Effect of coffee alkaloids and phenolics on egg-laying by the coffee leaf miner Leucoptera coffeella

Pereira E.J., Picanço M.C., Bacci L., Crespo A.L., Guedes R.N.

AbstractSeasonal population fluctuation of the coffee leafminer,Leucoptera coffeella(Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae), led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. Life-table data were colleted from insecticide-free plots within a 3 ha coffee plantation on the upper, medium and lower canopy. Leafminer mortality was similar among the canopy parts but varied in the two seasons studied. During the rainy season, the generational mortality averaged 94.3%, with 50.2, 33.7 and 10.4% occurring during egg, larval and pupal stages, respectively. During the dry season, total mortality was 89%, with 13.2, 61.0 and 14.8% occurring during egg, larval and pupal stages, respectively. Marginal mortality rates during the rainy season were highest for physiological disturbances, rainfall and egg inviability; but, in the dry season, they were highest for predaceous wasps, physiological disturbances and parasitoids. Egg and larval stages accounted for most of the mortality variation in the rainy season, while the combination of larval and pupal mortality better described the generational mortality in the dry season. Variation in mortality during the rainy season was primarily associated with egg inviability, rainfall and parasitoids. In contrast, predatory wasps and physiological disturbances were the main factors associated with mortality variation during the dry season. These results suggest that weather conditions, natural enemies and plant quality attributes are the main determinants of the population dynamics ofL. coffeella.

Ramiro D.A., Guerreiro-Filho O., Mazzafera P.

We examined the role of phenolic compounds, and the enzymes peroxidase and polyphenol oxidase, in the expression of resistance of coffee plants to Leucoptera coffeella (Lepidoptera: Lyonetiidae). The concentrations of total soluble phenols and chlorogenic acid (5-caffeoylquinic acid), and the activities of the oxidative enzymes peroxidase (POD) and polyphenol oxidase (PPO), were estimated in leaves of Coffea arabica, C. racemosa, and progenies of crosses between these species, which have different levels of resistance, before and after attack by this insect. The results indicate that phenols do not play a central role in resistance to the coffee leaf miner. Differences were detected between the parental species in terms of total soluble phenol concentrations and activities of the oxidative enzymes. However, resistant and susceptible hybrid plants did not differ in any of these characteristics. Significant induction of chlorogenic acid and PPO was only found in C. racemosa, the parental donator of the resistance genes against L. coffeella. High-performance liquid chromatography (HPLC) analysis also showed qualitative similarity between hybrids and the susceptible C. arabica. These results suggest that the phenolic content and activities of POD and PPO in response to the attack by the leaf miner may not be a strong evidence of their participation in direct defensive mechanisms.

Ashihara H.

Coffee beans contain two types of alkaloids, caffeine and trigonelline, as major components. This review describes the distribution and metabolism of these compounds. Caffeine is synthesised from xanthosine derived from purine nucleotides. The major biosynthetic route is xanthosine -> 7-methylxanthosine -> 7-methylxanthine -> theobromine -> caffeine. Degradation activity of caffeine in coffee plants is very low, but catabolism of theophylline is always present. Theophylline is converted to xanthine, and then enters the conventional purine degradation pathway. A recent development in caffeine research is the successful cloning of genes of N-methyltransferases and characterization of recombinant proteins of these genes. Possible biotechnological applications are discussed briefly. Trigonelline (N-methylnicotinic acid) is synthesised from nicotinic acid derived from nicotinamide adenine nucleotides. Nicotinate N-methyltransferase (trigonelline synthase) activity was detected in coffee plants, but purification of this enzyme or cloning of the genes of this N-methyltransferase has not yet been reported. The degradation activity of trigonelline in coffee plants is extremely low.

Johnson K.S.

