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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.

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Additional index words. cool-season, Cynodon dactylon x C. transvaalensis, Lolium perenne, warm season Abstract. Research was conducted to determine the influence of the rate of seeding perennial ryegrass (Lolium perenne L.) over bermudagrass [Cynodon dactylon (L.) Pers x C. transvaalensis Burtt-Davy] on both the establishment of the ryegrass and the quality of bermudagrass golf greens. Increasing seeding rate from 90 to 180 g·m -2 resulted in more rapid establishment and a linear increase in turf quality. Turf density, as measured by leaf number, displayed linear and quadratic responses to seeding rates, with higher rates producing the greatest leaf numbers. Leaf width declined linearly with seeding rate, suggesting higher putting quality, as did tillers per plant. Spring transition to bermudagrass was slowed at high (150-180 g·m -2 ) seeding rates, with significantly more ryegrass present in late May. Emergence and growth of bermudagrass were suppressed longer at the higher overseeding rates. We conclude that the choice of seeding rate for ryegrass is a compromise between rapid development of, and maintenance of, quality turf vs. early smooth transition to bermudagrass in the spring.

The effects of frost and freezing on hydrocyanic acid potential (HCN‐p) of plants of ‘Greenleaf’ and ‘Piper’ sudangrass and ‘Suhi‐1’, a sorghum ✕ sudangrass hybrid, were studied.The HCN‐p of plants of all plant heights and cultivars decreased during the autumn until frost occurred. Significant increases in HCN‐p were measured after most frosts. These increases were most evident from 1 to 6 days after frost. The response of HCN‐p to frost was greater in shorter than in taller plants. Plants of Suhi‐1 had a greater increase in HCN‐p than plants of Greenleaf or Piper. Freezes (−5 C or lower) resulted in death of the plants and caused a decrease in HCN‐p which continued until little or none was detected. This decrease in HCN‐p was observed for plants of all heights and cultivars.