Hugo D. Chludil

Soybean resistance to stink bugs (Nezara viridula and Piezodorus guildinii) increases with exposure to solar UV‐B radiation and correlates with isoflavonoid content in pods under field conditions

Solar UV-B radiation (280-315 nm) has a significant influence on trophic relationships in natural and managed ecosystems, affecting plant-insect interactions. We explored the effects of ambient UV-B radiation on the levels of herbivory by stink bugs (Nezara viridula and Piezodorus guildinii) in field-grown soybean crops. The experiments included two levels of UV-B radiation (ambient and attenuated UV-B) and four soybean cultivars known to differ in their content of soluble leaf phenolics. Ambient UV-B radiation increased the accumulation of the isoflavonoids daidzin and genistin in the pods of all cultivars. Soybean crops grown under attenuated UV-B had higher numbers of unfilled pods and damaged seeds than crops grown under ambient UV-B radiation. Binary choice experiments with soybean branches demonstrated that stink bugs preferred branches of the attenuated UV-B treatment. We found a positive correlation between percentage of undamaged seeds and the contents of daidzin and genistin in pods. Our results suggest that constitutive and UV-B-induced isoflavonoids increase plant resistance to stink bugs under field conditions.

Changes in Lupinus albus and Lupinus angustifolius Alkaloid Profiles in Response to Mechanical Damage

The aim of this work was to evaluate chemical responses to biomass removal mimicking large herbivore action in Lupinus albus and Lupinus angustifolius aerial parts. GC and GC-MS were used to determine total alkaloid content (TAC) and alkaloid relative abundances in bitter and sweet varieties of each species. Bitter genotypes Vila vehla (Vv; 3.95 +/- 0.26 mg/g of DM) and El Harrach (EH; 3.99 +/- 0.19 mg/g of DM) showed after damage 22 and 32.8% TAC increases, respectively. Even sweet varieties, with very low alkaloid contents, Gungurru (Gu; 0.51 +/- 0.09 mg/g of DM) and Rumbo (Ru; 0.53 +/- 0.09 mg/g of DM) exhibited higher induced responses of 58.8 and 67.9%, respectively, and their final TAC values remained low, distinctly apart from those corresponding to bitter species. Moreover, minor components such as ammodendrine, reported to exhibit teratogenic potential, showed no significant changes in their relative abundances in response to biomass removal in these genotypes.

Genistin and quinolizidine alkaloid induction in L. angustifolius aerial parts in response to mechanical damage

Lupinus species are commonly used as annual forage and for grain production. They are considered alternative crops to soybean due to their adaptation to cool environments and dry soils. The present study is an analysis of the chemical changes coming from biomass removal in a sweet genotype of Lupinus angustifolius. Mechanical damage induced significant increases in antioxidant activity (12.4%), as well as in flavonoid and phenolic content (36.6% and 12.0%, respectively). This sweet lupin also exhibited a higher induced response (68.2%) in the alkaloid content after the damage. These same alkaloids were identified in the control samples and all of them, except lupanine, showed higher relative abundances in response to mechanical damage. Traces of α-isolupanine were detected in control samples and showed a 23.5-fold increase in response to biomass removal. Mechanical damage also produced a striking increase (8.6-fold) in relative abundance of genistin.

Anasterocerebroside A, a New Glucosylceramide from the Patagonian Starfish Anasterias minuta

Abstract Eight glucosylceramides (1-8) were isolated from the water-insoluble lipid fraction of a methylene chloride/methanol/water extract of the Patagonian starfish Anasterias minuta. One of the constituents was identified as a new glucosylceramide, anasterocerebroside A (1), while the known glucosylceramide 7 was isolated and characterized for the first time as a pure compound. The structures of 1 and 7 were established by spectroscopic and chemical methods.

Host selection, oviposition behaviour and leaf traits in a specialist willow sawfly on species of Salix (Salicaceae)

Plant genotype influences plant–herbivore interactions by affecting insect attraction, acceptance and development. Here we linked oviposition behaviour of the specialist willow sawfly Nematus oligospilus Förster (Hymenoptera: Tenthredinidae) with leaf traits on different Salix L. (Salicaceae) genotypes. This was done as a first step to find oviposition cues that guide females to their host plants. By means of choice and no‐choice bioassays we analysed host selection according to willow genotype and leaf surface. We also studied larval performance, adult fecundity and effect of experience on host selection. Nematus oligospilus prefers to oviposit on S. nigra. The least preferred genotype, S. viminalis, showed better larval performance and highest adult fecundity. Host preference was not modified by larval feeding experience. By means of light and scanning electron microscopy we described ovipositor and leaf micromorphology. The egg is laid inside the epidermis or between the epidermis and adjacent chlorenchyma, showing a tight association with the leaf. Leaf toughness was lowest for S. nigra and higher for S. viminalis and S. babylonica. Total nitrogen and protein content were higher on S. viminalis and S. babylonica. Total phenolics and phenolic glycosides were the highest and more diverse on S. nigra. Salicin content levels correlate with oviposition preference, suggesting the role of salicylates as oviposition stimulants. Results suggest that oviposition preference on S. nigra may be related to lower leaf toughness and ease of injection of female saw‐like ovipositor, and motivated by the presence of phenolic glycosides. Nitrogen levels may explain better larval performance and adult fecundity in S. viminalis. Thus, a balance among the different leaf traits determines the outcomes observed in this study.

