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ISHS Acta Horticulturae 901: XII International Symposium on Virus Diseases of Ornamental Plants

NOVEL INSIGHTS IN THE WORKING MECHANISMS OF NATURAL HOST RESISTANCE TO VIRUSES

Author:   R. Goldbach
Abstract:
Globally, viruses form a major threat to (ornamental) crops and they can be countered by propagation of virus-free plant material, by taking certain cultivation measures, by vector control, and by resistance breeding. In this contribution some novel insights in natural forms of host resistance to viruses will be presented. There are different forms of natural resistance to viruses in (ornamental) crops and these can be a.o. categorised into dominant versus recessive resistance. Sofar major achievements can be reported on the identity of single dominant resistance genes, due to the nowadays well developed (marker assisted) cloning techniques. A draw-back is the limited durability though, as viruses are rather able to break such forms of genetic resistance. Recessive resistance genes do not receive much attention among plant breeders, yet their identification sheds light on the viral dependency of certain host factors. Often these recessive genes encode factors involved in the translational machinery of the plant cell. Most insights have been obtained for recessive resistance genes against potyviruses, revealing that the 5-terminal protein, VPg, is often the avirulence protein. Over recent years, much progress has been obtained in understanding another form of natural resistance to viruses, i.e. antiviral RNA silencing (or RNA interference; shortly RNAi). RNA silencing comprises a set of sequence specific RNA breakdown mechanisms in fungi, plants, invertebrates and vertebrates including man, and at least for plants and insects an antiviral function of RNAi has been established. An overview will be presented of antiviral RNAi in plants and how this defence mechanism can be used to control viruses.

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