The effect of modifying the glucosinolate content of leaves of oilseed rape (Brassica napus ssp. oleifera) on its interaction with specialist and generalist pests

Abstract

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 glucosinolates and in the ratio of different side chain structures. The lines were used in field experiments to assess the manner by which glucosinolates mediate the interactions between Brasssica and specialist pests (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 greater incidence of Pieris rapae larvae, but reduced the extent of grazing by pigeons and slugs. Decreasing the side chain length of aliphatic glucosinolates and reducing the extent of hydroxylation of butenyl glucosinolates increased the extent of adult flea beetle feeding. The implications of modifying the glucosinolate content of the leaves of oilseed rape and the role of these secondary metabolites in plant/herbivore interactions are discussed.

Glucosinolates and disease resistance in oilseed rape (Brassica napus ssp. oleifera)

“…The results of this paper and those of Giamoustaris & Mithen (1995) have provided preliminary data on the potential effects of modifying leaf glucosinolate content of oilseed rape on several pest/pathogen interactions. Some of these interactions will result in glucosinolate induction (Doughty et al, 1991), the extent and importance of which remains to be fully evaluated, particularly in field experiments, and several of the pests and pathogens will also interact with each other.…”

“…The NK lines described by Giamoustaris & Mithen (1995) with very low levels of leaf glucosinolates were originally selected as being resistant to Alternaria in laboratory screening tests (Mary MacDonald, PBI Cambridge, personal communication, 1992;MacDonald & Ingram, 1986). Subsequent field tests in unprotected disease nurseries were not successful because the lines were highly palatable to pigeons and hares due to their lack of glucosinolates (Mithen, 1992;Giamoustaris & Mithen, 1995).…”

“…Details of the development of all the lines are described by Giamoustaris (1995). The glucosinolate content of the lines and cultivars was described in detail by Giamoustaris & Mithen (1995).…”

“…The range of glucosinolate concentrations exhibited by the experimental lines was previously shown to have significant effects on Brassica-herbivore interactions (Giamoustaris & Mithen, 1995).…”

Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?

“…Insect pests are directly targeted by plant toxic secondary compounds (Giamoustaris & Mithen 1995;van Dam et al 2000;Rausher 2001;van Dam 2009) and they have evolved various strategies to circumvent plant defense mechanisms (Futuyma 1983;Nitao 1989;Berenbaum & Zangerl 1992;Evans et al 2000;Ode et al 2004;Zhu-Salzman & Zeng 2008). Because of the intimate trophic interactions between immature parasitoids and their hosts, plant chemistry also indirectly affects the fitness of parasitoids (Bottrell et al 1998;Turlings & Benrey 1998).…”