Leonardo Parra

Variation in highbush blueberry floral volatile profiles as a function of pollination status, cultivar, time of day and flower part: implications for flower visitation by bees

BACKGROUND AND AIMS Studies of the effects of pollination on floral scent and bee visitation remain rare, particularly in agricultural crops. To fill this gap, the hypothesis that bee visitation to flowers decreases after pollination through reduced floral volatile emissions in highbush blueberries, Vaccinium corymbosum, was tested. Other sources of variation in floral emissions and the role of floral volatiles in bee attraction were also examined. METHODS Pollinator visitation to blueberry flowers was manipulated by bagging all flowers within a bush (pollinator excluded) or leaving them unbagged (open pollinated), and then the effect on floral volatile emissions and future bee visitation were measured. Floral volatiles were also measured from different blueberry cultivars, times of the day and flower parts, and a study was conducted to test the attraction of bees to floral volatiles. KEY RESULTS Open-pollinated blueberry flowers had 32 % lower volatile emissions than pollinator-excluded flowers. In particular, cinnamyl alcohol, a major component of the floral blend that is emitted exclusively from petals, was emitted in lower quantities from open-pollinated flowers. Although, no differences in cinnamyl alcohol emissions were detected among three blueberry cultivars or at different times of day, some components of the blueberry floral blend were emitted in higher amounts from certain cultivars and at mid-day. Field observations showed that more bees visited bushes with pollinator-excluded flowers. Also, more honey bees were caught in traps baited with a synthetic blueberry floral blend than in unbaited traps. CONCLUSIONS Greater volatile emissions may help guide bees to unpollinated flowers, and thus increase plant fitness and bee energetic return when foraging in blueberries. Furthermore, the variation in volatile emissions from blueberry flowers depending on pollination status, plant cultivar and time of day suggests an adaptive role of floral signals in increasing pollination of flowers.

Carbendazim dissipation in the biomixture of on-farm biopurification systems and its effect on microbial communities.

The impact of repeated carbendazim (CARB) applications on the extent of CARB dissipation, the microbial diversity, the community level physiological profile (CLPP), and the enzymatic activity within the biomixture of an on-farm biopurification system was evaluated. After three successive CARB applications, the CARB dissipation efficiency was high; the efficiency of dissipation was 87%, 94% and 96% after each application, respectively. Although microbial enzymatic activity was affected significantly by CARB application, it could recover after each CARB pulse. Likewise, the numbers of cultivable bacteria, fungi and actinomycetes (as measured in CFUs) were slightly affected by the addition of CARB, but the inhibitory effect of the pesticide application was temporary. Denaturing gradient gel electrophoresis (DGGE) and Biolog Ecoplate assays demonstrated that the microbial populations remained relatively stable over time when compared to the control. The results obtained herein therefore demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.

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.

Fungal volatiles: an environmentally friendly tool to control pathogenic microorganisms in plants

Abstract Fungi are an extraordinary and immensely diverse group of microorganisms that colonize many habitats even competing with other microorganisms. Fungi have received recognition for interesting metabolic activities that have an enormous variety of biotechnological applications. Previously, volatile organic compounds produced by fungi (FVOCs) have been demonstrated to have a great capacity for use as antagonist products against plant pathogens. However, in recent years, FVOCs have been received attention as potential alternatives to the use of traditional pesticides and, therefore, as important eco-friendly biotechnological tools to control plant pathogens. Therefore, highlighting the current state of knowledge of these fascinating FVOCs, the actual detection techniques and the bioactivity against plant pathogens is essential to the discovery of new products that can be used as biopesticides.

Combined microbiological test to assess changes in an organic matrix used to avoid agricultural soil contamination, exposed to an insecticide

Combined microbiological and molecular test (BiologEcoplate TM , denaturing gradient gel electrophoresis (DGGE) and Real Time PCR (qPCR)) were carried out to evaluate the impact of repeated diazinon (DZN) applications at high concentration (40 mg kg -1 ) on microbial communities in a microcosm simulating the organic matrix (straw (50%): peat (25%): soil (25%) vv -1 ) of a pesticide biopurification system (PBS). Pesticide dissipation was also evaluated. After three successive exposures with DZN the dissipation efficiency was high; DZN dissipation clearly accelerated in the organic matrix, achieving 87%, 93% and 96% respectively after the three applications. The results obtained with BiologEcoplate TM showed that the physiological profiles of

Domestication in Murtilla (Ugni molinae) Reduced Defensive Flavonol Levels but Increased Resistance Against a Native Herbivorous Insect

ABSTRACT Plant domestication can have negative consequences for defensive traits against herbivores, potentially reducing the levels of chemical defenses in plants and consequently their resistance against herbivores.We characterized and quantified the defensive flavonols frommultiple cultivated ecotypes with wild ancestors of murtilla, Ugni molinae Turcz, an endemic plant from Chile, at different times of the year, and examined their effects on a native insect herbivore, Chilesia rudis Butler (Lepidoptera: Arctiidae). We hypothesized that domestication results in a decrease in flavonol levels in U. molinae plants, and that this negatively affected C. rudis performance and preference. Ethanolic extracts were made from leaves, stems, and fruit of murtilla plants for flavonol analysis. Flavonols identified were kaempferol, quercetin, rutin, and quercetin 3-D-&bgr;-glucoside, the last two being themost abundant.More interestingly, we showed differences in flavonol composition between wild and cultivated U. molinae that persisted for most of the year. Relative amounts of all four flavonols were higher in wild U. molinae leaves; however, no differences were found in the stem and fruit between wild and cultivated plants. In choice and no-choice assays, C. rudis larvae gained more mass on, and consumed more leaf material of, wild as compared with cultivated U. molinae plants.Moreover, when applied to leaves, larvae ate more leaf material with increasing concentrations of each flavonol compound. Our study demonstrates that domestication in U. molinae reduced the amount of flavonols in leaves as well as the performance and preference of C. rudis, indicating that these compounds stimulate feeding of C. rudis.

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.

Morphology and Distribution of Sensilla on the Antennae of Hylamorpha elegans Burmeister (Coleoptera: Scarabaeidae)

Considering that sensilla constitute important functional elements of sensory systems in insects, the aim of this study was to determine the type and distribution of sensilla in the antennae of Hylamorpha elegans Burmeister examined by scanning electron microscopy. Hylamorpha elegans antennae are lamellate and consist of the scape, pedicel, and flagellum. The antennal club of this beetle consists of three terminal plates: proximal, middle, and distal lamellae. Four types of sensilla were observed in the lamellae from both sexes: sensilla trichoidea, chaetica, coeloconica, and placodea. Antennal length was larger in males than in females, and significant sexual variation in the number of sensilla placodea and sensilla coeloconica was observed.