First report of sunflower chlorotic mottle virus infecting sunflower plants in Brazil

Sunflower (Helianthus annuus) plants showing symptoms of chlorosis, mosaic, chlorotic ringspot, and necrosis on younger leaves were found in a small experimental plot in Piracicaba, in the state of São Paulo, Brazil. Preliminary examinations by transmission electron microscopy of symptomatic leaf tissue revealed flexuous filamentous particles 13-15 nm wide and 700-750 nm long, and cytoplasmatic cylindrical inclusions typical of those found in plant cells infected by members of the Potyvirus genus. Total RNA extracted from symptomatic leaves and subjected to RT-PCR followed by partial nucleotide sequencing confirmed the presence of a potyvirus in the affected plants, which was identified as sunflower chlorotic mottle virus (SuCMoV), a member of the Sunflower chlorotic mottle virus (genus Potyvirus, family Potyviridae) species. Mechanical transmission assays with extracts of symptomatic sunflower leaves reproduced the original symptoms in sunflowers, mosaic symptoms in Zinnia elegans, and chlorotic local lesions in Chenopodium amaranticolor and C. quinoa. Sunflower and zinnia plants became infected after aphid transmission experiments with Myzus persicae. RT-PCR tests using specific primers for SuCMoV confirmed the presence of this virus in experimentally infected plants, meeting the criteria of Koch's postulate. This is the first report of SuCMoV infecting sunflower plants in Brazil.

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.