To evaluate the prooxidant versus antioxidant properties of plant phenolics toward leaf-feeding caterpillars, quenching of the stable ABTS radical by five phenolics was measured in two physiological contexts: hemolymph and midgut fluid. Addition of tannic acid, chlorogenic acid, quercetin, or catechin to Manduca sexta (L.) gut fluid increased its total antioxidant capacity by 12−45%, with tannic acid and quercetin being the most powerful in this regard. The antioxidant contribution of the phenolics increased with longer (30−60 min) incubation time in gut fluid. Chlorogenic acid and caffeic acid exhibited the weakest antioxidant activity in gut fluid. The total antioxidant capacity of hemolymph is considerably less than that of gut fluid, and in hemolymph chlorogenic and caffeic acids sometimes acted as mild prooxidants, particularly after longer incubation periods (30−60 min), although this trend was not statistically significant. Tannic acid, catechin, and quercetin behaved as antioxidants in hemolymph. These results suggest that many phenolics have radical scavenging activity in the digestive tract, but some may have more detrimental effects after absorption into the hemolymph compartment. Keywords: Herbivore; ABTS radical; total antioxidant capacity; phenolic; tannin

Fisone G., Borgkvist A., Usiello A.

The popularity of caffeine as a psychoactive drug is due to its stimulant properties, which depend on its ability to reduce adenosine transmission in the brain. Adenosine A1 and A2A receptors are expressed in the basal ganglia, a group of structures involved in various aspects of motor control. Caffeine acts as an antagonist to both types of receptors. Increasing evidence indicates that the psychomotor stimulant effect of caffeine is generated by affecting a particular group of projection neurons located in the striatum, the main receiving area of the basal ganglia. These cells express high levels of adenosine A2A receptors, which are involved in various intracellular processes, including the expression of immediate early genes and regulation of the dopamine- and cyclic AMP-regulated 32-kDa phosphoprotein DARPP-32. The present review focuses on the effects of caffeine on striatal signal transduction and on their involvement in caffeine-mediated motor stimulation.

Guerreiro Filho O., Mazzafera P.

The role of caffeine as a chemical defense of coffee against the berry borer Hypothenemus hampei was investigated. No positive correlation was observed between resistance and caffeine content in experiments in which seeds from several coffee species presenting genetic variability for the alkaloid were exposed to adult insects. The same was observed in an experiment with coffee seeds that had their caffeine content doubled by imbibition with caffeine aqueous solutions. Other experiments showed that the attractiveness to insects was not related to the caffeine content of mature fruits. These results indicate that H. hampei has evolved an adaptation to handle the toxic effects of caffeine.

HOLLINGSWORTH R.G., ARMSTRONG J.W., CAMPBELL E.

Summary In this study, caffeine is shown to act as both a repellent and toxicant against slugs and snails. This research is the first to document the potential of caffeine as a molluscicide. A drench treatment using a 1% or 2% solution of caffeine caused 100% of slugs (Veronicella cubensis) to exit treated soil, and the majority of these slugs subsequently died from caffeine poisoning. A 2% solution of caffeine applied to the growing medium of orchids killed 95% of orchid snails, (Zonitoides arboreus), and gave better control than a liquid metaldehyde product representing the standard commercial control for this pest. Using leaf-dip bioassays, we discovered that slugs tended to avoid feeding on plant material treated with caffeine solutions 0.1%, and caffeine solutions as low as 0.01% significantly reduced overall feeding by slugs. Due to concerns about chemical residues, available molluscicides generally cannot be applied directly to food crops for control of slug and snail pests. Caffeine is a natural product which is approved as a food additive. Therefore, caffeine may prove useful for protecting food crops from slugs and snails.

Glendinning J.I.

Herbivorous insects use a variety of physiological mechanisms to cope with noxious (i.e., unpalatable and/or toxic) compounds in their food plants. Here, I review what is known about this coping process, focusing on one species of caterpillar, the tobacco hornworm (Manduca sexta). Herbivorous insects possess both preingestive (i.e., chemosensory) and postingestive response mechanisms for detecting plant secondary compounds. Stimulation of either class of detection mechanism inhibits feeding rapidly by reducing biting rate and/or bite size. This aversive response is highly adaptive during encounters with secondary plant compounds that are toxic. The insect’s dilemma is that many harmless or mildly toxic compounds also activate the aversive response. To overcome this dilemma, herbivorous insects employ at least three mechanisms for selectively deactivating their aversive response to relatively harmless secondary plant compounds: (1) the presence of carbohydrates can mask the unpalatable taste of some secondary plant compounds; (2) prolonged dietary exposure to some unpalatable secondary plant compounds can initiate long-term adaptation mechanisms in the peripheral and central gustatory system; and (3) dietary exposure to toxic compounds can induce production of P450 detoxication enzymes. Thus, herbivorous insects utilize an integrated suite of physiological mechanisms to detect potentially toxic compounds in foods, and then selectively adapt to those that do not pose a serious threat to their growth and survivorship.

