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Infection of tall fescue (Festuca arundinacea Schreb.) with its endemic Neotyphodium coenophialum-endophyte (Morgan-Jones and Gams) Glenn, Bacon and Hanlin appears to reduce copper (Cu) concentrations in forage and serum of grazing animals, contributing to a range of immune-related disorders. A greenhouse experiment was conducted to identify effects of novel endophyte strains on Cu acquisition by tall fescue (Festuca arundinacea Schreb.) varieties Grasslands Flecha and Jesup infected with a novel, non ergot producing endophyte strain AR542, and two perennial ryegrass (Lolium perenne L.) varieties Aries and Quartet infected with a novel, non lolitrem B producing strain AR1, and their noninfected (E−) forms. Individual endophyte/grass associations were cultivated in nutrient solutions at 1.0 (P+) and 0.0 mM (P−) phosphorus concentrations. The Cu 2+ -binding activity of extracellular root exudates, and concentrations of Cu and other heavy metals in roots and shoots were measured. Extracellular root exudates of AR542-infected vs. E− tall fescue had higher Cu 2+ -binding activity only in P− nutrient solution as shown by lower concentration of free Cu 2+ (0.096 vs. 0.188 mmol Cu 2+ g −1 root DM, respectively). The Cu 2+ -binding activity by root exudates of perennial ryegrass was not affected by endophyte infection, but was higher (i.e., lower concentration of free Cu 2+ ) in P− vs. P+ nutrient solution (0.068 vs. 0.114 mmol Cu 2+ g −1 root DM). In this hydroponic experiment, Cu concentrations in shoots of both grasses were not a function of Cu 2+ -binding activity and endophyte effects on heavy metal concentrations in shoots and roots were specific for each variety. The Cu 2+ -binding activity of extracellular root exudates may affect Cu accumulation by field-grown, endophyte-infected tall fescue under P-limiting growth conditions and warrants verification by more specific methods.

from early March, when grazing on dual-use wheat must be terminated to produce grain crop, until May when Introduced cool-season perennial grasses may become an imporgrazing on warm-season perennial grass pastures can be tant complementary winter forage to dual-use wheat (Triticum aestivum L.) in high-risk semiarid environments of the southern Great initiated (Reuter et al., 1999). Plains. Currently recommended, summer semidormant cultivars are Introduced cool-season perennial grasses are becomnot adapted to prolonged and severe summer drought and not producing an important source of high quality winter forage tive in the autumn grazing season. In an experiment planted at Vernon, to complement or replace wheat forage and perennial TX, on a Miles fine sandy loam (fine-loamy, mixed, thermic Udic warm-season grass pastures in the southern Great Plains Paleustalfs) in October 2000, we evaluated productivity and plant (Reuter and Horn, 2002). Perennial cool-season grasses survival of an obligatory summer-dormant 'Grasslands Flecha' and may potentially be a more reliable and economically summer semidormant 'Georgia 5', 'Jesup', and 'Kentucky 31' tall sound source of early-season forage than wheat, saving fescue (Festuca arundinacea Schreb.); a highly summer semidormant farmers about $100 per ha annually (Redmon, 1997). 'Grasslands Maru' hardinggrass (Phalaris aquatica L.); and summer They also contribute to environmental sustainability of semidormant 'Grasslands Matua' and 'Grasslands Tango' prairiegrass (Bromus wildenowii Kunth) under two defoliation intensities of 7.5 the agroecosystems by reducing water runoff and soil and 15 cm. Georgia 5, Jesup, and Grasslands Flecha were either erosion (Brady and Weil, 1996), conserving soil water infected with the novel Neotyphodium coenophialum Glenn, Bacon, during summer drought (Hanselka et al., 1994), improvand Hanlin endophyte strain AR542, with their endemic endophytes ing soil physical and chemical properties (Dormaar et (except for Grasslands Flecha), or noninfected (E-). Only Grasslands al., 1995), and providing habitat for wildlife (Duebbert Flecha and Grasslands Maru successfully survived summer droughts et al., 1981). during 2001-2004. Prairiegrass behaved as an annual but did not Severe and often prolonged summer droughts and reseed in 2003. Aboveground biomass was greater at 15-vs. 7.5-cm poorly understood management practices adversely afdefoliation height, except for 2004 growing season. In Grasslands fect persistence and productivity of introduced cool-Flecha, the novel endophyte increased tiller survival during summer season perennial grassland ecosystems at the margin of drought by 150% (2001) and 121% (2002) when compared with Eplants. Obligatory and highly summer semidormant cultivars of peren-

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Alfalfa (Medicago sativa L.) is an important hay crop produced under rain‐fed conditions or various levels of irrigation in the southern Great Plains of the USA. The objective of this study was to determine the role of fall dormancy (FD) on productivity and forage nutritive value of alfalfa in rain‐fed and supplemental irrigation systems in a semiarid, subtropical climate with a bimodal pattern of precipitation. Cultivars with FD ratings of 1 to 3 (dormant), 4 to 6 (moderately dormant), and 7 to 8 (nondormant) were planted in November 2001 on a Miles fine sandy loam (fine‐loamy, mixed, Thermic Udic Paleustalfs) near Vernon, Texas in two adjacent, randomized, complete‐block experiments representing rain‐fed and supplemental irrigation systems. In the supplemental irrigation system, water was supplied during April to October to meet the long‐term average monthly precipitation. During 2002–2005, plants were defoliated to 5 cm height at 5 to 15% bloom in all cultivars. In the rain‐fed system, FD had no effect on productivity (5.6–6.0 Mg ha−1). Nondormant cultivars produced higher dry matter yield (20.2 Mg ha−1) than dormant cultivars (15.9 Mg ha−1) under supplemental irrigation. Moderately dormant cultivars were intermediate (18.6 Mg ha−1). Forage nutritive value was greater in the spring (rain‐fed) or spring and autumn (supplemental irrigation) than in the summer. Weather patterns and harvest time interacted with FD in determining forage nutritive value under supplemental irrigation. Cultivars with FD ratings of 5 to 8 may be used in similar environments of the southern Great Plains to maximize productivity of alfalfa.

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