Fitness reduction of Bactrocera oleae (Rossi) due to the alteration of the endosymbiotic bacteria titer

Depending on the yearly fluctuations of the climate conditions, the olive fruit fly (Bactrocera oleae, Rossi) may cause severe damage and economic losses in the olive production due to yield reduction and degradation of products composition, quality, and properties (Pereira et al., 2004). The impact of this pest on the olive oil and olive table sector is frequently extremely detrimental and the average annual loss caused by olive fruit fly infestation is estimated to be 5% of the total world production with an estimated economic loss of 800 million US$ a year (Montiel Bueno & Jones, 2002). During the last 40 years, the control strategies of B. oleae have been based on the wide use of chemicals insecticides but since 1970, it is well known that B. oleae may potentially develop noteworthy levels of insecticides resistance (Tsakas & Krimbas, 1970; Stasinakis et al., 2001, Skouras et al., 2007) thus, traditional control strategies might lose their efficacy in the near future (Daane & Johnson 2010). Therefore, the development of noninsecticidal control strategies is essential to avoid the resistance occurrence reducing the selection pressure on the field populations (Daane & Johnson 2010). Furthermore, alternative control methods to chemical pesticides may significantly reduce the environmental impact of olive crop and guarantee a safer product for consumers (Saour & Makee, 2004). Recent studies demonstrated that the primary endosymbiotic bacterium of the olive fruit fly, “Candidatus Erwinia dacicola”, plays an essential role in the larval development in unripe olive fruits since B. oleae larvae that lack their specific endosymbiont cannot develop (Ben-Yosef et al., 2015). While some investigations on the olive fruit fly fitness advantages due to its endosymbiotic bacterium have been recently pinpointed(Estes et al., 2009; 2012; Ben-Yosef et al., 2010; 2014), little is known about the possibility of utilizing symbioticides compounds that may interfere with the “Ca. Erwinia dacicola" / Olive Fly interaction reducing the destructiveness of this widespread pest. Therefore, the identification of environmentally friendly compounds that could act as symbiosis inhibitors seems to be an interesting but poorly explored field of research that could lead to the development of new solutions/options to enhance the olive fruit fly integrated pest management. In the present study the efficacy of Copper Oxychloride and of some secondary microbial metabolites (Viridiol, Harzianic Acid, 6PP and Lipopepdides mixture)as symbioticides of B. oleae beneficial bacteria is verified. In vivo fitness tests were carried out to verify if the oral administration of these compounds lead to a fitness reduction in terms of adult mortality, females fecundity and capability of larvae to develop in unripe olive fruits. Furthermore, molecular analysis on the treated females were performed to achieve the quantification of the endosymbiotic bacterial titer in DNA samples of mid-gut and oesophageal bulb by qPCR

Description of a new species of Oligosita Walker (Chalcidoidea: Trichogrammatidae), egg parasitoid of Balclutha brevis Lindberg (Homoptera: Cicadellidae) living on Pennisetum setaceum, from Italy

A new species of Oligosita Walker (Chalcidoidea: Trichogrammatidae), O. balcluthae Viggiani et Laudonia n. sp., is described as a parasitoid of the eggs of Balclutha brevis Lindberg (Homoptera: Cicadellidae) associated with crimson fountain grass, Pennisetum setaceum (Poaceae) in Italy. Morphological features and biology of the new species are discussed and illustrated. The 28S-D2 and ITS2 regions were successfully amplified and sequenced

