Diverse phytoplasmas associated with potato stolbur and other related potato diseases in Russia

A large scale survey on diseased potato plants that exhibited symptoms similar to those of stolbur, potato purple top wilt, potato witches’-broom, and potato round-leaf in eight Economical Regions of Russia was conducted from 2006 to 2012. A total of 1228 potatoes were collected and the associated phytoplasmas were identified. Phytoplasmas belonging to five 16S rRNA (16Sr) phytoplasma groups (16SrI, 16SrII, 16SrIII, 16SrVI, and 16SrXII) and at least eight subgroups (16SrI-B, 16SrI-C, 16SrI-P, 16SrII-A, 16SrIII-B, 16SrVI-A, 16SrVI-C, and 16SrXII-A) were identified. To our knowledge, subgroup 16SrIII-B and 16SrVI-C phytoplasmas have not been reported to infect potatoes. Based on the results of the survey, the percentages of infection caused by various phytoplasmas were: 40.2 % (16SrXII), 25.5 % (16SrIII), 20.9 % (16SrI), 12.4 % (16SrVI), and 1.2 % (16SrII). The results also indicated potato diseases exhibiting stolbur or similar symptoms could be caused by stolbur phytoplasma (16SrXII-A) alone or by other phytoplasma groups (e.g., 16SrI and 16SrIII). A survey on potential insect vectors was conducted from 2009 to 2012 in the Moscow oblast of the Central Region. A total of 23 different species of Hemiptera insects were screened for the presence of phytoplasmas. Eight leafhopper and three froghopper species carried phytoplasmas. Euscelis incisus and Macrosteles laevis were the most prevalent. The other species were present in very low populations.