Epichloë fungal endophytes affect germination responses of Bromus auleticus seeds to temperature and water availability.

SCAMBATO, A.A.; IANNONE, L.J. ; STEFANONI RUBIO, P.J.; NOVAS, M.V.; GUNDEL, P.E.

Pergamino

Conferencia; 9th International Herbage Seed Group (IHSG) Conference.; 2017

INTA

Bromus auleticus is high-quality forage and drought-resistance cool-season perennial grass, distributed in the Pampas region (Argentina), Uruguay and southern Brazil. Seeds ripen in December and remain dormant during summer. Aiming to evaluate the role of Epichloë on seed germination under different environmental conditions, endophyte-infected (E+) and endophytefree (E−) seeds from ecotypes La Pampa (LP) and El Palmar (EP), associated with E. pampeana andEpichloë sp., respectively, were subjected to different temperatures (15, 20, 25, 30 and alternated 15/25°C) and water potentials (Ψw) (0, −0.5, −1.0 and −1.5 MPa). Final germination percentage and germination rate were recorded. Response to water availability was characterized by fitting a hydrotime model. According to this, germination rate is correlated to Ψw. Biological time can be calculated by the amount by which Ψw exceeds base water potential. Endophyte transmission to seedling was also checked. Germination response to temperature depended on the ecotype (being higher for EP) and E+ seeds presented significantly higher germination percentage than E− ones at 15/25°C for both ecotypes and at 25°C for LP. At 30°C secondary dormancy was induced and germinated when transferred to 20ºC, although the transmission of the endophyte to the seedlings was negatively affected. For the Ψw experiments, germination decreased as medium Ψw decreased. For EP seeds, Ψw −1.0 and −1.5 MPa inhibited germination more in E+ seeds thanin E− ones and endophyte presence was associated with a higher base Ψw. Germination percentage at low Ψw for LP seeds was not significantly different between E+ and E−. Dormancy release and promoting germination could be an endophyte strategy, since it loses viability faster than the seed. Alternatively, the endophyte inhibitory effect at low Ψw may be a safeguard toprevent germination under limiting water levels, ensuring seedling emergence and establishment when environmental conditions are appropriate.