Allelopathic Potential of Sweet Sorghum Cultivars.

Sweet sorghum (Sorghum bicolor) is a drought tolerant C4 grass that is currently being researched as a first and second generation biofuel.  Allelopathic effects of grain sorghum on a number of species are well documented, however, little is known about potential allelopathic effects of sweet sorghum genotypes.  Thus, a study was designed to examine allelopathic effects of various sweet sorghum genotypes using a wheat seedling bioassay. Root and stem tissues extracts from 12 diverse cultivars were examined for their effect on wheat seedling root elongation. Initial studies were conducted to determine the minimum root and shoot extract concentrations that result in significant root growth inhibition.  Extracts of M81E, Sugar Drip, and Topper 76-6 were substituted for water when mixing agar to generate media containing 0, 5, 10, 20, 30, 45% tissue extract.  The mixtures (0.8% agar) were added to test tubes and a germinated wheat seed was placed in each tube after the media solidified.  Wheat seedling root lengths were recorded after 48 hours of growth.  Media containing 20% stem tissue extract resulted in significant reductions in root length.