An Assessment of Allelopathic Potential inAvenaGerm Plasm

Three thousand accessions of the U.S. Dep. Agric. World Collection ofAvenasp. germ plasm were screened for their ability to exude scopoletin (6-methoxy-7-hydroxy coumarin), a naturally occurring compound shown to have root growth inhibiting properties. Twenty-five accessions exuded more blue-fluorescing materials than a standard oat cultivar (Avena sativaL. ‘Garry’). Analysis of the exuded materials revealed that four accessions exuded up to three times as much scopoletin as ‘Garry’. When PI 266281 was grown with wild mustard [Brassica kaber(D.C.) L.C. Wheeler var.pinnatifida(Stokes) L.C. Wheeler] for 16 days in sand culture, the growth of the wild mustard was significantly less than that obtained when the weed was grown with ‘Garry’. Wild mustard plants grown in close association with PI 266281 exhibited severe chlorosis, stunting, and twisting which appeared indicative of chemical or allelopathic effects rather than simple competition. Analysis of the culture solution indicated that levels of scopoletin were too low to cause the observed effects and it is postulated that the final toxic effects were possibly due to the exudation of scopoletin and other allelopathic compounds.