Russian Wheat Aphid Research Articles

Puccinia triticina and Salicylic Acid Stimulate Resistance Responses in Triticum aestivum Against Diuraphis noxia Infestation

Wheat plants encounter both biotic and abiotic pressure in their surroundings. Among the biotic stress factors, the Russian wheat aphid (RWA: Diuraphis noxia Kurdjumov) decreases grain yield and quality. The current RWA control strategies, including resistance breeding and the application of aphicides, are outpaced and potentially environmentally harmful. Alternatively, priming can stimulate defence responses to RWA infestation. This study investigated the priming potential of two priming agents, avirulent Puccinia triticina (Pt) isolates and salicylic acid (SA), against RWA infestation. The priming effect of Pt isolates and SA in reducing RWA-induced leaf damage and increased antioxidant activities is an indication of defence responses. Selected South African wheat cultivars and Lesotho landraces, grown under greenhouse conditions, were inoculated with Pt isolates (UVPt13: avirulent, UVPt26: virulent) and treated with SA at the seedling or booting stages. The leaf damage rating score was used for phenotyping. The antioxidant-mediated defence responses were evaluated in three selected cultivars for further priming investigation. Our results revealed that the priming agents significantly reduced the leaf damage in most cultivars at both growth stages, and UVPt13 and SA priming significantly (p ≤ 0.05) increased superoxide dismutase, peroxidase, and ascorbate peroxidase activities. However, catalase activity exhibited a more pronounced decline in plants treated with the UVPt13 isolate. The Pt isolate priming was more efficient than the SA application. However, it is crucial to investigate the potential of effectors from the avirulent Pt isolate to prime wheat plants for resistance against RWA infestation. This could contribute to developing strategies to enhance crop protection and relieve pest pressure in wheat production.

Cereal aphid species: their natural enemies and efficiency of Lysiphlebus testaceipes (Cresson, 1880) to control Rhopalosiphum maidis (Fitch, 1856)

AbstractCereal grains both for human consumption and animal feed are an essential component of global food systems. However, during production they are often targeted by various pest insects, including aphids. A survey was carried out from 2017 to 2021 in six cereal production sites in Tunisia to evaluate aphid diversity and identify natural enemies on Triticum turgidum subsp. durum (durum wheat), Hordeum vulgare (barley), Avena sativa (oat) and Triticum secale (triticale). Six aphid species belonging to four genera were recorded: Diuraphis noxia, Rhopalosiphum maidis, R. padi, Schizaphis graminum, Sitobion avenae and Sitobion fragariae. Among these, S. avenae and R. padi emerged as the most prevalent species across the majority of sites, infesting durum wheat, barley and triticale. Sc. graminum, R. maidis and D. noxia were less frequent, while S. fragariae was exclusively found on oat plants. Common aphid predators observed included Coccinella algerica, Hippodamia variegata and C. undecimpunctata, as well as syrphid flies such as Episyrphus balteatus and Sphaerophoria rueppellii. Lysiphlebus testaceipes was the sole parasitoid species detected, emerging exclusively from R. padi and R. maidis mummies. Furthermore, the study on the efficacy of L. testaceipes against R. maidis indicated that parasitism levels increased with the number of introduced parasitoid pairs. Aphid and natural enemy diversity were also evaluated.

Characterization of a gene conferring resistance to US Russian wheat aphid biotypes in the Iranian wheat landrace PI 625139

