Leaf Discs Research Articles

Pure Camphor and a Thujone-Camphor Mixture as Eco-Friendly Antifeedants against Larvae and Adults of the Colorado Potato Beetle.

The Colorado potato beetle (CPB) is a serious pest of economically important Solanaceae species. The use of essential oil compounds in pest management has been proposed as an alternative to harmful chemical insecticides that disturb human health and ecosystem functioning. We examined the antifeedant activity of three concentrations (0.125%, 0.25% and 0.5%) of pure camphor and a thujone-camphor mixture against 3rd instar larvae and adults. Their efficacy was evaluated according to the degree of leaf damage and avoidance of treated leaves by the CPB. Treatment of potato leaves significantly reduced leaf damage compared to the control. Leaf protection increased at higher concentrations of the examined compounds. Camphor was more effective against larvae and the thujone-camphor mixture was more effective against adults. Additionally, adults moved faster towards the control leaf disc in the two-choice olfactometer assay if an alternative disc was treated with a thujone-camphor mixture, whereas larvae responded similarly to the two potential repellents. However, after contact with the leaf disc treated with the highest compound concentration, the larvae escaped faster from the thujone-camphor mixture than from pure camphor. In conclusion, both examined compounds are promising eco-friendly antifeedants, but their efficacy depends on the developmental stage of the beetle, compound type and applied concentration.

Preliminary Valuation Activity of Calotropis gigantea L. Extracts against Several Insect Pests

Calotropis gigantea produces secondary metabolites. Some toxicity tests on several pest species had been conducted, yet the most susceptible pest species towards C. gigantea extract is still unknown. This study aims to determine the susceptible insect species and study the behavior of susceptible insects to C. gigantea extract. The test methods used in this research were leaf dipping and spraying upon four insect pest species of different orders (Bactrocera carambolae [Diptera: Tephritidae], Nilapavata lugens [Hemiptera: Delphacidae], Sitophilus zeamais [Coleoptera: Curculionidae], and Plutella xylostella [Lepidoptera: Plutellidae]). The concentration used to determine susceptible insects was 25 g.L-1 and control. Deterrence test of susceptible insects using a choice test and no-choice for 1.5 hours observed every five minutes. Five replication were used for each concentration. Behavioral test of susceptible insects using dietary toxicity test. Five bok choy leaf disc was immersed into solutions for 1 minute and air-dried on a petri dish. Observations were carried out for 12 hours with an observation period of every 1.5 hours. A leaf dipping test for 12 hours with an observation period of every 1.5 hours using the feed method. The concentrations used were 12.5 µgL-1and control. The concentration used was the toxicity test of C. gigantea leaf extract 25, 12.50, 6.25. 3.12, 1.56, 0.78, 0.39, 0.19, 0.09, 0.04 µgL-1. P. xylostella was considered a more susceptible test insect towards C. gigantea leaf extract than B. carambolae, N. lugens, and S. zeamais. C. gigantea leaf extract showed a toxic and feeding deterrent to P. xylostella larvae. The LC50 value of C. gigantea extract against P. xylostella by dipping was 16.9 µg.l-1 and 18.5 µg.l-1 by spray. The components of C. gigantea leaf extract consist of alkaloid, tannin, phenol, flavonoid, saponin, and terpenoid. The result of the research showed that C. gigantea leaf extract has a toxic and deterrent substance against P. xylostella and potential to control P. xylostella.

Evaluation of prey stage preference of the phytoseiid predator, Neoseiulus longispinosus (Evans) to the spider mite pest, Tetranychus macfarlanei Baker and Pritchard (Acari: Tetranychidae)

