Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/1998
Publication Date: N/A
Interpretive Summary: Crambe is an industrial oilseed crop grown primarily in North Dakota for its oil which is used to make nylon and other polymers. The seedmeal that remains after the oil is extracted from the seeds has been used as animal feed, but its use is limited due to toxicity concerns. We are examining the use of crambe seedmeal as a soil amendment for the inhibition of weeds and soil pathogens. In this study, we have identified the active compound, abbreviated CHB, that is present in the crambe seedmeal and is primarily responsible for the inhibition of weeds. Because CHB should break down rapidly in the environment and is of relatively low toxicity to humans, crambe seedmeal may be a viable weed control alternative for organic farmers, home garden, and landscape uses.
Technical Abstract: Crambe (Crambe abyssinica Hochst ex. R. E. Fries) seedmeal was found to suppress seedling emergence and biomass when added to a sandy loam soil containing wheat (Triticum aestivum L. "Cardinal") and hemp sesbania (Sesbania exaltata (Raf.) Rydb. ex A. W. Hill) seeds. Hexane, CH2Cl2, MeOH, and water extracts of the seedmeal were prepared and bioassayed against wheat and velvetleaf (Abutilon theophrasti L.) radicle elongation. The CH2Cl2 extract was the most inhibitory, while the other extracts inhibited the bioassay species only slightly (MeOH) or not at all (hexane, water). Fractionation of the CH2Cl2 extract by high performance liquid chromatography identified the major phytotoxin as 1-cyano-2-hydroxy-3-butene (CHB), comprising 96.1% of the active CH2Cl2 fraction. Radicle elongation of wheat and velvetleaf were inhibited by CHB with I50 (the concentration required to inhibit growth by 50%) values of 2.1 x 10**-4 M for wheat and 2.7 x 10**-3 M for velvetleaf.