Wheat (Triticum aestivum L.) is known for its ability to produce and release allelopathic compounds, which have potential for controlling weeds and diseases. Previous reports have shown the fungitoxic effects of allelochemicals present in wheat. Thus, these compounds can be exuded by roots to protect the tissues directly affected by Gaeumannomyces graminis var. tritici (Ggt) fungus that causes wheat take-all disease. The aim of this research was to evaluate in vitro the allelopathic effect of root exudate extracts from four Chilean wheat cultivars on Ggt growth. Root exudates were released from wheat seedlings to a sterile culture medium without nutrients. Afterward, the exudates in the culture medium were separated by liquid-liquid extraction using ethyl acetate. Eight different concentrations were tested for each cultivar. The results showed that the degree to which the extracts strongly inhibit the phytopathogen growth is highly dependent on both the concentration and the cultivar. The root extract of the Domo cultivar was significantly active against Ggt (MIC=0.36 mg mL(-1)). IC50 and MIC values obtained for Dollinco and Domo root exudate extracts showed toxicity to Ggt. These findings may be considered in future studies related to the use of allelopathic potential as a selection factor in order to reduce the yield losses caused by various take-all diseases, as an alternative to chemical controls.

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.

The raspberry weevil, Aegorhinus superciliosus (Guerin) (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 alpha-pmene Electroantennogram recordings from both sexes indicated that males of A supercihosus possess olfactory sensitivity for the R isomer of limonene and a-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.

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.

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 (Guerin) (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. corymboston. 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.

In Chile, the horn fly, Hematobia irritans (L., 1758), is a major pest of grazing cattle and affects livestock production during the summer. Previous studies in Europe and the United States have shown that cattle flies, including H. irritans, are differentially attracted to individual cattle within herds and that volatile semiochemicals are responsible for this phenomenon. This study provides evidence that similar differential attractiveness occurs for the interaction between Chilean Holstein-Friesian cattle herds and local H. irritans populations. Thus, Holstein-Friesian dairy cattle, Bos taurus, which were of similar age and physiological condition, were shown to possess an uneven distribution of H. irritans. Heifers h6904 and h8104 were defined as low-carrier heifers and h5804, h2304 and h1404 as high-carrier heifers. Gas chromatography (GC) and coupled GC-mass spectrometric (GC-MS) analysis of samples collected from heifers revealed the presence of compounds previously reported as semiochemicals for cattle flies, including meta- and para-cresol, methylketones (C8-C11), and 6-methyl-5-hepten-2-one. Other compounds identified included carboxylic acids (butanoic, 3-methylbutanoic, pentanoic, and hexanoic acids), 1-hexanol, and 3-octanone. In Y-tube olfactometer studies, both m- and p-cresol attracted H. irritans at the highest doses tested (10(-6) g), as did the positive control 1-octen-3-ol. Of the other compounds tested, only 2-decanone and 2-undecanone produced a behavioral response, with significantly more flies being recorded in the control arm when the former compound was tested (at 10(-6) and 10(-8) g), and more flies being recorded in the treated arm for the latter compound (at 10(-7) g). This demonstration of behavioral activity with the identified compounds represents a first step for research into the application of semiochemicals in monitoring and control of cattle flies in Chile.

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 female's 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.

Root extracts from 1.5 and 2.5-year-old red clover (Trifolium pratense) were obtained using supercritical fluid extraction (SFE). GC-MS analysis and Kovats indices allowed identification of the volatile compounds as butyl acetate, E-2-hexenal, alpha-pinene, benzaldehyde, 6-methyl-5-hepten-2-one, limonene, acetophenone, methyl benzoate, nonanal, octanoic acid and decanal.The extracts obtained and pure synthetic samples of the identified volatile components were tested in olfactometric bioassays with the insect Hylastinus obscurus (Coleoptera: Scolytidae). The results showed that the insect was attracted to root volatiles of 1.5-year-old extracts but not to those from 2.5-year-old extracts. A 10 mu g dose of methyl benzoate and E-2-hexenal attracted the insect, whereas the same dose of limonene repelled the red clover borer. An increase in limonene content and a decrease in E-2-hexenal content were correlated with a loss of attraction to 2.5-year-old clover roots. (c) 2006 Elsevier Ltd. All rights reserved.

