Search Results (118)

Comparative morphological analysis of the labrum and labium among nine aphid species—Uroleucon sp., Glyphina betulae, Myzus cerasi, Panaphis juglandis, Chaitophorus sp., Lachnus roboris, Forda sp., Paracletus cimiciformis, and Trama sp., belonging to six subfamilies—reveals marked interspecific variation in structure, segmentation, and sensilla equipment. The labrum is generally triangular and plate-like, ranging from 88.8 μm (M. cerasi) to 358.1 μm (L. roboris). However, Trama sp. exhibits a distinctive conical labrum (311.1 μm) bearing three pairs of sensilla trichodea (St2)—unique among the examined taxa. Most species possess a four-segmented labium, while Trama sp. and L. roboris exhibit five segments. The second segment is the longest and most elaborate, bearing dense arrays of sensilla or spiniform tubercles in several species. Sensilla trichodea (St1–St5) are widespread across taxa, showing the highest densities in Chaitophorus sp St1, Trama and L. roboris St2, Uroleucon sp St3, and P. cimiciformis St4, whereas Trama sp. uniquely combines sensilla St2, St3, St5, and sensilla basiconica (Sb2). Sensilla basiconica (Sb1) are consistently positioned at the base of the labrum and the fourth labial segment, except in Trama sp., which presents sensilla St3. Distinct cuticular modifications—including apical cuticular processes and granular protrusions—occur only in Trama sp. and L. roboris, suggesting lineage-specific adaptations. These morphological patterns indicate that aphid mouthpart diversity reflects functional specialisation linked to host-plant structural variation. Full article

Upland cotton (Gossypium hirsutum L.) is a major global commodity crop whose production is threatened by the reniform nematode (Rotylenchulus reniformis Linford and Oliveira), a plant-parasitic pest that causes substantial yield losses. Host-plant resistance offers a sustainable management strategy, but currently available resistant cotton cultivars provide only partial protection and often require supplemental control methods. In this study, Clustered Regularly Interspaced Palindromic Repeats (CRISPR)–CRISPR-associated 9 (Cas9) gene editing was used to generate targeted knockouts of Mildew Resistance Locus O (GhiMLO3) in cotton and assess its role in resistance to R. reniformis. Four independent knockout lines (A1, D3, E1, and P3) were developed, confirmed by sequencing, and evaluated for nematode resistance under controlled greenhouse conditions. Nematode reproduction was significantly reduced on lines D3 and E1, with lower egg counts and fewer vermiform life stages compared with the control genotypes, Coker 312 (WT), Delta Pearl, and Jin668. The edited lines also showed characteristic mesophyll cell-death phenotypes, suggesting potential pleiotropic effects associated with MLO-mediated resistance. Sequence analysis confirmed multiple homozygous and heterozygous mutations in MLO3 alleles from both the A and D subgenomes, with D3 and E1 lines displaying the strongest resistance profiles. These findings demonstrate that MLO3 gene editing is a promising approach for improving R. reniformis resistance in cotton. Full article

Longhorn beetles mainly harm trees, flowers, and certain crops. They are closely associated with their host plants and often climb on vertical trunks, branches, and the underside of leaves. Their tarsi have numerous micro-scale adhesive setae on the ventral side. These setae provide sufficient force to enable the beetles to adhere firmly to smooth or slightly micro-structured surfaces. This study observed and analyzed the ultrastructures of the adhesive setae of three species from different subfamilies of Cerambycidae and one species from Vesperidae using a scanning electron microscope. The comparative analysis focused on characterizing the types, morphology, distribution patterns and adhesion mechanisms of the adhesive ultrastructures in four longhorn beetle species. The results showed that the longhorn beetles generally had pseudotetramerous tarsi (except An. chinensis, which had tetramerous tarsi), and that tarsomeres I–III were expanded and widened to increase the contact area between the tarsi and the substrate. Furthermore, a large number of micro-scale adhesive setae were present on the ventral surface of these tarsomeres. In total, five types of adhesive setae were found in the four species studied. The three species belonging to the Cerambycidae family exhibited adhesive setae with numerous short setules, while in the species Mantitheus pekinensis belonging to Vesperidae, there are two types of adhesive setae without any short setules. The differentiation of the adhesive structures in longhorn beetles is shaped by the combined effects of phylogeny, sexual dimorphism, and host-plant adaptations. Full article

