Behavioural responses of the Colorado potato beetle to trichomes and leaf surface chemicals of Solanum tarijense

Abstract

Wild Solanum species constitute a source of resistance to several pests and diseases of potato. Several species of wild tuber-bearing potato have been identified as resistant to the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), including Solanum tarijense Hawkes (Solanaceae). Our objective was to determine the mechanism of resistance of S. tarijense to the Colorado potato beetle and, because the resistance is limited to the adult stage of the insect, to study the host selection behaviour on resistant plants. In the field, Colorado potato beetles demonstrated a unique behaviour when in contact with S. tarijense , abandoning the plant by falling to the ground after a few minutes. The abundant trichomes on the leaves of S. tarijense induced the falling behaviour. However, on S. tarijense feeding remained low even after the trichomes were mechanically removed. Observations demonstrated that the normal sequence of behaviour leading to feeding was interrupted before adult beetles fed on S. tarijense leaves. Feeding experiments using volatile and non-volatile fractions of leaf surface extracts identified a phagodeterrent effect of the volatile fraction. Our results contrast with a similar evaluation of the mode of resistance of Solanum berthaultii Hawkes, a close relative of S. tarijense , on which some feeding occurred and adults did not show falling behaviour. This study presents information on S. tarijense as a new source of resistance to the Colorado potato beetle that can be used for potato breeding.

Managing the Colorado potato beetle; the need for resistance breeding

“…Extract of leaves of S. berthaultii that were rinsed with methylene chloride and acetone deterred CBP adults from feeding ). Extracts of S. tarijense leaves also have a deterrent effect on the CPB (Pelletier and Dutheil 2006). Morphological characters may also play a role in deterring CPB feeding.…”

“…The CPB displays a unique behaviour when it comes into contact with S. tarijense leaves, which are abundantly populated by trichomes, as it abandons the plant by letting itself fall to the ground after a few minutes. However, feeding of CPB is also limited after trichome removal, suggesting that there are also other compounds in leaves or the leaf structure itself, apart from the glandular tricomes, that deter CPB feeding (Pelletier and Dutheil 2006). In S. berthaultii the presence of type A trichomes is a fundamental prerequisite for resistance to the CPB, while the presence of type B droplets containing sucrose esters increase the level of resistance in the presence of trichome type A (Neal et al 1989).…”

“…The glandular trichomes of S. berthaultii, S. tarijense, and S. neocardenasii have been linked to CPB resistance (Dimock et al 1986;Neal et al 1989;Jansky et al 1999;Pelletier et al 1999;Pelletier and Dutheil 2006). Next to potato, glandular trichome based CPB resistance has also been found in tomato (Kennedy and Sorenson 1985;Carter et al 1989).…”

Potato Resistance Against Insect Herbivores

“…S. tarijense negatively impacts the biological performance of the CPB but has a more pronounced effect on the adults Smilyanets et al 2007). Thanatosis reaction is observed in adults deposited on S. tarijense foliage; This reaction is greatly reduced when type-A trichomes are removed, but feeding remains low; The volatile fraction of methylene chloride dip extracts from S. tarijense has been shown to act as a feeding deterrent when applied to potato foliage and changes host selection behavior of adult beetles (Pelletier and Dutheil 2006). Table 1 List of wild Solanum species that were studied for their effects on the biological performance of the CPB.…”

“…allandiae Carter 1987S. berthaultii Gibson 1979Casagrande 1982;Mehlenbacher et al 1984;Wright et al 1985;Gregory et al 1986;Groden and Casagrande 1986;Carter 1987;Dimock and Tingey 1987;Castanera et al 1988;Neal et al 1989;Pelletier and Smilowitz 1990;Neal et al 1991;Steffens and Walters 1991;Flanders et al 1992;Franca and Tingey 1994;Tingey and Yencho 1994;Yencho and Tingey 1994;Yencho et al 1994;Castanera et al 1996;Smilyanets et al 1996;Sikinyi et al 1997;Pelletier et al 1999;Pelletier and Dutheil 2006;Smilyanets et al 2007 S. brevicaule Smilyanets et al 2007S. bukasovii Carter 1987Smilyanets et al 2007 S. capsicibaccatum Sikinyi et al 1997;Pelletier et al 1999;Clark 2004 S. chacoense Torka 1950;Hawkes 1958;Sinden et al 1986;Carter 1987;Sagredo et al 1988;Flanders et al 1992;Sikinyi et al 1997;Sanford et al 1998;Yencho et al 2000;Sagredo et al 2006;Smilyanets et al 2007 S. chomatophilum Pelletier et al 2007S.…”