Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

The tree species Alnus acuminata and Morella pubescens, native to South America, are candidates for soil quality improvement and afforestation of degraded areas and may serve as nurse trees for later inter-planting of other trees, including native crop trees. Both species not only form symbioses with arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF), but also with N2-fixing actinobacteria. Because tree seedlings inoculated with appropriate mycorrhizal fungi in the nursery resist transplanting stress better than non-mycorrhizal seedlings, we evaluated for A. acuminata and M. pubescens the potential of inoculation with mycorrhizal fungi for obtaining robust tree seedlings. For the first time, a laboratory-produced mixed AMF inoculum was tested in comparison with native soil from stands of both tree species, which contains AMF and EMF. Seedlings of both tree species reacted positively to both types of inocula and showed an increase in height, root collar diameter and above- and belowground biomass production, although mycorrhizal root colonization was rather low in M. pubescens. After 6 months, biomass was significantly higher for all mycorrhizal treatments when compared to control treatments, whereas aboveground biomass was approximately doubled for most treatments. To test whether mycorrhiza formation positively influences plant performance under reduced water supply the experiment was conducted under two irrigation regimes. There was no strong response to different levels of watering. Overall, application of native soil inoculum improved growth most. It contained sufficient AMF propagules but potentially also other soil microorganisms that synergistically enhance plant growth performance. However, the AMF inoculum pot-produced under controlled conditions was an efficient alternative for better management of A. acuminata and M. pubescens in the nursery, which in the future may be combined with defined EMF and Frankia inocula for improved management practices.

Abstract:

An arbuscular mycorrhizal fungus (AMF) was isolated from a south Ecuadorian reforestation site in the vicinity of a pristine mountain rainforest ecosystem. Morphologically, it corresponded with the description of an AMF first described from Cuba as Gigaspora savannicola, before it was placed in Scutellospora. No living culture of this species has been available previously to allow detailed morphological review or DNA barcoding. After comparison of the morphology of the holotype and authenticated specimens with that of the Ecuadorian isolate, it was concluded that they are conspecific. A detailed redescription of the species is provided, including morphological characters not included in the original description, and an epitype is designated. To provide an extended DNA barcode for this AMF species, intraspecific variants of the near full-length small subunit rRNA gene (SSU) and a rDNA region comprising part of the SSU, the internal transcribed spacer (ITS) region including the 5.8S rRNA gene, and part of the large subunit rRNA gene (LSU) were sequenced. Phylotaxonomic analyses confirmed the classification in the genus Scutellospora sensu lato in a phylogenetic clade that, based on questionable evidence, was considered to circumscribe a distinct genus, Fuscutata. Recently, this genus was merged with Dentiscutata. Consequently, we move S. savannicola (=Fuscutata savannicola?=?Gigaspora savannicola) to the genus Dentiscutata (Gigasporaceae).

Abstract:

- Presently, molecular ecological studies of arbuscular mycorrhizal fungi (AMF) are only possible above species-level when targeting entire communities. To improve molecular species characterisation and to allow species-level community analyses in the field, a set of newly designed AMF specific PCR primers is successfully tested. - Nuclear rDNA fragments from diverse phylogenetic AMF lineages were sequenced and analysed to design four primer mixtures, each targeting one binding site in the small (SSU) or large subunit rDNA (LSU). To allow species resolution, they span a fragment covering the partial SSU, whole internal transcribed spacer rDNA region (ITS), and partial LSU. - The new primers are suitable to i) specifically amplify AMF rDNA from material that may be contaminated by other organisms, e.g., samples from pot cultures or the field, ii) characterise the diversity of AMF species from field samples, and iii) amplify a SSU-ITS-LSU fragment that allows phylogenetic analyses with species-level resolution. - The described PCR primers can be used for monitoring of entire AMF field communities, based on a single rDNA marker region. Their application will improve the base for deep sequencing approaches, and moreover they can be efficiently used as DNA barcoding primers.