AbstractRussian wheat aphid (RWA, Diuraphis noxia Kurdjumov) is a highly invasive and destructive wheat pest evolving rapidly to overcome host resistance. Novel genes conferring resistance to multiple RWA biotypes are needed to sustain wheat production. The Iranian landrace PI 625139 is resistant to all five US RWA biotypes. To map the RWA resistance gene in PI 625139, both F2 and F2:3 populations were developed from cross PI 625139 × Smith's Gold, and the F2:3 population was evaluated for responses to five RWA biotypes, RWA1, RWA2, RWA3/7, RWA6, and RWA8. RWA assays identified a single gene in PI 625139, designated Dn625139, conditioning resistance to all five US RWA biotypes. Selective genotyping of a subset of F2 plants using genotyping‐by‐sequencing (GBS) revealed a set of single‐nucleotide polymorphism (SNP) markers on the short arm of chromosome 7D that are closely associated with RWA resistance. Kompetitive allele‐specific PCR (KASP) markers were developed from selected GBS‐SNPs in 7DS. Genetic analysis using the new KASP and simple sequence repeat (SSR) markers placed Dn625139 to a 2.6 cM interval. Dn625139 was 1.2 cM proximal to the KASP marker Stars‐KASP1007 (169.57 Mb) and 1.4 cM distal to the SSR marker Stars1039 (195.27 Mb) in the International Wheat Genome Sequencing Consortium (IWGSC) RefSeq v2.1 reference sequence, and co‐segregated with the SSR marker Stars1029 (180.82 Mb). Dn625139 is a valuable gene conferring resistance to multiple RWA biotypes, and the molecular markers developed in this study can facilitate its rapid introgression into locally adapted cultivars to enhance wheat RWA resistance.

Influence of genetic and environmental factors on the success of endosymbiont transfers in pest aphids.

There is increasing interest in exploring how endosymbionts could be useful in pest control, including in aphids, which can carry a diversity of endosymbionts. Endosymbionts often have a large impact on host traits, and their presence can be self-sustaining. Identifying useful host-endosymbiont combinations for pest control is facilitated by the transfer of specific endosymbionts into target species, particularly if the species lacks the endosymbiont. Here, we complete a comprehensive literature review, which included 56 relevant papers on endosymbiont transfer experiments in aphids, to uncover factors that might influence transfer success. We then report on our own microinjection attempts of diverse facultative endosymbionts from a range of donor species into three agriculturally important aphid species as recipients: the green peach aphid (Myzus persicae), bird cherry-oat aphid (Rhopalosiphum padi), and Russian wheat aphid (Diuraphis noxia). Combining this information, we consider reasons that impact the successful establishment of lines carrying transferred endosymbionts. These include a lack of stability in donors, deleterious effects on host fitness, the absence of plant-based (versus vertical) transmission, high genetic variation in the endosymbiont, and susceptibility of an infection to environmental factors. Taking these factors into account should help in increasing success rates in future introductions.

Elucidating β-1,3-Glucanase and Peroxidase Physicochemical Properties of Wheat Cell Wall Defense Mechanism against Diuraphis noxia Infestation.

Wheat plants infested by Russian wheat aphids (RWA) induce a cascade of defense responses, including the hypersensitive responses (HR) and induction of pathogenesis-related (PR) proteins, such as β-1,3-glucanase and peroxidase (POD). This study aims to characterize the physicochemical properties of cell wall-associated POD and β-1,3-glucanase and determine their synergism on the cell wall modification during RWASA2-wheat interaction. The susceptible Tugela, moderately resistant Tugela-Dn1, and resistant Tugela-Dn5 cultivars were pregerminated and planted under greenhouse conditions, fertilized 14 days after planting, and irrigated every 3 days. The plants were infested with 20 parthenogenetic individuals of the same RWASA2 clone at the 3-leaf stage, and leaves were harvested at 1 to 14 days post-infestation. The Intercellular wash fluid (IWF) was extracted using vacuum filtration and stored at -20 °C. Leaf residues were crushed into powder and used for cell wall components. POD activity and characterization were determined using 5 mM guaiacol substrate and H2O2, monitoring change in absorbance at 470 nm. β-1,3-glucanase activity, pH, and temperature optimum conditions were demonstrated by measuring the total reducing sugars in the hydrolysate with DNS reagent using β-1,3-glucan and β-1,3-1,4-glucan substrates, measuring the absorbance at 540 nm, and using glucose standard curve. The pH optimum was determined between pH 4 to 9, temperature optimum between 25 and 50 °C, and thermal stability between 30 °C and 70 °C. β-1,3-glucanase substrate specificity was determined at 25 °C and 40 °C using curdlan and barley β-1,3-1,4-glucan substrates. Additionally, the β-1,3-glucanase mode of action was determined using laminaribiose to laminaripentaose. The oligosaccharide hydrolysis product patterns were qualitatively analyzed with thin-layer chromatography (TLC) and quantitatively analyzed with HPLC. The method presented in this study demonstrates a robust approach for infesting wheat with RWA, extracting peroxidase and β-1,3-glucanase from the cell wall region and their comprehensive biochemical characterization.

