Changes in the sulphur and glucosinolate content of developing pods and seeds of oilseed rape (Brassica napus L.) in relation to different cultivars

Since the introduction of double low oilseed rape varieties in the 1980's the complete physiological background of a lower glucosinolate content in seeds of double low varieties is still not known. Double low varieties contain virtually the same amount of sulphur in the vegetative plant parts as single lows but the seeds show much lower glucosinolate contents. There are opposing theories how these differences can be explained. It is commonly accepted that seed glucosinolates are synthesised in the pod walls. The lower glucosinolate content in double low varieties might be caused by a metabolic block in the glucosinolate biosynthesis in combination with a reduced transport of glucosinolates into the seeds. It was the aim of this investigation to elucidate this question. From 1999 to 2001 various field trials were conducted with summer and winter oilseed rape varieties under low and high sulphur supply. The glucosinolate and the total sulphur contents were determined in developing pods of single low and double low oilseed rape varieties. The accumulation pattern of glucosinolates and total sulphur in pod walls and seeds support the hypothesis of a metabolic block in the glucosinolate biosynthesis of double low oilseed rape varieties. Only intact glucosinolates can be transported into the seeds while intermediary products of the glucosinolate biosynthesis were enriched in pod walls of double low varieties where a quick degradation into sulphate may occur.