Chapter 2 - Graft and vegetative transmission of phytoplasma-associated diseases in Asia and their management

Abstract

The propagation materials infected with phytoplasmas, such as rootstocks and other types of grafting materials used as scions play an important role in the dissemination of phytoplasma-associated diseases in new areas. Since the phytoplasma infection is systemic in the plants, the vegetative propagation of many horticultural crops allows their spread through cuttings, bud wood, tubers, runners, and bulbs. Grafting is therefore an efficient method of phytoplasma spreading and establishing infection in vegetatively propagated plants. The phytoplasma spreads through vegetative plant propagation and occurs in nature over short and long distances by natural scattering and transportation of infected propagation materials. The transmission of phytoplasmas in Asian countries is also mainly attributed to grafting of infected propagation materials in woody and herbaceous plant species. In Asia, the phytoplasma associated with stone fruits, pome fruits, citrus, jujube, ornamentals, other trees species, and grapevine are majorly transmitted by grafting. However, possibility of phytoplasma vegetative propagation through basal shoots, stems, rhizomes, tubers, stolons, corms, buds, and bulbs is reported in sugarcane, cassava, potato, sweet potato, and many ornamentals such as rose, carnations, marigold, chrysanthemum. Dodder species are also efficiently utilized for vegetative phytoplasma transmission. The importance of phytoplasma infection spread by grafting, vegetatively propagated plants, and possible management practices are discussed in this chapter.