Symbiotic control of the olive fruit fly, Bactrocera oleae

The olive fruit fly Bactrocera oleae (Rossi) (OLF) is a major pest, which causes severe yield losses and quality decay of olive oil. The widespread use of chemical insecticides to control this pest is a major concern for the resulting environmental impact and food safety issues. Therefore, the development of sustainable control strategies is highly desirable. The primary endosymbiotic bacterium of the OLF, “Candidatus Erwinia dacicola”, is essential for successful larval development in unripe olive fruits. Then, targeting this endosymbiont with antimicrobial compounds may exert a control action against OLF. Here we evaluate the impact on OLF endosymbiont of Copper Oxychloride (CO) and the fungal metabolites Viridiol and Harzianic Acid (HA) produced by two biocontrol strains of Trichoderma spp. Laboratory bioassays were carried out on OLF wild populations to assess the effect of the oral administration of these compounds on mortality and fecundity of adult flies, and on larval development of their progeny in unripe olive fruits. Treated females were processed by qPCR to measure the endosymbiont load in the oesophageal bulb and in the midgut. Exposure to Viridiol and HA had a strong negative impact on endosymbiont load and OLF larval survival, while CO negatively affected both adults and larval stages, showing a combined toxic action and an anti-symbiotic effect, which was dose-dependent. These results provide new insights on the symbiotic control of the OLF and pave the way for developing new strategies based on the use of natural compounds with antimicrobial activity

A soil fungus confers plant resistance against a phytophagous insect by disrupting the symbiotic role of its gut microbiota

Plants generate energy flows through natural food webs, driven by competition for resources among organisms, which are part of a complex network of multitrophic interactions. Here, we demonstrate that the interaction between tomato plants and a phytophagous insect is driven by a hidden interplay between their respective microbiotas. Tomato plants colonized by the soil fungus Trichoderma afroharzianum, a beneficial microorganism widely used in agriculture as a biocontrol agent, negatively affects the development and survival of the lepidopteran pest Spodoptera littoralis by altering the larval gut microbiota and its nutritional support to the host. Indeed, experiments aimed to restore the functional microbial community in the gut allow a complete rescue. Our results shed light on a novel role played by a soil microorganism in the modulation of plant-insect interaction, setting the stage for a more comprehensive analysis of the impact that biocontrol agents may have on ecological sustainability of agricultural systems

Terellia fuscicornis Loew (Diptera: Tephritidae): biologia, fenologia, infestazioni ed alterazioni del microbiota

Terellia fuscicornis Loew è una specie infeudata su Cynara cardunculus L. (Asterales: Asteracee), coltura che sta suscitando in Italia un interesse crescente per il basso impatto per l’alimentazione di bioraffinerie e l’utilizzazione in processi di produzione ad alto valore aggiunto (bio-plastiche, biochemicals, ecc). Il tefritide sverna da larva matura all’interno del ricettacolo fiorale del cardo e riprende l’attività dall’inizio dell’estate deponendo le uova nel capolino dell’ospite, mediante l’ovipositore di sostituzione. Le larve si sviluppano all’interno del ricettacolo provocando, inizialmente la formazione di piccole galle superficiali e approfondendosi poi al suo interno. In alcuni casi, in corrispondenza delle gallerie larvali, nella parte esterna dell’organo fiorale colpito, al di sotto del calice, sono visibili dei rigonfiamenti. La larva matura costruisce un astuccio dentro il quale si impupa utilizzando residui di organi fiorali. Gli adulti fuoriescono dal capolino fiorale agli inizi dell’estate. A seconda della fase fenologica della pianta in cui avviene l’attacco, il danno può essere più o meno esteso con il ricettacolo che presenta zone necrotiche e conseguente riduzione di produzione di semi o mancata maturazione degli stessi. Prove con trappole di diversi colori hanno consentito di individuare il colore rosa (rosa-caprifoglio PANTONE 18-2120; viola erica RAL 4003) come quello maggiormente attrattivo, mentre sono risultate non attrattive le trappole chemiotropiche innescate con bicarbonato di ammonio. L’andamento delle infestazioni rilevate in Campania nel biennio 2014-2015 rivela la presenza di 2 picchi di volo corrispondenti alle fasi di fioritura e maturazione dei semi dell’ospite vegetale. Nella famiglia dei Tefritidi sono note inoltre, da più di un secolo, interazioni simbiotiche con batteri. Il complesso simbiotico è ospitato all’interno di un bulbo esofageo localizzato nel capo e le cui caratteristiche morfo-istologiche sono tipiche per la tribù dei Terellini. Nel bulbo esofageo di T. fuscicornis si è accertata la presenza di diversi batteri per i quali è in corso l’identificazione delle specie. Come i simbionti dei Terellini agiscano influenzando la fitness dei ditteri resta largamente sconosciuto. Si presentano pertanto i primi dati sugli effetti dell’utilizzo di sostanze batteriostatiche e battericide sul complesso simbiotico e sulla fitness degli adulti della mosca