Psyllids are vectors of fastidious plant pathogenic ‘Candidatus Liberibacter’ species that infect both the psyllid vector and plant host. Understanding the molecular and cellular basis of ‘Ca. Liberibacter’ interactions with the psyllid host will aid in identification of effectors involved in invasion and multiplication and facilitate transmission to the host plant. The differential expression of previously identified genes/loci with predicted involvement in tomato host–plant– ‘Ca. L. solanacearum’–prophage–Wolbachia endosymbiont dynamics was quantified by RT-qPCR amplification. Fifteen ‘Ca. Liberibacter solanacearum genes and/or prophage loci and four predicted Wolbachia spp. loci were analyzed in potato psyllids in a 14-day time-course study, post-48-h acquisition-access period by potato psyllids on ‘Ca. L. solanacearum’-infected tomato plants. The ‘Ca. L. solanacearum’-infected tomato host plants were used as an infected host ‘calibrator’ species lacking involvement of psyllid effectors. ‘Ca. L. solanacearum’ genes with predicted functions in adhesion, motility, transport, and virulence that are associated with the prophage lysogenic lifestyle were differentially expressed. In contrast, the prophage-loci expression was synchronous with early or late phase of psyllid-‘Ca. L. solanacearum’ infection, respectively. The observations are consistent with the previously in silico-predicted ‘Ca. L. solanacearum’ gene and prophage/Wolbachia loci functions and time-course global expression patterns. Knockdown of ‘Ca. L. solanacearum’ genes involved in invasion, biofilm formation, and colonization would be expected to impair the vertical and horizontal transmission of ‘Ca. L. solanacearum’ to psyllid offspring and host plants, respectively. Full article

Using metrics from network theory allows us to understand the structural organization of epiphyte communities and identify the host trees (phorophytes) that are fundamental to their establishment. In this study, we applied ecological network metrics to examine the structure of interactions between vascular epiphytes and phorophytes in a woody inselberg community in southeastern Brazil. The recorded network comprised 30 epiphyte species and 13 phorophyte species, exhibiting a nested structure, low specialization (H₂′), low connectance, and low modularity, like other epiphyte–phorophyte networks. The main roles in the network were played by the generalist epiphyte Tillandsia loliacea and the lithophytic phorophytes Tabebuia reticulata and Pseudobombax petropolitanum, which interacted with 100% of the recorded epiphytic species. Epiphyte species were organized vertically into modules that correlate with the ecological zones of the phorophytes, suggesting that their distribution responds to microclimatic variation along the vertical gradient. These results reinforce the importance of particular phorophyte species as key structuring agents of epiphytic communities and highlight their central role in extreme environments such as inselbergs. Full article

Aphis craccivora significantly affects cowpea (Vigna unguiculata L.) production, leading to yield reductions. Management strategies encompass physical barriers and biological and chemical methods, which can be costly and detrimental to the environment. Host-plant resistance offers a more sustainable alternative. This study evaluated cowpea genotypes in a screenhouse experiment. Tswana and B261-B were resistant, while B301, B259, and ER7 showed a tolerance phenotype. Tswana exhibited a low aphid population and minimal plant damage, probably due to suppression of reproduction and fecundity. Conversely, IT97K-556-6, SARI-21KTA-6, SARC 1-57-2, B013-F, B339, and Blackeye were susceptible to aphids, as shown by high aphid populations and dense sooty molds. Severe damage to plant vigor may be linked to direct aphid feeding and reduced photosynthesis efficiency. SNP1_0912 and CP 171F/172R markers confirmed aphid resistance in Tswana and ER7 as well as in the IT97k-556-6 and SARI-21KTA-6 controls. The inverse susceptible phenotype in the control group suggests that the markers may not function properly due to negative interactions between quantitative trait loci (QTL) and environmental factors. This could also indicate the presence of different aphid biotypes that severely damage Western African breeding lines. This study offers essential insights for breeding aphid-resistant cowpea varieties. Future efforts will involve sequencing Tswana to identify more resistance sources and create novel markers. Full article

Root-knot nematodes (RKNs; Meloidogyne spp.) are significant plant–parasitic nematodes that cause major yield losses worldwide. With growing awareness of the harmful effects of chemical pesticides on human health and the environment, there is an urgent need to develop alternative strategies for controlling RKN in agricultural fields. In recent years, implementing multiple approaches based on transcriptomics, genomics, and genome engineering, including modern platforms like CRISPR/Cas9, along with traditional genetic mapping, has led to great advances in understanding the plant–RKN interactions and the underlying molecular mechanisms of plant RKN resistance. In this literature review, we synthesize the contributions of relevant studies in this field and discuss key findings. This includes, for instance, transcriptomics studies that helped expand our understanding of plant RKN-resistance mechanisms, the overexpression of plant hormone-related genes, and the silencing of susceptibility genes that lead to plant RKN resistance. This review was conducted by searching scientific sources, including PubMed and Google Scholar, for relevant publications and filtering them using keywords such as RKN–plant defense mechanisms, host–plant resistance against RKN, and genetic mapping for RKN. This knowledge can be leveraged to accelerate the development of RKN-resistant plants and substantially improve RKN management in economically important crops. Full article