Plant Secondary Metabolites: Structure–Activity Relationships in Human Health Prevention and Treatment of Common Diseases

Abstract Mankind has used plants for different purposes, such as disease prevention and treatment, among them. Ancient folk medicine has taken advantage of some of their effects against insect attack, parasitic, bacterial, viral, and fungal infections, and also of anti-inflammatory, analgesic, and/or antipyretic properties of some of their components. Moreover, bioactive natural products have been early used in agriculture to protect crops from pests and are revised nowadays to contribute in integrated pest management in order to improve agroecosystems sustainability and quality of crop-derived foodstuff directly affecting human health (nutraceuticals, toxins). Plant secondary metabolites have been the source of lead molecules in drug development because of their permanently growing diversity and their high level of specificity in biological activities, some of them being able to act in additive or synergistic ways. In combination with one another, structurally different plant-derived products may increase their efficacy and/or have a broader spectrum of activity. Current concerns about deleterious effects of synthetic chemicals used for medical purposes have encouraged a worldwide research work on natural products and derived structures potentially useful in the development of alternative treatments for most common illnesses associated with aging process. Phenolic derivatives, flavonoids, and isoflavones have been proved to play preventive roles against degenerative diseases triggered by free radical action, having potential to diminish intake of some dangerous synthetic antioxidants. It has been demonstrated for most secondary metabolite families that small changes in the basic representative structure may result in significant qualitative and quantitative changes in their biological activity. Among those families, phenolics, flavonoids, terpenoids, and nitrogen and sulfur derivatives are currently tested to prevent and/or treat a wide spectrum of human diseases. The aim of this review is the analysis of structure–activity relationships in most common plant secondary metabolite families known to contribute to human health prevention, including those involved in the treatment of neurological degenerative diseases, cancer, parasitic infections, and blood vessel diseases.

Chemical Defenses in Eucalyptus Species: A Sustainable Strategy Based on Antique Knowledge to Diminish Agrochemical Dependency

A large number of tree species from different genera have being used world over for their timber resources. Most of them produce roundwood for sawmill and commercial valuable derivatives such as those related to pulp and paper, hardboard and particleboard industries (FAO 2011b). Species within Fabaceae, Pinaceae, Myrtaceae, Cupressaceae, Araucariaceae, Meliaceae, Fagaceae, and Proteaceae families are exploited by those industries.

Insecticidal activity of young and mature leaves essential oil from Eucalyptus globulus Labill. against Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

The confused flour beetle, Tribolium confusum Jaquelin Du Val, 1868, is a common pest insect known for attacking and infesting stored flour and grain. Biodegradable and ecologically natural products such as essential oils are emerging candidates for replacement of usually applied chemical pesticides. This work reported the chemical composition and effects caused by young and mature leaves essential oils (EOs) from Eucalyptus globulus Labill. against T. confusum. For both oils, no significant differences between yields were observed, being 1,8-cineole the main common constituent. Mature leaves extracts were rich in oxygenated mono- and sesquiterpenes, whereas young leaves showed greater content of non-oxygenated compounds. Bioassay was performed using EOs and 1,8-cineole solutions at different concentrations and time intervals. Adult mortality increased according to concentration and exposure time; young leaves extracts exhibited the greater effectiveness, highest mortalities (31.67%) at the minor time (2 h). At the lowest concentrations, 1,8-cineole solutions and mature leaves EOs did not achieve 100% mortality even when the bioassay was concluded (12 h), while at major doses no insects were alive. These results suggested that young and mature EOs from E. globulus constitute an alternative natural product to the control of T. confusum, since young leaves extracts, rich in monoterpene and sesquiterpene hydrocarbons, may be potential eligible candidates considering their noticeable insecticidal effects at low applied concentrations and short times of exposure.

Bioactive Steroidal Glycosides from the Starfish Anasterias Minuta

Cytotoxic fractions obtained by purification of the ethanolic extract of Anasterias minuta contain sulfated hexasaccharide glycosides. These compounds show antifungal activity against Cladosporium cucumerinum.

Solar UV-B radiation and ethylene play a key role in modulating effective defenses against Anticarsia gemmatalis larvae in field-grown soybean

Solar UV-B radiation has been reported to enhance plant defenses against herbivore insects in many species. However, the mechanism and traits involved in the UV-B mediated increment of plant resistance are unknown in crops species, such as soybean. Here, we studied defense-related responses in undamaged and Anticarsia gemmatalis larvae-damaged leaves of two soybean cultivars grown under attenuated or full solar UV-B radiation. We determined changes in jasmonates, ethylene (ET), salicylic acid, trypsin protease inhibitor activity, flavonoids, and mRNA expression of genes related with defenses. ET emission induced by Anticarsia gemmatalis damage was synergistically increased in plants grown under solar UV-B radiation and was positively correlated with malonyl genistin concentration, trypsin proteinase inhibitor activity and expression of IFS2, and the pathogenesis protein PR2, while was negatively correlated with leaf consumption. The precursor of ET, aminocyclopropane-carboxylic acid, applied exogenously to soybean was sufficient to strongly induce leaf isoflavonoids. Our results showed that in field-grown soybean isoflavonoids were regulated by both herbivory and solar UV-B inducible ET, whereas flavonols were regulated by solar UV-B radiation only and not by herbivory or ET. Our study suggests that, although ET can modulate UV-B-mediated priming of inducible plant defenses, some plant defenses, such as isoflavonoids, are regulated by ET alone.