THE EFFECT OF MODIFYING THE GLUCOSINOLATE CONTENT OF LEAVES OF OILSEED RAPE (BRASSICA-NAPUS SSP OLEIFERA) ON ITS INTERACTION WITH SPECIALIST AND GENERALIST PESTS

Twenty eight Brassica napus lines were developed which had contrasting leaf glucosinolate profiles to those found in commercial oilseed rape cultivars. The lines varied both in the total amount of aliphatic glu cosinolates and in the ratio of different side chain structures. The l ines were used in field experiments to assess the manner by which gluc osinolates mediate the interactions between Brasssica and specialist p ests (Psylliodes chrysocephala and Pieris rapae) and generalist pests (pigeons and slugs). Increases in the level of glucosinolates resulted in greater damage by adult flea beetles (P. chrysocephala) and a grea ter incidence of Pieris rapae larvae, but reduced the extent of grazin g by pigeons and slugs. Decreasing the side chain length of aliphatic glucosinolates and reducing the extent of hydroxylation of butenyl glu cosinolates increased the extent of adult flea beetle feeding. The imp lications of modifying the glucosinolate content of the leaves of oils eed rape and the role of these secondary metabolites in plant/herbivor e interactions are discussed.