This technique includes thermotherapy of the diseased in vitro shoots, followed by shoot tip culture. Ĭombining thermotherapy with shoot tip culture For example, shoot tip cryotherapy completely failed to eradicate raspberry bushy dwarf virus (RBDV) and apple stem grooving virus (ASGV), while combining thermotherapy with shoot tip cryotherapy produced 33% and 100% of plants free of RBDV and ASGV. 1) are much more efficient for virus eradication than single use of them. Accumulative data have proven combining thermotherapy with each of them (herein called thermotherapy-based methods, Fig. So far, various methods have been established for eradication of plant viruses, including shoot tip culture (also called meristem culture), micrografting, chemotherapy, thermotherapy and shoot tip cryotherapy. In vitro culture techniques represent the most successful strategies for production of virus-free plants. In addition, preservation of plant germplasm also emphasizes use of virus-free plants. Virus-free materials are required in importing novel cultivars from other countries and exchanging breeding materials between countries or regions. Virus-free plants are currently widely grown throughout the world to control viral diseases in many of economically important crops like tuber crops, fruit trees, herbaceous ornamentals. As early as 1968, the European Union (EU) issued an EU Council directive, which required that propagative materials of fruit crops must meet the phytosanitary requirements. Although the use of chemicals had potential applications to control viral diseases, cultivation of virus-free plants has been/is an agricultural strategy for efficient control of them. Plant viruses are obligate intracellular parasites that colonize only inside the living cells of the host and can be transmitted by vegetative propagation from generation to generation and insect vectors from the virus-infected plants to the healthy ones. By 2013, over €33 million had been invested in research projects on PPV control in Europe. Annual yield losses caused by PPV infection were 1.5 million for plum and 0.6 million metric tons for apricot, approximately valuing at €5400 million and €3600 million for the former and latter in Europe. Plum pox virus (PPV), one of the most serious viral diseases attacking Prunus fruit trees, widely occurred in almost all stone fruit producing countries. Mixed infection with two viruses resulted in a much larger loss of yield than the single infection. Single infection caused yield losses of 40–60% by PLRV, 10–20% by PVS, 10–50% by PVX and 20–50% by PVY. For example, potato leafroll virus (PLRV), potato virus S (PVS), potato virus X and potato virus Y (PVY) are among the most serious viruses attacking potato. Virus diseases cause great losses of crop yield and have long been a constraint for sustainable developments of agricultural production.
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