Tetranychus macfarlanei Baker and Pritchard is considered as a major spider mite pest infesting various agricultural crops across the globe. It is a highly polyphagous species, inducing heavy yield loss annually, thereby affecting the agriculture sector drastically. As an eco-friendly pest management strategy, biological control using phytoseiid predators is gaining significant attention all over the world during the past few decades. Evaluation of predatory potential and prey stage preference provides valuable information on the efficacy of the predatory species in controlling the pest population. Considering this, a comparative evaluation of the feeding preference of a phytoseiid predator, Neoseiulus longispinosus (Evans), was made on different life stages of T. macfarlanei under laboratory conditions of 30±20C and 70±5% RH. The experimental arena used for the feeding experiments consisted of mulberry leaf discs (2 cm2) uniformly arranged over 2% semi-solidified agarose medium placed inside a glass Petri dish. The results revealed that the feeding preference of the adult predator towards the prey stages after 24 hours of experiment followed a decreasing sequence of egg (68%)> nymph (13.3%)> larva (6.6%). The predator nymph also followed a similar order of preference with respective consumption rates of 22%, 6.6% and 6.6% on the egg, larva and nymph of the prey mite, indicating that both the nymphs and the adult females of the predator displayed a significant preference to feed on the eggs of T. macfarlanei. Both predatory life stages showed no preference to the adult females of T. macfarlanei. Statistical analysis using ANOVA revealed a significant variation (p < 0.05) in the feeding preference of the predatory life stages towards the varied prey stages. Thus, the results of the study clearly showed the bio-control potential of N. longispinosus against T. macfarlanei.

Obstructor, a Frankliniella occidentalis protein, promotes transmission of tomato spotted wilt orthotospovirus.

Tomato spotted wilt orthotospovirus (TSWV) causes substantial economic losses to vegetables and other crops. TSWV is mainly transmitted by thrips in a persistent and proliferative manner, and its most efficient vector is the western flower thrips, Frankliniella occidentalis (Pergande). In moving from the thrips midgut to the salivary glands in preparation for transmission, the virions must overcome multiple barriers. Although several proteins that interact with TSWV in thrips have been characterized, we hypothesized that additional thrips proteins interact with TSWV and facilitate its transmission. In the current study, 67 F.occidentalis proteins that interact with GN (a structural glycoprotein) were identified using a split-ubiquitin membrane-based yeast 2-hybrid (MbY2H) system. Three proteins, apolipoprotein-D (ApoD), orai-2-like (Orai), and obstructor-E-like isoform X2 (Obst), were selected for further study based on their high abundance and interaction strength; their interactions with GN were confirmed by MbY2H, yeast β-galactosidase and luciferase complementation assays. The relative expressions of ApoD and Orai were significantly down-regulated but that of Obst was significantly up-regulated in viruliferous thrips. When interfering with Obst in larval stage, the TSWV acquisition rate in 3 independent experiments was significantly decreased by 26%, 40%, and 35%, respectively. In addition, when Obst was silenced in adults, the virus titer was significantly decreased, and the TSWV transmission rate decreased from 66.7% to 31.9% using the leaf disk method and from 86.67% to 43.33% using the living plant method. However, the TSWV acquisition and transmission rates were not affected by interference with the ApoD or Orai gene. The results indicate that Obst may play an important role in TSWV acquisition and transmission in Frankliniella occidentalis.

Influence of bisphenol A on growth and metabolism of Vicia faba ssp. minor seedlings depending on lighting conditions

The effect of one of anthropogenic pollutants, i.e., 4,4′-isopropylidenediphenol, called 2,2-bis (4-hydroxyphenyl) propane (BPA), at 30 and 120 mg L−1 concentrations in the darkness (DK) or dark/light (DK/LT) on growth and selected elements of metabolism of seedlings and leaf discs of Vicia faba ssp. minor was studied. Treatment with 120 mg L−1 BPA had greater effects which were reflected by increase in the number of necrotic changes in roots and stems as well as in leaf discs and reduction of the length of roots DK and DK/LT, and volume of roots in the DK group. However, minimal and no influence on the fresh and dry weight of roots and stems in plants growing under both types of lighting conditions were observed. In both DK and DK/LT groups these effects were correlated with reduced amounts of storage and cell wall-bound sugars as well as of proteins while in the DK/LT additionally with reduced soluble sugar levels in the roots and increased amounts of hydrogen peroxide and phenols in roots and stems as well as in treatment solutions, where these compounds were released. We suggest that endogenous phenols and BPA can be metabolised in roots and stems to quinones. It seems that TB-1,4-BQ, is the one of that of the five studied quinones. We expect that the results of this paper will help to answer the following question: does the phytomeliorative and phytosanitative V. faba ssp. minor plant is enough to be resistant on negative effects, and to be useful to reduce increasing amount of BPA in the environment?