Glendinning J.I., Brown H., Capoor M., Davis A., Gbedemah A., Long E.

Animals have evolved several chemosensory systems for detecting potentially dangerous foods in the environment. Activation of specific sensory cells within these chemosensory systems usually elicits an aversive behavioral response, leading to avoidance of the noxious foods. Although this aversive behavioral response can be adaptive, there are many instances in which it generates “false alarms,” causing animals to reject harmless foods. To minimize the number of false alarms, animals have evolved a variety of physiological mechanisms for selectively adapting their aversive behavioral response to harmless noxious compounds. We examined the mechanisms underlying exposure-induced adaptation to specific “bitter” compounds inManduca sextacaterpillars.M. sextaexhibits an aversive behavioral response to many plant-derived compounds that taste bitter to humans, including caffeine and aristolochic acid. This aversive behavioral response is mediated by three pairs of bitter-sensitive taste cells: one responds vigorously to aristolochic acid alone, and the other two respond vigorously to both caffeine and aristolochic acid. We found that 24 hr of exposure to a caffeinated diet desensitized all of the caffeine-responsive taste cells to caffeine but not to aristolochic acid. In addition, we found that dietary exposure to caffeine adapted the aversive behavioral response of the caterpillar to caffeine, but not to aristolochic acid. We propose that the adapted aversive response to caffeine was mediated directly by the desensitized taste cells and that the adapted aversive response did not generalize to aristolochic acid because the signaling pathway for this compound was insulated from that for caffeine.

Johnson K.S., Felton G.W.

High foliar phenolics are generally assumed to increase resistance to insect herbivores, but recent studies show that tobacco lines modified to over– and underexpress phenolics do not exhibit higher constitutive resistance to caterpillars. This is contrary to the expectation that ingestion of tobacco phenolics, particularly chlorogenic acid, should cause oxidative stress in herbivores. We investigated free radical production and antioxidant capacity of fresh crushed leaves of tobacco lines exhibiting over a sixfold difference in chlorogenic acid content to test whether high phenolic concentrations are associated with increased production of reactive oxygen species (ROS). The effects of in planta phenolic levels on feeding behavior, growth, biochemical markers of oxidative stress, and the antioxidant capacity of midgut fluid and hemolymph were assessed in tobacco budworm, Heliothis virescens. The experiments showed that high phenolic foliage was more prooxidant than low phenolic foliage, but the net balance in crushed tissue was antioxidant in comparison to buffer and the commercial antioxidant standard, Trolox. In H. virescens, the antioxidant capacity of midgut fluid was also powerful, and caterpillars fed high phenolic foliage did not exhibit the expected markers of oxidative stress in midgut tissues (altered ascorbate ratios, disulfides, or total hydroperoxides). Instead, hemolymph of larvae fed high phenolic foliage exhibited improved total Trolox equivalent antioxidant capacity (TEAC). These results suggest that the elevated foliar phenolics in some plants may have beneficial antioxidant properties for herbivorous insects, much as dietary phenolics do in mammals.

Reis Jr. R., Lima, Vilela E.F., Barros R.S.

To accomplish systematic studies with coffee leafminer, it is necessary to establish a mass rearing system under artificial conditions. It is possible to rear this species, from egg to adult, under laboratory conditions, without using coffee seedlings but detached leaves maintained in vitro. Synthetic cytokinins are routinely used for maintenance of plant cell and plant tissues in vitro. Two plant growth regulators, benzyladenin and kinetin, in concentrations 10-6 and 10-7 M were used to mantain the leaves. Green leaves collected in the field were maintained in the solution to be tested. Distilled water served as control. The experiment lasted 30 days, a period longer than the necessary for the complete development of the insect. Both artificial cytokinines indeed increased the lifetime of the coffee leaves, maintaining them green and healthy. Leaves placed in the cages for oviposition were attractive to the insect, with significant number of eggs per leaf. In most cases, eggs resulted in individuals that completed the whole developmental cycle. Tests with regulator in different concentrations with healthy leaves showed efficiency. However, we believe that hormone concentrations to be used with mined leaves should be larger, because these when maintained at 10-7 M leaves did not present a satisfactory lifetime. Therefore, tests with mined leaves with different hormone concentrations should be made to find out the ideal concentration for leaf survival. In our laboratory we are successfully using 10-6 M benzyladenin for the maintenance of mined leaves.

