PHYTOTOXICITY OF SORGOLEONE FOUND IN GRAIN-SORGHUM ROOT EXUDATES

Root exudates of Sorghum bicolor consist primarily of a dihydroquinone that is quickly oxidized to a p-benzoquinone named sorgoleone. The aim of this investigation was to determine the potential activity of sorgoleone as an inhibitor of weed growth. Bioassays showed 125-mu-M sorgoleone reduced radicle elongation of Eragrostis tef. In liquid culture, 50-mu-M sorgoleone treatments stunted the growth of Lemna minor. Over a 10-day treatment period, 10-mu-M sorgoleone in the nutrient medium reduced the growth of all weed seedlings tested: Abutilon theophrasti, Datura stramonium, Amaranthus retroflexus, Setaria viridis, Digitaria sanguinalis, and Echinochloa crusgalli. These data show sorgoleone has biological activity at extremely low concentrations, suggesting a strong contribution to Sorghum allelopathy.