Functional characterisation of cell wall-associated β-glucanases and peroxidase induced during wheat-Diuraphis noxia interactions

Wheat plants infested by Russian wheat aphids (RWA) induce a cascade of defence responses, which include increased activity of β-1,3-glucanase and peroxidase (POD). There is a lack of information regarding β-1,3-glucanase and POD synergistic effects on the plant cell wall modification and characterisation during wheat-RWA infestation. This study aimed to characterise the physicochemical properties of the cell wall-bound POD and β-1,3-glucanase during RWA-wheat interaction. The susceptible Tugela, moderately resistant Tugela-Dn1, and resistant Tugela-Dn5 cultivars were planted in a glasshouse to a seedling stage before being infested with RWASA2 for 14 days. The findings showed a significant increase in β-1,3-glucanase and POD activities in the infested Tugela-Dn5 and Tugela-Dn1 cultivars over the 14 days. However, in the Tugela enzymes were repressed. In addition, it was shown for the first time that β-1,3 − 1,4-glucanase activity specific toward mixed-linked glucan was significant in the resistant cultivar over 14 days. β-1,3-glucanase, β-1,3 − 1,4-glucanase and POD displayed optimum at pH 5. β-1,3-glucanase and POD displayed temperature optimum at 40 and 50 °C, respectively. However, β-1,3 − 1,4-glucanase had temperature optimum at 25 °C. β-1,3-glucanase and POD had a thermo-stability at 37 °C followed by about 80% relative activity at 70 °C, but β-1,3 − 1,4-glucanase displayed thermostability at 25 °C and retained more than 75% at 70 °C, confirming that β-1,3 − 1,4-glucanase and β-1,3-glucanase induced in the resistant cultivars cell wall were two different enzymes. Mechanism of actions and oligosaccharide displayed that β-1,3-glucanase was highly active against β-1,3-glucan and required a triose and higher oligosaccharide to be active. Our findings demonstrated cell-wall bound POD and β-1,3-glucanase activities significantly increased in wheat after RWASA2 infestation, revealing they acted synergistically to reinforce the cell wall to deter RWASA2 feeding in resistant cultivars.

Novel transinfections of Rickettsiella do not affect insecticide tolerance in Myzus persicae, Rhopalosiphum padi, or Diuraphis noxia (Hemiptera: Aphididae).

Aphids (Hemiptera: Aphidoidea) are economically important crop pests worldwide. Because of growing issues with insecticide resistance and environmental contamination by insecticides, alternate methods are being explored to provide aphid control. Aphids contain endosymbiotic bacteria that affect host fitness and could be targeted as potential biocontrol agents, but such novel strategies should not impact the effectiveness of traditional chemical control. In this work, we used a novel endosymbiont transinfection to examine the impact of the endosymbiont Rickettsiella viridis on chemical tolerance in 3 important agricultural pest species of aphid: Myzus persicae (Sulzer) (Hemiptera: Aphididae), Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae), and Diuraphis noxia (Mordvilko ex Kurdjumov) (Hemiptera: Aphididae). We tested tolerance to the commonly used insecticides alpha-cypermethrin, bifenthrin, and pirimicarb using a leaf-dip bioassay. We found no observed effect of this novel endosymbiont transinfection on chemical tolerance, suggesting that the strain of Rickettsiella tested here could be used as a biocontrol agent without affecting sensitivity to insecticides. This may allow Rickettsiella transinfections to be used in combination with chemical applications for pest control. The impacts of other endosymbionts on insecticide tolerance should be considered, along with tests on multiple aphid clones with different inherent levels of chemical tolerance.