Filho O.G., Mazzafera P.

The larvae of Perileucoptera coffeella, a leaf miner, is one of the main pests attacking coffee plantations. Caffeine is the major alkaloid in this crop and may have a role in insect resistance. Since there is genetic variability in both resistance to the coffee leaf miner and in caffeine content among different coffee species, we investigated the role of this alkaloid as an antiherbivory compound. Coffee plants containing different levels of caffeine were exposed to oviposition of the insect, and the caffeine content and damaged leaf area were evaluated. The same procedure was carried out with interspecific hybrids between C. arabica and C. racemosa, varying in resistance against the leaf miner. In addition, plants were exposed to the insect, but one leaf of each pair was protected from oviposition with paper bags. In another experiment, leaf disks from plants with known susceptibility to attack by the leaf miner were infiltrated with 0–2% aqueous caffeine solutions and exposed to oviposition. When one leaf of a pair was protected from the insect, there was an increase in caffeine in the infested leaves, particularly in younger leaves. None of the experiments established a significant correlation between reduction of leaf damage and caffeine content of the tissue. The results indicate that P. coffeella is well adapted to coffee, and it has evolved a mechanism to tolerate the potentially toxic effects of caffeine.

Bernays E.A., Oppenheim S., Chapman R.F., Kwon H., Gould F.

Sensitivity of caterpillars of Heliothis virescens, a generalist, and H. subflexa, a specialist, to eight different plant secondary compounds was examined behaviorally. The compounds were nicotine hydrogen tartrate, hordenine, caffeine, sinigrin, linamarin, arbutin, chlorogenic acid, and salicin. All compounds deterred feeding, at least at the higher concentrations, but the generalist was less affected than the specialist. Thus the hypothesis that specialists have greater sensitivity to deterrents than generalists was supported. In most cases deterrence occurred on first encounter, indicating that the response was sensory; in some cases short-term postingestive effects also appeared to play a role. The larger quantities of deterrent-containing food ingested by H. virescens sometimes resulted in measurable postingestive effects during the second control test. This did not occur in H. subflexa, which more commonly rejected the deterrent-containing food on first contact. The contrast between the species is discussed in relation to tradeoffs involved in different diet breadths.

KONO Y., KASHINE S., YONEYAMA T., SAKAMOTO Y., MATSUI Y., SHIBATA H.

Chlorogenic acid, a dietary antioxidant, effectively inhibited the iron-induced lipid peroxidation of bovine liver microsomes in a concentration-dependent manner. In the Fenton-type reaction, chlorogenic acid inhibited the production of the hydroxyl radical by iron-EDTA or iron-ADP, while iron plus chlorogenic acid did not generate the hydroxyl radical. The formation of an iron complex with chlorogenic acid was demonstrated by UV/vis absorbance spectroscopic, ESR and 1H-NMR studies. The ferric complex with chlorogenic acid was in the ferric high-spin state near rhombicity, and had no radical scavenging activity. The results indicate that chlorogenic acid prevented the formation of the hydroxyl radical by forming a chelate with iron whose complex cannot catalyze the Fenton-type reaction.

Bi J.L., Felton G.W., Murphy J.B., Howles P.A., Dixon R.A., Lamb C.J.

The impact of phenolics on a specialist herbivore, Manduca sexta, and a generalist herbivore, Heliothis virescens, was investigated using transgenic tobacco with differential expression of phenylalanine ammonia-lyase. Foliar phenolics such as chlorogenic acid, rutin, and total flavonoids differentially accumulated in the respective transgenic tobacco lines; the amount of chlorogenic acid ranged from 201 to 2202 μg g-1 of fresh leaf, that of total flavonoids from 211 to 500 μg g-1 of fresh leaf, and that of rutin from 73 to 172 μg g-1 of fresh leaf. However, the levels of the phenolics and larval growth of M. sexta or H. virescens were not significantly correlated. Likewise, phenolic levels were not correlated with larval survival of M. sexta. These results suggest that plant phenolics are not a determining factor for host plant resistance against these insects in this system. Keywords: Phenylalanine ammonia-lyase; phenolics; host plant resistance; Manduca sexta; Heliothis virescens

Walerius A.H., Pallini A., Venzon M., Santana Júnior P.A., Costa T.L., Paes J.D., Pimentel E.D., Picanço M.C.

