Interactions between tomato volatile organic compounds and aphid behaviour

In the tritrophic system consisting of tomato, Solanum lycopersicum (L.), the aphid Macrosiphum euphorbiae (Thomas) and its natural enemy, the parasitoid Aphidius ervi (Haliday), it has been shown that the release of volatile organic compounds following aphid attack is responsible for attracting aphid parasitoids in wind tunnel experiments. The main compounds involved in these multitrophic interactions have been characterized and quantified. In this work, the possible activity of such compounds on plant direct defences against the aphid M. euphorbiae was assessed in laboratory tests. The selected compounds were applied to uninfested tomato plants, either by evaporation or contact, and performance of aphids, in terms of plant acceptance, fixing behaviour and aphid development, calculated in standard conditions. The results showed that two compounds, namely methylsalicylate and cishex3en1ol, alter aphid performance. These two compounds have been reported to be those eliciting the best response by A. ervi in terms of flight behavior (wind tunnel bioassay) and antennal stimulation (EAG bioassay)

EXPANSION: A Webserver to Explore the Functional Consequences of Protein-Coding Alternative Splice Variants in Cancer Genomics

EXPANSION (https://expansion.bioinfolab.sns.it/) is an integrated web-server to explore the functional consequences of protein-coding alternative splice (AS) variants. We combined information from Differentially Expressed (DE) protein-coding transcripts from cancer genomics, together with domain architecture, protein interaction network, and gene enrichment analysis to provide an easy-to-interpret view of the effects of protein-coding splice variants. We retrieved all the protein-coding Ensembl transcripts and mapped Interpro domains and Post-translational modifications (PTMs) on canonical sequences to identify functionally relevant splicing events. We also retrieved isoform-specific protein-protein interactions (PPIs) and binding regions from IntAct to uncover isoform-specific functions via gene-sets over-representation analysis. Through EXPANSION, users can analyse pre-calculated or user-inputted DE transcript datasets, to easily gain functional insights on any protein spliceform of interest

Dryocosmus kuriphilus (Hymenoptera cynipidae) in Sardegna

The chestnut gall wasp Dryocosmus kuriphilus was detected in Sardinia in 2007. Two years later its biological control agent, Torymus sinensis, was released and was started the monitoring of native oak gall wasp parasitoids recruited by D. kuriphilus. Five years after its introduction the exotic parasitoid T. sinensis established itself in the study sites and more than 25 morphospecies of native parasitoids emerged from D. kuriphilus galls

Effects of single or combined water deficit and aphid attack on tomato volatile organic compound (VOC) emission and plant-plant communication

Plants release a broad spectrum of volatile organic compounds (VOCs). The composition of the released VOC blend is dependent on the physiological status and, consequently, is affected by biotic and abiotic stresses. Stress-related VOCs can be perceived by different organisms, including natural enemies of herbivores and neighboring plants. Here, the responses of tomato plants (emitters) to single or combined abiotic (water stress) and biotic (aphid attack) stresses, and the effect of VOC released by emitters on neighboring unstressed plants (receivers), have been investigated. Emissions of α-pinene and methyl salicylate from plants exposed to single or combined stress, and of camphene from plants exposed to water or combined stress were significantly higher than in unstressed plants. In receivers, only the release of methyl salicylate increased when companion emitters were stressed. The expression of genes related to VOC biosynthesis and plant defense responses was unaffected or declined in water-stressed emitters, and was generally higher in receivers than in emitters. The gene coding for methyl salicylate biosynthesis was particularly active in aphid-attacked emitters and in receivers that were conditioned by the infested emitters. In addition, VOCs emitted by stressed plants induce VOC emission in unstressed receivers, and this increases attraction of parasitic wasps, which may improve protection against aphid attacks under conditions of reduced water availability

Trichoderma atroviride P1 Colonization of Tomato Plants Enhances Both Direct and Indirect Defense Barriers Against Insects

