History and Current Status of Phytoplasma Diseases in the Middle East

Simple Summary Phytoplasmas are microorganisms that have been reported to be associated with hundreds of plant diseases in most parts of the world. Several reviews were published regarding diseases associated with phytoplasmas in different countries. However, no comprehensive review is available on the phytoplasma diseases in the Middle East, which is an important region with arid to semi-arid conditions. This review describes the most common phytoplasmas that are associated with diseases in this part of the world. It also describes some of the insect vectors that help to transmit these phytoplasmas. Information is also presented regarding the distribution of the diseases and host ranges. Phytoplasmas that are associated with fruit crops, vegetables, cereal and oilseed crops, trees, ornamental, and weeds are increasing at an alarming rate in the Middle East. Up to now, fourteen 16Sr groups of phytoplasma have been identified in association with more than 164 plant species in this region. Peanut witches' broom phytoplasma strains (16SrII) are the prevalent group, especially in the south of Iran and Gulf states, and have been found to be associated with 81 host plant species. In addition, phytoplasmas belonging to the 16SrVI, 16SrIX, and 16SrXII groups have been frequently reported from a wide range of crops. On the other hand, phytoplasmas belonging to 16SrIV, 16SrV, 16SrX, 16SrXI, 16SrXIV, and 16SrXXIX groups have limited geographical distribution and host range. Twenty-two insect vectors have been reported as putative phytoplasma vectors in the Middle East, of which Orosius albicinctus can transmit diverse phytoplasma strains. Almond witches' broom, tomato big bud, lime witches' broom, and alfalfa witches' broom are known as the most destructive diseases. The review summarizes phytoplasma diseases in the Middle East, with specific emphasis on the occurrence, host range, and transmission of the most common phytoplasma groups.