|Paul Jr, Rex|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2003
Publication Date: 8/1/2003
Citation: BERTIN, C., PAUL JR, R.N., DUKE, S.O., WESTON, L.A. LABORATORY ASSESSSMENT OF THE ALLELOPATHIC POTENTIAL OF FINE LEAF FESCUES. JOURNAL OF CHEMICAL ECOLOGY. 2003. V. 29(8). P. 1919-1937. Interpretive Summary: Highly allelopathic grasses could greatly reduce the need for synthetic herbicides in turf and areas such as roadsides. Seven fescue types selected from prior field evaluations were evaluated for allelopathic activity in the lab. All of them suppressed weed growth through production of herbicidal compounds from their roots. The phytotoxic compound(s) are generated by actively growing fibrous root cells. This work paves the way for determination of the exact chemical nature of the compound(s) involved in allelopathy of these fescue varieties. This information will help genetecists produce more allelopathic varieties that could be used to reduce herbicide use.
Technical Abstract: Laboratory screening studies were conducted to evaluate the allelopathic potential of fine leaf fescues. Of the seven accessions selected from prior field evaluations for weed suppressive ability, all inhibited root growth of large crabgrass and curly cress in laboratory assays. Grown in agar as a growth medium and in the presence of living fescue seedlings for 14 or 21 days, test species were sensitive depending on the fesue cultivars. Growth inhibition increased when fescue was grown for increasing periods of time in agar. Seedling fescues produced significant quantities of bioactive root exudates, which were released into the agar medium. Bioactive root exudates were extracted from living fescue roots using methylene chloride. Shoot tissue was extracted in water and then the aqueous extract was partitioned with hexane, ethyl acetate and methylene chloride. Extracts were tested for inhibitory activity on seedling growth as measured by inhibition of curly cress germination and radicle elongation. Root exudates were more toxic (70% inhibition) than shoot extracts (up to 40% inhibition), when formulated at 0.25 mg/ml concentration. Light and transmission electron microscopy were utilized in an attempt to identify the cellular location of production of secondary produts contained in bioactive root exudates. Ultrastructural anlaysis indicated that the exudate is produced in actively dividing tips of fibrous root cells. The mode of release of these exudates into the environment remains unknown.