Sustainable Production of Bioactive Compounds From Persea indica

In this work we have investigated the accumulation of ryanoids in different plant parts (leaves, stems roots) of aeroponically grown Persea indica cloned trees (one year old cloned individuals) and a selected mature wild tree. We have tested the insect antifeedant (against Spodoptera littoralis, Myzus persicae and Rhopalosiphum padi) and nematicidal (against Meloidogyne javanica) effects of ethanolic extracts from these different plant parts. The HPLC-MS analysis of P. indica extracts showed that the mature tree (wild) leaves had 2 times more chemical diversity than the stems. The aeroponic plants showed lower differences in chemical diversity between leaves and stems, with the lowest diversity found in the roots. The ryanodane epiryanodol (1) was present in all the plant parts, with the mature stems (wild) having the highest amount. The aeroponic stems also accumulated ryanoids including 1, cinnzeylanol 2 and cinnzeylanone 4. The insect Spodoptera littoralis was strongly affected by the stem extracts while the leaf ones were moderately active. Based on the predicted vs. the real antifeedant values we conclude that the ryanoid content (1 or a combination of 2, 4 and 1) explained the antifeedant effects of the stem extracts while addition-al components contributed to the activity of the leaf ones. Therefore, careful individual selection of P. indica seedlings should be carried out prior to proceed with its aeroponic cultivation in or-der to obtain ryanodane-rich stem or leaf extracts with strong antifeedant effects on S. littoralis.

Epichloë Fungal Endophytes Influence Seed-Associated Bacterial Communities

Seeds commonly harbour diverse bacterial communities that can enhance the fitness of future plants. The bacterial microbiota associated with mother plant’s foliar tissues is one of the main sources of bacteria for seeds. Therefore, any ecological factor influencing the mother plant’s microbiota may also affect the diversity of the seed’s bacterial community. Grasses form associations with beneficial vertically transmitted fungal endophytes of genus Epichloë. The interaction of plants with Epichloë endophytes and insect herbivores can influence the plant foliar microbiota. However, it is unknown whether these interactions (alone or in concert) can affect the assembly of bacterial communities in the produced seed. We subjected Lolium multiflorum plants with and without its common endophyte Epichloë occultans (E+, E-, respectively) to an herbivory treatment with Rhopalosiphum padi aphids and assessed the diversity and composition of the bacterial communities in the produced seed. The presence of Epichloë endophytes influenced the seed bacterial microbiota by increasing the diversity and affecting the composition of the communities. The relative abundances of the bacterial taxa were more similarly distributed in communities associated with E+ than E- seeds with the latter being dominated by just a few bacterial groups. Contrary to our expectations, seed bacterial communities were not affected by the aphid herbivory experienced by mother plants. We speculate that the enhanced seed/seedling performance documented for Epichloë-host associations may be explained, at least in part, by the Epichloë-mediated increment in the seed-bacterial diversity, and that this phenomenon may be applicable to other plant-endophyte associations.

Field-Evolved Sulfoxaflor Resistance of Three Wheat Aphid Species in China

Sulfoxaflor belongs to a new class of insecticides which are effective against many sap-feeding pests. Sitobion miscanthi, Rhopalosiphum padi, and Metopolophium dirhodum are the predominant pests coexisting on wheat plants. It is unknown whether these aphid species have developed resistance to sulfoxaflor. Here, the susceptibilities of three wheat aphid species from different regions of China to sulfoxaflor were evaluated. The results showed that two S. miscanthi, one R. padi, and two M. dirhodum field populations were highly resistant to sulfoxaflor. Additionally, 13 S. miscanthi, 9 R. padi, and 4 M. dirhodum field populations were moderately resistant to sulfoxaflor. Analysis of differences in toxicity showed that the susceptibility levels of R. padi in 9 of 20 regions, M. dirhodum in 5 of 9 regions, and M. dirhodum in 3 of 9 regions to sulfoxaflor were greater than those of S. miscanthi, S. miscanthi, and R. padi in the same regions, respectively. Thus, each wheat aphid species has field populations that are highly sulfoxaflor resistant. The R. padi and M. dirhodum populations were more susceptible to sulfoxaflor than those of S. miscanthi. These findings provide new insights into insecticide resistance development and rational sulfoxaflor use.

