Fernando Perich

Phytotoxic Iridoid Glucosides from the Roots of Verbascum thapsus

The iridoid glucosides lateroside 1, harpagoside 2, ajugol 3, and aucubin 4 were isolated from an ethanolic extract of the roots of the weed Verbascum thapsus that exhibits antigermination activity on seeds of barley (Hordeum vulgare). Bioassays indicated that at 3 mM concentration, compounds 1, 2, and 4 showed moderate inhibition of seed germination. These compounds also reduced root length when they were assayed on pregerminated seeds at 1 mM to 0.001 mM concentration range. Of all compounds tested, aucubin 4 was the most active against root elongation. Compound 3 showed no activity in the bioassays.

Volatiles Released From Vaccinium corymbosum Were Attractive to Aegorhinus superciliosus (Coleoptera: Curculionidae) in an Olfactometric Bioassay

ABSTRACT The objective of this study was to evaluate the role of host volatiles in the relationship between a blueberry plant Vaccinium corymbosum L. and the raspberry weevil Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), the principal pest of blueberry in the south of Chile. Volatiles from the aerial part of different phenological stages of the host were collected on Porapak Q and analyzed by coupled gas chromatography-mass spectrometry (GC-MS). Several chemical groups were identified including green leaf volatiles, aromatic compounds, and terpenes. The olfactometric responses of A. superciliosus toward different odor sources were studied in a four-arm olfactometer. Blueberry shoots at the phenological stages of fruit set, and blue-pink fruit color elicited the greatest behavioral responses from weevils. Five compounds (2-nonanone, eucalyptol, R- and S-limonene, and 4-ethyl benzaldehyde) elicited an attractant behavioral response from A. superciliosus. The results suggest the host location behavior of A. superciliosus could be mediated by volatiles derived from V. corymbosum. This work has identified a number of compounds with which it is possible to develop a lure for the principal pest of blueberry in southern Chile.

Evidence of Contact Pheromone Use in Mating Behavior of the Raspberry Weevil (Coleoptera: Curculionidae)

ABSTRACT Numerous studies of insect species have shown that a subset of female cuticular hydrocarbons is used as short-range or contact pheromones. Here, we studied the possible use of contact pheromones in the mating behavior of the weevil Aegorhinus superciliosus, a native species of Chile. Males mounted females only after antennal contact with the females cuticle, and only 33% of the males attempted to mate with dead females washed with solvent. When a glass rod (dummy) was coated with female cuticular extracts, males exhibited behaviors similar to those observed with females. A preliminary gas chromatography-mass spectrometry (GC-MS) analysis of cuticular extracts indicated that males and females share a series of aliphatic hydrocarbons but that the relative abundance of some of these compounds differ between the sexes. These results suggest that cuticular lipids mediate mating behavior of the raspberry weevil and provide the first evidence of contact pheromones in curculionids.

Behavioral Responses of Clover Root Borer to Long-Chain Fatty Acids from Young Red Clover (Trifolium pratense) Roots

ABSTRACT The olfactory and contact behavioral responses of clover root borer, Hylastinus obscurus (Marsham) (Coleoptera: Curculionidae), against fatty acid components present in 9-mo-old red clover, Trifolium pratense L., roots were investigated by using an automated behavioral observation system. From GC-MS analysis of dichloromethane extracts of T. pratense roots, of 15 compounds identified in total, four long-chain free fatty acids lauric, palmitic, oleic, and stearic acids were found to be main components in the extracts. In a four-arm olfactometer the clover root extract significantly attracted both male and female H. obscurus. When solutions of the four individual synthetic fatty acids and their blend at the ratio found in the root extract (10 µg/ml) were assayed with H. obscurus, lauric, palmitic, and oleic acid elicited an attractant behavioral response from females, whereas all substances tested did not elicit a response from males. In contact bioassays, wood dummies coated with root extract, the four fatty acids, or their respective blend of the same composition found in the root extract at 100 µg/ ml, were significantly preferred by female H. obscurus. In contrast, males showed preference only for dummies treated with root extract, or palmitic or oleic acid. The behavioral evidences suggest that long-chain free fatty acids present in 9-mo-old red clover roots may play a role as close-range olfactory, tactile cues, or both in the host-finding process of H. obscurus.

Stigmast-4-ene-3,6-dione an unusual phytotoxic sterone from the roots of Echium vulgare L.

Stigmast-4-ene-3,6-dione an unusual phytotoxic sterone from the roots of Echium vulgare L.

