Effect of cultivar and harvest date on the glucosinolate and s‐methylcysteine sulphoxide content of swedes (Brassica napus ssp rapifera)

Eighteen plants of each of four cultivars and two inbred lines of swede (Brassica napus ssp rapifera L) were harvested at monthly intervals from 25 July 1988 to 6 March 1989 and divided into leaf and bulb (swollen hypocotyl). On average, the yield per plant of bulb dry matter increased from 51 g to 277 g on 14 November and then slowly fell to 241 g, whereas that of leaf dry matter decreased from 81 g to 17 g on 9 January and then rose to 32 g. Bulb S‐methylcysteine sulphoxide concentration increased from 5.9 g kg −1 DM to over 9.4 g kg −1 from 14 November to 9 January and then fell to 7.3 g kg −1 . Leaf SMCO concentration rose from under 5 g kg −1 DM to over 27g kg −1 on 6 February and then fell to 17 g kg −1 . Bulb glucosinolate concentration was 11.2 mM kg −1 DM on 25 July, then fluctuated between 7.9 and 6.5 mM kg −1 before falling below 5.0 mM kg −1 on 6 February. Leaf glucosinolate concentration rose from under 4 mM kg −1 DM to over 37 mM kg −1 on 6 February and then fell to 28 mM kg −1 . All cultivars showed these patterns despite some statistically significant cultivar × harvest date interactions. There were large and consistent differences between cultivars in glucosinolate composition. The implications for swede breeding are discussed.