Resposta fotossintética de citros a isolados de Citrus tristeza virus com potencial para proteção cruzada

The objective of this work was to evaluate the photosynthetic response of citrus varieties to the inoculation of isolates T30 and T3 of Citrus tristeza virus (CTV) characterized as having potential to provide cross‑protection against severe CTV isolates in citrus. Citrus plants of 'Campbell' orange, 'Persian' lime, and 'Key' lime were subjected to inoculations by both isolates by patch. Noninoculated plants were used as the control. Symptom expression, photosynthetic and transpiration rates, and stomatal conductance were evaluated by IRGA. Stomatal density and size were evaluated by epidermal impressions. The CTV isolates were also evaluated and molecularly characterized by RT-PCR and Sanger sequencing. 'Campbell' orange and 'Persian' lime plants remained asymptomatic after the inoculations. The inoculation treatments with both CTV isolates did not reduce photosynthetic capacity, transpiration rate, and stomatal conductance, in comparison with the control. Stomatal density and size varied according to the citrus species. T30 and T3 do not affect the photosynthetic responses of 'Campbell' orange and 'Persian' lime; therefore, these isolates have the potential to provide cross-protection to citrus varieties against severe isolates of CTV.O objetivo deste trabalho foi avaliar a resposta fotossintética de variedades de citros submetidas à inoculação dos isolados T30 e T3 de Citrus tristeza virus (CTV) caracterizados como tendo potencial para conferir proteção cruzada a citros contra isolados severos de CTV. Plantas de citros de laranja 'Campbell', limão 'Tahiti' e limão 'Galego' foram submetidas à inoculação de ambos os isolados por “patch”. Plantas não inoculadas foram utilizadas como controle. A expressão dos sintomas,  as taxas fotossintética e de transpiração, e a condutância estomática foram avaliadas por IRGA. A densidade e o tamanho estomáticos foram avaliados por impressões epidérmicas. Os isolados de CTV também foram avaliados e caracterizados molecularmente por RT-PCR e sequenciamento de Sanger. As plantas de laranja 'Campbell' e limão 'Tahiti' permaneceram assintomáticas após as inoculações. Os tratamentos de inoculação com ambos os isolados de CTV não reduziram capacidade fotossintética, taxas de transpiração e condutância estomática, em comparação ao controle. A densidade e o tamanho estomáticos variaram de acordo com a espécie. T30 e T3 não afetam as respostas fotossintéticas de laranja 'Campbell' e limão 'Tahiti'; portanto, estes isolados têm potencial para promover proteção cruzada a variedades de citros contra isolados severos de CTV

Antiviral RNA silencing suppression activity of \u3ci\u3eTomato spotted wilt virus\u3c/i\u3e NSs protein

In addition to regulating gene expression, RNA silencing is an essential antiviral defense system in plants. Triggered by double-stranded RNA, silencing results in degradation or translational repression of target transcripts. Viruses are inducers and targets of RNA silencing. To condition susceptibility, most plant viruses encode silencing suppressors that interfere with this process, such as the Tomato spotted wilt virus (TSWV) NSs protein. The mechanism by which NSs suppresses RNA silencing and its role in viral infection and movement remain to be determined. We cloned NSs from the Hawaii isolate of TSWV and using two independent assays show for the first time that this protein restored pathogenicity and supported the formation of local infection foci by suppressor-deficient Turnip mosaic virus and Turnip crinkle virus. Demonstrating the suppression of RNA silencing directed against heterologous viruses establishes the foundation to determine the means used by NSs to block this antiviral process

Diversidad de tisanópteros en crisantemo [dendranthema grandiflorum]

In order to determine the diversity of thrips species associated with Chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura] var. Harman, at four locations in the municipality of Texcoco, State of Mexico, larvae and adults were collected biweekly in the periods from March to June and August to November 2011. The collected individuals were subjected to clarification techniques and mounted for identification. Seventeen species of thrips were identified, included in the genera Frankliniella with 13 species and Anaphothrips, Chrirothrips, Neohydatothrips and Leptothrips with one species each. Most abundant species were F. occidentalis and F. brunnescens (88.6%). The diversity and abundance of thrips was similar in the four localities. The ecological relevance of our findings is discussedCon el objetivo de estimar la diversidad de especies de tisanópteros asociados al cultivo de crisantemo [Dendranthema grandiflorum (Ramat.) Kitamura] var. Harman en cuatro localidades en el municipio de Texcoco, Estado de México, se realizaron recolectas quincenales de larvas y adultos, en los periodos de marzo a junio y agosto a noviembre de 2011. Los individuos recolectados se sometieron a técnicas de aclaración y montaje para su identificación. Se identificaron 17 especies de trips, incluidas en los géneros Frankliniella con 13 especies; Neohydatothrips, Anaphothrips, Chrirothrips y Leptothrips con una especie cada uno. Las especies más abundantes fueron F. occidentalis y F. brunnescens (88.6%). La diversidad y abundancia de tisanópteros fue similar en las cuatro localidades estudiadas. Se discute la relevancia ecológica de nuestros hallazgos

Mexico: A Landscape of Viroid Origin and Epidemiological Relevance of Endemic Species

Viroids are single-stranded, circular RNA molecules (234-406 nt) that infect a wide range of crop species and cause economic losses in agriculture worldwide. They are characterized by the existence of a population of sequence variants, attributed to the low fidelity of RNA polymerases involved in their transcription, resulting in high mutation rates. Therefore, these biological entities exist as quasispecies. This feature allows them to replicate within a wide range of host plants, both monocots and dicots. Viroid hosts include economically important crops such as tomato, citrus, and fruit trees such as peach and avocado. Given the high risk of introducing viroids to viroid disease-free countries, these pathogens have been quarantined globally. As discussed herein, Mexico represents a geographical landscape of viroids linked to their origin and comprises considerable biodiversity. The biological features of viroid species endemic to Mexico are highlighted in this communication. In addition, we report the phylogenetic relationships among viroid and viroid strains, their economic impact, geographical distribution, and epidemiological features, including a broad host range and possible long-distance, seed, or insect-mediated transmission. In summary, this review could be helpful for a better understanding of the biology of viroid diseases and future programs on control of movement and spread to avoid economic losses in agricultural industries