Carlos Urcelay

Summary: Arbuscular mycorrhizal fungi (AMF) are key drivers of plant growth and nutrition, shaping the relationship between plant diversity and ecosystem productivity. In agroecosystems, AMF generally benefit crops but often have neutral or even negative effects on weeds, yet the mechanisms underlying these contrasting interactions remain poorly understood. In this Viewpoint, we propose a plant community‐level framework to investigate interactions between multiple crop and weed species and diverse AMF taxa, focusing on chemically mediated communication via root exudates, particularly flavonoids (FLVs) and strigolactones (SLs). These compounds can act as ‘cry for help’ signals that recruit beneficial soil microorganisms to alleviate environmental stress. We found that their composition varies widely among plant families, with crops typically producing more diverse and functionally distinctive FLV profiles than weeds. Similar patterns, though less documented, appear for SLs. Different FLV subclasses elicit contrasting AMF responses, influencing spore germination, hyphal growth, and root colonization. Notably, FLVs with stronger positive effects on AMF are more common in crops, whereas those with neutral effects tend to dominate in weeds. Our results are consistent with the idea that such molecular cues may shape AMF recruitment and could potentially feed back into plant community dynamics, although this hypothesis should be explicitly tested.

Cotylidia aurantiaca (Pat.) A.L. Welden is one of the most common stereoid stipitate fungi in the Neotropical region. Here, we report a noteworthy new record of this species from the Chaco Serrano ecosystem in central Argentina, marking its southernmost occurrence in the country. A brief morphological description and illustrations are provided. Additionally, we plotted the species from Argentina records on map, and the distribution of the species in the country is discussed.

It has been suggested that invasive plant species are more generalist than non-invasive species in their interactions with arbuscular mycorrhizal fungi (AMF), allowing them to associate with novel AMF communities. There is emerging evidence suggesting that the flavonoid quercetin may play a role in regulating these interactions as a signaling compound. In this study, we experimentally grew three invasive alien and three non-invasive native woody species with AMF communities collected from within (though foreign to invasives) and outside their current distribution ranges. After 96 days, we: (a) assessed mycorrhizal colonization rates; (b) evaluated the impact of these interactions on plant performance (growth and phosphorus nutrition); and (c) tested whether these responses were influenced by the addition of quercetin to the plant growth medium. Our findings reveal that the invasive species exhibited mycorrhizal colonization when grown with both novel AMF communities and benefited from them in terms of phosphorus (P) nutrition. In contrast, two of the three non- invasive native species showed mycorrhizal colonization and enhanced P nutrition only with AMF from their current distribution range, but not with novel AMF from outside their range, suggesting selective behavior in their mycorrhizal interactions. The addition of quercetin did not have a strong effect on mycorrhizal colonization in either invasive or non-invasive native species. However, quercetin promoted moderate increases in P nutrition in the two non-invasive native species when grown with the novel AMF communities. Overall, the results suggest that invasive species are more generalist in their AM symbiosis than two of the three non-invasive species, and that the addition of quercetin had a limited, moderate influence on their AM interactions.

Traditionally, characterisation and comparison of AMF communities has been carried out by morphological identification of asexual spores in soil. In recent decades, molecular methods such as soil metabarcoding have become more popular than morphological identification of spores, but direct comparisons of the efficiency of both approaches have been rare. In this study, we compared AMF communities in soil samples from vegetable farms using both morphological and molecular methods (internal transcribed spacer, ITS, markers). In addition, we performed a systematic literature search and retrieved nine studies that analysed AMF communities using both approaches in the same soil samples, mostly in agroecosystems. Our results show that AMF communities determined by morphological spore-based identification are different than those determined by molecular genetic markers, but not as often claimed. In some cases, the morphological spore-based characterisation of spores revealed more diverse glomeromycotan communities. Moreover, in several cases the spore-based methods recovered taxa that the molecular methods did not, while in other cases the opposite was observed. The field and literature-based results of this study indicate that for a comprehensive and exhaustive characterisation of AMF communities it is necessary to combine both approaches. However, if the aim is to compare communities under different environmental conditions, both approaches provide comparable patterns.

Increasing soil organic carbon (SOC) in agroecosystems is a key objective for enhancing agricultural sustainability and mitigating climate change. Arbuscular mycorrhizal fungi (AMF) can increase yield and provide several other ecosystem services. Still, studies conducted in agricultural soils have shown that their effects on SOC can be either positive, neutral or negative. In this study, we conducted a quantitative review of the literature to evaluate the role of AMF in influencing SOC across various crop species and conditions. Through a systematic search of publications, we compiled a dataset comprising 62 trials from 19 studies including field and pot experiments that directly manipulated the mycorrhizal status of plants. We conducted a meta‐analysis to quantitatively evaluate the role of AMF on SOC across several crop species and conditions. We found an overall positive effect of AMF on SOC, with an average increase of 21.5%. However, this positive effect was statistically significant only in pot experiments whereas in field experiments, the effect was mainly modulated by texture and organic matter content. The effect of AMF on SOC did not vary with crop species' functional type, AMF inoculation sources (single or mixed AMF species) or other soil variables considered. Our results highlight the significant potential for AMF‐mediated mechanisms to promote SOC accumulation in agricultural soils, although this effect is context‐dependent. However, future research with different approaches and scales is needed to evaluate the impact of AMF on SOC dynamics in agricultural systems and elucidate the mechanisms behind their contribution to SOC accrual. Read the free Plain Language Summary for this article on the Journal blog.