SWEET-POTATO ALLELOPATHIC SUBSTANCE INHIBITS GROWTH OF PURPLE NUTSEDGE (CYPERUS-ROTUNDUS)

The allelopathic influence of sweet potato cultivar 'Regal' on purple nutsedge was compared to the influence on yellow nutsedge under controlled conditions. Purple nutsedge shoot dry weight, total shoot length and tuber numbers were significantly lower than the controls (47, 36, and 19% inhibition, respectively). The influence on the same parameters for yellow nutsedge (35, 21, and 43% inhibition, respectively) were not significantly different from purple nutsedge. Sweet potato shoot dry weight was inhibited by purple and yellow nutsedge by 42% and 45%, respectively, The major allelopathic substance from 'Regal' root periderm tissue was isolated and tested in vitro on the two sedges, The I-50's for shoot growth, root number, and root length were 118, 62, and 44 mu g/ml, respectively, for yellow nutsedge, The I-50's for root number and root length were 91 and 85 mu g/ml, respectively, for purple nutsedge and the I-50 for shoot growth could not be calculated, Nomenclature: Purple nutsedge, Cyperus rotundus L. #(3) CYPRO, yellow nutsedge, Cyperus esculentus L. # CYPES, sweet potato, Ipomoea batatas (Lam.), 'Regal.'