The southern African species of the genus Rhamphus Clairville, 1798, is herein revised for the first time. Fourteen species are recognized, 13 of which are new to science. The single known species was Rhamphus namibicus Korotyaev, 1994 (Namibia), whereas the new species are R. carinatus sp. nov. (South Africa: Limpopo; Zimbabwe), R. densepunctatus sp. nov. (South Africa: Western Cape), R. gigas sp. nov. (Zambia), R. glaber sp. nov. (South Africa: Mpumalanga), R. globipennis sp. nov. (South Africa: Mpumalanga, Limpopo, KwaZulu-Natal, Eastern Cape, Western Cape), R. hispidulus sp. nov. (South Africa: Eastern Cape), R. indifferens sp. nov. (South Africa: Gauteng, KwaZulu-Natal, Eastern Cape), R. levipennis sp. nov. (South Africa: Mpumalanga; Zimbabwe), R. longitarsis sp. nov. (Southern Namibia; South Africa: Northern Cape), R. obesulus sp. nov. (South Africa: Eastern Cape), R. pilosulus sp. nov. (South Africa: Mpumalanga, KwaZulu-Natal; Zimbabwe), R. scaber sp. nov. (South Africa: KwaZulu-Natal, Eastern Cape), R. squamidorsum sp. nov. (South Africa: Eastern Cape, Western Cape). Based on morphological characters, the species are separated into four informal groups. In considering possible relationships between these species and those from other regions, host-plant associations are also discussed. Full article

Plant defensins (PDFs) are a group of cationic antimicrobial peptides that are distinguished by their unique tertiary structure and play significant roles in physiological metabolism, growth, and stress tolerance. Defensins are key components of plant innate immunity; they can target a wide variety of microorganisms. This study aimed to identify and investigate the role of Triticum durum PDFs (TdPDFs) in response to environmental stresses. Prior to this, in silico analyses of TdPDF genes were conducted to assess their chromosomal locations, conserved motifs, exon–intron distribution, and cis-regulatory elements in the promoter regions. Additionally, bioinformatic analyses were performed to characterize the structure of TdPDF proteins, evaluate their phylogenetic relationships, predict their subcellular localization, and estimate their physicochemical properties. Docking studies were conducted to assess the interactions between TdPDF proteins and the fungal plasma membrane. A total of 28 TdPDF genes were identified in durum wheat based on their conserved domain PF00304 (gamma-thionin). These genes are distributed across all chromosomes of the durum wheat genome, except for chromosomes 4A and 7A. Analysis of the promoters of these genes revealed numerous elements associated with development, hormone responsiveness, and environmental stress. The majority of TdPDF proteins were predicted to be located extracellular. In addition, TdPDF proteins were classified into three clusters based on sequence similarity. Phylogenetic analysis suggested that TdPDF proteins share ancestral similarities with the PDF sequences of other monocotyledonous species. Molecular docking studies revealed that TdPDF proteins interact with fungal plasma membranes, suggesting that they play a critical role in the resistance of plants to pathogen infections. Expression analysis underlined the crucial role of nine TdPDF genes in the defense responses of durum wheat against both pathogenic and environmental stressors. Overall, our findings underscore the potential of TdPDF genes in host-plant resistance and highlight opportunities for their application in crop improvement toward stress tolerance. Full article