Coffee is considered one of the most important commercial commodities globally, and in 2020, it moved to a global market of USD 102.02 billion. However, the attack of pests in coffee production can cause significant economic losses. Leucoptera coffeella is a critical pest in coffee-producing countries, with productivity losses reaching 87%. The knowledge of the spatial distribution patterns of L. coffeella is essential to developing an efficient sampling and control plan. Moreover, it allows us to target for control specific locations/seasons where L. coffeella occurrence is at its highest density before reaching the economic injury level. Therefore, our objective in this study was to determine the spatial distribution of L. coffeella in coffee crops through geostatistical analysis. Data on the population density of L. coffeella were collected over four years on a farm with 18 center pivots located in the Brazilian Cerrado. The presence of L. coffeella was recorded in all 18 pivots during the entire time of the study (2016 to 2020). The highest densities were from July to November. These high densities of L. coffeella positively correlated with maximum air temperatures and wind speed. It was also verified to negatively correlate with minimum air temperatures and rainfall. The surrounding vegetation does not affect the pest densities. The pest hotspots appeared in different pivots and different locations inside pivots. Furthermore, L. coffeella showed an aggregated distribution pattern. For three years, the colonization started at the edge of the crop. The sampling should be performed equidistant as the pest is distributed equally in all directions. The information found in this study provides valuable information to initiate timely management and control methods in coffee crops with a high incidence of L. coffeella, thus reducing production costs and the harmful effects of pesticide use.

Simões M.H., Salles B.C., Duarte S.M., Silva M.A., Viana A.L., Moraes G.D., Figueiredo S.A., Ferreira E.B., Rodrigues M.R., Paula F.B.

Johnson T.L., Elgar M.A., Symonds M.R.

Darwin argued a role for sexual selection in the evolution of male sensory structures, including insect antennae, the strength of which will depend upon the importance of early arrival at receptive females. There is remarkable variation in the nature and degree of sexual dimorphism in moth antennae, with males of some species having spectacular, feathery antennae. Although it is widely assumed that these elaborate structures provide greater sensitivity to chemical signals (sex pheromones), the factors underlying the interspecific diversity in male antennal structure and size are poorly understood. Because male antennal morphology may be affected by several female life–history traits, including flight ability, we conducted a phylogenetic comparative analysis to test how these traits are linked, using data from 93 species of moths across 11 superfamilies. Our results reveal that elaborate antennae in males have evolved more frequently in species where females are monandrous. Further, female loss of flight ability evolved more frequently in species where males have elaborate antennae. These results suggest that elaborate antennae have evolved in response to more intense male competition, arising from female monandry, and that the evolution of elaborate antennae in males has, in turn, shaped the evolution of female flightlessness.

Santiago‐Salazar C.M., Barrera J.F., Rojas J.C., Huerta‐Palacios G., Escamilla‐Prado E.

The coffee leaf miner, Leucoptera coffeella (Guérin-Mèneville), is one of the main coffee pests (Coffea spp.) in the Neotropical region. This moth species develops exclusively on leaves of Coffea plants. In this study, we investigated the oviposition preference and performance of L. coffeella in environmentally stressed Coffea arabica L. plants. These plants were exposed to three independent treatments: (a) shade levels (0%, 50%, and 100%), (b) water availability (constant and intermittent irrigation), and (c) the application of phytohormones (salicylic acid, SA; or methyl jasmonate, MeJA). Groups of leaves from these treatments were exposed to individual L. coffeella-mated females, and the number of eggs laid per leaf and the performance in terms of the duration of the immature stages and survival of L. coffeella was recorded. Our results showed that oviposition preference was indistinct among the evaluated treatments. However, leaf miner larvae developed faster under 50% shade level, whereas survival was lower in plants under 100% shade level. Individuals reared on plants under 100% shade level showed slower larval development and smaller adult size. Constant plant irrigation decreased the L. coffeella survival. The application of MeJA delayed larval development, while the application of SA increased adult size. Our results suggest that plant environmental stress should be considered when studying the performance of specialist insect herbivores.