Castor Seed Oil: A Promising Biomitecide for Sustainable Management of the Red Coffee Mite (Oligonychus ilicis) (McGregor, 1917) (Prostigmata: Tetranychidae)

The coffee red mite [Oligonychus ilicis (McGregor, 1917)] (Prostigmata: Tetranychidae) is one of the main causes of conilon coffee (Coffea canephora Pierre & Froehn) crop damage due to its phytophagous habit. Nowadays, environment and human harmful synthetic pesticides are used to control this pest. In this context, plant-derived bioactive compounds have been studied as a sustainable alternative for the pest mite management in crops. The aim of this study was to evaluate the castor (Ricinus communis) seed oil action on eggs, larvae, nymph (protonymph and deutonymph) and adults of O. ilicis. Coffee leaf discs (4 cm in diameter) containing 12 individuals of O. ilicis were sprayed with castor seed oil at concentrations of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% (v/v) using airbrush. The ovicidal and mortality activity of this extract were evaluated against O. ilicis. The effective concentration of castor oil to cause 50% inhibition of O. ilicis larvae hatching (LC 50) was 1.26% (v/v). Oligonychus ilicis treated with this oil at a concentration of 3.0% presented a larvae hatching percentage of 29.3%, lower than that obtained for the control treatment (79.1%). Castor seed oil 3.0% (v/v) was highly toxic to nymphs and adults of O. ilicis with mortality of 96 and 88%, respectively. Castor seed oil was effective for larvae hatching inhibition and nymphs and adults mortality of O. ilicis, being promising for the coffee red mite sustainable biocontrol.

Fungal Metabarcoding Data for Two Grapevine Varieties (Regent and Vitis vinifera ‘Cabernet-Sauvignon’) Inoculated with Powdery Mildew (Erysiphe necator) Under Drought Conditions

Fungal Metabarcoding Data for Two Grapevine Varieties (Regent and <i>Vitis vinifera</i> ‘Cabernet-Sauvignon’) Inoculated with Powdery Mildew (<i>Erysiphe necator</i>) Under Drought Conditions

"Metabolomic diversity of local strains of Beauveria bassiana (Balsamo) Vuillemin and their efficacy against the cassava mite, Tetranychus truncatus Ehara (Acari: Tetranychidae)".

A desirable substitute for chemical pesticides is mycopesticides. In the current investigation, rDNA-ITS (Internal transcribed spacer) and TEF (Transcriptional Elongation Factor) sequencing were used for molecular identification of six Beauveria bassiana strains. Both, leaf discs and potted plant bioassaye were carried out to study their pathogenicity against the cassava mite, Tetranychus truncatus. LC50 and LC90 values of potential B. bassiana strains were estimated. We also discovered a correlation between intraspecific B. bassiana strains pathogenicity and comprehensive metabolome profiles. Bb5, Bb6, Bb8, Bb12, Bb15, and Bb21 strains were identified as B. bassiana by sequencing of rDNA-ITS and TEF segments and sequence comparison to NCBI (National Center for Biotechnology Information) GenBank. Out of the six strains tested for pathogenicity, Bb6, Bb12, and Bb15 strains outperformed against T. truncatus with LC50 values 1.4×106, 1.7×106, and 1.4×106 and with a LC90 values 7.3×107, 1.4×108, and 4.2×108 conidia/ml, respectively, at 3 days after inoculation and were considered as potential strains for effective mite control. Later, Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the above six B. bassiana strains was done on secondary metabolites extracted with ethyl acetate revealed that the potential B. bassiana strains (Bb6, Bb12, and Bb15) have higher levels of acaricidal such as Bis(dimethylethyl)-phenol: Bb6 (5.79%), Bb12 (6.15%), and Bb15 (4.69%). Besides, insecticidal (n-Hexadecanoic acid), and insect innate immunity overcoming compound (Nonadecene) were also identified; therefore, the synergistic effect of these compounds might lead toa higher pathogenicity of B. bassiana against T. truncatus. Further, these compounds also exhibited two clusters, which separate the potential and non-potential strains in the dendrogram of Thin Layer Chromatography. These results clearly demonstrated the potentiality of the B. bassiana strains against T. truncatus due to the occurrence of their bioactive volatile metabolome.

Supplemental Figures and Tables for Alterations in carbohydrate quantities in freeze-dried, relative to fresh or frozen maize leaf disks.

