Molecular identification of two distinct phytoplasmas associated with symptoms similar to those of X-disease in peach and nectarine in Brazil

Peach and nectarine trees exhibiting symptoms similar to X-disease were found in commercial orchards located in the State of São Paulo, Brazil. This investigation was therefore performed to confirm the presence and verify the identity of phytoplasmas in the diseased plants. Samples from symptomatic plants showing chlorosis and leaf redness, reduced leaf size, reduced flower organs, shoot proliferation and decline were submitted to molecular analyses. Amplifications of 1.2 kb 16S rRNA gene fragments consistently revealed the presence of phytoplasmas only in the symptomatic plants. These phytoplasmas were identified as strains of ‘Candidatus Phytoplasma asteris’, enclosed in subgroups 16SrI-B and of a phytoplasma enclosed in subgroup 16SrIII-J, respectively. To the best of knowledge, no report is available about the presence of phytoplasmas in peach and nectarine in the Brazilian territory. This study allowed also to report plants of peach and nectarine as new hosts for phytoplasmas of the 16SrI-B subgroup in Brazil. Moreover, nectarine trees result infected with a 16SrIII-J strain. These findings can contribute to a precise and reliable dignosis of these disease, due to the lack or little knowledge of the producers and technicians, which have attributed the symptoms to other factors such as mineral nutrition, environmental conditions, characteristics of cultivars and abnormality caused by herbicides. Likewise, the phytosanitary evaluation of seedlings should be made more reliably, ensuring high quality seedlings for new orchards.