Prove preliminari di alterazione del microbioma in Bactrocera oleae (Diptera: Tephritidae)

In Bactrocera oleae la presenza di endosimbionti è nota da oltre un secolo e diversi sono gli studi sulla loro funzione sul ciclo biologico della Mosca delle olive. Solo di recente è stato identificato il microrganismo “Candidatus Erwinia dacicola” come la specie maggiormente rappresentata nel microbioma di B. oleae. Il microrganismo gioca, probabilmente insieme alle altre specie che compongono il complesso endosimbiontico, un ruolo sostanziale nella nutrizione degli adulti ed è noto che alterazioni dello stesso microbioma riducono notevolmente la fitness della Mosca delle olive. Se l’influenza dell’endosimbionte sullo stadio adulto sembra essere in parte chiarita, poco si conosce del suo contributo agli adattamenti funzionali e nutrizionali degli stadi larvali. Al fine di studiare questi aspetti e di valutare la possibilità di un controllo applicato a basso impatto ambientale, sono in corso prove di alterazione quantitativa e qualitativa del microbioma di B. oleae. Allo scopo sono state saggiate, mediante somministrazione orale, sostanze di origine naturale tra le quali il 6-pentil-α-pirone, l’Acido harzianico, e Gliotossine ottenute da microrganismi fungini benefici del genere Trichoderma, Biosurfattanti prodotti da Bacillus subtilis, nonché l’Ossicloruro di Rame, scelto per la nota attività nei confronti delle batteriosi. Le sostanze sono state somministrate ad individui adulti di B. oleae di diverse età (0, 5 e 10 giorni) e per diversi periodi (7, 14 e 21 giorni). Gli individui così trattati sono stati successivamente sottoposti a dissezione. Sono stati raccolti l’intestino medio ed il bulbo gastro-esofageo, e da questi organi è stato estratto il DNA utilizzando il protocollo Chelex®100. Sono in corso amplificazioni, tramite real-time PCR, per determinare il titolo batterico dell’endosimbionte relativamente ai diversi protocolli di trattamento. In laboratorio, sono state allestite, contestualmente, prove di alterazione della fitness. Allo scopo, le mosche, di entrambi i sessi, sono state alimentate con zucchero e proteine con l’aggiunta delle sostanze a varie concentrazioni. Si illustrano i dati ottenuti espressi come numero di uova deposte e schiusura delle stesse. Le larve ottenute hanno altresì fornito indicazioni in merito alla mortalità. Il numero di uova deposte registrato nelle femmine sottoposte a trattamento rispetto al controllo si è dimostrato significativamente inferiore e le larve da esse ottenute si sono dimostrate meno vitali. Gli individui sopravvissuti sono stati seguiti fino allo sfarfallamento dei nuovi adulti. Senza alcun ulteriore trattamento, si è dunque proceduto al rilievo dei dati relativi alla loro capacità di accoppiarsi ed ovideporre

Symbiosis disruption in the olive fruit fly, Bactrocera oleae (Rossi), as a potential tool for sustainable control

International audienceBACKGROUND: The olive fruit fly Bactrocera oleae (Rossi) (OLF) is a major agricultural pest, whose control primarily relies on the use of chemical insecticides. Therefore, development of sustainable control strategies is highly desirable. The primary endo-symbiotic bacterium of OLF, 'Candidatus Erwinia dacicola', is essential for successful larval development in unripe olive fruits. Therefore, targeting this endosymbiont with antimicrobial compounds may result in OLF fitness reduction and may exert control on natural populations of OLF.RESULTS: Here, we evaluate the impact of compounds with antimicrobial activity on the OLF endosymbiont. Copper oxychlor-ide (CO) and the fungal metabolite viridiol (Vi), produced by Trichoderma spp., were used. Laboratory bioassays were carried out to assess the effect of oral administration of these compounds on OLF fitness and molecular analyses (quantitative polymer-ase chain reaction) were conducted to measure the load of OLF-associated microorganisms in treated flies. CO and Vi were both able to disrupt the symbiotic association between OLF and its symbiotic bacteria, determining a significant reduction in the endosymbiont and gut microbiota load as well as a decrease in OLF fitness. CO had a direct negative effect on OLF adults. Conversely, exposure to Vi significantly undermined larval development of the treated female's progeny but did not show any toxicity in OLF adults.CONCLUSIONS: These results provide new insights into the symbiotic control of OLF and pave the way for the development of more sustainable strategies of pest control based on the use of natural compounds with antimicrobial activity

