THE ALLELOPATHIC EFFECT OF SORGHUM AND ITS LINKS TO THE EXTRACT COMPOSITION AND THE SORGOLEONE

Abstract

The use of sorghum on the no-tillage system has contributed to weed control but has generated problems infuture soybean development. The objective of this work was to extract and quantify sorghum root exudate ofthree genotypes to determine the sorgoleone content, the chromatographic profile, and the relative toxicity of the root extracts through the evaluation of germination parameters in soybean (Glycine max), brachiaria grass (Brachiaria decumbens) and beggarticks (Bidens subalternans) seeds under laboratory conditions.Considering the average root density, BRS 716 presented 50% more numbers of hairs per mm² than the othertwo sorghum genotypes. Sorgoleone was found predominantly in the three evaluated sorghum extracts, andthe chromatographic profile detected five other compounds for the BR 007, CMSXS 206 B, and 6 BRS 716compounds. There was a difference between the dry mass of roots, dry mass of extract, and sorgoleone content among the three genotypes, with BRS 716 having the highest ratio of sorgoleone per dry mass of roots, followed by BR 007 B, and CMSXS 206 B. The BR 007 B extract was the one that reduced germination and the germination speed index (GSI) of soybean and hairy beggarticks, followed by BRS 716 and CMSXS 206B. The results showed that sorgoleone is a potent inhibitor of plant germination, but the allelopathic actionmay be linked to the composition of each extract and not specifically to the sorgoleone.