The Almario research group, led by Juliana Almario, is part of the Rhizosphere team and the Microbial Ecology Lab of the University of Lyon (France). It focuses on finding novel microbial-based solutions to improve plant phosphorus nutrition by tapping into the microbiota of wild plants growing under harsh nutrient-limited conditions.

Just like us humans, plants rely on their microbiota to process and assimilate nutrients via their roots. For example, most terrestrial plants live in symbiosis with arbuscular mycorrhizal (AM) fungi and rely on this association to scavenge the macronutrient phosphorus (P) from soil. Interestingly, some plants that have abandoned this partnership with AM fungi (non-mycorrhizal plants), can still thrive in extremely P-limited habitats, prompting the question: how do they do it? We believe the answer is in their microbiota.

Juliana Almario 3x2

P-delivering beneficial fungi

By studying the fungal microbiota in the roots of one of these non-mycorrhizal plants we uncovered its association with a new kind of beneficial fungus, capable of extracting P from the soil and delivering it to the plant, thereby promoting plant P uptake and growth, and potentially facilitating its adaptation to low-P environments. We have since continued to study the microbiota of wild non-mycorrhizal plants growing on P-poor environments like alpine soils, with the aim of identifying novel microbial partnerships improving their nutrition. To do so, we use microbial metagenomics and bioinformatics to describe their microbiota, and large-scale isolation of root-endophytic microbes to test their effects on plant nutrition. Fungus-to-plant nutrient transfers are followed using a P radioisotope (33P). Our long-term aim is to develop a new technology to trace P in the rhizosphere to identify all the microbes that are key for P mobilisation.

P fertilisers and the P crisis: a major societal issue

Despite the massive usage of mineral fertilisers by humans, it is estimated that 30% of arable fields lack sufficient available P, and the demand for crop P fertilisers is increasing much faster than the supply, limited by the extraction and the size of the reserves. A ‘P crisis’ is thus expected by 2050 when the world’s ‘easily accessible’ P reserves are predicted to become depleted. Nevertheless, the geopolitical crisis in Ukraine has accelerated this process and we are now undergoing a major fertiliser crisis (with a doubling of fertiliser prices), which is causing, in its turn, a food crisis. Given this context, one of our major goals is to translate our research into tangible solutions that can help us grapple with ongoing and upcoming fertiliser crises, by developing new microbial biofertilisers that can partially replace mineral fertilisers.

Sampling for non-mycorrhizal plants in the French Alps (July 2020).

Source: Juliana Almario.

Sampling for non-mycorrhizal plants in the French Alps (July 2020).

New fungal biofertilisers

Maintaining crop yields entails ensuring adequate nutrient supplies to plants. In the case of P, the easy fix is massive mineral fertilisation, but the introduction of fungal inoculants that can deliver the applied P to plants could provide a new way to ensure a more efficient and smarter utilisation of fertilisers. We plan to test our collection of beneficial fungi for their capacity to deliver P to economically important crops like wheat and rapeseed, with the aim of developing new types of bioinoculants. These would add up to the array of available biofertiliser solutions that can partially replace fertilisers. This would contribute to promoting sustainable food production, and particularly a better use of agricultural biodiversity.