Growth Response of Agrostis palustris to Adventitious Root Infection by Acremonium rutilum and Acremonium alternatum

Acremonium rutilum and Acremonium alternatum are reported as pathogens of the adventitious roots of Agrostis palustris. Both organisms have been isolated from root and leaf tissue of diseased A. palustris on high-sandcontent golf greens. The presence of the organisms on adventitious roots is usually associated with other potential root pathogens. Three isolates of A. rutilum and one isolate of A. alternatum were evaluated for their ability to infect adventitious roots of A. palustris under high and low temperature regimes and to affect plant growth and symptom expression. Both species of Acremonium infected roots and decreased shoot and root dry weight. The decreases in dry weight were more pronounced under low temperatures than under high temperatures. With the exception of isolate AR-1 of A. rutilum under the high temperature regime, the decrease in shoot dry weight was disproportionately greater than that of root weight in response to both A. rutilum and A. alternatum. The number of stolons per plant decreased in response to both species of Acremonium under the high and low temperature regimes except for isolate AR-1 of A. rutilum which increased stoion numbers under the high temperature regime. Foliar symptoms associated with the organisms in the field were not expressed by the rootinoculated plants. The observations of the study are discussed relative to A. rutilum and A. alternatum as potential emerging pathogens and/or participants in a root disease complex, and relative to the role of high-sandcontent golf green management practices in the process