Genome-Wide Comparative Analysis of the Cytochrome P450 Monooxygenase Family in 19 Aphid Species and Their Expression Analysis in 4 Cereal Crop Aphids.

Cytochrome P450 monooxygenases (CYP450s) play a variety of physiological roles, including pesticide resistance, plant allelochemical detoxification, and hormone metabolism catalysis. However, limited information is available on the classification and expression profiles of the CYP450 gene family in aphid species. This is the first study to identify the cytochrome P450 gene family in 19 aphid species at the whole genome level. A total of 1100 CYP450 genes were identified in 19 aphid species. Three hundred CYP450 genes belonged to six cereal crop aphid species, which were further classified into four subfamilies according to the phylogenetic relationship. The conserved motifs, exon-intron structures, and genomic organization of the same subfamilies were similar. Predictions of subcellular localization revealed that the endoplasmic reticulum harbored the majority of CYP450 proteins. In Sitobion avenae and Rhopalosiphum maidis, the increase in the CYP450 gene was primarily caused by segmental duplication events. However, only tandem duplication occurred in the CYP450 gene family of Diuraphis noxia, Rhopalosiphum padi, Schizaphis graminum, and Sitobion miscanthi. Synteny analysis found three continuous colinear CYP450 gene pairs among six cereal crop aphid species. Furthermore, we obtained the expression profiles of four cereal crop aphids, including R. padi, D. noxia, S. graminum, and S. avenae. Differential expression analysis provided growth stage specificity genes, tissue specificity genes, organ specificity genes and some detoxification metabolic genes among these four cereal crop aphids. Meanwhile, their expression patterns were showed. The related functions and pathways of CYP450s were revealed by GO and KEGG enrichment analysis. Above all, we picked the differentially expressed CYP450 genes from all of the differentially expressed genes (DEGs). These differentially expressed CYP450 genes provided some new potential candidates for aphid control and management. This work establishes the foundation for further investigations into the regulatory functions of the CYP450 gene family in aphid species and beyond.

Host-specific co-evolution likely driven by diet in Buchnera aphidicola

BackgroundRussian wheat aphid (Diuraphis noxia Kurd.) is a severe pest to wheat, and even though resistance varieties are available to curb this pest, they are becoming obsolete with the development of new virulent aphid populations. Unlike many other aphids, D noxia only harbours a single endosymbiont, Buchnera aphidicola. Considering the importance of Buchnera, this study aimed to elucidate commonalities and dissimilarities between various hosts, to better understand its distinctiveness within its symbiotic relationship with D. noxia. To do so, the genome of the D. noxia’s Buchnera was assembled and compared to those of other aphid species that feed on diverse host species.ResultsThe overall importance of several features such as gene length and percentage GC content was found to be critical for the maintenance of Buchnera genes when compared to their closest free-living relative, Escherichia coli. Buchnera protein coding genes were found to have percentage GC contents that tended towards a mean of ~ 26% which had strong correlation to their identity to their E. coli homologs. Several SNPs were identified between different aphid populations and multiple isolates of Buchnera were confirmed in single aphids.ConclusionsEstablishing the strong correlation of percentage GC content of protein coding genes and gene identity will allow for identifying which genes will be lost in the continually shrinking Buchnera genome. This is also the first report of a parthenogenically reproducing aphid that hosts multiple Buchnera strains in a single aphid, raising questions regarding the benefits of maintaining multiple strains. We also found preliminary evidence for post-transcriptional regulation of Buchnera genes in the form of polyadenylation.

Chemotaxis response and age-stage, two-sex life table of the Cheilomenes sexmaculata (Fabricius) (Coccinellidae: Coleoptera) against different aphid species.

The Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae), is one of the most beneficial and identifiable predators of numerous soft-bodied and sucking insect pests of several crops. Biological parameters and olfactory response of C. sexmaculata were investigated under laboratory conditions by providing three different aphid species i.e., mustard aphid (Lipaphis erysimi Kaltenbach), citrus black aphid (Toxoptera citricida Kirkaldy), and peach aphid (Diuraphis noxia Kurdjumov) as a food source. The developmental period of immature stages of C. sexmaculata was shorter on D. noxia as compared to other aphid species. The adult longevities were longer on D. noxia and T. citricida while shorter on L. erysimi. Female fecundity was highest on D. noxia while lowest on L. erysimi. Life table parameters i.e., intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (Ro), and gross reproductive rate (GRR) were maximum on D. noxia while minimum on L. erysimi. The mean generation time C. sexmaculata was 20.90, 23.69, and 26.2 days on D. noxia, L. erysimi, T. and citricida, respectively. These findings were further confirmed from the olfactory experiment where D. noxia proved to be the most preferred prey. This study provides necessary information for mass-rearing of C. sexmaculata.

Population Dynamics of Aphid Pests of Wheat and Their Natural Enemies

Four aphid species (Schizaphis graminum, Sitobion avenae, Rhopalosiphum padi and Diuraphis noxia) were observed when the population dynamics of aphids in four wheat varieties were analysed. Maximum population abundance (104± 1.79 aphids/ plant) was observed during middle of March. Rhopalosiphum padi and D. noxia were predominant throughout (52.86.1± 0.21 and 56.10± 0.24 aphids/ plant, respectively). The variety ANAJ-2017 showed the least incidence (26.28± 0.27 aphids/ plant) being more resistant. Aphid parasitism was also more in ANAJ-2017 with the parasites Aphidius ervi (15.35± 0.13) and Praon volucre (12.45± 0.12). Abundance of predators (ladybird beetle, green lace wing, syrphid fly and spiders) was observed with the highly infested varieties UJALA-2016 and FSD-2008. With incidence of aphids, temperature showed positive correlation while relative humidity (RH) and rainfall did not show any significant effect. The yield varied significantly among the tested varieties and it was found positively correlated with aphid incidence with ANAJ-2017 exhibiting the maximum 1000 grain weight (55 g).

Synergistic effects of Aphidius colemani (Hymenoptera: Aphidiidae) and Coccinella undecimpunctata (Coleoptera: Coccinellidae) releases for the biological control of Diuraphis noxia in wheat fields

ABSTRACT The Russian wheat aphid, Diuraphis noxia, is a significant pest for grain crops worldwide. Bioagents such as the parasitoid, Aphidius colemani and the predator, Coccinella undecimpunctata have been shown to be effective against many aphid species. This study aimed to investigate the combined effect of releasing these two bioagents on controlling D. noxia without using pesticides. To achieve this, three systems of release were evaluated in the field: (1) the parasitoid A. colemani at rate of 4 mummies/m2, (2) the predator C. undecimpunctata at rate of 10 individuals (3rd larval instar)/m2, and (3) A. colemani (4 mummies/m2) + C. undecimpunctata (10 individuals/m2) and control. After four releases, the combination of A. colemani and C. undecimpunctata resulted in the highest percentage of reduction in aphid population, with a reduction of 95.58, 95.53% in 2020 and 2021, followed by 86.94, 83.92% in A. colemani plots and the lowest reduction percentage in C. undecimpunctata plots, with 65.1, 68.92%, in 2020 and 2021, respectively. Based on these results, it is recommended to use the combination of the two bioagents, A. colemani and C. undecimpunctata for controlling D. noxia in a wheat field. Therefore, the use of a combination of natural enemies, carefully timed and repeated releases, and consideration of intraguild predation dynamics can help to achieve effective biological control of aphids in wheat crops. The use of natural enemies such as A. colemani and C. undecimpunctata can reduce the application of pesticides and promote sustainable pest management practices.