Supplemental Figures and Tables for Alterations in carbohydrate quantities in freeze-dried, relative to fresh or frozen maize leaf disks.

AcdS gene of Bacillus cereus enhances salt tolerance of seedlings in tobacco (Nicotiana tabacum L.)

Previous studies show that 1-aminocyclopropane-1-carboxylate (ACC) deaminase can facilitate the growth and stress tolerance of hosts by reducing ethylene levels. In this study, the acdS gene encoding ACC deaminase from Bacillus cereus (HK012) was cloned and transformed into tobacco (Nicotiana tabacum L.) by the leaf disc method using Agrobacterium. Molecular detection and physiological analysis of the transgenic tobacco plants were performed. Our results showed the acdS gene was integrated into the tobacco genome and fluorescence microscopy showed that the fusion protein was located on the cell membrane of tobacco root. Compared with control, the transgenic plants showed increases in plant height, root length, dry weight, fresh weight and chlorophyll content; and significant increases in the concentration of proline of 55.15% and 42.7% under salt stress conditions (150 mmol L−1 and 300 mmol L−1 NaCl, respectively). The superoxide dismutase, peroxidase, catalase and ACC deaminase activities of transgenic tobacco were higher than those of control tobacco at 150 and 300 mmol L−1 salt concentrations. Transgenic tobacco seedlings expressing the acdS gene of B. cereus HK012 showed higher salt tolerance than the control plants. The obtained results suggest that the acdS gene of B. cereus can be used to promote salt tolerance in glycophytes by using biotechnology strategies.

Artificial shelters enhance the establishment of the aphidophagous predator Scymnus interruptus on sweet pepper plants

The success of biological control programs often depends on the establishment of natural enemies in or around the crop. An emerging strategy that aims to improve establishment is through the provision of niches that act as shelters. These shelters can enhance the natural enemies’ effectiveness by providing: a suitable microclimate; protection against other predators or pesticides; and/or alternative food. Generally, shelters are natural habitats such as flower strips, intercropped areas, hedgerows, or banker plants. The use of artificial devices as shelters remains underexplored. In this study, we assessed the functionality of an artificial shelter for the aphidophagous predator, Scymnus interruptus Goeze (Coleoptera: Coccinellidae). A tailor-made artificial shelter for oviposition was developed and tested in both laboratory and greenhouse conditions. Our results showed that S. interruptus females strongly preferred to use the shelters as an oviposition site compared with sweet pepper (Capsicum annuum L.) leaf discs supporting the aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), its primary prey. Furthermore, S. interruptus oviposition rate was doubled when shelters were supplied. In a greenhouse experiment, population densities of S. interruptus larvae increased twofold when shelters were provided. Additionally, providing artificial shelters in a sweet pepper crop has the potential to enhance aphid control and could also be a valuable method for monitoring predator densities in the crop.

DEVELOPMENT OF THE CRISPR/CAS9 SYSTEM FOR THE GENOME&#x0D; EDITING OF THE NtPDS GENE OF TOBACCO (NICOTIANA TABACUM)

The CRISPR/Cas9 system is one of the most powerful tools for the editing of plant genomes. In the presented study, the vector constructs developed on the basis of the CRISPR/Cas9 system were used to edit the Nicotiana tabacum genome. The NtPDS gene encoding the 15-cis-phytoene desaturase enzyme was chosen as the target. A knockout of this gene in plants results in the albinism phenotype and dwarfism. Using the in silico bioinformatics platforms, three vector constructs based on the binary pRGEB31 vector were modeled: pRGEB31 + gRNA4-pds, pRGEB31 + gRNAJp2-pds, and pRGEB31 + gRNADeT186-pds, carrying in its composition the CRISRP/Cas9 system with spacers to different parts of the structural domains of the NtPDS gene. Vector constructs were assembled using molecular cloning techniques. The accuracy and correctness of their assembly was confirmed by Sanger sequencing. Вy means of Agrobacteriummediated transformation of leaf discs, the genetic constructs were introduced into the genome of the N. tabacum cv.&#x0D; Petit Havana SR1 model object. During the cultivation of tobacco leaf discs, it was possible to initiate callusogenesis and morphogenesis processes using all three constructs, however, the maximum frequency of these processes was observed when using the pRGEB31 + gRNA4-pds construct.

