B-genome derived resistance to Leptosphaeria maculans in near isogenic Brassica napus lines is independent of glucosinolate profile

The role of the glucosinolate-myrosinase system in resistance to Leptosphae ria maculans was studied by monitoring changes in glucosinolate profiles in leaf tissue surrounding the site of inoculation. Susceptible Brassica napa s cv. Hanna, resistant B. nigra and near isogenic lines derived from inters pecific hybrids between the two species were compared. Expression of myrosi nase binding protein and presence of genetic markers were also assayed. No correlation between degree of resistance and amount of sinigrin or other al iphatic glucosinolates was found. However, in time course experiments the g lucosinolate profile of the L. maculans inoculated plants differed signific antly from the mater-inoculated control plants in the amount of 4-methoxy-g lucobrassicin observed. Five to eight days post-inoculation an increased le vel of 4-methoxy glucobrassicin, ranging from 30% to 47% on average, was fo und in the inoculated plants, whilst controls varied between 7.6% and 9.2%, This increase was seen both in susceptible and resistant material. Other c hanges observed could mainly be assigned as effects of mounding. Although i noculation with L. maculans elicited changes in the leaf indolyl glucosinol ate profiles, in the material studied, these changes could not be correlate d to resistance against the fungus.