Towards an understanding of perceptual odour space - 

Identification of behaviourally active odorants

 

Semiochemicals convey messages between individuals of the same species (pheromones)

and between different species (kairomones). Airborne chemical signals transmit information

over a distance and mediate attraction to food sources and sex partners.

 

Sex pheromones

Female moths produce sex pheromone in specific glands. The male antennae are tuned to the compounds released by the calling females. The female signal, consisting of a handful of compounds, is species-specific and males recognize conspecific females from a distance, which greatly facilitates mate-finding in night-active insects. Female production and male response to sex pheromones are to some extent correlated.

 

Pheromones are active at minute amounts: female moths release a few nanogram per hour. The message is subtle and powerful alike, and immediately triggers a strong behavioural response.

 

We have identified the sex pheromones of several lepidopteran insects, and the tools for collection, chemical analysis, and bioassays of pheromone compounds have been established. These are now available for the current task, which is the identification of plant volatile compounds attracting insects to egglaying sites.

 

Plant volatile compounds

Plants release hundreds of compounds, different species release partly the same compounds, and the volatile emissions of neigbouring plants intermix. In addition, the volatile release from individual plants is not constant, but changes during phenological development and in response to abiotic and biotic stress.

 

How does the insect make sense of this nosiy multidimensional signal? It is entirely unclear how insects achieve coding of such a complex bouquet. Understanding this perceptual odour space is a frontier in biology.

 

Tomato and potato have been selected as model plants. Following thorough chemical analysis, we will study and compare the behavioural response of several tomato and potato insects. A first question is whether different herbivores, from different phylogenies, use different chemicals for host-finding.

 

A comparative behavioural and neurophysiological analysis of several species, using synthetic mimics and mutant tomato lines with altered volatile profiles, will lead towards an under-

standing of how insect recognize and discriminate their food plants from non-host plants.

 

Personnel

Saveer Ahmed, Paul Becher, Nimal Punyasiri, Marie Bengtsson, Peter Witzgall

 

Selected references

Bengtsson M, Bäckman A-C, Liblikas I, Ramirez MI, Borg-Karlson A-K, Ansebo L, Anderson P, Löfqvist J & Witzgall P (2001) Plant odor analysis of apple: antennal response of codling moth females to apple volatiles during phenological development. Journal of Agricultural and Food Chemistry 49, 3736-3741

 

Bengtsson M, Jaastad G, Knudsen G, Kobro S, Bäckman A-C, Pettersson E, Witzgall P (2006) Plant volatiles mediate attraction to host and non-host plant in apple fruit moth,Argyresthia conjugella. Entomol exp appl 118, 77-85

 

Tasin M, Anfora G, Ioriatti C, Carlin S, De Cristofaro A, Schmidt S, Bengtsson M, Versini G, Witzgall P (2005) Antennal and behavioral responses of grapevine moth Lobesia botrana females to volatiles from grapevine. J chem Ecol 31, 77-87

 

Tasin M, Bäckman A-C, Bengtsson M, Ioriatti C, Witzgall P (2006) Essential host plant cues in the grapevine moth. Naturwissenschaften 93, 141-144

 

Witzgall P, Bengtsson M, Rauscher S, Liblikas I, Bäckman A-C, Coracini M, Anderson P, Löfqvist J (2001) Identification of further sex pheromone synergists in the codling moth,Cydia pomonella.Entomol exp appl 101, 131-141

 

Witzgall P, Tasin M, Buser H-R, Wegner-Kiß G, Mancebón VSM, Ioriatti C, Bäckman A-C, Bengtsson M, Lehmann L, Francke W (2005) New pheromone components of the grapevine mothLobesia botrana.J chem Ecol 31, 2923-2932