Local and systemic induced responses to cabbage root fly larvae (Delia radicum) in Brassica nigra and B. oleracea

Abstract

Feeding by belowground herbivores may induce systemic changes in shoot defence levels that affect the performance of above ground herbivores and higher trophic levels. In this paper two wild Brassica species, B. nigra and B. oleracea were experimentally infested with 10 larvae of the cabbage root fly, Delia radicum. Plant dry masses and glucosinolate levels in shoots, main roots, and fine roots were determined at 3, 7, 12 and 14 days after infestation and compared to those of control plants.The systemic response in the leaves differed between plant species. In B. nigra shoot glucosinolate levels in D. radicum infested plants steadily increased with time until they were almost twice those of controls 14 days after infestation. B. oleracea plants infested with D. radicum did not show significant changes in shoot glucosinolate levels within 14 days, which may be due to the unexpected poorer performance of D. radicum on this species.Both plant species showed a local increase in indole glucosinolates in the main roots, which are the preferred feeding site of D. radicum larvae. B. oleracea plants however showed a stronger (1.9 -4.7 times) increase in indole glucosinolate levels than B. nigra (1.5 -2.6 times). The increase in indole glucosinolates in B. nigra main roots, was counterbalanced by a significant decrease in aromatic glucosinolate levels. These differences in local responses to D. radicum feeding between the two species may have contributed to the slower growth rates of the larvae on B. oleracea. D. radicum feeding did not result in altered glucosinolate levels in the fine roots in either plant species. The differences in glucosinolate induction patterns between the summer annual B. nigra and the perennial B. oleracea are discussed in the light of their different life histories.

Herbivore induction of the glucosinolate–myrosinase defense system: major trends, biochemical bases and ecological significance

“…Furthermore, aliphatic and aromatic glucosinolates sometimes even decline after herbivory (Birch et al 1992;Gols et al 2008;Hopkins et al 1998;Koritsas et al 1989Koritsas et al , 1991Müller and Sieling 2006;van Dam and Raaijmakers 2006), a behavior almost never reported for indolic glucosinolates.…”

Metabolomic analysis of the interaction between plants and herbivores

“…An earlier study on the growth of the generalist herbivore Mamestra brassicae that fed on JA-treated B. oleracea plants revealed that M. brassicae caterpillars performed worst on shoot-induced plants, but unlike P. rapae caterpillars also perform worse on root-induced plants than on control plants (van Dam and Oomen 2008). This indicates the CoQAs could not (fully) explain the performance differences between M. brassicae feeding on differently treated plants.…”

“…Even though the increases in JA levels after herbivory may be transient (Schittko et al 2000), they may result in long-lasting chemical changes in the plant, that may last from days to weeks and even years (Agrawal et al 1999;Karban and Baldwin 1997). Moreover, many induced responses are not only localized at the damage site, but expressed in other undamaged plant parts, referred to as the systemic plant response Martin and Muller 2007;Soler et al 2005;Soler et al 2007;van Dam and Oomen 2008;van Dam and Raaijmakers 2006). As induced responses may also be present for long periods of time they may affect not only current, but also successive herbivores and herbivores feeding on plant parts that were not damaged before (Bodnaryk 1994;Broeckling et al 2005).…”

“…In this earlier study plants were treated with the aforementioned plant hormone JA, thereby mimicking the response upon attack by a chewing herbivore (Karban and Baldwin 1997). Moreover, it enables identical induction of roots and shoots, which is not possible with real herbivores (Delano-Frier et al 2004;Galletti et al 2006;Gols et al 1999;Thaler 1999;van Dam and Oomen 2008). Both root and shoot JA induction resulted in the detection of significantly elevated secondary metabolite levels in extracts prepared from the shoots.…”

“…It was observed that both Pieris species grow slower when fed on shoot induced B. oleracea plants compared to when fed on root induced or on control plants (van Dam and Oomen 2008). Moreover, when the larvae of the endoparasitoid wasp Cotesia glomerata fed on either caterpillar species, they were observed to develop more slowly on caterpillars that fed on shoot-induced plants (B.L.…”