Effect of Polyphenolic Compounds of Rosa Canina (L.) Against The Acetylcholinesterase Activity of Rhopalosiphum Padi (L.) (Homoptera: Aphididae)

Rhopalosiphum padi (L.) is among the most aggressive cereal pests worldwide. The pest causes economically heavy crop loss. Chemical insecticides were used for the control of multiple insects. However, the harmful consequences of these chemical products are well known. Seeking more ecological alternatives, respect to the environment is, therefore, a necessity. The phytochemicals are known for their various biological activities of pharmaceutical and agri-food interest. Several plant species have been found to have effective bioinsecticide properties against a variety of insects. In this study, the plant Rosa canina (L.) has made the objective of an in-silico research using molecular docking by screening the inhibitory potential of its polyphenolic compounds against the enzyme acetylcholinesterase of R. padi (L.). The enzyme 3D structure was first modeled, then its stereochemical quality was validated. The result of molecular docking allowed the selection of seven phytocompounds (Ellagic acid, Dihydroquercetin, Bilobalide A, Luteolin 5-methyl ether, Rosmarinic acid, Kaempferol, and Quercetin) with binding energy lower than that of the commercial insecticide Malathion. These components showed intense links with the catalytic site key residues of the enzyme, indicating their high inhibitor potential. The environmental and health safety of these components and their bio-availability were also validated by the verification of several pharmacokinetic and ADMET criteria, suggesting the interest of the plant R. canina (L.) as promising bioinsecticide material against the pest R. padi (L.).

Biological Activity of Essential Oils of Four Juniper Species and Their Potential as Biopesticides

The objective of this study was to assess the biological activity of essential oils (EOs) of four Juniperus species obtained via two different distillation methods and their potential as biopesticides. The studied factors were juniper species (Juniperus communis L., J. oxyсedrus L., J. pygmaea C. Koch., and J. sibirica Burgsd), plant sex (male (M) and female (F)), and distillation method (hydrodistillation via a standard Clevenger apparatus (ClevA) and semi-commercial (SCom) steam distillation). The hypothesis was that the EO will have differential antioxidant, antimicrobial, and insecticidal activities as a function of plant species, plant sex, and distillation method. The two distillation methods resulted in similar EO composition within a given species. However, there were differences in the EO content (yield) due to the sex of the plant, and also differences in the proportions of some EO components. The concentration of α-pinene, β-caryophyllene, δ-cadinene and δ-cadinol was dissimilar between the EO of M and F plants within all four species. Additionally, M and F plants of J. pygmaea, and J. sibirica had significantly different concentrations of sabinene within the respective species. The EOs obtained via ClevA extraction showed higher antioxidant capacity within a species compared with those from SCom extraction. All of the tested EOs had significant repellent and insecticidal activity against the two aphid species Rhopalosiphum padi (bird cherry-oat aphid) and Sitobion avenae (English grain aphid) at concentrations of the EO in the solution of 1%, 2.5%, and 5%. The tested EOs demonstrated moderate activity against selected pathogens Fusarium spp., Botrytis cinerea, Colletotrichum spp., Rhizoctonia solani and Cylindrocarpon pauciseptatum. The results demonstrate that the standard ClevA would provide comparable EO content and composition in comparison with SCom steam distillation; however, even slight differences in the EO composition may translate into differential bioactivity.

First Report of Sugarcane Mosaic Virus in Zea mays L. in Ukraine

Maize viral diseases especially maize dwarf mosaic disease (MDMD), which is caused by potyviruses, lead to significant crop losses worldwide. Aim. The aim of this work was to identify the causal agent of mosaic symptoms, observed on maize plants during 2018—2020 in Kyiv region. Methods. Enzyme-linked immunosorbent assay in the DAS-ELISA modification using commercial Loewe Biochemica test systems for Maize dwarf mosaic virus (MDMV), Sugarcane mosaic virus (SCMV), Wheat streak mosaic virus (WSMV) were applied to identify the causal agent of maize disease in collected samples. Transmission electron microscopy was used in order to direct viral particle visualisation. Aphids, which are natural vectors of plant viruses, were found on diseased plants. Results. Plants with typical mosaic symptoms were observed in corn crops of the Kyiv region in early June 2018. The pathogen was transmitted by mechanical inoculation to maize and sweet maize plants with the manifestation of mosaic symptoms. Electron microscopy of the sap from diseased plants revealed the presence of flexible filamentous virions 750 nm long and 13 nm in diameter, typical for the genus Potyvirus. In August, mosaic symptoms and aphids Rhopalosiphum padi were found on previously healthy plants in the same maize crop. In 2020, in the same sown area, maize plants were free of viral infection during inspection in June, but a re-inspection in September revealed mosaic symptoms on maize crop and the presence of aphids in the leaf axils. The presence of SCMV in maize samples collected in June and August/September 2018 and 2020, as well as in inoculated maize and sweet maize plants, was confirmed by ELISA using a commercial test system. The obtained data allow suggesting that Rhopalosiphum padi is a natural vector of SCMV in agrocenoses of Ukraine. It should be noted that co-infection with MDMV and WSMV in the affected plants was not detected. Conclusions. This study presents the first report of SCMV in maize in Ukraine.

