THE EFFECT OF CULTIVAR, SAMPLE DATE AND GRAZING ON THE CONCENTRATION OF S-METHYLCYSTEINE SULFOXIDE IN OILSEED AND FORAGE RAPES (BRASSICA-NAPUS)

A study of the S-methylcysteine sulphoxide (SMCO) concentration in fol iage from four double-zero, three single-zero cultivars of oilseed rap e and four cultivars of forage rape revealed little inter-cultivar var iation. Significant differences were however found with respect to har vest date, with the concentration of SMCO remaining fairly constant ov er the early winter period but then increasing as the plants commenced regrowth in the late winter-early spring. Continual exposure of plots to grazing wild rabbits produced small but statistically significant changes in SMCO concentration but compared with seasonal differences t he changes due to grazing were small and inconsistant. These findings are discussed in relation to the recently reported harmful effects of double zero oilseed rape cultivars on browsing wildlife.