Seasonal variation and environmental effects on endophyte transmission in tall fescue
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Tall fescue (Festuca arundinacea Schreb.) pastures are infected with a mutualistic toxin-producing endophyte (Neotyphodium coenophialum). Non-toxic endophyte-infected cultivars have been developed and a better understanding maternal transmission of endophyte is needed. Field, greenhouse, and growth chamber experiments were used to examine the effects of drought stress and temperature on plant and endophyte growth. Mean monthly endophyte frequency varied from 52 to 98% within field-grown plants, and mean monthly temperature was correlated with endophyte data. Growing plants at different temperature regimes demonstrated that endophyte concentration decreased within plants when temperatures decreased and increased when temperatures increased. Plant mass accumulated faster than endophyte mass at lower temperatures. Cardinal minimum temperature for endophyte growth was 10 o C but was 5 o C for the host plant. There was no water stress effect on endophyte frequency or concentration in tall fescue. Temperature appears to be the major variable affecting endophyte presence in field-grown plants.