Chapter 1 - Updates on phytoplasma diseases associated with cereals in Asia

Abstract

Cereal crops provide food to majority of human beings and livestock feed around the world and are the major sources of nutritional resources. Cereal crops are affected mainly by fungus and viral pathogens, but recently phytoplasma diseases have also been reported to cause serious losses to important cereal crops in Asian countries. Among the major phytoplasma diseases associated with rice are rice orange leaf and rice yellow dwarf, widespread in China, Japan, Vietnam, Thailand, Philippines, and India. However, the wheat crop is reported to be affected with two major phytoplasma diseases, wheat blue dwarf from China and wheat streak, yellowing, and stunting from Central India. Other cereal crops are having minor importance like maize leaf redness disease, sorghum green, and are restricted in distribution in some of the Asian countries. Out of different phytoplasma diseases reported in cereals, the most important and alarming diseases in Asian region are wheat blue dwarf disease in China, wheat stint and streak disease of wheat India, and rice yellow dwarf and orange leaf in most of the Asian countries. The phytoplasma diseases have been assigned to four different groups: aster yellows (16SrI), clove proliferation (16SrVI), rice yellow dwarf (16SrXI), and Bermuda grass white leaf (16SrXIV) groups. Several leafhopper species representing the Cicadellidae family and wild weeds species are reported as putative and natural reservoirs of phytoplasma strains detected in cereal crops in the Asian continent. The occurrence of diverse phytoplasma strains in poaceae species in Asian region indicates an ongoing threat toward cereal crops in Asia. This chapter provides a comprehensive overview of the presence of phytoplasma strains and their vectors associated with different cereal crops in Asian countries and their potential impact on cereal crops cultivation in Asia.