Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 16, 2004
Publication Date: December 15, 2004
Citation: Vaughn, S.F., Isbell, T.A., Weisleder, D., Berhow, M.A. 2005. Biofumigant compounds released by field pennycress (Thlaspi arvense) seedmeal. Journal of Chemical Ecology. 31:167-177. Interpretive Summary: Biofumigation is the exploitation of plant biochemicals with pesticidal properties. Certain plants from the mustard family have been shown to act as biofumigants by releasing inhibitory chemicals when grown as green manure crops and subsequently incorporated into the soil. Field pennycress is a winter annual member of the mustard family which we are researching as an alternative crop for Midwest farmers. In the current study we have found that the ground seeds (seedmeal) from field pennycress inhibited the germination and growth of weed seeds when applied to soil in both greenhouse and field trials. We also identified the chemicals primarily responsible for this activity. Our results suggest that field pennycress seedmeal may be useful as a biofumigant not only for organic growers who cannot use synthetic soil fumigants but also for conventional growers as an environmentally-friendly replacement for methyl bromide.
Technical Abstract: Defatted field pennycress (Thlaspi arvense L.) seedmeal was found to completely inhibit seedling germination/emergence when added to a sandy loam soil containing wheat (Triticum aestivum L.) and arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] seeds at levels of 1.0 % w/w or higher. Covering the pots with petri dishes containing the soil-seedmeal mixture decreased germination of both species at the lowest application rate (0.5 % w/w), suggesting that the some of the phytotoxins were volatile. CH2Cl2, MeOH and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod (Senna obtusifolia (L.) H.S. Irwin & Barneby) radicle elongation. Only the CH2Cl2 extract was found to be strongly inhibitory to both species. Fractionation of the CH2Cl2 extract identified two major phytotoxins, identified by GC-MS and NMR as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8 %, respectively, of the active fraction. When seeds of wheat, arugula, and sicklepod were exposed to volatilized AITC and ATC, the germination of all three species were completely inhibited by both compounds at concentrations of 5 ppm or less. In field studies where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m2 and tarped with black plastic mulch, all of the treatments significantly reduced dry weight of bioassay plants as compared to the tarped control, with the highest seedmeal rate decreasing dry matter to less than 10% of the control 30 days after seedmeal application. From the results of this study, field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.