Acerola shoot proliferation induced by a phytoplasma enclosed in the subgroup 16SrIII-F

Acerola bushes were observed showing symptoms of shoot proliferation, generalized stunting, yellowing and decline. Since these symptoms are typically induced by phytoplasmas, this survey was carried out with the aim of detecting, identifying and classifying the supposed phytoplasma present in symptomatic bushes. Total DNA was extracted from symptomatic and asymptomatic samples and used in nested PCR conducted by the primer pairs R16mF2/mR1 followed by R16F2n/R2. Amplifications of expected genomic fragments of 1.2 kb revealed the presence of phytoplasma in 73 % of the symptomatic samples. Molecular analyses, using computer-simulated RFLP patterns, similarity coefficient calculation and phylogenetic analysis allowed for classifying the bacterium as a 'Candidatus Phytoplasma pruni' - related strain (subgroup 16SrIII-F). The phytoplasma induced the same symptoms in healthy acerola plants inoculated by grafting and showed molecular identity with the strain identified in naturally infected bushes. Although various strains belonging to distinct subgroups within the 16SrIII group have been previously identified in Brazil, this is the first report of the presence of a representative of the 16SrIII-F subgroup in the Brazilian agroecosystem. Considering that phytoplasmas can be systemically distributed throughout the plant and acerola plants are vegetatively propagated, it is recommended that propagation material be obtained from mother plants free of the pathogen.

Phytoplasma of 16SrVII-B subgroup associated to shoot proliferation in Physalis peruviana plants

Physalis is an herbaceous species native to the Andes region. Currently, it is cultivated in various Brazilian states due to the economic interest of growers for this new fruit. Physalis plants grown in the field showed symptoms of shoot proliferation, leaf malformation, and chlorosis. Since these symptoms are commonly induced by phytoplasmas, this study investigated to confirm the presence of these prokaryotes in symptomatic plants. After DNA extraction from symptomatic and asymptomatic plants, phytoplasmas were found in all affected plants through the nested PCR. Examination by transmission electron microscopy (TEM) using appropriately prepared segments of leaf veins allowed the visualization of typical pleomorphic cells of phytoplasmas in the phloem of symptomatic plants. The computer-simulated RFLP patterns and the phylogenetic analysis allowed identifying the detected phytoplasmas as a 'Candidatus Phytoplasma fraxini'-related strain belonging to the 16SrVII-B subgroup. Moreover, physalis was identified as an additional host species for phytoplasmas in the 16SrVII group, expanding the current knowledge on the host range of phytoplasmas in this group.