PRESENT STATUS AND FUTURE PERSPECTIVES OF WHEAT (TRITICUM AESTIVUM L.) RESEARCH IN UZBEKISTAN

Wheat (Triticum spp.) is one of the premier staple foods consumed by one-third of the world’s population. Bread wheat (Triticum aestivum L.) is the only allohexaploid species with a genome formula BBAADD. Until now, from a selection point of view, a decline showed in the genetic potential of this type of wheat. However, the solution to this problem can be by developing high-yielding, disease- and pest-resistant cultivars using wheat-related species, ancient local landraces, and germplasm resources. Therefore, extensive study of the wheat gene pool using molecular tools, including identifying primary sources, is highly beneficial. For wheat improvement, breeding opportunities offer significant enhancements via genetic mapping approaches. The review focuses on the common wheat germplasm, wheat genetic approaches for genetic mapping, identification, and RWA (Russian wheat aphid) resistance, nested association mapping (NAM) population, DNA barcoding of Uzbekistan elite bread wheat cultivars, DNA marker-based screening of wheat germplasm for RWA resistance, future perspectives of wheat breeding in Uzbekistan, marker-assisted selection for abiotic stress tolerance, wheat stripe rust and its control strategies in Uzbekistan, epidemiology of the rust pathogens, pathogen characterization, and varietal resistance.

Effects of different industrial cannabis (Cannabis sativa (Linnaeus 1753) (Cannabaceae)) genotype extracts on Diuraphis noxia Kurdjumov, 1913 Myzus persicae Sulzer, 1776 and Aphis fabae Scopoli, 1763 (Hemiptera: Aphididae)

In this study, the effect of methanol extracts of three different genotypes (Narlısaray, Kavacık, Maltepe) of Cannabis sativa L. on Diuraphis noxia Kurdjumov, Myzus persicae (Sulzer) and Aphis fabae (Scopoli) (Hemiptera: Aphididae) were investigated. In the first stage of the study, 10% concentrations of each cannabis extract were applied on the 2nd and 3rd nymphal stages of aphid species by spraying method. After the end of 24 - 48 and 72 hours of the applications, the alive and dead individuals were recorded and mortality rates were determined. In the second stage, the genotype with the highest effect was used in dose-death trials and LD50 and LD90 values at different doses (2.5%, 5%, 7.5% and 10%) were specified. In the census after 72 hours, Narlısaray genotype showed the highest mortality rate with 54.04% on D. noxia. While the effect of Kavacık genotype on M. persicae was found as 23.13%, the highest toxicity record of the same genotype was determined on A. fabae (as 91.76%). According to the dose measurement studies of Kavacık genotype on A. fabae, LD50 and LD90 values were calculated to be 0.33 and 0.110 (mg/individual), respectively. At the results of study, it has been observed that extracts of different genotypes of the industrial cannabis plant are found effective on aphid species and it is thought that they can be used in controlling of these pests.

Endophytic Effect of the South African Beauveria bassiana Strain PPRI 7598 on the Population Growth and Development of the Russian Wheat Aphid, Diuraphis noxia

The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is one of the main pests of small-grain cereal crops, including bread wheat, Triticum aestivum (Poaceae). In a series of glasshouse experiments, we evaluated the systemic effect of endophytic Beauveria bassiana strain PPRI 7598 on D. noxia biotype RWASA1 using three South African wheat cultivars, Gariep, Molopo, and Kariega. The objectives of the study were: (a) to determine the effect of endophytism on RWA reproduction and population growth, and (b) to assess the effect of the endophyte on aphid biomass and T. aestivum response to D. noxia herbivory using a damage rating index. Plant endophytic colonisation was confirmed before each trial using a B. bassiana-selective medium. Three independent trials were performed 10 days apart under glasshouse conditions. The effect of the endophyte-treated versus non-treated plants varied significantly in terms of net reproductive rate (R0) and the intrinsic rate of increase (rm) of the D. noxia population. Overall, the endophyte significantly reduced D. noxia R0 by approximately 14 nymphs/female and decreased the aphid mass by 13% in treated plants, whereas the mean aphid mass increased by 17% in control plants in all pooled cultivars. These findings demonstrated the endophytic potential of B. bassiana strain PPRI 7598 for suppression of D. noxia populations in RWASA1-susceptible cultivars. The integration of B. bassiana endophytism with host plant resistance may counteract biotype development and support a more sustainable approach towards RWA control in integrated pest management programmes.

