Allelopathy of Root exuded of Two Sunflower Cultivars (Helianthus annuus L.) on weed companion

Abstract

Two field experiments were conducted during 2015-2016 in Wasit province, Iraq to test the allelopathic potential of sunflower (Helianthus annuus .L). Two genotypes introduced to Iraq to screened allelopathic of root exuded against weeds in sunflower field. Two sunflower genotypes significantly inhibited total number and biomass of companion weeds and the inhibition is genotype dependent. Genotypes tested Asgria was the most allelopathic cultivars with the reduction in total weed number by 68.6% of control and weed biomass by 61.0% of the control respectively. Flamme was the less allelopathic genotypes comparted Asgria Genotypes , which inhibition in total weed number by 24% and weed biomass by 35.4% respectively of the control respectively. A staircase experiment indicated that root exudates of the Asgria cultivar suppressed weeds more than Flamme giving additional evidence for the superiority of the Asgria cultivar in its allelopathic weed suppression. Chemical analysis indicated the presence of phenols compound in root exudates of both cultivars with a significantly higher amount in the Asgria cultivar (0.403 mg/g) compared to cultivar Flamme( 0.220 mg/g ) and that total phenolic started to increase at 28 day then declined at end season. Chemical analysis on these phenolics by HPLC indicated the presence of several allelochemicals, viz, protocatechuic, , vanillic, syringic, , ferulic and p-coumaric acid.Chromatographic analyses indicated the presence phytotoxins in the root exudes of the tested sunflower genotypes. All the isolated compounds appeared to have different retention times and were identified as phenolic compounds