Identification of a ‘Candidatus Phytoplasma asteris’ strain infecting pear trees in Brazil

Pear plants exhibiting leaves with reddening and curling, slow growth, reduced and delayed flowering, and fruit malformation were observed in orchards located in the municipality of Bento Gonçalves in the state of Rio Grande do Sul, in Brazil. These symptoms are commonly reported in temperate fruits infected by phytoplasmas in other countries. Thus, the objective of this work was verify the presence of phytoplasmas in symptomatic plants. A total of 23 pear trees, 16 symptomatic and 7 asymptomatic were sampled. After DNA extraction, the samples were used as template in nested PCR conducted with R16mF2/mR1 and R16F2n/R16R2 primer pairs. The purified and quantified PCR products were cloned and sequenced bidirectionally. The molecular differentiation was processed using virtual RFLP analysis with 17 restriction enzymes in the iPhyClassifier. The detection results confirmed the presence of phytoplasmas in 15 of the symptomatic plants. In contrast, no amplification was obtained for all seven asymptomatic plants. Based on the sequence analyses and phylogenies, the phytoplasma identified in pear plants resulted a ‘Ca. P. asteris’ strain, belonging to 16SrI-B subgroup. The present investigation report pear tree as a new host species for this phytoplasma.