Detecção e caracterização molecular de um fitoplasma do grupo 16SrIII associado ao amarelo da videira na região serrana do Rio Grande do Sul

Abstract

The grapevine is one of the most cultivated fruit trees in the world, having great socio-economic importance in Brazil, particularly in the highlands of Rio Grande do Sul. Numerous diseases affect grapevine worldwide, interfering in grape production and generating economic losses. One of these diseases is the grapevine yellow, whose etiologic agent is a phytoplasma. These wall-less prokaryotes live and multiply in phloem vessels of plants and hemolymph of insect vectors. In Brazil, there are reports of the presence of phytoplasma infecting grapevines in the states of São Paulo and Paraná. In Rio Grande do Sul has been found infecting apple trees, causing the apple rubbery wood disease, as well as the presence of their possible insect vectors in vineyards, leafhoppers of the Cicadellidae group. In recent cycles of production, grapevines showing typical symptoms of phytoplasma infection had been observed in the vineyards of the highlands of Rio Grande do Sul. This study aimed to confirm the presence of phytoplasma infecting grapevines in vineyards of the highlands of Rio Grande do Sul and rank the phytoplasmas on the group and subgroup to which they belong. Branches and roots of plants showing symptoms such as, reddening or yellowing of leaves on red or white cultivars respectively, leaf downwards rolling, proliferation of axillary buds resulting in a witches’ broom behavior, abnormal internodes elongation, phloem necrosis and stunting, were sampled during the years 2014 and 2015 vintage. Total DNA was extracted and used for phytoplasmas detection by nested PCR with primers mF2 R16/R16 R1, P1/P7 and P1/Tint in the first reaction and F2n R16/R16 R2 in the second reaction. For molecular identification the second reaction product, corresponding to the region 16S rDNA fragments were sequenced and generated sequences were aligned. A representative sequence of grapevine phytoplasma was used for RFLP analysis in silico, with 17 restriction enzymes, and phylogenetic analysis. Phytoplasmas were detected in four samples deriving from three symptomatic vines. The aligned sequences showed 99% similarity with phytoplasma sequences deposited in GeneBank. The RFLP patters and the phylogenetic analysis, allowed concluding that the phytoplasmas found belongs to the group16SrIII, and 16SrIII- J subgroup. Thus, this study confirms the presence of phytoplasma infecting grapevines in the highlands of Rio Grande do Sul, indicating the occurrence of grapevine yellow disease hitherto none diagnosed in the region.