differentiation of allelopathic potential of sorghum (sorghum bicolor) cultivars using chemical and molecular techniques. al-khateeb, t.a., alsaadawi, i.s., and hadwan, h.a. (iraq)

Laboratory tests were conducted to detect the differential allelopathic potential of two sorghum (Sorghum bicolor) cultivars (Enqath and Rabeh) residues. Chemical analysis of residues indicated that total phenolics were found to be higher in Enqath than in Rabeh plants suggesting the superiority of the allelopathic potential of the first cultivar over the second one against weeds. Results indicated that total phenolics were two folds in shoot than in root of both cultivars. These compounds appeared to be higher in Enqath shoot and root (1.60 and 0.80 mg/g, respectively) than in Rabeh shoot and root (1.2 and 0.50 mg/g, respectively). The increments in total phenolics in root and shoot of Enqath were clearly reflected on the increase of total phenolics in the whole plant reaching about 2.40 mg/g compared to Rabeh (1.70 mg/g). Chemical analysis by high performance liquid chromatography (HPLC) revealed the presence of seven allelochemicals namely ferulic, p-coumaric, gallic, vanillic, syringic, phydroxybenzoic, and sinapic acid in the residues of both cultivars. Total phenolic acids were found to be higher in Enqath than in Rabeh. Results of RAPD-PCR technique performed for sorghum genomic DNA revealed that all the 10 primers used in this study scored different amplification monomorphic and polymorphic bands in the tested genotypes with the exception of 3 RAPD primers which generated a unique amplification bands, one of them (125 bp) scored by OPN 16 primer, present in high allelopathic sorghum genotypes and absent in the low allelopathic ones (Rabeh). Further work is recommended to analyze the sequence of this band to find out whether it is related to allelopathic trait or not. These results recommend screening more sorghum cultivars in order to offer a potential source of allelopathic germplasm that could be manipulated to enhance weed suppression in an effective and environmentally sustainable approach.