Seed Production in Tall Fescue as Affected by Fungal Endophyte

Abstract

Relative seed yields should be an important measure of the effects of the endophytic fungus Acremonium coenophialum Morgan‐Jones & Gams on relative fitness in tall fescue ( Festuca arundinacea Schreb.). Two field experiments were conducted on Cecil sandy‐loam soils (clayey, kaolinitic, thermic Typic Kanhapuldults) to investigate the effects of endophyte infection on seed production and associated traits. The studies used endophyte‐infected and uninfected clones of the same plant genotypes. In Exp. I and II, endophyte infection resulted in 79 and 32% more total seed by weight, 60 and 33% more seeds per plant, 20 and 34% more panicles per plant, and 32 and 4% more seeds per panicle, respectively. The 300‐seed wt. was greater for infected plants in Exp. I but not in Exp. II. Plant genotype ✕ fungal status interactions occurred for all traits except for seeds per plant and seeds per panicle in Exp. II. These interactions occurred largely because the effect of the endophyte varied from no or small increases to significant increases in trait expression for different plant genotypes. The results indicate that endophyte‐infected tall fescue plants have much higher relative fitness for seed production than uninfected plants. Populations with low fungal incidence could rapidly shift toward high levels of infestation during seed increase or in pastures when seed production is allowed, leading to establishment of volunteer plants.