The impact of endophyte infection, seed aging and imbibition on selected sugar metabolite concentrations in seed

This study investigated effects of seed aging and imbibition on sugar metabolite levels in Epichloë-infected and endophyte-free seed of Festuca arundinacea. Two treatments: accelerated aging and imbibition were applied to seeds, with embryo and endosperm tissues analyzed separately. Gas chromatography with flame ionization detection was employed for analysis of sugar metabolites within seed. Mannitol, ribitol and trehalose were more abundant in embryo than endosperm tissues and were identified at consistently higher levels within endophyte-infected compared to endophyte-free samples. The ratio of raffinose to sucrose significantly increased with seed aging in both endophyte-free and endophyte-infected embryo tissues while significantly lower concentrations of trehalose were detected in tissues dissected from aged-seed regardless of endophyte status. This research provides fundamental insight into the metabolic details of endophyte survival in seed and provides a first evaluation of key carbohydrates present in the fungal-plant symbiosis.