Do Epichloë endophytes affect mycorrhizal colonization and biomass production of neighbor grasses? A field study

IANNONE L.J.; VIGNALE, M.V.; NOVAS, M.V.

Salamanca

Simposio; 10th International Symposium on Fungal Endophytes of Grasses; 2018

Epichloë endophytes may affect the interaction between their hosts and other fungal microorganisms. Our previous studies demonstrate that in native wild grasses, such as Bromus auleticus, the association with Epichloë increases the colonization of arbuscular mycorrhizal fungi (AMF). AMF generally promote plant growth by providing plants with inorganic nutrients from the soil, therefore, AMF are potentially valuable in environment-friendly agriculture. The objective of this work was to study the effect of Epichloë endophytes associated with Bromus auleticus, on mycorrhizal colonization, seedling emergence and growth parameters in three grasses of agronomic interest.Eight plots were established in 2012 in the EEA-INTA of Concepción del Uruguay, Entre Ríos Province, Argentina. Each one consisted of three lines (2 m each), where we planted 12 grams of B. auleticus (B.a) E+ or E- seeds per line. Three years later, seeds (4g) of Lolium multiflorum (L.m) (E+ (Epichloë occultans) or E-), Schedonorus arundinaceus (S.a) (E+ (Epichloë coenophiala) or E-) and Bromus catharticus (B.c) (which does not establish associations with Epichloë) were sown in lines of 50 cm, built around the previous 2m-lines, and were considered as B. auleticus neighbors.Supporting figure. Eschematic representation of a block The combination between B. auleticus endophytic status and the identity of the neighbor grass, determined 10 treatments. Two months after sowing, the emergence of the seedlings was measured. Ten plants of each treatment were randomly chosen in each plot to measure the length of the longest leaf, the length of the root and the number of leaves. Three 6 months old plants per treatment in each plot were harvested including their root system and mycorrhization was measured [1]. After harvesting and taking the measurements mentioned above, the shoots were dried and the dry weight (g) was calculated. Statistical analyses were performed using Generalized Linear Mixed Models. Bromus auleticus endophytic status and neighbors were analyzed as fixed effects factors. The plots were considered as blocks and their effects were included as a random effect factor.B. auleticus E+ plants produced a significative increase in total mycorrhizal colonization, and in the abundance of arbuscules and vesicles in the neighbor grasses. This effect was higher on E- plants of S. arundinaceus and L. multiflorum in comparison with their E+ counterparts. Coils were not affected.Regarding the neighbor parameters, seedling emergence, the length of the root and the number of leaves were not affected by B. auleticus E+ plants. Although not significant, differences were observed in the length of the leaves and shoot dry weight due to endophytic status of B. auleticus. Interestingly, neighbors responded in dissimilar way. While B. catharticus and L. multiflorum presented lower leaf length and shoot weight when they were close to B.a E+ plants, S. arundinaceus exhibit higher values.The results indicate that neighbor grasses of different endophytic status presented a differential response to B.a E+ plants, suggesting an interaction among endophytes at the rhizosphere level. In addition, the significant increase of mycorrhizal colonization, particularly in arbuscules, did not correlate with growth parameters. However, when considering mycorrhizal symbioses in the context of sustainable agriculture, in which AMF improve overall plant fitness, alleviating the damage caused by abiotic stresses, improving water-use efficiency and increasing P and N plant content, more studies are needed to achieve a better understanding of these complex associations.