Glucosinolate Levels during Seed Development and Maturation of Meadowfoam.

Meadowfoam, Limnanthes alba  Hartw. ex Benth. (Limnanthaceae), is an oilseed crop grown in the Willamette Valley of Oregon. After extraction the oil, the seed meal contains a glucosinolate (GSL).  GSLs are metabolizd to isothiocyanates and nitriles, some of which have allelopathic effects and have potential for use as bio-herbicides in organic farming. The objective of this study was to measure the GSL levels during seed development and maturation to determine the optimum time to harvest the crop with high level of GSL.  Seeds from two cultivars, Ross and MF189, were planted in two locations, Lewis Brown and Hyslop farms near Corvallis, Oregon. Standard cultural practices were followed. Seeds were collected at weekly intervals, starting from anthesis until the physiological (highest dry matter content) and harvest maturity (Moisture content 10-15%). The GSL content was measured by the HPLC. Glucosinolate concentration of Ross at Lewis Brown farm remained 0.0 µmol g^-1 starting from seed formation until physiological maturity (PM). At harvest maturity (HM), when seed moisture content was 15%, the concentration reached 97.8 µmol g^-1. A similar trend was observed in MF189 in the same location, but the concentration at HM was 103.9 µmol g^-1. In the same manner, the GSL concentration of Ross at Hyslop farm remained 0.0 µmole g^-1 until PM, and then increased to 103.7. µmol g^-1 at HM. Cultivar MF189 had GSL concentration of 5.3 µmol g^-1 at PM, 85.9 µmol g^-1 at HM at Hyslop farm. The GSL concentration reached the highest level at HM in both cultivars at the two locations. Therefore, if the objective is to use the meal as a bio-herbicide, it is recommended not to harvest the crop before HM.