Pepper golden mosaic virus (PepGMV) is a bipartite begomovirus of pepper and tomato from North America. In ‘Anaheim’ pepper plants PepGMV-Mo strain (Mo) causes systemic yellow foliar mosaic symptoms, while PepGMV-D strain (D) causes distortion of 1st–6th expanding leaves, and asymptomatic infection of subsequently developing leaves, like other known ‘recovery’ phenotypes. Infections established with DNA-A Mo and D components expressing red-shifted green fluorescent protein in place of coat protein and in situ hybridization, showed PepGMV-Mo localized to phloem and mesophyll cells, while -D was mesophyll restricted. Alignment of PepGMV-Mo and -D DNA-B components revealed three indels upstream of the BC1 gene that encodes the movement protein (MP). To determine if this non-coding region (*BC1) D-strain MP putative promoter contributed to ‘recovery’, plants were inoculated with chimeric DNA-B Mo/D components harboring reciprocally exchanged *BC1, and wild-type DNA-A Mo and D components. Symptoms were reminiscent but not identical to wild-type -Mo or -D infection, respectively, suggesting ‘recovery’ cannot be attributed solely to the *BC1. Both BC1 and D*BC1 were targeted by post-transcriptional gene silencing; however, ‘recovered’ leaves accumulated fewer transcripts and 21–24 nt vsiRNAs. Thus, inefficient in planta movement of PepGMV-D is associated with a non-pepper-adapted ‘defective’ BC1 that facilitates hyper-efficient PTGS, leading to BC1 transcript degradation that in turn limits virus spread, thereby recapitulating disease ‘tolerance’. Full article

Flavonoids have multiple functions, including host-plant defense against attacks from herbivorous insects. This manuscript reviewed and analyzed the scientific literature to test the hypothesis that flavonoids can be utilized to manage pests without causing significant harm to beneficials. The methodology involved using recognized literature databases, e.g., Web of Science, Scopus, and CAB Abstracts, via the USDA-ARS, National Agricultural Library, DigiTop literature retrieval system. Data were compiled in tables and subjected to statistical analysis, when appropriate. Flavonoids were generally harmful to true bugs and true flies but harmless to honey bees. Flavonoid glycosides showed a tendency to harm true bugs (Heteroptera) and true flies (Diptera). Flavonoid glycosides were harmless to sawflies. Flavonoids and flavonoid glycosides produced a mixture of harmful and harmless outcomes to herbivorous beetles, depending on the species. Flavonoid glycosides were harmless to butterflies. In conclusion, specific flavonoids could function as feeding stimulants or deterrents, oviposition stimulants or deterrents, chemical protectants from pesticides, mating attractants, less-toxic insecticides, and other functions. Flavonoids could manage some insect pests without causing significant harm to beneficials (e.g., honey bees). Flavonoid-based insecticides could serve as environmentally benign alternatives to broad-spectrum insecticides against some pests, but field testing is necessary. Full article

Foliage-feeding wild caterpillars have been collected and reared year-round by 1–30 rural resident parataxonomists in the Area de Conservación Guanacaste (ACG) in northwestern Costa Rica since 1978. The aim of the work was to describe the diversity and interactions of Lepidoptera and their associations with larval food plants and parasitoids in a diverse tropical community. A total of 457,816 caterpillars developed into a moth or butterfly, and these were identified to the family and species/morphospecies, with 151,316 having been successfully barcoded and assigned a Barcode Index Number (BIN) and/or “scientific name”. The host food plant was usually identified to the species or morphospecies. In addition to adult moths and butterflies, rearings also yielded many hundreds of species of parasitic wasps and tachinid flies, many of which were also DNA-barcoded and assigned a name and/or BIN. Increasingly over recent years, these have been identified or described by expert taxonomists. Here, we provide a summary of the number of species of ichneumonoid (Ichneumonidae and Braconidae) parasitoids of the caterpillars, their hosts, the host food plants involved, the bi- and tritrophic interactions, and their relationships to the caterpillar sampling effort. The dataset includes 16,133 and 9453 independent rearings of Braconidae and Ichneumonidae, respectively, collectively representing 31 subfamilies, all with parasitoid barcodes and host and host food plant species-level identifications. Host caterpillars collectively represented 2456 species, which, in turn, were collectively eating 1352 species of food plants. Species accumulation curves over time for parasitoids, hosts, and plants show various asymptotic trends. However, no asymptotic trends were detected for numbers of unique parasitoid–host and host–plant bitrophic interactions, nor for tritrophic interactions, after 1983, because climate change then began to conspicuously reduce caterpillar densities. Parasitoid host ranges, the proportions of specialists at the host species and host genus levels, host family utilisation, and host guild sizes show some differences among taxa and are discussed in turn. Ichneumonidae are shown to preferentially parasitise caterpillars of larger-bodied hosts compared to Braconidae. Several of the host plant species from which caterpillars were collected have been introduced from outside of the Americas and their utilisation by endemic parasitoids is described. The obligately hyperparasitoid ichneumonid subfamily Mesochorinae is dealt with separately and its strong association with microgastrine braconid primary parasitoids is illustrated. We discuss the implications for studies of tropical insect community food web ecology and make suggestions for future work. The aim was to make available the data from this remarkable study and to provide an overview of what we think are some of the more interesting relationships that emerge—other scientists/readers are expected to have different questions that they will go on to explore the data to answer. Full article

