227 AJCS 7(2):227-233 (2013) ISSN:1835-2707 Combined herbicidal effect of two natural products (sorgoleone and hairy root extract of tartary buckwheat) on crops and weeds Md Romij Uddin 1 , Kee Woong Park 1* , Jong Yeong Pyon 2 , and Sang-Un Park 1* 1 Department of Crop Science, College of Agriculture & Life Sciences, Chungnam National University, 79 Daehangno, Yuseong-gu, Daejeon 305-764, Korea 2 ReSEAT Program, Korea Institute of Science and Technology Information, Daejeon 305-806, Korea *Corresponding author: parkkw@cnu.ac.kr, supark@cnu.ac.kr Abstract Sorgoleone, a root exudate of sorghum [(Sorghum bicolor (L.) Moench] and hairy root extract of tartary buckwheat (Fagopyrum tataricum Gaertn.) were mixed and applied to different broadleaf and grass weed species and crop species in the greenhouse arranging a randomized complete block design with four replications to evaluate their combined herbicidal activity and crop selectivity. A mixture of these two natural products (sorgoleone and root extract of tartary buckwheat) showed significantly greater inhibitory effects than either one alone. Broadleaf weed species were more susceptible to the application of the mixture than grass weed species. Galium spurium, Rumex japonicus, Aeschynomene indica, and Amaranthus retroflexus were the most susceptible among the broadleaf species and Setaria viridis was the most susceptible among the grass species. Broadleaf weed species demonstrated more growth suppression than grass weed species. For example, growth of G. spurium was reduced by 80.9% at 150 μg ml -1 of sorgoleone alone and by 33.7% at 7.5 mg ml -1 of hairy root extract alone; however their mixture reduced G. spurium growth by 100%. Moreover, the mixture reduced studied crop growth slightly more than sorgoleone or hairy root extract used individually. The ability of weed growth suppression using sorgoleone and hairy root extract of tartary buckwheat together offers interesting possibilities for effective weed management. Keywords: Allelochemicals; Crop selectivity; Hairy root extract; Sorgoleone; Weed management. Abbreviations: ANOVA- Analysis of variance, HPLC-High Performance Liquid Chromatography, IBA- indole-3-butyric acid, LSD-Least Significance difference, MS, Murishage and Skoog, SAS- Statistical Analysis Systems, SH- Schenk and Hildebrandt’s, USDA-ARS- United States Department of Agriculture-Agricultural Research Service. Introduction Allelochemicals, which are naturally derived plant products, may provide new, effective, and reduced-risk alternative methods for suppressing weeds in crop fields with lower impact on the environment. Natural products relatively have short half-life and therefore considered safe at environmental toxicology standpoint (Duke et al., 2002). Natural products such as allelochemicals offer an attractive alternative to synthetic herbicides because they are generally more environmental friendly (Dayan et al., 2009 a). In addition, many allelochemicals and other natural phytotoxins may inhibit molecular target sites distinct from those targeted by commercially available herbicides (Duke et al., 2002; Dayan et al., 2012). Many plant species possess the capability to produce and release allelochemicals to suppress the growth of other plants (Weston, 1996). Sorgoleone, the oily exudate secreted by the root hair of sorghum (Sorghum bicolor), contains the lipid benzoquinone sorgoleone (2-hydroxy-5- methoxy-3-[(8′ Z, 11′ Z)-8′, 11′,14′ -pentadecatriene]-p- benzoquinone), which is a potent allelochemical (Netzly and Butler, 1986; Czarnota et al., 2001; Inderjit and Duke, 2003; Dayan et al., 2010). Plants in the genus Fagopyrum produce a wide array of biologically active constituents. Common buckwheat (Fagopyrum esculentum Moench) and tartary buckwheat (Fagopyrum tataricum Gaertn. are important members of this genus. Tartary buckwheat has various pharmacological and biological properties, including anticancer (Guo et al., 2007), antidiabetic (Yao et al., 2008) and herbicidal activities (Fujii et al., 2005). The importance of mixtures of allelochemicals is recognized both in herbicide research and in research exploring plant chemical interference (allelopathy) in situ. Previously, mixtures are often used to enhance efficiency and efficacy, and reduce selectivity (Green et al., 1995). Latter, it has been stated (Einhellig, 1995) that nearly all allelopathic activities are due to mixtures of two or more compounds. Therefore, in this study, herbicidal potential of a combination of natural products-sorgoleone from sorghum root and hairy root of tartary buckwheat to different weeds and crops were studied, in order to determine their efficacy as a potential bioherbicide. Results and discussions Combined effect of sorgoleone and hairy root extract on weeds Combination of both natural products (sorgoleone and hairy root extract) inhibited weed growth more than either product used singly, with the broadleaf weed species being more susceptible than grass weed species (Fig. 1 and Fig. 2). The broadleaf weeds G. spurium, R. japonicus , and A. indica