Burger H.F., Hylander K., Ayalew B., van Dam N.M., Mendesil E., Schedl A., Shimales T., Zewdie B., Tack A.J.

While sustainable agriculture relies on natural pest control, we lack insights into the relative importance of bottom-up and top-down factors on pest levels, especially along broad environmental and management gradients. To this aim, we focused on bottom-up and top-down control of herbivore damage in sixty sites in the centre of origin of Arabica coffee in southwestern Ethiopia, where coffee grows along a management gradient ranging from little or no management in the natural forest to commercial plantations. More specifically, we examined how canopy cover, percentage of surrounding forest and management intensity affected caffeine and chlorogenic acid concentration (bottom-up process) and attack of dummy caterpillars by ants and birds (top-down process), and how these in turn affected pest levels. Caffeine and chlorogenic acid concentrations were negatively related to canopy cover, while ant attack rate was positively related to canopy cover. Both ant and bird attack rate increased with the percentage of surrounding forest. Yet, secondary chemistry and caterpillar attack rates were unrelated to herbivory, and herbivory was only directly and positively affected by management intensity. Our study highlights that canopy cover can have contrasting effects on plant defence and predation, and that changes in bottom-up and top-down factors do – unlike often assumed – not necessarily translate into reduced pest levels. Instead, direct effects of management on pest levels may be more important than bottom-up or top-down mediated effects.

Zhang G., Xu P., Wang Y., Cao S., Qi X., Ren X., Niu C.

The adaptation of phytophagous insects to host defense is an important aspect of plant–insect interactions. The reciprocal adaptability between specialist insects and their hosts have been adequately explored; however, the mechanisms underlying the adaptation of tephritid fruit fly specialists, a group of notorious pests worldwide, to unripen host fruits remain elusive. Here, plant metabolomes and insect transcriptomes were analyzed for the first time to explore the interaction between unripe citrus fruits and the Chinese citrus fly Bactrocera minax. Eighteen citrus secondary metabolites, mainly flavones, alkaloids and phenylpropanoids, were identified in the unripe citrus fruit metabolome, and they accumulated during larval feeding. Three detoxification genes (1 P450 gene, 2 ABCs genes) were highly expressed in B. minax larvae collected from unripe citrus fruits compared with the ones fed on artificial diets and ripe citrus fruits. Based on omics data, a novel ABC gene was screened through plant allelopathy tests, and the gene was significantly upregulated in B. minax larvae treated with defensive secondary metabolites (N-Methylcytisine, tryptamine, coixol, limonin, nomilin and quercetin), respectively; additionally, the mortality rate of the larvae reached 51% after silencing the ABC gene by RNAi technique. Overall, these results shed light on the mechanisms underlying the biological interactions between tephritid fruit fly specialists and host fruits.

Monteiro Â., Colomban S., Azinheira H.G., Guerra-Guimarães L., Do Céu Silva M., Navarini L., Resmini M.

Natural polyphenols are important dietary antioxidants that significantly benefit human health. Coffee and tea have been shown to largely contribute to the dietary intake of these antioxidants in several populations. More recently, the use of coffee leaves to produce tea has become a potential commercial target, therefore prompting studies on the quantification of polyphenols in coffee leaves. In this study a variety of coffee leaf species, at different development stages, were analyzed using ultra-high pressure liquid chromatography. The results demonstrate that both the botanical origin of the samples and their maturity influence significantly the concentration of the antioxidants; for total chlorogenic acids a two-fold difference was found between different species and up to a three-fold variation was observed between young and mature leaves. Furthermore, the range of concentrations of chlorogenic acids in young leaves (35.7–80.8 mg/g of dry matter) were found to be comparable to the one reported for green coffee beans. The results provide important data from which potential new commercial products can be developed.

Campbell L.G., Blanchette C.M., Small E.

