Field Inoculation of Bread Wheat with Rhizophagus Irregularis under Organic Farming: Variability in Growth Response and Nutritional Uptake of Eleven Old Genotypes and A Modern Variety

Arbuscular mycorrhizal fungi (AMF) promote crop growth and yield by increasing N and P uptake and disease resistance, but the role of field AMF inoculation on the uptake of micronutrients, such as Fe and Zn, and accumulation in plant edible portions is still not clarified. Therefore, we studied the effect of field inoculation with Rhizophagus irregularis in an organic system on 11 old genotypes and a modern variety of bread wheat. Inoculation increased root colonization, root biomass and shoot Zn concentration at early stage and grain Fe concentration at harvest, while it did not modify yield. Genotypes widely varied for shoot Zn concentration at early stage, and for plant height, grain yield, Zn and protein concentration at harvest. Inoculation differentially modified root AMF community of the genotypes Autonomia B, Frassineto and Bologna. A higher abundance of Rhizophagus sp., putatively corresponding to the inoculated isolate, was only proved in Frassineto. The increase of plant growth and grain Zn content in Frassineto is likely linked to the higher R. irregularis abundance. The AMF role in increasing micronutrient uptake in grain was proved. This supports the introduction of inoculation in cereal farming, if the variable response of wheat genotypes to inoculation is considered

Occurrence and diversity of arbuscular mycorrhizal fungi colonising of‑season and in‑season weeds and their relationship with maize yield under conservation agriculture

Weeds are responsible for major crop losses worldwide but can provide beneficial agroecosystem services. This study aimed to elucidate how arbuscular mycorrhizal fungi (AMF) in weeds respond to host identity and conservation agricultural practices. The study was carried out at two locations in Southern Africa during off-season and in-season maize cultivation. Off-season AMF root colonisation, diversity indices and community composition significantly differed among weed species at both locations. Glomus sp. VTX00280 explains most of the AMF community differences. In-season, implementation of conventional tillage with mulching alone (CT + M) or together with crop rotation (CT + M + R) resulted in a 20% increase in AMF colonisation of the constantly occurring weed species, Bidens pilosa (BIDPI) and Richardia scabra (RCHSC), compared with conventional tillage plus rotations (CT + R). The diversity of AMF was highest under no-tillage plus mulching (NT + M). Off-season and in-season AMF structures of both BIDPI and RCHSC were not related, but 39% of the taxa were shared. Structural equation modelling showed a significant effect of the cropping system on weed AMF diversity parameters and weed and maize root colonisation, but no significant influence of weed root AMF traits and maize colonisation was detected on maize yield. This may be explained by the improvement in weed competitive ability, which may have offset the AMF-mediated benefits on yield. Our findings highlight that implementing M and CR to CT and NT positively affected weed AMF colonisation and diversity. The similarity between the off-season and in-season AMF composition of weeds supports the fact that weeds functionally host AMF during the non-crop period

Cultivable fungal endophytes in roots, rhizomes and leaves of Posidonia oceanica (L.) Delile along the Coast of Sicily, Italy

The presence of endophytic fungi in the roots, rhizomes, and leaves of Posidonia oceanica was evaluated in different localities of the Sicilian coast. Samples of roots, rhizomes, and leaves were submitted to isolation techniques, and the obtained fungal colonies were identified by morphological and molecular (rRNA sequencing) analysis. Fungal endophytes occurred mainly in roots and occasionally in rhizomes and leaves. Lulwoana sp. was the most frequent of the isolated taxa, suggesting a strong interaction with the host. In addition, eight other fungal taxa were isolated. In particular, fungi of the genus Ochroconis and family Xylariaceae were identified as endophytes in healthy plants at all sampling stations, whereas Penicillium glabrum was isolated at only one sampling station. Thus, several organs, especially roots of Posidonia oceanica, harbor endophytic fungi, potentially involved in supporting the living host as ascertained for terrestrial plants

Descrizione delle micorrize del gruppo Thelephorales ed ecologia specifica delle specie più importanti trovate in un impianto di conifere alloctone in Sardegna

La famiglia delle Thelephoraceae include diverse specie di funghi basidiomiceti imenomiceti con corpi fruttiferi dalla forma assai variabile, coriacei o carnosi e a habitat tipicamente terricolo o lignicolo (saprotrofi, cariogeni e micorrizici, in prevalenza). A tale famiglia, la cui sistematica è ancora incerta, si attribuisce attualmente una decina di generi, fra i quali Thelephora, Tomentella, Tomentellopsis, Pseudotomentella e Lenzitopsis sono frequentemente riportati in letteratura come ectomicorrizici (ECM) in simbiosi con radici di piante forestali (aghi- e latifoglie), in vari ecosistemi. In particolare, studi dettagliati riguardano la descrizione morfologica delle ECM che essi instaurano e, quindi, la loro caratterizzazione molecolare. Le specie di questa famiglia formano corpi fruttiferi criptici o difficilmente individuabili sul terreno e per tale motivo sono spesso ignorate nel corso delle indagini micocenologiche. Nell’ambito dell’indagine sulla “Diversità della comunità ectomicorrizica presente in un impianto artificiale di conifere alloctone in Sardegna” (Monte Limbara - Tempio Pausania, OT) recentemente condotta, sono state raccolte, descritte e caratterizzate differenti ectomicorrize di Thelephoraceae associate a vari ospiti. In particolare, dopo aver prelevato campioni di radici delle piante oggetto di studio, in laboratorio è stata eseguita la caratterizzazione morfo-anatomica delle ectomicorrize rinvenute, rilevando, per ciascuna di esse: ospite, tipo di ramificazione, colore, organizzazione del mantello e delle rizomorfe, presenza di cistidi e di emanazioni ifali. Inoltre, per ciascun morfotipo così definito sono state condotte analisi molecolari attraverso il sequenziamento della regione ITS per identificare il simbionte fungino. Dall’indagine condotta è emerso che, tra i funghi ECM oggetto di studio, la famiglia più rappresentata è stata proprio quella delle Thelephoraceae con 3 generi e 15 specie. Di queste, 2 specie appartenevano al genere Tomentellopsis, 10 al genere Tomentella e 2 a Pseudotomentella. Per una specie è stato possibile individuare solo l’appartenenza alla famiglia Thelephoraceae. Infine, confrontando le sequenze ottenute con quelle presenti nelle banche dati GenBank e UNITE, sono state ottenute ulteriori indicazioni sull’ecologia e la distribuzione delle diverse specie trovate

