of AMF propagules increased from 79 cm-3 soil in the conventional system to 110 cm-3 soil in the organic system. Microbial carbon, CO2 emission, and FDA activity were increased by 100 to 200% in the organic crop. Thirteen species of AMF were identified, the majority in the organic cultivation system. Acaulospora excavata, Entrophospora infrequens, Glomus sp.3 and Scutellospora sp. were found only in the organically managed crop. S. gregaria was found only in the conventional crop. Organically managed vineyards increased mycorrhization and general soil microbial activity

Effects of ectomycorrhizas and vesicular-arbuscular mycorrhizas, alone or in competition, on root colonization and growth of Eucalyptus globulus and E. urophylla

Eucalyptus species are considered to have ectomycorrhizas (ECM), but many also have vesicular–arbuscular mycorrhizas (VAM) and their relative importance is unclear. Interactions between ECM and VAM fungi colonizing roots of Eucalyptus species were examined in a glasshouse experiment. This experiment investigated competition between these two types of fungi and compared benefits provided to Eucalyptus globulus and E. urophylla. Eucalyptus seedlings were inoculated with spores of the ECM fungus Laccaria lateritia and/or pot- culture soil for a VAM fungus (species of Glomus, Acaulospora or Scutellospora). Initial inoculum levels were important, as VAM fungi became established much more rapidly than Laccaria. In plants with both types of mycorrhizas, Laccaria mycorrhizas substantially increased after 2 or 3 months and the proportion of roots with VAM declined. However, the proportion of roots with VAM also decreased significantly in plants without ECM after 2 months. Thus, the relative susceptibility of eucalypt roots to these mycorrhizal associations changed. Substantial growth responses to mycorrhizal inoculation occurred when a low concentration of phosphorus fertilization was used (5 mg kg−1), but not at a higher concentration (10 mg kg−1). Treatments where Laccaria was applied, alone or in combination with a VAM fungus, resulted in the largest growth increases relative to nonmycorrhizal plants. An Acaulospora isolate was the most effective VAM fungus for E. urophylla although other VAM fungi also increased growth relative to the control. VAM fungi alone had little effect on E. globulus growth, but plants inoculated with both ECM and VAM fungi were larger than plants only inoculated with Laccaria. ECM fungi had a major impact on root system form by reducing the proportion of fine roots (specific root length) relative to nonmycorrhizal plants or those with VAM. Changes in root colonization patterns over time must be considered in studies of ECM/VAM interactions, as there can be substantial changes in the relative importance of the two associations

A transgenic dTph1 insertional mutagenesis system for forward genetics in mycorrhizal phosphate transport of Petunia

The active endogenous dTph1 system of the Petunia hybrida mutator line W138 has been used in several forward-genetic mutant screens that were based on visible phenotypes such as flower morphology and color. In contrast, defective symbiotic phosphate (Pi) transport in mycorrhizal roots of Petunia is a hidden molecular phenotype as the symbiosis between plant roots and fungi takes place below ground, and, while fungal colonization can be visualized histochemically, Pi transport and the activity of Pi transporter proteins cannot be assessed visually. Here, we report on a molecular approach in which expression of a mycorrhiza-inducible bi-functional reporter transgene and insertional mutagenesis in Petunia are combined. Bi-directionalization of a mycorrhizal Pi transporter promoter controlling the expression of two reporter genes encoding firefly luciferase and GUS allows visualization of mycorrhiza-specific Pi transporter expression. A population of selectable transposon insertion mutants was established by crossing the transgenic reporter line with the mutator W138, from which the Pitransporter downregulated (ptd1) mutant was identified, which exhibits strongly reduced expression of mycorrhiza-inducible Pi transporters in mycorrhizal roots

FungalRoot: Global online database of plant mycorrhizal associations

- Testing of ecological, biogeographical and phylogenetic hypotheses of mycorrhizal traits requires a comprehensive reference dataset about plant mycorrhizal associations. - Here we present a database, FungalRoot, which summarizes publicly available data about vascular plant mycorrhizal type and intensity of root colonization by mycorrhizal fungi, accompanied with rich metadata. We compiled and digitized data about plant mycorrhizal colonization in nine widespread languages. - The present version of the FungalRoot database contains 36 303 species-by-site observations for 14 870 plant species, tripling the previously available compiled information about plant mycorrhizal associations. Based on these data, we provide a recommended list of genus-level plant mycorrhizal associations, based on the majority of data for species and careful analysis of conflicting data. The majority of ectomycorrhizal and ericoid mycorrhizal plants are trees (92%) and shrubs (85%), respectively. The majority of arbuscular and nonmycorrhizal plant species are herbaceous (50% and 70%, respectively).} - Our publicly available database is a powerful resource for mycorrhizal scientists and ecologists. It features possibilities for dynamic updating and addition of data about plant mycorrhizal associations. The new database will promote research on plant and fungal biogeography and evolution, and on links between above- and belowground biodiversity and ecosystem functioning