Incidence of Begomovirus and Crinivirus in tomato and potato crops in Paraná state, Brazil / Incidência de Begomovirus e Crinivirus nas culturas do tomateiro e batateira no estado do Paraná, Brasil

In the last decades, the high incidence of viruses transmitted by whiteflies has become a problem in the tomato fields, threatening, more recently, the potato crops. The present study carried out a survey of begomoviruses and criniviruses in tomato and potato crops, from 2015 to 2018, in the municipalities of Araucária, Campo do Tenente, Campo Largo, Contenda, Lapa, Faxinal, Morretes, Reserva, Castro, Palmeira and São Mateus do Sul, in Paraná State, Brazil. Total DNA and RNA from leaves were extracted and used as templates to detect, respectively, begomoviruses by PCR and criniviruses by RT-PCR. Out of 215 tomato samples, 14 from Faxinal were infected by crinivirus. The other tomato samples and 243 potato samples showed negative results for begomovirus and crinivirus. Results indicated a low incidence (6.5%) of crinivirus infecting tomato crops in Paraná State, and the nucleotide sequence of one amplified fragment shared 99.71% identity with tomato chlorotic virus (ToCV).

Nas últimas décadas, a alta incidência de vírus transmitidos por mosca-branca tornou-se um problema nos campos de tomateiros, ameaçando, mais recentemente, a cultura da batateira. O presente trabalho teve como objetivo realizar um levantamento de begomovírus e crinivírus em lavouras de tomateiro e batateira nos municípios de Araucária, Campo do Tenente, Campo Largo, Contenda, Lapa, Faxinal, Morretes, Reserva, Castro, Palmeira e São Mateus do Sul, no Estado do Paraná, Brasil, de 2015 à 2018. DNA e RNA totais de folhas foram extraídos e utilizados como molde para detectar begomovírus por PCR e crinivírus por RT-PCR. Das 215 amostras de tomateiros coletadas, 14 provenientes de Faxinal estavam infectadas por crinivírus. As demais amostras de tomateiro e as 243 amostras de batateira analisadas apresentaram resultados negativo para begomovírus e crinivírus. Os resultados indicaram baixa incidência (6,5%) de crinivírus infectando lavouras de tomateiros no Estado do Paraná e a sequência de nucleotídeos de um amplicon apresentou 99,71% de identidade com o crinivírus tomato chlorotic virus (ToCV).

A Novel Lineage of Cile-Like Viruses Discloses the Phylogenetic Continuum Across the Family Kitaviridae.

An increasing number of plant species have been recognized or considered likely reservoirs of viruses transmitted by Brevipalpus mites. A tiny fraction of these viruses, primarily those causing severe economic burden to prominent crops, have been fully characterized. In this study, based on high-throughput sequencing, transmission electron microscopy analyses of virions in plant-infected tissues, viral transmission experiments, and the morphoanatomical identification of the involved Brevipalpus mites, we describe molecular and biological features of viruses representing three new tentative species of the family Kitaviridae. The genomes of Solanum violifolium ringspot virus (SvRSV, previously partially characterized), Ligustrum chlorotic spot virus (LigCSV), and Ligustrum leprosis virus (LigLV) have five open reading frames (ORFs) > 500 nts, two distributed in RNA1 and three in RNA2. RNA1 of these three viruses display the same genomic organization found in RNA1 of typical cileviruses, while their RNA2 are shorter, possessing only orthologs of genes p61, p32, and p24. LigCSV and LigLV are more closely related to each other than to SvRSV, but the identities between their genomic RNAs were lower than 70%. In gene-by-gene comparisons, ORFs from LigCSV and LigLV had the highest sequence identity values (nt sequences: 70-76% and deduced amino acid sequences: 74-83%). The next higher identity values were with ORFs from typical cileviruses, with values below 66%. Virions of LigLV (≈ 40 nm × 55 nm) and LigCSV (≈ 54 nm × 66 nm) appear almost spherical, contrasting with the bacilliform shape of SvRSV virions (≈ 47 nm × 101 nm). Mites collected from the virus-infected plants were identified as Brevipalpus papayensis, B. tucuman, and B. obovatus. Viruliferous B. papayensis mites successfully transmitted LigCSV to Arabidopsis thaliana. SvRSV, LigCSV, and LigLV seem to represent novel sub-lineages of kitaviruses that descent on parallel evolutionary branches from a common ancestor shared with the tentative cile-like virus hibiscus yellow blotch virus and typical cileviruses. Biological and molecular data, notably, the phylogenetic reconstruction based on the RdRp proteins in which strong support for monophyly of the family Kitaviridae is observed, mark an advance in the understanding of kitavirids.

Reaction of sugarcane genotypes to brown and to orange rust by leaf whorl inoculation / Reação de genótipos de cana-de-açúcar às ferrugens marrom e alaranjada por inoculação no cartucho foliar

In this research eleven sugarcane genotypes were classified in relation to their resistance to brown rust, and eleven to their resistance to orange rust. Artificial inoculation was carried out in the leaf whorl of 165-day-old plants in the city of Paranavaí, Paraná State, Brazil, in 2017. The evaluation was performed 30 days after inoculation, using a rating scale. Among the genotypes tested for brown rust, four were classified as susceptible, six as moderately susceptible and one presented moderate resistance. For orange rust, three genotypes were classified as susceptible, seven as moderately susceptible and one as moderately resistant. The evaluation and classification of the reaction of sugarcane genotypes to the rusts is an important tool that assist in preliminary trials and selection of promising genotypes for more advanced stages of breeding programs and provides information to producers on the choice of cultivars to be planted.(AU)

