RESUMO
Soybean stem necrosis is caused by cowpea mild mottle virus (CPMMV), transmitted by the whitefly Bemisia tabaci. CPMMV has already been recorded in all major soybean-producing areas of Brazil. The impacts caused by CPMMV to the current Brazilian soybean production are unknown, thus the main objective of this study was to evaluate the effects of CPMMV infection on the main important soybean cultivars grown in the Southern and Midwestern regions of Brazil. Although asymptomatic in some of the tested cultivars, CPMMV infection significantly reduced the plant height, the number of pods per plant and the 1,000-grain weight. In addition, estimated yield losses ranged from 174 to 638 kg ha-1, depending on the cultivar. Evidence of seed transmission of CPMMV was observed in the BMX POTÊNCIA RR cultivar. These results suggest that CPMMV could have an important role in the reduction of soybean productivity in Brazil, but symptomless infections might be hiding the actual impact of this pathogen in commercial fields and infected seeds could be the primary inoculum source of the virus in the field.
RESUMO
The complete nucleotide sequence of a new member of the family Potyviridae, which we propose to name "Arachis virus Y" (ArVY), is reported from forage peanut plants (Arachis pintoi) exhibiting virus-like symptoms. The ArVY positive-sense RNA genome is 9,213 nucleotides long and encodes a polyprotein with 2,947 amino acids that is predicted to be cleaved into 10 mature proteins. The complete single open reading frame (ORF) of ArVY shares 47% and 34% nucleotide and amino acid sequence identity, respectively, with the closest related virus, soybean yellow shoot virus. Electron microscopic analysis revealed elongated viral particles typical of those found in plant cells infected with potyviruses.
Assuntos
Arachis/virologia , Genoma Viral , Filogenia , Potyviridae/genética , RNA Viral/genética , Proteínas Virais/genética , Brasil , Fases de Leitura Aberta , Doenças das Plantas/virologia , Folhas de Planta/virologia , Potyviridae/classificação , Potyviridae/isolamento & purificação , Potyviridae/ultraestrutura , Vírion/genética , Vírion/isolamento & purificação , Vírion/ultraestruturaRESUMO
The whitefly, Bemisia tabaci, is a species complex of more than 40 cryptic species and a major agricultural pest. It causes extensive damage to plants mainly by transmitting plant viruses. There is still a lack of genomic data available for the different whitefly species found in Brazil and their bacterial endosymbionts. Understanding the genetic and transcriptomic composition of these insect pests, the viruses they transmit and the microbiota is crucial to sustainable solutions for farmers to control whiteflies. Illumina RNA-Seq was used to obtain the transcriptome of individual whiteflies from 10 different populations from Brazil including Middle East-Asia Minor 1 (MEAM1), Mediterranean (MED) and New World 2 (NW2). Raw reads were assembled using CLC Genomics Workbench and subsequently mapped to reference genomes. We obtained whitefly complete mitochondrial genomes and draft genomes from the facultative bacterial endosymbiont Hamiltonella for further phylogenetic analyses. In addition, nucleotide sequences of the GroEL chaperonin gene from Hamiltonella from different populations were obtained and analysed. There was concordance in the species clustering using the whitefly complete mitogenome and the mtCOI gene tree. On the other hand, the phylogenetic analysis using the 12 ORF's of Hamiltonella clustered the native species NW2 apart from the exotics MEAM1 and MED. In addition, the amino acid analysis of GroEL chaperonin revealed a deletion only in Hamiltonella infecting NW2 among whiteflies populations analysed which was further confirmed by PCR and Sanger sequencing. The genomic data obtained in this study will aid understanding the functions that Hamiltonella may have in whitefly biology and serve as a reference for further studies regarding whiteflies in Brazil.