Submitted to: International Allelopathy Congress
Publication Type: Proceedings
Publication Acceptance Date: June 18, 2005
Publication Date: September 23, 2005
Citation: Dayan, F.E., Cook, D., Baerson, S.R., Rimando, A.M. 2005. Manipulating the lipid resorcinol pathway to enhance allelopathy in rice. Harper, J.D.I., An, M., Wu, H., Kent, J.H., Editors. Charles Sturts Unviersity, Wagga Wagga, Australia. Proceedings of the 4th World Congress on Allelopathy. p. 175-181. Technical Abstract: About 4% of rice cultivars have demonstrated allelopathic potential against some of the most troublesome weed species in paddy fields, such as barnyardgrass (Echinochloa crus-galli), redstem (Ammannia species), Cyperus species and ducksalad (Heteranthera limosa). A tremendous international effort is underway to produce rice lines with enhanced allelopathy through breeding techniques. Quantitative Trait Loci (QTL) analysis has associated the allelopathic trait with several rice chromosomes, suggesting that these weed-repressing varieties may produce more than one phytotoxin. Recent publications have shed some light on the nature of these phytotoxins. Allelopathic rice produces glycosides of lipid resorcinols, flavones, and benzoxazinoids, as well as momilactones and cyclohexenones. Lipid resorcinols are of particular interest to our research group because these secondary metabolites have been associated with pathogen resistance and allelochemical traits of other monocotyledonous species. Furthermore, these compounds have been identified as markers to evaluate the allelopathic potential of rice varieties. Genes putatively involved in the ring formation of these unusual resorcinols in rice have been identified. These novel polyketide synthases accept long chain fatty acid-CoA substrates instead of the usual coumaroyl-CoA substrate used by the more common polyketide synthases such as chalcone and stilbene synthases. The substrate specificity of some of these rice enzymes indicate that they may be involved in the biosynthetic pathway of lipid resorcinols.