- Università di Torino (Italy)
- Università di Padova (Italy)
- Consiglio Nazionale delle Ricerche (Italy)
Legumes develop two types of beneficial symbioses with soil microbes: symbiotic nitrogen fixation (SNF) with rhizobiacean bacteria and arbuscular mycorrhizas (AM) with a small group of symbiotic soil fungi. This uncommon symbiotic aptitude raises great interest in legumes as major sources of staple foods in the frame of sustainable agriculture based on low fertilizer input and food security strategies that can feed the increasing global population.
Through AM fungi, host plants obtain preferential access to soil water and mineral nutrients, especially phosphorus (P) and nitrogen (N).
SNF of atmospheric N2 to NH3 is of major interest in agriculture, allowing a significant reduction in the use of N fertilizers, with positive consequences on soil and air pollution.
Anyway, plant symbiotic aptitudes have not always been favored by breeders and only recent studies have investigated the possibility to improve the symbiotic status of crop plants.
In this frame we demonstrated that short chain (tetra- and pentameric) chito-oligosaccharides (Myc-COs) released by AM fungi trigger a symbiotic signaling pathway, altogether preparing the plant to fungal colonization.
This discovery opened the way to possible applications of Myc-COs as stimulants of AM establishment in agricultural conditions. On this line, an ongoing collaboration with a consortium of farmers (La Granda) has shown that plant treatment with Myc-COs induces a robust and reproducible enhancement of AM colonization in both legumes and non-legumes, under lab conditions as well as in the field, also increasing biomass production (AMforQuality project). Furthermore, preliminary observations from these field samples suggest that Myc-CO treatment may also enhance legume nodulation. In fact, Myc-COs could serve as substrates for Nod factor biosynthesis by soil borne rhizobia.
Importantly, Myc-COs are affordable by-products of industrial food processing and completely bio-degradable.
In the frame of agricultural application of symbiotic interactions, COSYM represents a breakthrough study, with the main goals of clarifying how Myc-COs enhance AM, how they impact on the efficiency of SNF, and shed light on their off-target effects on plant nutrition.
COSYM expected results will pave the way for a fruitful transfer of information from model to field plant systems. Consistently, our experimental approach is based on the model legume Lotus japonicus, which will be integrated for specific investigations with Medicago truncatula, and for field treatments with Glycine max (soybean).
By applying the specific expertise of each research unit, COSYM will investigate the balance between AM and SNF under Myc-CO treatment; the impact on plant signaling (calcium, strigolactones) and transcriptome (through both untargeted and targeted approaches); the crosstalk between Myc-CO treatments and nutrient availability and transport (N and P); the perception of Myc-COs by AM fungi and rhizobia; lastly, our studies will be expanded to the major crop legume soybean, with field experiments validating the results obtained in controlled lab conditions (AM-SNF balance, gene regulation).