Production of Sitobion avenae-resistant Triticum aestivum cvs using laccase as RNAi target and its systemic movement in wheat post dsRNA spray.

Among the wheat biotic stresses, Sitobion avenae is one of the main factors devastating the wheat yield per hectare. The study's objective was to find out the laccase (lac) efficacy; as a potential RNAi target against grain aphids. The Sitobion avenae lac (Salac) was confirmed by Reverse Transcriptase-PCR. Gene was sequenced and accession number "ON703252" was allotted by GenBank. ERNAi tool was used to design 143 siRNA and one dsRNA target. 69% mortality and 61% reduction in lac expression were observed 8D-post lac DsRNA feeding. Phylogenetic analysis displayed the homology of grain aphid lac gene with peach potato, pea, and Russian wheat aphids. While Salac protein was found similar to the Russian grain, soybean, pea, and cedar bark aphid lac protein multi-copper oxidase. The dsRNAlac spray-induced silencing shows systematic translocation from leaf to root; with maximum lac expression found in the root, followed by stem and leaf 9-13D post-spray; comparison to control. RNAi-GG provides the Golden Gate cloning strategy with a single restriction ligation reaction used to achieve lac silencing. Agrobacterium tumefaciens mediated in planta and in-vitro transformation was used in the study. In vitro transformation, Galaxy 2012 yielded a maximum transformation efficiency (1.5%), followed by Anaj 2017 (0.8%), and Punjab (0.2%). In planta transformation provides better transformation efficiencies with a maximum in Galaxy 2012 (16%), and a minimum for Punjab (5%). Maximum transformation efficiency was achieved for all cultivars with 250 μM acetosyringone and 3h co-cultivation. Galaxy 2012 exhibited maximum transformation efficiency, and aphid mortality post-feeding transgenic wheat.

Estimating the Global Geographical Distribution Patterns of the Invasive Crop Pest Diuraphis noxia Kurdjumov under Current and Future Climatic Scenarios

Invasive crop pests (ICPs) are a major cause of crop losses and adversely affect global food security. Diuraphis noxia Kurdjumov is a significant ICP that feeds on the sap of crops, reducing crop yield and quality. Although estimating the geographical distribution patterns of D. noxia under climate change is critical for its management and global food security, such information remains unclear. Based on 533 global occurrence records and 9 bioclimatic variables, an optimized MaxEnt model was used to predict the potential global geographical distribution of D. noxia. The results showed that Bio1, Bio2, Bio7, and Bio12 were significant bioclimatic variables that influenced the potential geographical distribution of D. noxia. Under current climatic conditions, D. noxia was mainly distributed in west-central Asia, most of Europe, central North America, southern South America, southern and northern Africa, and southern Oceania. Under the SSP 1-2.6, SSP 2-4.5, and SSP 5-8.5 scenarios for the 2030s and 2050s, the potential suitable areas increased, and the centroid migrated to higher latitudes. The early warning of D. noxia in northwestern Asia, western Europe, and North America should be attended to further. Our results provide a theoretical basis for early monitoring and warning of D. noxia worldwide.

Modeling the effects of plant resistance, herbivore virulence, and parasitism, on the population dynamics of aphids and parasitoids in wheat and soybean in different climates