Neste trabalho onze genótipos de cana-de-açúcar foram classificados em relação à sua resistência à ferrugem marrom, e onze quanto à resistência à ferrugem alaranjada. Foi realizada a inoculação no cartucho foliar de colmos com 165 dias, no município de Paranavaí, PR, em 2017. A avaliação foi feita aos 30 dias após a inoculação, utilizando uma escala de notas. Dos genótipos avaliados para ferrugem marrom, quatro foram classificados como suscetíveis, seis como moderadamente suscetíveis e um apresentou resistência moderada. Para a ferrugem alaranjada, três genótipos foram classificados como suscetíveis, sete como moderadamente suscetíveis e um como moderadamente resistente. A avaliação e classificação da reação de genótipos de cana-de-açúcar às ferrugens é uma ferramenta importante que auxilia em ensaios preliminares, na escolha de genótipos promissores para fases mais avançadas dos programas de melhoramento além de fornecer informações aos produtores na seleção das cultivares que serão plantadas.(AU)

Reaction of sugarcane genotypes to brown and to orange rust by leaf whorl inoculation / Reação de genótipos de cana-de-açúcar às ferrugens marrom e alaranjada por inoculação no cartucho foliar

ABSTRACT: In this research eleven sugarcane genotypes were classified in relation to their resistance to brown rust, and eleven to their resistance to orange rust. Artificial inoculation was carried out in the leaf whorl of 165-day-old plants in the city of Paranavaí, Paraná State, Brazil, in 2017. The evaluation was performed 30 days after inoculation, using a rating scale. Among the genotypes tested for brown rust, four were classified as susceptible, six as moderately susceptible and one presented moderate resistance. For orange rust, three genotypes were classified as susceptible, seven as moderately susceptible and one as moderately resistant. The evaluation and classification of the reaction of sugarcane genotypes to the rusts is an important tool that assist in preliminary trials and selection of promising genotypes for more advanced stages of breeding programs and provides information to producers on the choice of cultivars to be planted.

RESUMO: Neste trabalho onze genótipos de cana-de-açúcar foram classificados em relação à sua resistência à ferrugem marrom, e onze quanto à resistência à ferrugem alaranjada. Foi realizada a inoculação no "cartucho foliar" de colmos com 165 dias, no município de Paranavaí, PR, em 2017. A avaliação foi feita aos 30 dias após a inoculação, utilizando uma escala de notas. Dos genótipos avaliados para ferrugem marrom, quatro foram classificados como suscetíveis, seis como moderadamente suscetíveis e um apresentou resistência moderada. Para a ferrugem alaranjada, três genótipos foram classificados como suscetíveis, sete como moderadamente suscetíveis e um como moderadamente resistente. A avaliação e classificação da reação de genótipos de cana-de-açúcar às ferrugens é uma ferramenta importante que auxilia em ensaios preliminares, na escolha de genótipos promissores para fases mais avançadas dos programas de melhoramento além de fornecer informações aos produtores na seleção das cultivares que serão plantadas.

Arabidopsis thaliana as a model host for Brevipalpus mite-transmitted viruses

Brevipalpus-transmitted viruses (BTV) are a taxonomically diverse group of plant viruses which severely affect a number of major crops. Members of the group can be sub-classified into cytoplasmic (BTV-C) or nuclear type (BTV-N) according to the accumulation sites of virions in the infected plant cells. Both types of BTV produce only local infections near the point of inoculation by viruliferous mites. Features of BTV-plant interactions such as the failure of systemic spread in their natural hosts are poorly understood. In this study we evaluated Arabidopsis thaliana, a model plant commonly used for the study of plant-virus interactions, as an alternative host for BTV. Infection of Arabidopsis with the BTV-N Coffee ringspot virus and Clerodendrum chlorotic spot virus, and the BTV-C Solanum violaefolium ringspot virus, were mediated by viruliferous Brevipalpus mites collected in the wild. Upon infestation, local lesions appeared in 7 to 10 days on leaves of, at least, 80 % of the assayed plants. Presence of viral particles and characteristic cytopathic effects were detected by transmission electron microscopy (TEM) and the viral identities confirmed by specific reverse-transcriptase polymerase chain reaction (RT-PCR) and further amplicon sequencing. The high infection rate and reproducibility of symptoms of the three different viruses assayed validate A. thaliana as a feasible alternative experimental host for BTV.

Arabidopsis thaliana as a model host for Brevipalpus mite-transmitted viruses

Brevipalpus-transmitted viruses (BTV) are a taxonomically diverse group of plant viruses which severely affect a number of major crops. Members of the group can be sub-classified into cytoplasmic (BTV-C) or nuclear type (BTV-N) according to the accumulation sites of virions in the infected plant cells. Both types of BTV produce only local infections near the point of inoculation by viruliferous mites. Features of BTV-plant interactions such as the failure of systemic spread in their natural hosts are poorly understood. In this study we evaluated Arabidopsis thaliana, a model plant commonly used for the study of plant-virus interactions, as an alternative host for BTV. Infection of Arabidopsis with the BTV-N Coffee ringspot virus and Clerodendrum chlorotic spot virus, and the BTV-C Solanum violaefolium ringspot virus, were mediated by viruliferous Brevipalpus mites collected in the wild. Upon infestation, local lesions appeared in 7 to 10 days on leaves of, at least, 80 % of the assayed plants. Presence of viral particles and characteristic cytopathic effects were detected by transmission electron microscopy (TEM) and the viral identities confirmed by specific reverse-transcriptase polymerase chain reaction (RT-PCR) and further amplicon sequencing. The high infection rate and reproducibility of symptoms of the three different viruses assayed validate A. thaliana as a feasible alternative experimental host for BTV.(AU)