Allelopathic Effect of Root Exudates of Two Sunflower Cultivars on Companion Weeds


The effects of root exudates of two sunflower cultivars (Shumoose and Sin Altheeb) were studied on companion weeds during the growing season of 2012. Results showed the ability of both cultivars to affect weed population and growth with the superiority of cultivar Shumoose in suppression of weed density at 60 and 120 days after sowing compared to Sin Altheeb. Weed biomass was significantly reduced up to 90 and 71% by Shumoose and Sin Altheeb cultivars, respectively. Stair case experiment indicated that root exudates of Shumoose cultivar showed more suppression to weeds than Sin Altheeb giving additional evidence for the superiority of Shumoose cultivar in its allelopathic weed suppression. Chemical analysis by High performance liquid chromatography indicate the presence of nine compounds in root exudates of Sin Altheeb and eight compounds in Shumoose, and all are Phenolic in nature with differential concentrations between these cultivars. Most of the isolated chemicals known for their inhibiting ability for germination and growth of plants, including weeds. Total of the isolated phenolics was doubled in Shumoose than in Sin Altheeb.