Conservation tillage and N fertilization affect soil aggregate distribution, carbon storage and enzymatic activities

Conservation agriculture is globally recommended for increasing carbon (C) stock in soil and reducing greenhouse gases emissions by modifying soil physical, chemical and biological processes. In the present study, soil aggregate fractions, soil organic C (SOC) and soil enzymatic activities in bulk soil and microaggregates within macroaggregates (mM) were measured in a long-term field experiment comparing conventional tillage (CT) and minimum tillage (MT) and N fertilizer to the rotation bread wheat (Triticum aestivum L.) – soybean (Glicine max L. Merr.). Under MT, a higher proportion of free microaggregates and a lower proportion of silt and clay was recorded compared to conventional tillage, suggesting a greater potential to form macroaggregates, despite their proportion was not modified by tillage. However, when macroaggregates were further fractionated, MT resulted in higher proportion of microaggregates. In bulk soil and in mM, all soil enzymatic activities were higher under MT than CT. Conversely, SOC in bulk soil was not modified by tillage, but was higher under MT in mM. These results demonstrate the crucial role of mM for C sequestration under reduced tillage. Thus, this fraction is proposed as an effective diagnostic tool to assess variations in carbon storage induced by agricultural practices

TILLAGE INTENSIFICATION AFFECTS AMF DIVERSITY, SOC AND ENZYMATIC ACTIVITIES WITHIN SOIL AGGREGATES AT VARIOUS SCALES

Long-term agricultural management may change soil C sequestration and alter soil organic matter content, structure and biological activity. The objective of this study was to investigate the impact of tillage and N fertilization within a field experiment with a soybean/ wheat rotation, originally established in 1982 in Central Italy. Treatments were ploughing at 30-cm depth (P30) and minimum tillage (MT) in combination with two N fertilizer rates to wheat, 0 (N0) and 200 kg N ha-1 (N200). In spring 2016, soil samples were collected from the 0–15 and 15–30 cm soil layers. Bulk density (BD), NH4-N and NO3-N concentration were assessed. After wet-sieving fractionation, SOC, total N and available P, enzymatic activities and AMF diversity were assessed in both bulk soil and microaggregates within macroaggregates (mM). AMF diversity was characterized by SSU-ITS-LSU fragment. At both soil layers, BD did not vary between tillage intensities, but was 7% higher in N200 than N0. At 15-30 cm depth, the proportion of mM was 21% higher in MT than P30, while no differences were detected in the surface layer. Tillage did not change soil total N and available P, whereas N fertilization affected NH4-N (15%) and NO3-N (28%) concentration at both soil layers. SOC, enzymatic activities and AMF diversity in bulk soil and in mM changed in P30 respect to MT. Our results showed co-occurrence patterns in SOC, enzymatic activities and AMF diversity of bulk soil and mM fraction, suggesting that the contribution of soil biota to C sequestration within aggregates varied with tillage

Microbiome structure and interconnection in soil aggregates across conservation and conventional agricultural practices allow to identify main prokaryotic and fungal taxa related to soil functioning

Under conservation agriculture (CA), soil aggregates physically protect soil organic C, creating microhabitats with heterogeneities in nutrient availability. These may become rich in microbial taxa with structured interconnections, and thus maintain the equilibrium between C sources and sinks. A long-term experiment on tillage and N fertilization was used to investigate the microbiome within small macroaggregates (sM), and within occluded microaggregates (mM). At surface layer, N fertilization was the main determinant of prokaryotic and fungal alpha-diversity in sM and mM, whereas at subsurface tillage intensity was the primary driver. Moreover, although along soil profile a conserved microbial compositional core was found across managements, some taxa were uniquely found in certain treatments and microbiota structure was modified by tillage and N fertilization. Overall sM had a higher diversity of prokaryotes and a lower diversity of fungi than mM. Prokaryotic taxa, such as Actinobacteria, Chloroflexi and Thermomicrobia, and fungi, such as Agaricomycetes, Dydimellaceae, and Mortierellaceae, characterized sM, whereas others prokaryotes (Betaproteobacteria, Sphingobacteriia, Blastocatellia) and fungi (Sordariales, Lasiosphaeriaceae and Glomeraceae) characterized mM. Cross-domain networks were more complex in mM than sM at surface layer, and the opposite occurred at subsurface layer. Some prokaryotic and fungal taxa, retrieved in hubs, were positively linearly related to C cycling and soil structuring (e.g., Chloroflexi and Sordariomycetes). Our results suggest that diversity and structure of microbiome is positively shaped by CA, and there are microbial taxa and network traits suitable as indicators of nutrient stocks and soil structuring under an agriculture focused on soil health