Diverse phytoplasmas associated with diseases in various crops in Russia - pathogens and vectors

Over a long-term survey (2006-2014), we detected that at least 22 species of cultivated plants from 10 families ( Amaranthaceae, Apiaceae, Asteraceae, Brassicaceae, Cucurbitaceae, Fabaceae, Vitaceae, Poaceae, Rosaceae, Solanaceae ) were infected with phytoplasma. Most of the plant species are herbaceous plants used as food, commercial, and forage crops, including vegetables (tomato Solanum lycopersicum, potato Solanum tuberosum, pepper Capsicum annuum, carrots Daucus carota, horseradish Armoracia rusticana ), cereals (wheat Triticum aestivum, barley Hordeum vulgare ), legumes (chickpeas Cicer arietinum, kidney beans Phaseolus vulgaris, beans Vicia faba ), gourds (gourd Cucurbita pеро ), oilseeds (rapeseed Brassica napus ), essential oil (coriander Coriandrum sativum, tarragon Artemisia dracunculus ), fodder (alfalfa Medicago sativa ) and commercial (sugar beet Beta vulgaris ) crops. Phytoplasma was also detected in fruit trees and shrubs (pear Pyrus communis, cherry Prunus subg. Cerasus, apple Malus domestica, raspberry Rubus idaeus, grapes Vitis vinifera ). Leaves, roots, or fruits of infected plants with characteristic symptoms of phytoplasma infection were collected in six economic regions of the Russian Federation including Western Siberia, Volga, Northern, North Caucasus, Central and Central-Black Soil region. In total, phytoplasmas belonging to eight groups or subgroups, i.e. 16SrI, 16SrI-C, 16SrII, 16SrIII, 16SrVI-A, 16SrVI-C, 16SrX, and 16SrXII-A, were found in infected plants in these six economic regions. Phytoplasma diversity differed in each region. The most diverse phytoplasma populations were found in the Volga and Central regions, which contained six and five phytoplasma groups or subgroups, respectively. Some phytoplasmas caused disease in multiple plant species, while certain crops were infected by multiple phytoplasmas. For example, both 16SrVI-A and 16SrXII-A caused diseases in 12 plant species, 16SrI caused disease in seven species, and 16SrIII caused disease in six ones, while potato was infected by six phytoplasma groups or subgroups. In general, there were 4 phytoplasma groups/subgroups: 16SrIII, 16SrVI 16SrI-A and 16SrXII-A almost equally represented in cultural plants in the Central Economic Region. In more southern areas, such as Volga, Central Black Earth and North-Caucasian, the stolbur subgroup (16SrXII-A) phytoplasma dominated. Phytoplasma subgroup 16SrVI-A occurred predominantly in the Western Siberia Region.