Barcoding of parasitoid wasps (Braconidae and Chalcidoidea) associated with wild and cultivated olives in the Western Cape of South Africa

Wild and cultivated olives harbor and share a diversity of insects, some of which are considered agricultural pests, such as the olive fruit fly. The assemblage of olive-associated parasitoids and seed wasps is rich and specialized in sub-Saharan Africa, with native species possibly coevolving with their hosts. Although historical entomological surveys reported on the diversity of olive wasp species in the Western Cape Province of South Africa, no comprehensive study has been performed in the region in the molecular era. In this study, a dual approach combining morphological and DNA-based methods was used for the identification of adult specimens reared from olive fruits. Four species of Braconidae and six species of Chalcidoidea were morphologically identified, and DNA barcoding methodologies were used to investigate conspecificity among individuals, based on randomly selected representative specimens. Morphological identifications were congruent with DNA data, as NJ and ML trees correctly placed the sequences for each species either at the genus or species level, depending on the available taxa coverage, and genetic distances strongly support conspecificity. No clear evidence of cryptic diversity was found. Overall seed infestation and parasitism rates were higher in wild olives compared to cultivated olives, and highest for Eupelmus spermophilus and Utetes africanus. These results can be used for early DNA-based detection of wasp larvae in olives, and investigating the biology and ecology of these species.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

NOT ONLY SYSTEMIN: PROSYSTEMIN HARBOURS OTHER ACTIVE REGIONS ABLE TO PROTECT TOMATO PLANTS

Prosystemin is a 200-amino acid precursor expressed in Solanaceae plants which releases at the C-terminal part a peptidic hormone called Systemin in response to wounding and herbivore attack. We recently showed that Prosystemin is not only a mere scaffold of Systemin but, even when deprived of Systemin, is biologically active. These results, combined with recent discoveries that Prosystemin is an intrinsically disordered protein containing disordered regions within its sequence, prompted us to investigate the N-terminal portions of the precursor, which contribute to the greatest disorder within the sequence. To this aim, PS1-70 and PS1-120 were designed, produced, and structurally and functionally characterized. Both the fragments, which maintained their intrinsic disorder, were able to induce defense-related genes and to protect tomato plants against Botrytis cinerea and Spodoptera littoralis larvae. Intriguingly, the biological activity of each of the two N-terminal fragments and of Systemin is similar but not quite the same and does not show any toxicity on experimental non-targets considered. These regions account for different anti-stress activities conferred to tomato plants by their overexpression. The two N-terminal fragments identified in this study may represent new promising tools for sustainable crop protection

Selection of Endophytic Beauveria bassiana as a Dual Biocontrol Agent of Tomato Pathogens and Pests

Endophytic fungi (EF) can enhance both plant growth and defense barriers against pests and pathogens, contributing to the reduction of chemical pesticides and fertilizers use in agriculture. Beauveria bassiana is an entomopathogenic fungus showing endophytism in several crops, often associated with a good capacity to limit the development of pests and disease agents. However, the diversity of the protective efficacy and plant response to different strains can be remarkable and needs to be carefully assessed for the successful and predictable use of these beneficial microorganisms. This study aims to select B. bassiana strains able to colonize tomato plants as endophytes as well as to control two important disease agents, Botrytis cinerea and Alternaria alternata, and the pest aphid, Macrosiphum euphorbiae. Nine wild-type isolates and one commercial strain were screened for endophytism, then further characterized for plant-growth promotion plus inhibition of disease development and pest infestation. Four isolates proved to have a good control activity against the biotic stressors tested, but only Bb716 was also able to promote plant growth. This work provides a simple workflow for the selection of beneficial EF, paving the way towards more effective use of B. bassiana in Integrate Pest Management (IPM) of tomato