Diatraea saccharalis (Fabricius) is a major pest of rice crops, and its early detection—before any visible plant damage occurs—is crucial to prevent yield losses and establish effective, rational control methods. This study aimed to model the infrared-thermal responses of rice cultivars to D. saccharalis infestation levels. Between 2019 and 2020, two experiments were conducted in a controlled environment using the cultivars IR 40 and BR IRGA 409, previously identified as having different resistance reactions. Rice plants grown in pots were manually infested with first-instar larvae of D. saccharalis, ranging from 0 to 10 caterpillars per plant, with the plants maintained in cages covered with voile fabric throughout the trial. After 30 days of infestation, the number of live and dead caterpillars, the number of damaged and healthy stems, and the dry mass of the aerial parts were evaluated. A generalized linear mixed model was applied to the data obtained from leaf temperature as a function of infestation level throughout the infestation period, using the F-test to detect significant differences between cultivars. Generalized Additive Models for Location, Scale, and Shape (GAMLSS) were fitted to the variables related to resistance. It was observed that leaf surface temperature is related to the level of infestation and could be used to detect susceptibility in IR 40. In both cultivars, leaf temperatures were higher within the first 15 days post-infestation. Full article

The brown planthopper (Nilaparvata lugens, BPH) is a serious insect pest responsible for causing immense economic losses to rice growers around the globe. The development of high-throughput sequencing technologies has significantly improved the research on this pest, and its genome structure, gene expression profiles, and host–plant interactions are being unveiled. The integration of genomic sequencing, transcriptomics, proteomics, and metabolomics has greatly increased our understanding of the biological characteristics of planthoppers, which will benefit the identification of resistant rice varieties and strategies for their control. Strategies like more optimal genome assembly and single-cell RNA-seq help to update our knowledge of gene control structure and cell type-specific usage, shedding light on how planthoppers adjust as well. However, to date, a comprehensive genome-wide investigation of the genetic interactions and population dynamics of BPHs has yet to be exhaustively performed using these next-generation omics technologies. This review summarizes the recent advances and new perspectives regarding the use of omics data for the BPH, with specific emphasis on the integration of both fields to help develop more sustainable pest management strategies. These findings, in combination with those of post-transcriptional and translational modifications involving non-coding RNAs as well as epigenetic variations, further detail intricate host–brown planthopper interaction dynamics, especially regarding resistant rice varieties. Finally, the symbiogenesis of the symbiotic microbial community in a planthopper can be characterized through metagenomic approaches, and its importance in enhancing virulence traits would offer novel opportunities for plant protection by manipulating host–microbe interactions. The concerted diverse omics approaches collectively identified the holistic and complex mechanisms of virulence variation in BPHs, which enables efficient deployment into rice resistance breeding as well as sustainable pest management. Full article

I report on long-term patterns of outbreak cycling in four study systems across Canada and illustrate how forecasting in these systems is highly imprecise because of complexity in the cycling and a lack of spatial synchrony amongst sample locations. I describe how a range of bottom-up effects could be generating complexity in these otherwise periodic systems. (1) The spruce budworm in Québec exhibits aperiodic and asynchronous behavior at fast time-scales, and a slow modulation of cycle peak intensity that varies regionally. (2) The forest tent caterpillar across Canada exhibits eruptive spiking behavior that is aperiodic locally, and asynchronous amongst regions, yet aggregates to produce a pattern of periodic outbreaks. In Québec, forest tent caterpillar cycles differ in the aspen-dominated northwest versus the maple-dominated southeast, with opposing patterns of cycle intensity between the two regions. (3) In Alberta, forest tent caterpillar outbreak cycles resist synchronization across a forest landscape gradient, even at very fine spatial scales, resulting in a complex pattern of cycling that defies simple forecasting techniques. (4) In the Border Lakes region of Ontario and Minnesota, where the two insect species coexist in a mixedwood landscape of hardwood and conifers, outbreak cycle intensity in each species varies spatially and temporally in response to host forest landscape structure. Much attention has been given to the effect of top-down agents in driving synchronizable population cycles. However, foliage loss, tree death, and forest succession at stem, stand, and landscape scales affect larval and adult dispersal success, and may serve to override regulatory processes that cause otherwise top-down-driven periodic, synchronized, and predictable population oscillations to become aperiodic, asynchronous, and unpredictable. Incorporating bottom-up effects at multiple spatial and temporal scales may be the key to making significant improvements in forest insect outbreak forecasting. Full article