Chemosensory and behavioural responses of the turnip sawfly, Athalia rosae, to glucosinolates and isothiocyanates

Abstract

The turnip sawfly Athalia rosae sequesters glucosinolates from its cruciferous host plants in the larval stage. Investigation of the chemosensory and behavioural responses of adult A. rosae to glucosinolates and their volatile hydrolysis products, isothiocyanates, revealed that females detect glucosinolates by contact chemoreception and isothiocyanates by antennal olfaction. In electroantennogram recordings, four isothiocyanates (allyl [2-propenyl] isothiocyanate, benzyl isothiocyanate, butyl isothiocyanate and iberverin [3-methylthiopropyl isothiocyanate]) were active at all doses presented, including the lowest (0.1 µg), whilst the threshold for detection of three others, iberin [3-methylsulphinylpropyl isothiocyanate], methyl isothiocyanate, and sulforaphane [4-methylsulphinylbutyl isothiocyanate], was higher, at between 1 and 10 µg (source concentration of volatiles). Allyl isothiocyanate attracted experienced females in a four-chambered olfactometer, whilst naïve females showed no response. Allyl isothiocyanate also attracted mature females to baited yellow water traps in field trials, although immature females were repelled at high isothiocyanate concentrations. In laboratory behavioural bioassays the glucosinolates sinigrin (allyl [2-propenyl] glucosinolate) and sinalbin (p-hydroxybenzyl glucosinolate), stimulated ovipositor probing in mature female A. rosae to an extent comparable to hot-water extracts of their host plants. These responses show that glucosinolates and isothiocyanates play an important role in host finding and host recognition in A. rosae.

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…Among cruciferous plants its preferred hosts are white mustard (S . alba) and turnip (B. rapa), but the pest can also rear on young oilseed rape (B. napus) crops (Barker et al, 2006).…”

Is flower scent influencing host plant selection of leaf-galling sawflies (Hymenoptera, Tenthredinidae) on willows?

“…However, at least in a sawfly laying eggs on cruciferous plants (Athalia rosae) the relevance of olfactory cues derived from vegetative plant parts for attraction of experienced females was shown (e.g. Barker et al 2006).…”

Multiple feeding stimulants in Sinapis alba for the oligophagous leaf beetle Phaedon cochleariae

“…Therefore, glucosinolates with variable side chains obviously affect the mustard leaf beetle differently. Specificity in host selection behaviour due to glucosinolates with varying side chains and their resulting hydrolysis products were also shown for other Brassicaceae specialists (Nielsen 1978a;Giamoustaris & Mithen 1995;Barker et al 2006;Renwick et al 2006). The velocity and the range of degradation products of glucosinolate hydrolysis by myrosinases depend on the composition of glucosinolates and activity of myrosinases and cell conditions (Bones & Rossiter 2006).…”

“…nitriles and isothiocyanates. Glucosinolates and their break-down products were shown to deter and repel generalists (Louda & Mole 1991;Renwick 2002), whereas various herbivorous insects specialised on Brassicaceae use glucosinolates as stimulants for oviposition, as for example larvae of Pieris rapae L., Pieris brassicae L. (Lepidoptera: Pieridae) (Renwick et al 1992;van Loon et al 1992) and the sawfly Athalia rosae L. (Hymenoptera: Tenthredinidae) (Barker et al 2006), or for feeding, as for example weevils (Larsen et al 1992) and various leaf beetles (Nielsen 1978a, b;Nielsen et al 1979). Larvae of the oligophagous mustard leaf beetle Phaedon cochleariae can be attracted to the hydrolysis product of 2-propenylglucosinolate (sinigrin), 2-propenylisothiocyanate (Tanton 1977).…”