Probing behavior of the corn leafhopper Dalbulus maidis on susceptible and resistant maize hybrids.

The corn leafhopper Dalbulus maidis is the main vector of the pathogens that cause corn stunt, a major disease of maize in the Americas. In line with plant resistance being an efficient tool to control diseases, the findings of a previous work showed that some corn hybrids are resistant to D. maidis. In this work, we assessed the probing behavior of D. maidis on susceptible and resistant corn hybrids using EPG (Electrical Penetration Graph) technology. Feeding of fifteen-day-old, non-inoculative females was recorded for 20 hours, with access to hybrids DK390, DK670, DK79-10, and DK72-10. Compared to the susceptible hybrid DK670, the other hybrids shifted D. maidis probing behavior in a way consistent with plant resistance to insects. This shift consisted of a higher number of probes of short duration, difficulties in attaining phloem ingestion and increase in xylem ingestion. In addition to this common shift in probing behavior, a phloem-located resistance factor was inferred in DK72-10 based on the longer time spent in phloem conditioning to attain phloem ingestion. In contrast, DK390 expressed the highest level of mesophyll and phloem-based resistance, in both cases seen with repeated attempts of short duration, a behavior typically associated with failed attempts to ingest. These findings support and are consistent with previous research, providing useful information to characterize maize hybrids resistant to D. maidis, and consequently to corn stunt.

Development of efficient RNAi methods in the corn leafhopper Dalbulus maidis, a promising application for pest control.

BACKGROUND: The corn leafhopper Dalbulus maidis is the main vector of important stunting pathogens that affect maize production. Currently, there are no effective methods available to manage this pest without adverse impact on the environment. In this context, genomic-based technologies such as RNA interference (RNAi) provide a more environmentally friendly pest control strategy. Therefore, we aimed to assess the application of RNAi in D. maidis and determine the function of a candidate gene related to insect reproduction and propagation. RESULTS: We have characterized the core RNAi genes and evaluated the functionality of the RNAi machinery. We assessed the potential of RNAi technology in D. maidis via injection or ingestion of double-stranded RNA (dsRNA) to adult females. We chose Bicaudal C (BicC) as a target gene due to its important role during insect oogenesis. Administration of dsRNABicC caused significant reductions in the transcript levels (fold changes up to 170 times) and ovipositions. Phenotypic analysis of the ovaries revealed alterations in oocyte development, providing additional confirmation for our results and supporting the idea that Dmai-BicC is a key player of D. maidis oogenesis. CONCLUSION: This is, to our knowledge, the first report of efficient RNAi in D. maidis. We believe our findings provide a starting point for future control strategies against one of the most important maize pests in the Americas. © 2022 Society of Chemical Industry.

Characterization of components of resistance to Corn Stunt disease.

Corn Stunt is an important disease in the Americas due to it high prevalence and the yield reductions that can cause when present. However, changes in the presence of this disease across years hampers the effective identification of resistant genotypes to this disease. To avoid the limitations of phenotypic selection under natural pressure, this research aimed to devise an effective strategy to screen disease-resistant genotypes in the absence of high and constant natural pressures. To do so, we investigated the presence of antixenosis and antibiosis as components of resistance to the vector Dalbulus maidis as well as resistance to the pathogen Spiroplasma kunkelii under artificial inoculation conditions in four maize hybrids. The hybrids shown differences in their levels of resistance and target organisms, either the insect vector or the pathogen. Antixenosis and antibiosis to D. maidis were observed in DK72-10. Resistance to S. kunkelii by DK79-10 was seen as a delayed onset of symptoms, and DKB390 showed antixenosis to D. maidis and resistance to S. kunkelii. An association between symptom severity and yield reduction was found, but not between accumulation of pathogen S. kunkelii and symptom severity nor yield. In conclusion, the proposed methodology was efficacious and can aid in the screening of resistant genotypes in breeding programs to reduce the impact of Corn Stunt disease, ensuring that hybrids with good resistance level will be planted by farmers whenever disease occurs.

Nezara viridula (Hemiptera: Pentatomidae) transcriptomic analysis and neuropeptidomics.

Stinkbugs (Hemiptera: Pentatomidae) are of major economic importance as pest of crops. Among the species composing the stinkbug complex, Nezara viridula is one of the most abundant in Brazil, Argentina and the Southern USA. However, this species has been poorly characterized at the genetic and physiological level. Here we sequenced and analyzed the complete transcriptome of N. viridula male and female adults. We identified neuropeptide precursor genes and G-protein coupled receptors for neuropeptides in this transcriptome. Mature neuropeptides were identified in N. viridula brain extracts by liquid chromatography-tandem mass spectrometry. We also analyzed the neuropeptide precursor complement in the genome sequence of Halyomorpha halys, another pentatomid of economic relevance. We compared the results in both pentatomids with the well-characterized neuropeptide repertoire from the kissing bug Rhodnius prolixus (Hemiptera: Reduviidae). We identified both group-specific features (which could be related to the different feeding habits) and similarities that could be characteristic of Heteroptera. This work contributes to a deeper knowledge of the genetic information of these pests, with a focus on neuroendocrine system characterization.

