Chapter 7 - An update on phytoplasma diseases associated with ornamentals in Asia

Abstract

The economic importance of ornamentals has been progressing significantly in many Asian countries with international demand expanding continuously. Cut flowers represent the largest segment of the industry followed by flowering potted plants, trees, shrubs, annuals, flower bulbs, and other propagation materials. Like other crops, ornamental plants are also affected by several pathogens such as fungi, bacteria, viruses, phytoplasmas. Among them, the phytoplasmas are an important group of pathogens which drastically damage growth and marketing potentials of ornamental plants thereby affecting their commercial value. Phytoplasmas are associated with diseases in several commercial cut flowers and ornamental plants causing serious economic losses all over the Asia. They are a major constraint of phytoplasma infection in commercial production of ornamental plants by lowering the quantum and quality worldwide. The ‘Ca. P. asteris’ belonging to 16SrI group is the major group detected in ornamentals in Asian countries followed by peanut witches' broom (16SrII) group. Phytoplasma diseases of ornamentals in Asia have been described in a wide range of ornamental species, and phytoplasma associated belong to 11 different 16Sr groups and to about more than 27 different subgroups and are reported on more than 100 ornamental species. The major floriculture crops affected with phytoplasma diseases in Asia are roses, chrysanthemums, marigold, petunias, Chinese asters, calendulas, catharanthus, jasmines, and several seasonal ornamentals. The major number of phytoplasma reports associated with ornamentals are from India, Iran, Turkey, Japan, Korea, and China. Limited reports are available on natural reservoir sources of phytoplasma associated with ornamentals from Asian countries. Major management practices adapted for ornamental phytoplasma disease are using tetracycline treatment, insecticides for vector control and micropropagation of shoot tips for elimination of phytoplasmas. In this review, an update status of progress on research work done on phytoplasma diseases of ornamentals in Asia is discussed.