Numerous microbial root symbionts are known to induce different levels of enhanced plant protection against a variety of pathogens. However, more recent studies have demonstrated that beneficial microbes are able to induce plant systemic resistance that confers some degree of protection against insects. Here, we report how treatments with the fungal biocontrol agent Trichoderma atroviride strain P1 in tomato plants induce responses that affect pest insects with different feeding habits: the noctuid moth Spodoptera littoralis (Boisduval) and the aphid Macrosiphum euphorbiae (Thomas). We observed that the tomato plant–Trichoderma P1 interaction had a negative impact on the development of moth larvae and on aphid longevity. These effects were attributed to a plant response induced by Trichoderma that was associated with transcriptional changes of a wide array of defense-related genes. While the impact on aphids could be related to the up-regulation of genes involved in the oxidative burst reaction, which occur early in the defense reaction, the negative performance of moth larvae was associated with the enhanced expression of genes encoding for protective enzymes (i.e., Proteinase inhibitor I (PI), Threonine deaminase, Leucine aminopeptidase A1, Arginase 2, and Polyphenol oxidase) that are activated downstream in the defense cascade. In addition, Trichoderma P1 produced alterations in plant metabolic pathways leading to the production and release of volatile organic compounds (VOCs) that are involved in the attraction of the aphid parasitoid Aphidius ervi, thus reinforcing the indirect plant defense barriers. Our findings, along with the evidence available in the literature, indicate that the outcome of the tripartite interaction among plant, Trichoderma, and pests is highly specific and only a comprehensive approach, integrating both insect phenotypic changes and plant transcriptomic alterations, can allow a reliable prediction of its potential for plant protectio

Small volatile lipophilic molecules induced belowground by aphid attack elicit a defensive response in neighbouring un-infested plants

In pioneering studies on plant-aphid interactions, we have observed that Vicia faba plants infested by aphids can transmit signals via the rhizosphere that induce aboveground defence in intact, neighbouring plants. The aphid parasitoid Aphidius ervi is significantly attracted towards intact broad bean plants grown in a hydroponic solution previously harbouring Acyrtosiphon pisum-infested plants. To identify the rhizosphere signal(s) possibly mediating this belowground plant-plant communication, root exudates were collected using Solid-Phase Extraction (SPE) from 10-day old A. pisum-infested and un-infested Vicia faba plants hydroponically grown. To verify the ability of these root exudates to trigger defence mechanisms against the aphids we added them to V. fabae plants grown in hydroponic solution, and tested these plants in the wind-tunnel bioassay to assess their attractiveness towards the aphids’ parasitoids A. ervi. We identified three small volatile lipophilic molecules as plant defence elicitors: 1-octen-3-ol, sulcatone and sulcatol, in SPE extracts of A. pisum-infested broad bean plants. In wind tunnel assays, we recorded a significant increase in the attractiveness towards A. ervi of V. faba plants grown in hydroponic solution treated with these compounds, compared to plants grown in hydroponic treated with ethanol (control). Both 1-octen-3-ol and sulcatol have asymmetrically substituted carbon atoms at positions 3 and 2, respectively. Hence, we tested both their enantiomers alone or in mixture. We highlighted a synergistic effect on the level of attractiveness towards the parasitoid when testing the three compounds together in respect to the response recorded against them singly tested. These behavioural responses were supported by the characterization of headspace volatiles released by tested plants. These results shed new light on the mechanisms underlying plant-plant communication belowground and prompt the use of bio-derived semiochemicals for a sustainable protection of agricultural crops

Combination of the Systemin peptide with the beneficial fungus Trichoderma afroharzianum T22 improves plant defense responses against pests and diseases