Addictive “social drugs” that are derived from plants range from reputable stimulants (e.g., coffee and tea) to stigmatized and dangerous preparations (e.g., ephedrine and cocaine). Both legal and illicit global trade has increased the geographic distribution of plants from which the principal social drugs are obtained. In turn, this range expansion increased opportunities to transfer genes controlling production of high levels of secondary chemicals because of increases in overlapping geographic distributions with sexually compatible domesticated, wild, and weedy relatives. We review the literature for evidence that the introduction of these chemicals into ecosystems could occur through gene flow in ten common, addictive, social drug crops: coca, coffee, cola, ephedra, khat, marijuana, opium poppy, tea, tobacco and yerbe maté. From the published literature of the potential evolutionary and environmental consequences of gene flow from popular social drug crops, we also analyse the subsequent unintended ecological or evolutionary consequences, such as increased weediness, loss of genetic diversity in sexually compatible wild relatives, or health and fitness consequences for herbivores of these crops. Given the rapid industrialization of many of these crops, we identify knowledge gaps and call for renewed attention to the study of their ecology and evolution.

da Silva R.S., Soares J.R., Barbosa dos Santos I., Pimentel M.F., Farias E.D., Martins J.C., Zambolim L., Picanço M.C.

Oligonychus ilicis (McGregor) (Acari: Tetranychidae), is one of the most important mite pests found in coffee plants. One way to reduce intensive pest attacks is management via resistant plants. The purpose of this study was to evaluate the resistance of 14 C. canephora genotypes to O. ilicis by antixenosis and antibiosis mechanisms and to determine the preimaginal conditioning effect on resistant genotypes using O. ilicis reared on C. canephora. Resistance by antixenosis was not found; however, nine genotypes showed resistance to O. ilicis via an antibiosis mechanism. Two of these resistant genotypes showed a more persistent resistance than the O. ilicis reared on C. canephora, which indicated that a previous host can affect the selection of a genotype by O. ilicis. The study may provide a model to evaluate the preimaginal conditioning effect on plant resistance, which can be useful for plant breeders.

Egonyu J.P., Torto B.

Xylosandrus compactus is a polyphagus pest that cultivates a symbiotic fungus Fusarium solani in tunnels of host plants for food and is a major threat to coffee production in East Africa. We hypothesized that the female X. compactus, which is the only sex capable of flying to attack its hosts, is attracted to volatiles from F. solani. We investigated responses of females to volatiles released by fungal cultures and bioactive components identified in the fungal volatiles. In Y-tube olfactometer assays, ~68% of females were attracted to volatiles emitted from F. solani over clean air. Bioactive compounds were identified in the fungal volatiles by coupled gas chromatography (GC)/electroantennographic detection (EAD) and GC/mass spectrometric analyses as methyl isovalerate and 2,3-butanediol. We also identified ethanol, a known attractant of X. compactus, using solid phase microextraction captured fungal volatiles analyzed by GC/MS. In field trapping trials, we compared captures of females in plastic bottle traps baited with a range of doses of methyl isovalerate, 2,3-butanediol, and blends of the two compounds, with similar traps baited with solvent only and ethanol. Females were caught by all the baited traps at all the concentrations tested except traps baited with solvent only. Trap captures were however 14–37-fold lower in traps baited with single components and the blends than those baited with ethanol. The possible use of these components as a tool for kairomonal monitoring of populations of X. compactus is discussed.

Feng B., Qian K., Du Y.

Hervé M.R., Delourme R., Leclair M., Marnet N., Cortesero A.M.

Oviposition of phytophagous insects is determined either by adaptive behaviours allowing evaluation and response to host plant quality and/or by nutritional constraints occurring during oogenesis. Besides differences found among host plant species, plant intraspecific diversity can also affect insect oviposition. However, to date few studies have extensively investigated the factors accounting for the effect of this intraspecific variation. We addressed this question using oilseed rape (Brassica napus) and the pollen beetle (Meligethes aeneus), a phytophagous insect that uses the same plants and plant organs both for feeding and laying eggs. Our objectives were to test for a genotypic effect of oilseed rape on pollen beetle oviposition and identify the origin of the possible intergenotypic differences. We tested three hypotheses: oviposition is directly linked to (1) the amount of food eaten; (2) the nutritional quality of the food eaten; (3) a preference of females for certain plant genotypes. Results showed intergenotypic differences in both the number and the size of eggs laid. The factor that best accounted for most of these differences was the amount of food eaten. Nutritional quality of the pollen was of minor importance and females exhibited no preference among genotypes. These results reveal the importance of adult feeding on subsequent oviposition in phytophagous insects, an often neglected factor which partly determines the amount of energy available for oogenesis. Taking into account this factor may be of crucial importance in studies conducted on synovogenic insect species feeding on the same plant on which they lay eggs.