Clover root borer Hylastinus obscurus (Marsham) (Coleoptera: Scolytidae) has no preference for volatiles from root extracts of disease infected red clover

Red clover, Trifolium pratense L., is an important forage legume grown in North America and Europe. Soil-climatic conditions in southern Chile are also favourable for the establishment of red clover stands. Although red clover is considered a perennial plant, red clover stands often decline to unsatisfactory levels within two years after sowing (Cuevas & Balocchi, 1983; Leath, 1985; Steiner & Alderman, 2003). Factors that may contribute to reduced persistence of red clover include root rot severity, and root borer Hylastinus obscurus (Marsham) infestations (Graham & Newton, 1959; Carrillo & Mundaca, 1974). At present there is no control for clover root borers other than rotation (Aguilera et al., 1996). A few studies have been carried out on the chemical interrelationship between the rootrot complex of red clover with borers feeding on clover roots. Leath and Byers (1973) reported that in preference tests performed in Petri dish chambers adult borers were more attracted to water-leached materials from diseased red clover roots than to leached materials from healthy roots. Some volatile compounds identified in a hexane extract of diseased red clover roots were also found attractive to borers in Petri dish preference tests, but in field tests no individual compound or mixture was attractive to adult borers (Kamm & Buttery, 1984). As the authors in the preceding behavioural studies used still-air bioassays, the present study attempted to determine whether adult borers could discern between odours released from ethanolic extracts of healthy and disease-infected red clover roots by using a four-arm olfactometer, a more powerful statistical design (Hare, 2000) that utilizes moving air.

Electroantennographic and Behavioral Responses of Adults of Raspberry Weevil Aegorhinus superciliosus (Coleoptera: Curculionidae) to Odors Released From Conspecific Females

ABSTRACT The raspberry weevil, Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), is the most important pest in blueberry and raspberry fields in the south of Chile. In this study, we investigated the electroantennographic and behavioral responses of A. superciliosus to semiochemicals released from conspecific individual adults, with particular attention to male attraction to females. Odors released from females significantly attracted males in a Y-tube olfactometer. Gas chromatographic and mass spectral analysis of female volatile extracts revealed the presence of limonene and &agr;-pinene. Electroantennogram recordings from both sexes indicated that males of A. superciliosus possess olfactory sensitivity for the R isomer of limonene and &agr;-pinene, whereas females only perceived R-limonene. Behavioral assays using synthetic compounds showed that only R-limonene elicited an attraction response from male weevils. Field experiments confirmed the laboratory results, showing that R-limonene was attractive to weevils. This is the first report of intraspecific chemical communication in this weevil. We discuss the origin of these compounds, their possible role in the sexual behavior of this species, and their potential use in a pest control strategy.

RELATIONSHIP BETWEEN RADICAL INFESTATION OF Hylastinus obscurus (MARSHAM) AND THE YIELD OF CULTIVARS AND EXPERIMENTAL LINES OF RED CLOVER (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is a valuable forage legume grown alone or in mixture with grasses in temperate regions of the world. Red clover is adapted to a wide range of soil types, pH levels, environmental and management conditions. However, the main limitation of this species is the lack of persistence related to the high mortality of plants. In Chile the main biotic factor affecting survival of plants is the root borer Hylastinus obscurus (Marsham) (Coleoptera; Scolytidae). In 1989, a red clover (T. pratense L.) breeding program was started at Carillanca Research Center of the Institute of Agricultural Research (INIA), Chile, with the main objectives of improving the survival of plants, forage yield and persistence. In 2002 a research line to study the interaction between the root borer and the plant was started. This paper describes briefly the improvement obtained in survival of young plants after twenty years of breeding and the importance of root borer population regarding forage yield. Experiments were conducted at Carillanca Research Center under irrigated conditions, comparing under cutting the dry matter yield of new synthetic lines and Redqueli-INIA with Quinequeli- INIA. The experimental lines Syn Int IV, Syn Pre III, Syn Int V and Syn Int VI were more productive than the cultivars Redqueli-INIA and Quinequeli-INIA at the second season. The evaluation of the biological parameter allowed identifying a tolerant line, Syn Pre I, and three potential new varieties: Syn Pre III, Syn Int V and Syn Int VI. This is the first report showing an inverse relation between dry matter yield of red clover and root borer population (P≤0.05). Moreover, we report the first evidence that H. obscurus start the colonization of red clover plant of 6-month-old.