The potential for using aerated steam to eradicate strawberry mite and two-spotted spider mite on strawberry transplants.

In this study, we investigated if a steam treatment program used to produce disease-free strawberry transplants has the potential to also eliminate strawberry mite (Phytonemus pallidus) and two-spotted spider mite (Tetranychus urticae). Crowns of strawberry plants collected in a commercial field, containing young, folded leaves with all life stages of P. pallidus, and strawberry leaf discs on water agar with T. urticae with non-diapausing adult females and eggs from a laboratory rearing, were exposed to warm aerated steam in a steam cabinet in a series of four experimental runs over 2years. The steam treatments constituted of a 1-h pre-treatment with 37°C steam followed by a 1-h recovery period at 21-25°C, and then a main steam treatment at 44°C for either 2, 4 (both P. pallidus and T. urticae) or 6h (the more heat tolerant T. urticae only). After steaming, the plant material with P. pallidus or T. urticae were incubated at 21-25°C until survival was assessed after 1-6days, depending on the mite species and life-stage. Non-steamed plant material with mites was used as controls. The 4-h treatment killed all P. pallidus eggs, larvae and adults, and the 2-h treatment killed all individuals in all three stages except for one egg in one of the runs. There were no or minor effects of the steam treatments on T. urticae adult and egg survival. Based on these results, the tested steam treatments may be used to eliminate the strawberry mite but not the two-spotted spider mite from strawberry planting material.

Supra-optimal temperatures induce photochemical leaf damage and reduce photosynthetic O2 evolution in Carica papaya L.

Carica papaya L. is a tropical and subtropical fruit tree. In such climatic regions, cultivation frequently includes exposure to supra-optimal temperatures, which may affect the leaf photosynthetic capacity. Two papaya genotypes, 'Candy' and 'Golden THB', were used to study the effects of supra-optimal temperatures on photochemical responses. The seedlings were cultivated in a greenhouse in 40 L pots. After 100 days, excised leaf discs were incubated at 25, 35, 40, 45, 50 or 55 °C, for 15, 30, 45 or 60 min. Emissions of chlorophyll a fluorescence and photosynthetic O 2 evolution rates were measured. In both genotypes, F 0 increased, while F m decreased after 15 min at 45 °C or above, indicating photochemical damage. An increase in non-photochemical dissipation in relation to photochemical dissipation (F v /F 0 ) was noted, resulting in decreased maximum (ΦP 0 ) and effective (QY Lss ) quantum yields of the PSII. A reduction in the probability of the electrons being transported beyond Q A - (Ψ 0 ), and in the efficiency of electron transport through the chain (ΦE 0 ) were observed, indicating an increase in the quantum efficiency of energy dissipation (ΦD 0 ). The high rate of reaction center deactivation (increase in RC/CS 0 ) in supra-optimal temperatures resulted in elevated absorption (ABS/RC), capture (TR 0 /RC), transport (ET 0 /RC), and dissipation (DI 0 /RC) of energy per active reaction center. An increase in energy absorption by the PSII antenna complex (ABS/CS 0 ) occurred above 40 °C. However, this additional energy was not effectively captured (TR 0 /CS 0 ), or transported (ET 0 /CS 0 ), resulting in high excess energy dissipation (DI 0 /CS 0 , NPQ Lss , NPQ D ). An increase in ΔV/Δt 0 reflected a reduction in the rate of photosynthetic O 2 evolution rate at temperatures above 30 °C. The reduction of three key parameters PI Abs , SFI abs and Rfd Lss occurred in leaf disks incubated at 40 °C for a period of 15 min, indicating a reduction in photochemical efficiency in both genotypes. Therefore, severe damage to the photosynthetic capacity of C. papaya L. can be observed at temperatures above 40 °C. • Temperatures higher than 40 °C cause photochemical damage to papaya leaves. • Chlorophyll fluorescence images show heterogeneity of photochemical damage. • Energy capture and transport are more sensitive than absorption by the LHCII. • Moderate temperatures excite PSI and optimize electron transport. • Reduction in the rate of evolution of photosynthetic O 2 from 35 °C.