Prevalence and management of aphids (Hemiptera: Aphididae) in different wheat genotypes and their impact on yield and related traits

Wheat (Triticum aestivum L.) production is significantly altered by the infestation of sucking insects, particularly aphids. Chemical sprays are not recommended for the management of aphids as wheat grains are consumed soon after crop harvests. Therefore, determining the susceptibility of different wheat genotypes and selecting the most tolerant genotype could significantly lower aphid infestation. This study evaluated the susceptibility of six different wheat genotypes (‘Sehar-2006’, ‘Shafaq-2006’, ‘Faisalabad-2008’, ‘Lasani-2008’, ‘Millat-2011’ and ‘Punjab-2011’) to three aphid species (Rhopalosiphum padi Linnaeus, Schizaphis graminum Rondani, Sitobion avenae Fabricius) at various growth stages. Seed dressing with insecticides and plant extracts were also evaluated for their efficacy to reduce the incidence of these aphid species. Afterwards, an economic analysis was performed to compute cost-benefit ratio and assess the economic feasibility for the use of insecticides and plant extracts. Aphids’ infestation was recorded from the seedling stage and their population gradually increased as growth progressed towards tillering, stem elongation, heading, dough and ripening stages. The most susceptible growth stage was heading with 21.89 aphids/tiller followed by stem elongation (14.89 aphids/tiller) and dough stage (13.56 aphids/tiller). The genotype ‘Punjab-2011’ recorded the lower aphid infestation than ‘Faisalabad-2008’, ‘Sehar-2006’, ‘Lasani-2008’ and ‘Shafaq-2006’. Rhopalosiphum padi appeared during mid-February, whereas S. graminum and S. avenae appeared during first week of March. Significant differences were recorded for losses in number of grains/spike and 1000-grain weight among tested wheat genotypes. The aphid population had non-significant correlation with yield-related traits. Hicap proved the most effective for the management of aphid species followed by Hombre and Husk among tested seed dressers, while Citrullus colocynthis L. and Moringa oleifera Lam. plant extracts exhibited the highest efficacy among different plant extracts used in the study. Economic analysis depicted that use of Hombre and Hicap resulted in the highest income and benefit cost ratio. Therefore, use of genotype Punjab-2011’ and seed dressing with Hombre and Hicap can be successfully used to lower aphid infestation and get higher economic returns for wheat crop.

Capsella bursa-pastoris Is a Key Overwintering Plant for Aphids in the Mediterranean Region

The reproduction of aphids depends to a great extent on their host plants, an integration that impacts on the successful expansion of overwintering populations. Therefore, a survey was conducted to evaluate the globally distributed Capsella bursa-pastoris as an overwintering host of economically important aphid species, their parasitoids and hyperparasitoids in the southern and western regions of Turkey from November to March in 2006 to 2013. During this survey, 395 samples of C. bursa-pastoris were collected with 25 aphid species recorded. Among aphids that feed on this host, Myzus persicae, Aphis gossypii, Rhopalosiphum padi, Aphis fabae, Aphis craccivora, Lipaphis erysimi, and Brevicoryne brassicae were the most frequently recorded. In total, 10,761 individual parasitoids were identified. Binodoxys angelicae, Aphidius colemani, Aphidius matricariae, Diaeretiella rapae, Ephedrus persicae, and Lysiphlebus confusus were the most abundant aphidiines that emerged from the aphids collected from C. bursa-pastoris. Alloxysta spp. (Hymenoptera: Cynipoidea), Chalcidoidea (unidentified at genus level), and Dendrocerus spp. (Hymenoptera: Ceraphronoidea) were identified as hyperparasitoids on the parasitoids. These findings indicate that C. bursa-pastoris is a key non-agricultural plant that significantly contributes to the overwintering of numerous aphids and their parasitoids, which should be given serious consideration when biological control strategies are designed.

Effects of Methyl Salicylate on Host Plant Acceptance and Feeding by the Aphid Rhopalosiphum padi

Methyl salicylate (MeSA) is a volatile shown to act as an inducer of plant defense against pathogens and certain herbivores, particularly aphids. It has been shown to have potential for aphid pest management, but knowledge on its mode of action is lacking, particularly induced plant-mediated effects. This study investigated the effects of exposing plants to MeSA on the host searching, host acceptance and feeding behavior of the bird cherry-oat aphid Rhopalosiphum padi. Barley plants were exposed to volatile MeSA for 24 h, after which biological effects were tested immediately after the exposure (Day 0), and then 1, 3 and 5 days after the end of the exposure. Aphid settling on MeSA-exposed plants was significantly reduced on days 0, 1 and 3, but not on day 5. In olfactometer tests, aphids preferred the odor of unexposed plants on days 1 and 3, but not on day 0 or 5. Analysis of volatiles from exposed and unexposed plants showed higher levels of MeSA from exposed plants, most likely absorbed and re-released from plant surfaces, but also specific changes in other plant volatiles on days 0, 1 and 3. High doses of MeSA did not affect aphid orientation in an olfactometer, but lower doses were repellent. Analysis of aphid feeding by Electronic penetration graph (EPG) showed that MeSA exposure resulted in resistance factors in barley plants, including surface factors and induced systemic factors in other tissues including the phloem. The results support the potential of MeSA as a potential tool for management of aphid pests.