New replacement name for Tricella Catalano & Dietrich, 2017 (Hemiptera: Cicadellidae: Typhlocybinae).

We recently established the leafhopper genus Tricella with the type species Tricella antonellae from Ecuador (Catalano & Dietrich 2017). Unfortunately, Tricella n.gen is junior homonym of Tricella Daniels, 1975 (Diptera). Therefore, we propose a new replacement name Carpaneura nom. nov. for Tricella Catalano & Dietrich, 2017 as required by Article 60 of the International Code of Zoological Nomenclature. The genus is named in honor of the first author's husband, Pablo Carpane. The name combines his family name with the suffix of the type genus of the tribe and is treated as a feminine noun. Replacement of the junior homonym also requires the following new combination for the originally designated type species: Carpaneura antonellae (Catalano & Dietrich), comb. nov.

Review of the genus Relaba (Hemiptera: Cicadellidae: Typhlocybinae: Alebrini) and description of two new species from Argentina.

The genus Relaba is reviewed, and two new species, R. forcipula n. sp. and R. globata n. sp. are added. Detailed morphological descriptions and illustrations of the new species, and a key to males of known species are provided.

Review of the genera Paulomanus Young, 1952 and Beamerana Young, 1952 (Hemiptera: Cicadellidae: Typhlocybinae: Empoascini) with description of a new species from Argentina.

The Neotropical microleafhopper genera Paulomanus and Beamerana are redescribed based on study of type material and newly collected specimens. Paulomanus is recorded for the first time from Argentina and a new species, P. falciformis n. sp., is described. Detailed morphological description and illustration of the new species and a key to males of the known species of Paulomanus are provided. A key to genera of the New World Empoascini is also provided.

First report on the leafhopper genus Balera Young (Hemiptera, Cicadellidae, Typhlocybinae, Alebrini) from Argentina, and description of a new species.

The genus Balera Young is reported for first time to Argentina and a new species is described, Balera floripara sp. n. Detailed morphological descriptions and illustrations of the new species and a key to males of known species are provided. Habralebra amoena is also recorded for the first time from Argentina.

ResumenEl género Balera Young es registrado por primera vez para Argentina y una nueva especie es descripta, Balera floriparasp. n. Se provee de detalladas descripciones morfológicas e ilustraciones de la nueva especie, y una clave de las especies conocidas. Además Habralebra amoena se registra por primera vez para Argentina.

Three new species of Neozygina Dietrich & Dmitriev (Hemiptera, Cicadellidae, Typhlocybinae) from Argentina, with a key to South American species.

Three new species of Neozygina Dietrich & Dmitriev are described from Argentina, N. apicalis sp. nov., N. bifurcata sp. nov. and N. spinula sp. nov. Detailed morphological descriptions and illustrations of the new species are provided, and a key to South American species of the genus is given.

Four new species of genus Parallaxis McAtee (Hemiptera: Cicadellidae: Typhlocybinae: Dikraneurini) from Argentina, with a key to known species.

Four new species of Parallaxis McAtee are described from Argentina, P. jujuiensis sp. n., P. misionensis sp. n., P. tucumanensis sp. n. and P. virlai sp. n. Detailed morphological descriptions and illustrations of the new species and a key to males of known species are provided.

Consideraciones taxonómicas y biológicas sobre edwardsiana froggatti (baker), la chicharrita amarilla del manzano (hemiptera-auchenorrhyncha- cicadellidae) / Biological and taxonomic considerations on edwardsiana froggatti (baker), the apple yellow leafhopper (hemiptera-auchenorrhyncha-cicadellidae) / Considerações biológicas e taxonômicas sobre edwardsiana froggatti (baker), a maçã amarela cigarrinha (hemiptera-auchenorrhyncha-cicadellidae)

Edwardsiana froggatti (Baker, 1925) es una especie ampliamente distribuida que causa severos perjuicios en zonas frutícolas. En la presente contribución, sobre la base de materiales provenientes de las principales zonas productoras de manzanos de la Argentina, se redescriben los caracteres morfológicos y se consideran nuevos elementos diagnósticos de ambos sexos. Se incluye información complementaria acerca de antecedentes taxonómicos, distribución geográfica, datos biológicos y enemigos naturales.

Edwardsiana froggatti (Baker, 1925) is a widely distributed species that causes severe damage in fruit growing areas. In this contribution, based on materials from the major apple-producing areas of Argentina, its morphological characteristics are re-described and new diagnostic elements of both sexes are considered. Additional information on taxonomic history, geographic distribution, biological data and natural enemies is also included.

Edwardsiana froggatti (Baker, 1925) é uma espécie amplamente distribuída, que causam graves prejuízos em fruticultura áreas. Nesta contribuição, com base em materiais das principais zonas de produção da maçã na Argentina, foi re-descritas os caracteres morfológicos e inclui elementos novos diagnósticos de ambos os sexos. Acrescenta também obter informações adicionais sobre a história taxonômica, distribuição geográfica, dados biológicos e inimigos naturais.