Physical and Chemical Traits of Grape Varieties Influence Drosophila suzukii Preferences and Performance

The cuticle-covered surface forms the interface between plant parts, including fruits, and their environment. The physical and chemical properties of fruit surfaces profoundly influence plant-frugivore interactions by shaping the susceptibility and suitability of the host for the attacker. Grapevine (Vitis vinifera, Vitaceae) serves as one of the various host plants of the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), which is invasive in several parts of the world and can cause major crop losses. The susceptibility of wine towards this pest species differs widely among varieties. The objective of our study was to identify physical and chemical traits of the berry surface that may explain the differences in susceptibility of five grape varieties to D. suzukii. Both preferences of adult D. suzukii and offspring performance on intact versus dewaxed (epicuticular wax layer mechanically removed) grape berries were investigated in dual-choice assays. Moreover, the morphology and chemical composition of cuticular waxes and cutin of the different varieties were analyzed. Bioassays revealed that the epicuticular wax layer of most tested grape varieties influenced the preference behavior of adult flies; even less susceptible varieties became more susceptible after removal of these waxes. In contrast, neither offspring performance nor berry skin firmness were affected by the epicuticular wax layer. The wax morphology and the composition of both epi- and intracuticular waxes differed pronouncedly, especially between more and less susceptible varieties, while cutin was dominated by ω-OH-9/10-epoxy-C18 acid and the amount was comparable among varieties within sampling time. Our results highlight the underestimated role of the epicuticular surface and cuticle integrity in grape susceptibility to D. suzukii.

Analysis of biosynthesis and composition of cuticular wax in wild type bilberry (Vaccinium myrtillus L.) and its glossy mutant

Cuticular wax plays an important role in fruits in protection against environmental stresses and desiccation. In this study, biosynthesis and chemical composition of cuticular wax in wild type (WT) bilberry fruit was studied during development and compared with its natural glossy type (GT) mutant. The cuticular wax load in GT fruit was comparable to WT fruit. In both fruits, triterpenoids were the dominant wax compounds with decreasing proportion during the fruit development accompanied with increasing proportion of aliphatic compounds. Gene expression studies supported the pattern of compound accumulation during fruit development. Genes CER26-like, FAR2, CER3-like, LTP, MIXTA, and BAS exhibited prevalent expression in fruit skin indicating role in cuticular wax biosynthesis and secretion. In GT fruit, higher proportion of triterpenoids in cuticular wax was accompanied by lower proportion of fatty acids and ketones compared to WT fruit as well as lower density of crystalloid structures on berry surface. Our results suggest that a marked reduction in ketones in cuticular wax may play a significant role in the formation of glossy phenotype leading to the loss of rod-like structures in epicuticular wax layer of GT fruit.HighlightChemical composition and morphology of cuticular wax along with gene expression for wax biosynthetic genes varied between glossy type mutant (GT) and wild type (WT) fruit.

Application of Nano-Silicon Dioxide Improves Salt Stress Tolerance in Strawberry Plants

Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were treated with salt (0, 25 or 50 mM NaCl), and the nano-silicon dioxide treatments were applied to the strawberry plants before (0, 50 and 100 mg L−1) or after (0 and 50 mg L−1) flowering. The salt stress treatments reduced plant biomass, chlorophyll content, and leaf relative water content (RWC) as expected. Relative to control (no NaCl) plants the salt treated plants had 10% lower membrane stability index (MSI), 81% greater proline content, and 54% greater cuticular transpiration; as well as increased canopy temperature and changes in the structure of the epicuticular wax layer. The plants treated with nano-silicon dioxide were better able to maintain epicuticular wax structure, chlorophyll content, and carotenoid content and accumulated less proline relative to plants treated only with salt and no nano-silicon dioxide. Analysis of scanning electron microscopic (SEM) images revealed that the salt treatments resulted in changes in epicuticular wax type and thickness, and that the application of nano-silicon dioxide suppressed the adverse effects of salinity on the epicuticular wax layer. Nano-silicon dioxide treated salt stressed plants had increased irregular (smoother) crystal wax deposits in their epicuticular layer. Together these observations indicate that application of nano-silicon dioxide can limit the adverse anatomical and biochemical changes related to salt stress impacts on strawberry plants and that this is, in part, associated with epicuticular wax deposition.