Invasions by insects that become pests are an increasing problem for agriculture. Introductions of parasitoids from the regions of pest origin and breeding plants resistant to invasive pests can reduce the abundances and impacts of pests, while providing safe, sustainable alternatives to insecticides. However, impacts of parasitoids and plant resistance are likely to interact, and the abiotic environment, and in particular, climate change is likely to affect these interactions. Here I report results from simulations with mathematical models of population dynamics of aphids and parasitoids on resistant versus susceptible plants, parameterized with published results, designed to test the following hypotheses: (1) parasitoids can reduce abundances and frequencies of virulent aphids able to overcome plant resistance, (2) temperature regime affects the impacts of parasitoids on virulent aphids, and (3) the outcomes of these interactions vary with crop. Two systems were modeled: the soybean aphid, Aphis glycines, on soybean, and the Russian wheat aphid, Diuraphis noxia, on wheat. The parasitoids in the models are in the genus Aphelinus, species of which have a long association with biological control of invasive pests. In the simulations with these models, parasitoids reduced the abundances, and on wheat, the percent of virulent aphids. The impacts of parasitoids on virulent aphids were greater in southern locations than in northern locations, and the impacts on virulent aphids were greater on wheat than on soybean. Indeed, parasitoids actually increased the frequencies of virulent aphids on soybean when only susceptible plants were present, while reducing the abundance of all aphids. If one accepts that comparisons of population dynamics in southern versus northern locations indicate the likely affects of climate change in the northern locations, these results suggest that climate change would lead to decreased abundance and frequency of virulent aphids in northern locations.

Estimating probability of visual detection of exotic pests and diseases in the grains industry—An expert elicitation approach

Participants in the grains industry undertake general surveillance monitoring of grain crops for early detection of pests and diseases. Evaluating the adequacy of monitoring to ensure successful early detection relies on understanding the probability of detection of the relevant exotic crop pests and diseases. Empirical data on probability of detection is often not available. Our aim was to both gain a better understanding of how agronomists undertake visual crop surveillance, and use this insight to help inform structured expert judgments about the probability of early detection of various exotic grain pests and diseases. In our study we surveyed agronomists under a state funded program to identify survey methods used to undertake visual inspection of grain crops, and their confidence in detecting pests and diseases using the associated methods. We then elicited expert judgments on the probabilities of visual detection by agronomists of key exotic pests and diseases, and compared these estimates with the self-assessments of confidence made by agronomists. Results showed that agronomists used a systematic approach to visual crop inspection but that they were not confident in detecting exotic pests and diseases, with the exception of pest and diseases that affect leaves. They were most confident in visually detecting Barley stripe rust and Russian wheat aphid; however, confidence in detecting the latter was influenced by recent training. Expert judgments on the ability of agronomists to visually detect exotic pests and diseases early was in accordance with agronomists’ self-rated confidence of detection but highlighted uncertainty around the ability of agronomists in detecting non-leaf pests and diseases. The outcomes of the study demonstrated the utility of structured expert elicitation as a cost-effective tool for reducing knowledge gaps around the sensitivity of general surveillance for early detection, which in turn improves area freedom estimates.

Confirmatory detection and identification of biotic and abiotic stresses in wheat using Raman spectroscopy.

Wheat is one of the oldest and most widely cultivated staple food crops worldwide. Wheat encounters an array of biotic and abiotic stresses during its growth that significantly impact the crop yield and consequently global food security. Molecular and imaging methods that can be used to detect such stresses are laborious and have numerous limitations. This catalyzes the search for alternative techniques that can be used to monitor plant health. Raman spectroscopy (RS) is a modern analytical technique that is capable of probing structure and composition of samples non-invasively and non-destructively. In this study, we investigate the accuracy of RS in confirmatory diagnostics of biotic and abiotic stresses in wheat. Specifically, we modelled nitrogen deficiency (ND) and drought, key abiotic stresses, and Russian wheat aphid (Diuraphis noxia) infestation and viral diseases: wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV), economically significant biotic stresses in common bread wheat. Raman spectra as well as high pressure liquid chromatography (HPLC)-based analyses revealed drastically distinct changes in the intensity of carotenoid vibration (1185 cm-1) and in the concentration of lutein, chlorophyll, and pheophytin biomolecules of wheat, triggered in response to aforementioned biotic and abiotic stresses. The biochemical changes were reflected in unique vibrational signatures in the corresponding Raman spectra, which, in turn could be used for ~100% accurate identification of biotic and abiotic stresses in wheat. These results demonstrate that a hand-held Raman spectrometer could provide an efficient, scalable, and accurate diagnosis of both biotic as well as abiotic stresses in the field.