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Open Access Research article

Tall fescue endophyte effects on tolerance to water-deficit stress

Padmaja Nagabhyru1, Randy D Dinkins2, Constance L Wood3, Charles W Bacon4 and Christopher L Schardl1*

Author Affiliations

1 Department of Plant Pathology, University of Kentucky, Lexington, KY 40546-0312, USA

2 USDA-ARS, Forage-Animal Production Research Unit, Lexington, KY 40546-0091, USA

3 Department of Statistics, University of Kentucky, Lexington, KY 40506-0027, USA

4 USDA-ARS, Toxicology and Mycotoxin Research Unit, Athens, GA 30605-2720, USA

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BMC Plant Biology 2013, 13:127  doi:10.1186/1471-2229-13-127

Published: 9 September 2013

Abstract

Background

The endophytic fungus, Neotyphodium coenophialum, can enhance drought tolerance of its host grass, tall fescue. To investigate endophyte effects on plant responses to acute water deficit stress, we did comprehensive profiling of plant metabolite levels in both shoot and root tissues of genetically identical clone pairs of tall fescue with endophyte (E+) and without endophyte (E-) in response to direct water deficit stress. The E- clones were generated by treating E+ plants with fungicide and selectively propagating single tillers. In time course studies on the E+ and E- clones, water was withheld from 0 to 5 days, during which levels of free sugars, sugar alcohols, and amino acids were determined, as were levels of some major fungal metabolites.

Results

After 2–3 days of withholding water, survival and tillering of re-watered plants was significantly greater for E+ than E- clones. Within two to three days of withholding water, significant endophyte effects on metabolites manifested as higher levels of free glucose, fructose, trehalose, sugar alcohols, proline and glutamic acid in shoots and roots. The fungal metabolites, mannitol and loline alkaloids, also significantly increased with water deficit.

Conclusions

Our results suggest that symbiotic N. coenophialum aids in survival and recovery of tall fescue plants from water deficit, and acts in part by inducing rapid accumulation of these compatible solutes soon after imposition of stress.

Keywords:
Fungal endophyte; Tall fescue; Water deficit stress; Metabolites; Neutral sugars; Amino acids and lolines