Relevance of Interactions between Starch-based Coatings and Plum Fruit Surfaces: A Physical-Chemical Analysis

In order to extend the shelf life of the fruit, improve appearance, and to keep all nutrition properties of the plum from diminishing, edible coatings comprised of wheat starch and wheat starch–whey protein isolate (in ratio 80/20) were created. Stand-alone films were produced to assess properties which helped to understand the phenomena occurring on the surface level of coated plums. The properties of coatings based on starch are similar to starch coatings containing oil because the natural epicuticular wax layer of plums merges with coating materials. Adding oil doubled the contact angle value and the dispersive component of the surface tension. The workings of adhesion and cohesion, spreading coefficient, water absorption, water content, and solubility in water of the films decreased. Similar processes were observed on the fruits’ surface. In appearance, the coating process is similar to polishing the plum surface for removing crystalline wax. The color parameters of coated fruits did not significantly change. Newly formed bonds or interactions established between starch, whey proteins, water, glycerol, and oil are displayed by Fourier transform infrared (FTIR) analysis. This work revealed how the interactions between the epicuticular wax on the fruit’s surface and the hydrocolloid-based coatings affect the efficiency of the coatings.

Ozone Treatment of Grapes During Withering for Amarone Wine: A Multimodal Imaging and Spectroscopic Analysis

The production of Amarone wine is governed by a disciplinary guideline to preserve its typical features; however, postharvest infections by the fungusBotrytis cinerea(B. cinerea) not only represent a phytosanitary problem but also cause a significant loss of product. In this study, we tested a treatment with mild ozoniztion on grapes for Amarone wine production during withering in thefruttaio(the environment imposed by the disciplinary guideline) and evaluated the impact on berry features by a multimodal imaging approach. The results indicate that short and repeated treatments with low O3concentrations speed up the naturally occurring berry withering, probably inducing a reorganization of the epicuticular wax layer, and inhibit the development ofB. cinerea,blocking the fungus in an intermediate vegetative stage. This pilot study will pave the way to long-term research on Amarone wine obtained from O3-treated grapes.

Analysis of Cuticular Lipids of the Pharaoh Ant (Monomorium pharaonis) and Their Selective Adsorption on Insecticidal Zeolite Powders

The pharaoh ant is a notorious and hard to eradicate pest, which poses a threat in hospitals, spreading pathogens and contaminating sterile equipment. When applied on ants, zeolites adsorb part of their epicuticular wax layer. The ants are then vulnerable to desiccation, since this layer regulates water exchange. We analyzed the chemical composition of this wax layer using GC-MS (Gas Chromatography-Mass Spectrometry). A hexane wash of M. pharaonis foragers resulted in the identification of 53 components, four of which were not previously defined in Monomorium species. Selective adsorption of specific compounds on zeolites assisted in the identification of compounds which could not be separated on the GC column and allowed for the identification of three additional compounds. Zeolites show different affinities for the wax compounds depending on pore structure and chemical composition. Selective adsorption of alkanes on zeolites is also investigated in the fields of refinery processes and catalysis. Pore mouth and key lock adsorption mechanisms and selectivity according to molecular weight and branching, investigated in these fields, are also involved in adsorption processes of epicuticular waxes. The insecticidal activity of a zeolite is related to adsorption selectivity rather than capacity. One of the best adsorbing zeolites showed limited insecticidal activity and can be considered as a non-lethal alternative for epicuticular wax sampling.

Cambios anatómicos en la corteza de Parkinsonia praecox (Ruiz et Pavón) Hawkins causados por la epífita Tillandsia recurvata L. (Bromeriaceae)

Tillandsia recurvata L. is commonly found growing on the branches and trunk of Parkinsonia praecox (Ruiz et Pavón) Hawkins in the semi-arid area of the Zapotitlán Salinas Valley, Mexico, and this relationship seems to affect the phorophyte in different ways. The purpose of this study was to evaluate the effect of the establishment of T. recurvata on bark tissues of the phorophyte P. praecox. The anatomical study of the bark allowed to recognize the presence of non-collapsed phloem, collapsed phloem, a cortex whose cells under the epidermis show chloroplasts and a multiple epidermis covered by a wide epicuticular wax layer. Tillandsia recurvata roots never penetrate the tissues. However, in those zones where the epiphyte occurs a wound periderm develops below the epidermis. Wound periderm provides protection against infection, but it probably also affects negatively the mobilization of carbon dioxide toward internal tissues or the dissipation of heat and light. These aspects seem to be more important than the photosynthesis decrease in branches where the epiphyte establishes. It is likely that the overweight caused by the large number of Tillandsia recurvata individuals on the branches prevents the adequate architectural development of the phorophyte Parkinsonia praecox.