Article

Journal of Chemical Ecology

, Volume 35, Issue 2, pp 141-153

First online:

Is (−)-Catechin a Novel Weapon of Spotted Knapweed (Centaurea stoebe)?

  • Stephen O. DukeAffiliated withNPURU, USDA, ARS, University Email author 
  • , Amy C. BlairAffiliated withDepartment of Bioagricultural Sciences and Pest Management, Colorado State UniversityDepartment of Natural Resources, Fernow Hall, Cornell University
  • , Franck E. DayanAffiliated withNPURU, USDA, ARS, University
  • , Robert D. JohnsonAffiliated withNPURU, USDA, ARS, University
  • , Kumudini M. MeepagalaAffiliated withNPURU, USDA, ARS, University
  • , Daniel CookAffiliated withNPURU, USDA, ARS, UniversityPoisonous Plant Research Laboratory, ARS, USDA
  • , Joanna BajsaAffiliated withNPURU, USDA, ARS, University

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Abstract

The novel weapons hypothesis states that some invasive weed species owe part of their success as invaders to allelopathy mediated by allelochemicals that are new to the native species. Presumably, no resistance has evolved among the native species to this new allelochemical (i.e., the novel weapon). In their native habitat, however, the plants that co-evolved with these invasive species have theoretically evolved defenses that obviate the allelochemical advantage. Previous studies have claimed that catechin is such a novel weapon of spotted knapweed (Centaurea stoebe = C. maculosa), an invasive species in the non-native habitat of North America. These studies indicated that (−)-catechin is more phytotoxic than (+)-catechin. Other studies have not found sufficient catechin in field soils to support this theory. We report that (−)-catechin and (+)-catechin are essentially equal, but poorly phytotoxic to a variety of plant species in bioassays without soil. In a dose/response experiment with Montana soils, we found the lowest dose for a growth reduction of two native Montana grasses (Koeleria macrantha and Festuca idahoensis) by a racemic mixture of (±)-catechin that ranged from about 25 to 50 mM, concentrations, orders of magnitude higher than expected in nature. Autoclaving the soil before adding the catechin did not affect the activity of catechin. We found (−)-catechin to be a potent antioxidant, in contrast to a previous claim that it acts as an allelochemical by causing oxidative stress. Our findings suggest that catechin is not a novel weapon of spotted knapweed and that other allelochemical(s) or alternative mechanisms must be found to explain the success of this species as an invader in North America.

Keywords

Allelochemical Allelopathy Catechin Centaurea maculosa Centaurea stoebe Invasive species Phytotoxin Soil Spotted knapweed