Effect of excess boron on growth, membrane stability, and functional groups of tomato seedlings

With the scarcity of good quality water, plants like tomatoes will be more susceptible to excess boron (EB) in Mediterranean regions. The effects of EB on the growth, free, semi-bound, and bound boron (B) concentrations, and macromolecules of the Solanum lycopersicum L. cultivar Castle Rock, were investigated in this study. Seedlings were exposed to four levels of EB using boric acid. The results manifested that EB inhibited tomato growth, total water content, and photosynthetic pigments. EB harmed the membrane stability, as seen by increased potassium (K) leakage, UV absorbance metabolites, and electrolyte conductivity (EC) in leaf disc solution. EB raised concentrations of free, semi-bound, and bound forms of B in seedlings. Fourier transform infrared spectroscopy (FTIR) data revealed that EB induced uneven wax deposition, altered the shape of cell walls, and lowered cellulose synthesis in seedlings. EB affected the amide I and amide II indicating damage to the protein pools. These results provide new insights into understanding the specific effects of EB on the functional groups of different macromolecules of tomato seedlings.

LbMYB48 positively regulates salt gland development of Limonium bicolor and salt tolerance of plants.

Limonium bicolor is a dicotyledonous recretohalophyte with several multicellular salt glands on the leaves. The plant can directly secrete excess salt onto the leaf surface through the salt glands to maintain ion homeostasis under salt stress. Therefore, it is of great significance to study the functions of genes related to salt gland development and salt tolerance. In this study, an R1-type MYB transcription factor gene was screened from L. bicolor, named LbMYB48, and its expression was strongly induced by salt stress. Subcellular localization analysis showed that LbMYB48 was localized in the nucleus. LbMYB48 protein has transcriptional activation activity shown by transcriptional activation experiments. The density of salt glands in the leaves and the salt secretion capacity of LbMYB48-silenced lines were decremented, as demonstrated by the leaf disc method to detect sodium ion secretion. Furthermore, salt stress index experiments revealed that the ability of LbMYB48-silenced lines to resist salt stress was significantly reduced. LbMYB48 regulates salt gland development and salt tolerance in L. bicolor mainly by regulating the expression of epidermal cell development related genes such as LbCPC-like and LbDIS3 and salt stress-related genes (LbSOSs, LbRLKs, and LbGSTs) as demonstrated by RNA-seq analysis of LbMYB48-silenced lines. The heterologous over-expression of LbMYB48 in Arabidopsis thaliana improves salt tolerance of plants by stabilizing ion and osmotic balance and is likely to be involved in the abscisic acid signaling pathway. Therefore, LbMYB48, a transcriptional activator regulates the salt gland development of L. bicolor and salt tolerance of L. bicolor and A. thaliana.

Management of Myzus persicae with leaves of Jatropha curcas and Ricinus communis in different vegetative stages

Although chemical insecticides are successfully used in agriculture, several problems may be related to their indiscriminate use. This has encouraged the development of alternative methods for pest insect control and societal pressure for pesticide-free products. The jatropha (J. curcas) and castor bean (Ricinus communis) are plants that have shown insecticidal potential. Thus, the objective of this work was to study the effects of leaves of R. communis and J. curcas of different ages on the cabbage aphid (Myzus persicae). Five solution concentrations and five leaf types were used. Each treatment consisted of ten individuals M. persicae, kept in Petri dishes (10.0 x 1.2 cm), about kale leaf discs. Each Petri dish was considered a repeat, totaling ten. An airbrush connected to a compressor calibrated at constant pressure and 5 mL of solution per repetition was used for direct application. The cabbage discs were immersed in the different treatments for five seconds and offered to aphids in the indirect application. For both tests, evaluations were performed 72 hours after application. Data were submitted to linear regression analysis and means test. There was an interaction between the application type, leaf type, and concentrations for both plants. We argue that at their different ages, jatropha and castor bean leaves have insecticidal potential in the management of M. persicae.

