Plant Virus Transmission Through Vegetative Propagules (Asexual Reproduction)

Abstract

Virus and virus-like diseases spread through vegetative propagules like tubers, rhizomes, stolons, corms, bulbs and buds of economically important crops like cassava, potato, sugarcane, banana, sweet potato, Dioscorea, beet root, onion and majority of fruit and ornamental plants. Throughout the world, one or two virus and virus-like diseases (viroid and phytoplasma) are threatening the economy of their country. Fruit tree propagation is usually carried out through asexual reproduction by grafting or budding of the desired variety, onto a suitable root stock as observed in citrus, apple, peach, plum, grape and others. Although the virus diseases spread through vegetative propagules to short distances and further through insect vectors. Man is responsible for the world wide movement of many virus and virus-like diseases through the vegetative propagules. Cassava is the major food crop in 39 African countries and some of the South Asian countries, and the cassava mosaic disease is the primary limiting factor. Similarly, sugarcane mosaic in sugarcane is wide spread where ever crop is grown. Even tristeza virus is devastating disease throughout the world. In South African countries, swollen shoot disease reduces the cocoa crop yields. To combat these virus diseases which are carried through vegetative propagules, the pathogen diagnosis is primary factor. Widely accepted techniques like ELISA, PCR, microarrays and also other molecular tests are well applicable in practice. For almost all crops, the virus-free plant certification schemes, clean seed certification schemes against each crop have been developed in every country. Based on the advanced techniques developed related to crop production, virus management measures are being applied in almost all countries.