Gonthier D.J., Dominguez G.M., Witter J.D., Spongberg A.L., Philpott S.M.

Nutrient availability and soil quality influence herbivores through changes in plant traits and can have cascading effects on herbivore interactions. In complex systems, with many positive and negative interactions, the consequences of these bottom-up effects are still not well established. We carried out a set of studies to determine the impact of soil quality (organic compost amendments) on a hemipteran herbivore (Coccus viridis), two ant mutualists, predators, pathogens, parasitoids of C. viridis, and an arboreal arthropod community on coffee (Coffea arabica). We also determined the impact of Azteca instabilis ants on the arthropod community with an exclusion experiment. In an observational study, the carbon to nitrogen ratio (C:N) of leaf tissue correlated negatively with C. viridis density, however caffeine content did not correlate with C. viridis. In a field experiment with coffee seedlings, both C. viridis and total arthropod abundance were greater on high-quality plants than on low-quality plants. Excluding A. instabilis resulted in higher C. viridis abundance and parasitism rate, and higher spider and total arthropod abundance. Although A. instabilis attendance of C. viridis only marginally differed across soil quality treatments, in a second experiment, Pheidole synanthropica ants recruited more workers per C. viridis individual on highrelative to low-quality plants. Soil quality treatments did not impact predator abundance or fungal pathogen prevalence. These results suggest soil quality impacts C. viridis herbivores, P. synanthropica ants, and total abundance of arthropods on coffee, but did not impact the third trophic level. Thus this study provides a complex case study of pathways in which bottom-up effects influence arthropod interaction webs. © 2013 Gonthier et al.

Miyashira C.H., Tanigushi D.G., Gugliotta A.M., Santos D.Y.

Leaf-cutting ants collect plant fresh material for the cultivation of their mutualistic fungus. Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) cause great economic losses through their foraging activity, mainly in agriculture. The main control method is the application of granulated toxic baits incorporated with an active ingredient (AI). The present goal is to evaluate the effect of caffeine on in vitro growth of the mutualistic fungus and on the survival of the leaf-cutting ants, aiming to verify the potential toxicity of this secondary metabolite over these organisms.Three distinct patterns of fungal growth correlated with caffeine concentration were observed: (1) no effect (0.01% caffeine); (2) intermediate growth reduction (0.05% caffeine); (3) drastic growth reduction (0.10 and 0.50% caffeine). The highest caffeine concentration causes fungus death in the first week. As for insect survival, caffeine does not seem to exert any effect. The treatments with diet containing caffeine showed similar values of M50, irrespective of caffeine concentration.As caffeine was shown to reduce growth of the mutualistic fungus of Atta sexdens rubropilosa, but with no conclusive effect on insect survival, a hypothetical explanation for the selection of different Coffea species by this leaf-cutting ant species might be associated with caffeine toxicity to the fungus.

Gonthier D.J., Witter J.D., Spongberg A.L., Philpott S.M.

Nitrogen (N) based secondary metabolite production is thought to be costly to plants because N is required for growth, as well as, the synthesis of these compounds. Therefore, variation in N availability may result in variation in N-based secondary metabolite production. Here, we determine the effect of N fertilization on caffeine (N-based alkaloid) production in coffee (Coffea arabica) seedlings. A growth chamber experiment was performed with three N treatments applied to seedlings. N fertilization increased plant growth, leaf biomass, and plant N. Caffeine concentration in phloem exudates was greater in high-N fertilized plants relative to intermediate- and low-N plants. However, leaf, stem, root, and total overall caffeine concentration and content did not differ across N treatments. These results suggest caffeine in coffee is strongly regulated by genetic factors, and environment is likely less important to caffeine phenotype. This is among the first studies to investigate the effect of N fertilization on caffeine within the phloem, which has important implications for herbivores that are sensitive to caffeine and plant N and feed from the phloem of coffee.