Evaluation of the Contact Toxicity and Physiological Mechanisms of Ginger (Zingiber officinale) Shoot Extract and Selected Major Constituent Compounds against Melanaphis sorghi Theobald

Botanical pesticides have gradually become accepted for use in the control of agricultural pests. In order to clarify the active compounds of the ginger (Zingiber officinale) shoot extract (GSE) and its inhibitory effect on the growth of sorghum aphids (Melanaphis sorghi). In this study, LC-MS/MS was used to determine the major active compounds of the GSE, and leaf disc method was used to explore the insecticidal effect of the active compounds of ginger on sorghum aphids and the response mechanism of sorghum aphids. The results showed that phenolic acids were identified as the main active compounds, followed by flavonoids. The aphidicidal activity test using the above compounds found that 6-gingerol, and quercetin-3-O-rutinoside exhibited aphidicidal activity (GSE &gt; quercetin-3-O-rutinoside &gt; 6-gingerol). The growth of sorghum aphid was evaluated by using different concentrations of the GSE. It was found that with the increase of concentration and treatment time, the litter size, longevity and molting of aphids significantly decreased, and the mortality of aphids increased. The enzyme activity of aphids treated with 15 mg·mL−1 GSE was determined, and it was found that the GSE could significantly inhibit the activities of pepsin, lipase and α-amylase of aphids, while the activity of superoxide dismutase (SOD) was significantly activated. The activities of peroxidase (POD) and catalase (CAT) increased at first and then decreased. In detoxification enzymes, the carboxylesterase (CarE) activity was significantly activated, the acetylcholinesterase (AChE) activity was significantly inhibited, and the glutathione S-transferase (GST) activity increased at first and then decreased. The above results indicated that the GSE may become a botanical pesticide for aphid control and provide new resources for the development of aphid biological agents.

Competition Between Plasmopara viticola Clade riparia and Clade aestivalis: A Race to Lead Grape Downy Mildew Epidemics.

There is evidence of five clades of Plasmopara viticola in the world. Only two clades, riparia and aestivalis, have been identified as responsible for downy mildew epidemics in Quebec, Canada. It was reported in 2021 that epidemics caused by clade riparia start 2 or 3 weeks before those caused by clade aestivalis and that clade aestivalis was more aggressive than clade riparia. The objective of this work was to study the competition between P. viticola clade riparia (A) and clade aestivalis (B) and to compare the aggressiveness of both clades in mono- and coinfection situations. Suspensions of sporangia from both clades with six percentage combinations (AB 100-0; AB 89-11; AB 74-26; AB 46-54; AB 23-77; and AB 0-100) were inoculated on leaf discs (cultivar Vidal), and three other combinations (AB 88-12; AB 68-32; and AB 47-53) were inoculated on living leaves of grape plants (cultivar Vidal). Then, sporangium production, expressed as the percentage of sporangia produced by each clade, was estimated on leaf discs after eight cycles of infection-sporulation and then validated on living grape leaves after five cycles. The aggressiveness of clades in monoinfection situations on leaf discs was compared with that in coinfection situations. The results show that the percentage of sporangia produced by clade aestivalis increases with the infection-sporulation cycle while that produced by clade riparia decreases. The area under the sporangium production progress curve (AUSPPC) of clade aestivalis was significantly higher than that of clade riparia. The aggressiveness of P. viticola clades riparia and aestivalis in coinfection situations was different from that in monoinfection situations and was strongly influenced by the percentage of each clade in competition. These results suggest that, on the grapevine cultivar Vidal, P. viticola clade aestivalis is more competitive than clade riparia and that the percentage of each clade present in the vineyard should be considered for management of downy mildew.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Effect of the Orientation of the Leaf Surface on the Growth, Development, and Reproduction of Three Populations of the Pea Aphid (Hemiptera: Aphididae)

Abstract The leaf disc method is widely used in laboratory studies of the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). We examined the effects of the orientation of the leaf discs (upright, inverted, and horizontally perpendicular to the surface) on the biological parameters of aphids from three populations (i.e., Gansu red, Gansu green, and Yunnan green) of A. pisum. We found that aphids feeding on inverted or horizontally perpendicular positioned leaf discs exhibited higher survival and fecundity rates than those aphids feeding on upright positioned leaf discs for all three populations. Overall, aphids in both the Gansu red and Gansu green populations performed best when feeding on the inverted leaf discs, whereas aphids of the Yunnan green population performed best in the horizontally perpendicular orientation. We postulate this may be related to body temperature adjustment by the aphids through adjusting the orientation angle between its body and the sun. Our results provide a theoretical basis for optimizing the rearing parameters of the pea aphid, reducing the systematic error of experiments, and facilitating the acquisition of more reliable data under laboratory conditions.