Chamran Hemmati

This study extensively examines phytoplasma-associated diseases in various fodder crops, including alfalfa, maize, sorghum, millet, napier grass and clover. The most severe phytoplasma diseases are alfalfa witches’ broom, maize bushy stunt, napier grass stunt and clover proliferation. This review encompasses the geographical distribution of these diseases, their symptoms, potential alternative hosts, the phytoplasma taxa involved, and their incidence rates. Additionally, insect vectors’ role in transmitting diseases is highlighted when available. Notably, phytoplasma ribosomal groups such as 16SrI, 16SrII, 16SrIII, 16SrVI, 16SrVII, 16SrXI, 16SrXII, 16SrXIV, 16SrXVI, and 16SrXXIV have been identified in these fodder crops. Furthermore, leafhopper species including Dalbalus maidis, Orosius albicinctus, Empoasca decipiens, Neoaliturus haematoceps and Recilia banda results as vectors for some of these phytoplasmas.

Phytoplasmas are cell wall-less and pleomorphic bacterial pathogens that cause considerable yield losses in more than 1000 plant species worldwide and transmitted by sap-feeding insects. Phytoplasma-infected plants exhibit symptoms including witches’ broom, phyllody, virescence, yellowing induced by the phytoplasma effector proteins. It has been revealed that phytoplasmas are capable of modulating biochemical responses of plants involved in defense mechanisms. In this respect, phenolic compounds, free amino acids in source leaves, protein contents, some secondary metabolites, and polyamines were found to increase, while chlorophyll content and photosynthetic activity and the number of chemical compounds were reduced as a consequence of phytoplasma infection. Therefore, the objective of this study was to review the chemical composition changes in phytoplasma-infected plants.

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.

Cacti are evergreen perennial succulent plants that are used as ornamental and hedge plants. The fruits and leaves are also used as forage in some areas (Dewir, 2016). Cactus species are susceptibl...

Cycas revoluta Thunb. (Cycadaceae) is native to southern Japan and used for production of Sago and is planted as an ornamental plant. In Oman, it is mainly used for ornamental purposes. In February...