Chapter 4 - Diversity, distribution, and status of phytoplasma diseases in Arab Gulf countries

Abstract

The Arab Gulf countries (AGCs) are located in the Arabian Peninsula that is generally characterized by an arid climate for most countries in the region. However, Oman and Saudi Arabia have distinct climatic and topographic diversity that allows for the cultivation of tropical, subtropical, and temperate crops. The most important economic crops growing in AGCs are fruit trees (e.g., date palm, citrus, mango, grape, banana, and pomegranate), field and greenhouse vegetables (e.g., cucurbits, potato, tomato, cabbage, and eggplant), and field crops (e.g., Alfalfa, chickpeas, fababean, sesame, and wheat). Many abiotic and biotic factors limit agricultural production and cultivated area expansion in AGCs that primarily include major plant diseases. Phytoplasma is one of the leading diseases that cause major losses in date palm, acid lime, alfalfa, and many other economic crops in these countries. Phytoplasma diseases have been reported to be associated with more than 50 plants including economic crops, medicinal, and wild plants belonging to different families. Detection and molecular characterization of phytoplasmas infecting different plants in AGCs were carried out using techniques such as the DAPI staining method, transmission electron microscopy, dot blot hybridization method, PCR technique, restriction fragment length polymorphism, and DNA sequencing. Phytoplasma classification was conducted using multilocus genes such as 16S rRNA gene secA, tuf, imp, and SAP11 genes. The phytoplasma diseases in AGCs were classified into 11 different groups and subgroups: 16SrI, 16SrII-B, 16SrII-D, 16SrII-W, 16SrII-X, 16SrIV, 16SrVI-A, 16SrIX, 16SrIX-J, 16SrIXIV-A, and 16SrXXIX-A phytoplasmas. Phytoplasma disease incidences were reported in countries with significant agricultural production such as Oman, Saudi Arabia, Kuwait, and the United Arab Emirates of Arabian Gulf countries.