GLUCOSINOLATES AND DISEASE RESISTANCE IN OILSEED RAPE (BRASSICA-NAPUSSSP OLEIFERA)

The hypothesis that enhancing the level of glucosinolates in leaves of oilseed rape would increase resistance to two fungal pathogens was te sted. Thirty-three Brassica napus lines with variable leaf glucosinola te contents were assessed for susceptibility to infection by Leptospha eria maculans and Alternaria spp. under field conditions. The data cle arly showed that there was not a simple positive relation between gluc osinolate content and resistance, and that the hypothesis can be refut ed. The level of Alternaria infection of both leaves and pods was posi tively correlated with glucosinolate content, while for L. maculans th ere was no significant relationship between the two variables. It is s uggested that these pathogens have become specialists on glucosinolate -containing taxa in an analogous way to insect herbivores.