Glucosinolate polymorphism in wild cabbage (Brassica oleracea) influences the structure of herbivore communities

Abstract

Natural plant populations often show substantial heritable variation in chemical structure of secondary metabolites. Despite a great deal of evidence from laboratory studies that these chemicals influence herbivore behaviour and life history, there exists little evidence for the structuring of natural herbivore communities according to plant chemical profiles. Brassica oleracea (Brassicaceae) produces aliphatic glucosinolates, which break down into toxins when leaf tissue is damaged. Structural diversity in these glucosinolates is heritable, and varies considerably at two ecological scales in the UK: both within and between populations. We surveyed herbivore attack on plants producing different glucosinolates, using 12 natural B. oleracea populations. In contrast to the results of previous studies in this system, which suffered low statistical power, we found significant differential responses of herbivore species to heritable glucosinolates, both within and between plant populations. We found significant correlations between herbivore infestation rates and the presence or absence of two heritable glucosinolates: sinigrin and progoitrin. There was variation between herbivore species in the direction of response, the ecological scale at which responses were identified, and the correlations for some herbivore species changed at different times of the year. We conclude that variation in plant secondary metabolites can structure the community of herbivores that attack them, and propose that herbivore-mediated differential selection deserves further investigation as a mechanism maintaining the observed diversity of glucosinolates in wild Brassica.

In Vitro Activity of Glucosinolates and Their Degradation Products against Brassica-Pathogenic Bacteria and Fungi

“…The biological effects of GSLs and GHPs have been known since the early 1990s, when several authors investigated their effects on the growth and development of bacteria (19,23), insects (24)(25)(26), fungi (27,28), and nematodes (29,30), and our knowledge about the deterrent or attractant effects of the main glucosinolates on different pests (generalists and specialists) and parasitoids is well documented. Other authors have tested the effects of GHPs and GSLs on soil pathogens by incorporating Brassica residues into soil or by testing their effect by using in vitro assays.…”

Host plant resistance towards the cabbage whitefly in Brassica oleracea and its wild relatives

“…However these accessions proved to be susceptible under greenhouse conditions with the exception of ''Kimmeridge'', a wild B. oleracea which was collected along the south coast of the United Kingdom (50°35 0 N, 2°03 0 E). The resistance in Kimmeridge may be explained by the elevated concentrations of sinigrin, an aliphatic glucosinolate that has been shown to be involved in defense against herbivore attack (Newton et al 2009). During a one-year survey of 12 wild cabbage populations of the coastline of Southwest UK, reduced infestation rates of cabbage whiteflies were positively correlated with increasing levels of sinigrin (Newton et al 2010).…”

Natural Enemies Drive Geographic Variation in Plant Defenses

“…Both individual glucosinolate compounds and full chemical profiles affect the susceptibility of a plant to specific herbivores (17,18); hence the aliphatic chemotype is likely under differential, qualitative selection by herbivores. In contrast, accumulation of the main indolic glucosinolates in A. thaliana is highly plastic and modulated by a large number of small-effect genetic loci, which are therefore less likely to show clear signatures of selection (19).…”