Local and systemic changes in glucosinolates in Chinese and European cultivars of oilseed rape (Brassica napus L.) after inoculation with Sclerotiniasclerotiorum (stem rot)

Four Chinese Brassica napus lines, generated through a breeding programme t o identify Sclerotinia sclerotiorum tolerant and susceptible lines, and thr ee European varieties were analysed for changes in glucosinolates (qualitat ive and quantitative), and general host reactions, after localised inoculat ion with a UK S. sclerotiorum isolate. Plants at the fifth leaf stage were either singly inoculated (third leaf) or were inoculated once (third leaf) and then challenged a second time (seventh leaf) 7 days after the first ino culation. The results showed very distinct reactions in the different lines and cultivars to the fungus, both locally and systemically. Of the European lines B. napus cv.. Bienvenu showed good resistance (small lesions and less host damage) both 3 and 7 days post-inoculation. Capricorn was the most susceptible followed by Cobra; the third leaves of these cult ivars were showing strong chlorotic and necrotic reactions by day 3 and les ions were well developed. By day 7 the third leaves of Capricorn were compl etely rotten whilst Cobra still had a little healthy tissue. Inoculation of the four Chinese lines showed that two had moderate resistan ce (014 and 020 - slightly less resistant than Bienvenu) and two were very susceptible (016 and 024 - similar reactions to Capricorn and Cobra), based on lesion size and host tissue damage. Glucosinolate induction in line 014 was good both locally and systemically, with clear local and systemic indu ction of indolylglucosinolates and 2-phenylethylglucosinolate both 3 and 7 days post-inoculation. Line 020 did not show no particular increases in glu cosinolates after inoculation either locally or systemically. In line 016 t here was a small local increase and a large systemic reduction in total glu cosinolates. Inoculation of line 024 caused no major local changes in gluco sinolates and again a big reduction in glucosinolates systemically. The dual inoculation system, with lines 014 and 016, produced comparable re sults, with line 014 showing good local and systemic induction of glucosino lates (after the first inoculation) and a further local and systemic induct ion after the second inoculation. This induction in pre-inoculated line 014 plants was associated with a reduction in lesion size of the second inocul um. Line 016 responded poorly both locally and systemically, and there were no real decrease in the lesion size of the second inoculum. It appears tha t in line 014 glucosinolate induction may be an important part of resistanc e, whereas in line 020 there are clearly other non-glucosinolate factors in volved. The poor local and systemic induction of glucosinolates in lines 01 6 and 024, and subsequent susceptibility, implies that glucosinolate induct ion may be an important marker of resistance to S. sclerotiorum in oilseed rape.