Trichoderma spp. are among the most widely used plant beneficial fungi in agriculture. Its interaction with the plant triggers resistance responses by the activation of Induced Systemic Resistance mediated by Jasmonic acid and Ethylene and/or Systemic Acquired Resistance, which involves Salicylic acid, with the consequent control of a wide range of plant parasites. However, the benefit they can confer to plants may be reduced or nullified by environmental conditions or fungal ecological fitness. A novel approach to enhance their effectiveness in plant defense is to combine them with bioactive molecules including plant-derived compounds. Here, we show that plant treatment with Trichoderma afroharzianum (strain T22) and Systemin, a tomato peptide active in triggering plant defense, confers protection against the fungal pathogens Fusarium oxysporum, Botrytis cinerea and the insect pest Tuta absoluta. The observed defensive response was associated with an increase of Jasmonic acid and related metabolites and a decrease of Salicili acid

Prospects for plant defence activators and biocontrol in IPM - Concepts and lessons learnt so far

There is an urgent need to develop new interventions to manage pests because evolution of pesticide resistance and changes in legislation are limiting conventional control options for farmers. We investigated β-aminobutyric acid (BABA), jasmonic acid (JA) and fructose as possible plant defence activators against grey mould disease, . Botrytis cinerea, and root knot nematode, . Meloidogyne incognita. We also tested . Trichogramma achaeae parasitoid wasps and an antifeedant plant extract for biocontrol of the invasive tomato leafminer, . Tuta absoluta. BABA and JA enhanced resistance of tomato plants to . B. cinerea but neither treatment provided complete protection and the efficacy of treatment varied over time with BABA being more durable than JA. Efficacy was partly dependent on tomato cultivar, with some cultivars responding better to BABA treatment than others. Furthermore, treatment of tomato with BABA, JA and fructose led to partial suppression of . M. incognita egg mass development. Biocontrol agent, . T. achaeae, performance against . T. absoluta could be enhanced by adjusting the rearing conditions. Both attack rate and longevity were improved by rearing the parasitoids on . T. absoluta rather than on other insects. Finally, . Ajuga chamaepitys extract was shown to have significant antifeedant activity against . T. absoluta. Our findings suggest that there are potential new solutions for protection of crops but they are more complicated to deploy, more variable and require more biological knowledge than conventional pesticides. In isolation, they may not provide the same level of protection as pesticides but are likely to be more potent when deployed in combination in IPM strategies

The Association With Two Different Arbuscular Mycorrhizal Fungi Differently Affects Water Stress Tolerance in Tomato

Arbuscular mycorrhizal (AM) fungi are very widespread, forming symbiotic associations with ∼80% of land plant species, including almost all crop plants. These fungi are considered of great interest for their use as biofertilizer in low-input and organic agriculture. In addition to an improvement in plant nutrition, AM fungi have been reported to enhance plant tolerance to important abiotic and biotic environmental conditions, especially to a reduced availability of resources. These features, to be exploited and applied in the field, require a thorough identification of mechanisms involved in nutrient transfer, metabolic pathways induced by single and multiple stresses, physiological and eco-physiological mechanisms resulting in improved tolerance. However, cooperation between host plants and AM fungi is often related to the specificity of symbiotic partners, the environmental conditions and the availability of resources. In this study, the impact of two AM fungal species (Funneliformis mosseae and Rhizophagus intraradices) on the water stress tolerance of a commercial tomato cultivar (San Marzano nano) has been evaluated in pots. Biometric and eco-physiological parameters have been recorded and gene expression analyses in tomato roots have been focused on plant and fungal genes involved in inorganic phosphate (Pi) uptake and transport. R. intraradices, which resulted to be more efficient than F. mosseae to improve physiological performances, was selected to assess the role of AM symbiosis on tomato plants subjected to combined stresses (moderate water stress and aphid infestation) in controlled conditions. A positive effect on the tomato indirect defense toward aphids in terms of enhanced attraction of their natural enemies was observed, in agreement with the characterization of volatile organic compound (VOC) released. In conclusion, our results offer new insights for understanding the molecular and physiological mechanisms involved in the tolerance toward water deficit as mediated by a specific AM fungus. Moreover, they open new perspectives for the exploitation of AM symbiosis to enhance crop tolerance to abiotic and biotic stresses in a scenario of global change