Root rot caused by Fusarium oxysporum is a disease that reduces red clover persistence. Agronomical management of red clover includes MCPA application, and there is no information regarding the effects of this herbicide on the disease. MCPA was evaluated for its effects on F. oxysporum root rot and red clover (Trifolium pratense) growth in a greenhouse experiment. Additionally, in vitro mycelial growth and conidial germination of F. oxysporum were studied. For shoot dry weight and crown diameter of seedlings, the interaction of herbicide and inoculum was significant at 30 d. The herbicide–inoculum treatment reduced shoot dry weight by 20% at 1X rate and by 24% at 2X rate, and crown diameter was reduced by 10% at the high rate. The MCPA treatment caused a 40% reduction of root dry weight by the end of the experiment. Application of MCPA caused fusarium root rot to increase in severity on red clover seedlings and caused phytotoxicity at the high rate. Interaction with the other growth parameters was not significant, indicating that the effects of herbicide and inoculum were independent. Conidial germination and mycelial growth in vitro were reduced by MCPA. Results suggest that red clover growth could be negatively affected by F. oxysporum after MCPA application and that root rot severity increases at high rates of MCPA.

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 clove...

Iridoids are naturally occurring oxygenated monoterpenes with wide range of pharmacological activities. Scrophulariaceae Juss. is a family of flowering plants with 74 genera and 1533 species well known as rich sources of iridoids.The aim of this review is to describe the phytochemistry and structural diversity of iridoids isolated from various genera of the family. Also, their reported activities and pharmacokinetics are highlighted to provide an overall overview of iridoids in Scrophulariaceae as a fundament for further studies on this important class of compounds.A literature survey was performed by searching for relevant information through different scientific databases as SciFinder, ScienceDirect, PubMed, Google Scholar and The World Flora Online.More than 190 scientific works of literature were consulted from 1980 to 2022. Nearly 250 compounds belonging to iridoid glycosides, seco-iridoids glycosides and non-glycosidic iridoids are reported herein from 102 species. They are isolated from polar alcoholic or aqueous alcoholic extracts of the plant. These compounds exhibit anti-inflammatory, antiprotozoal, neuroprotective, cardioprotective, antioxidant and anticancer activities. Pharmacokinetic studies reported differences in their behaviour due to structural variations. However, most of these iridoids showed low oral bioavailability.The collected data indicates that more than 70% of iridoids of the family were isolated and identified from Scrophularia, Verbascum and Buddleja genera. Moreover, glycosides of C9 iridoids are the major class representing more than 80% of the total iridoids and third of the identified compounds show activity against inflammation. Further future investigations are recommended regarding the molecular mechanism of action of iridoids, their structure activity relationship, effective doses, toxicity and clinical effects, in order to promote the use of iridoids from Scrophulariaceae as source of new therapeutic medications.

Plant growth inhibitory effects of acetophenones 1-6, tremetones 7-12, and MeOH and CH(2)Cl(2) extracts from the aerial parts of Baccharis linnearis, Baccharis magellanica, and Baccharis umbelliformis collected in Chile were assayed as growth inhibitory activity in ranges of 10-500 microM and 0.1-150 ppm, respectively. The effects on seedling growth, germination, and respiration of ryegrass, lettuce, green tomato, and red clover weedy target species were measured. In addition to the inhibitory activity on bleaching of crocin induced by alkoxyl radicals, these compounds also demonstrated scavenging properties toward 2,2-diphenyl-1-picrylhydrazyl in thin-layer chromatography autographic and spectrophotometric assays. In addition, acetophenones and tremetones also showed inhibition of H(+) uptake and oxygen uptake respiration in isolated chloroplasts and mitochondria, respectively. Our results indicate that 1, 4, 7-12, and CH(2)Cl(2) extracts interfere with the dicot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. These compounds appear to have selective effects on the radicle more than shoot growth of dicot seeds. Also, the levels of radicle inhibition obtained with some compounds on Physalis ixocarpa and Trifolium pratense are totally comparable to those of ovatifolin, a known natural growth inhibitor. This behavior might be responsible for its plant growth inhibitory properties and its possible role as an allelopathic agent.