RESUMO
The negative effects of viruses and the positive effects of arbuscular mycorrhizal fungi (AMF) on grapevine performance are well reported, in contrast to the knowledge about their interactive effects in perennial plants, e.g., in grapevine. To elucidate the physiological consequences of grapevine-AMF-virus interactions, two different AMF inoculum (Rhizophagus irregularis and 'Mix AMF') were used on grapevine infected with grapevine rupestris stem pitting virus, grapevine leafroll associated virus 3 and/or grapevine pinot gris virus. Net photosynthesis rate (AN), leaf transpiration (E), intercellular CO2 concentration (Ci) and conductance to H2O (gs) were measured at three time points during one growing season. Furthermore, quantum efficiency in light (ΦPSII) and electron transport rate (ETR) were surveyed in leaves of different maturity, old (basal), mature (middle) and young (apical) leaf. Lastly, pigment concentration and growth parameters were analysed. Virus induced changes in grapevine were minimal in this early infection stage. However, the AMF induced changes of grapevine facing biotic stress were most evident in higher net photosynthesis rate, conductance to H2O, chlorophyll a concentration, total carotenoid concentration and dry matter content. The AMF presence in the grapevine roots seem to prevail over virus infection, with Rhizophagus irregularis inducing greater photosynthesis changes in solitary form rather than mixture. This study shows that AMF can be beneficial for grapevine facing viral infection, in the context of functional physiology.
RESUMO
ABSTRACT: Grapevine rupestris stem pitting-associated virus (GRSPaV) is one of the most common viruses of grapevine. It is involved in the graft-transmissible disease rupestris stem pitting of the rugose wood complex. The objective of the research was to perform the molecular characterization of the coat protein (CP) gene of sixteen Brazilian GRSPaV isolates aiming to determine the occurrence of molecular variants (strains) of this virus. Nine grapevine samples were evaluated, from which dsRNA was extracted. Nucleotide sequences were generated by Next generation sequencing (NGS). Fifteen complete sequences of the GRSPaV CP gene were obtained and phylogenetically analyzed. Multiple alignments of the sequences showed identities of nucleotides ranging from 82% to 99%, suggesting high variability among the CPs of Brazilian isolates. The study revealed that genetic variability of GRSPaV comprising three molecular variants is also present in Brazilian grapevine genotypes.
RESUMO: O GRSPaV é um dos vírus mais comuns da videira. Está associado à doença transmissível por enxertia denominada caneluras de rupestris que compõe o complexo do lenho rugoso. O objetivo do trabalho foi realizar a caracterização molecular do gene da proteína capsidial (CP) de 16 isolados brasileiros de GRSPaV visando determinar a ocorrência de variantes moleculares desse vírus. Nove amostras de videira foram avaliadas das quais foi extraído dsRNA. As sequências de nucleotídeos foram geradas pelo sequenciamento de nova geração (NGS). Quinze sequências completas do gene CP de GRSPaV foram obtidas e filogeneticamente analisadas. Os alinhamentos múltiplos entre as sequências mostraram identidades de nucleotídeos variando de 82% a 99%, sugerindo alta variabilidade entre as CPs de isolados brasileiros. O estudo revelou que a variabilidade genética de GRSPaV compreendendo três variantes moleculares também está presente nos genótipos de videira no Brasil.
RESUMO
ABSTRACT: The absolute quantification determines the absolute amount of a targeted nucleic acid expressed as a copy number or concentration. The knowledge of virus concentrations in commercial crops possesses high relevance to ensure a reliable diagnosis. The objective of this study was to perform an absolute quantification of five viruses in infected grapevines (Vitis spp.). Different known amounts of the standard sample (cloned viral cDNA or in vitro transcribed viral RNA) were quantified by TaqMan RT-qPCR. Based on these data, standard curves were generated plotting Ct values (threshold cycle) against the log of the standard sample amount. Infected grapevine samples were evaluated to determine virus titers, which were highly variable. This result may contribute to improve virus diagnosis by accurately quantifying virus titre variations in grapevines.
RESUMO: A quantificação absoluta determina a quantidade absoluta de um ácido nucleico alvo expressa como número de cópias ou concentração. O conhecimento das concentrações virais em culturas comerciais tem grande relevância para assegurar um diagnóstico confiável. O objetivo deste trabalho foi realizar uma quantificação absoluta de cinco vírus em videiras infectadas (Vitis spp.). Diferentes quantidades conhecidas da amostra padrão (cDNA viral clonado ou RNA viral transcrito in vitro) foram quantificadas por RT-qPCR TaqMan. A partir destes dados, curvas padrão foram geradas plotando-se os valores de Ct (ciclo limiar) contra o log da quantidade da amostra padrão. Amostras de videiras infectadas foram avaliadas visando-se determinar os títulos virais que foram bastante variáveis. Este resultado contribui para melhorar o diagnóstico viral ao quantificar com precisão variações no título viral em videiras.
