ISHS Acta Horticulturae 349: V International Symposium on Orchard and Plantation Systems
CITRUS VIROIDS AND CITRUS DWARFING IN ISRAEL |
| Author: | M. Bar-Joseph |
| Keywords: | High density plantings (HDP), chimeric viroids, Viroid evolution, sustainable farming, beneficial microorganisms |
| Abstract:
The graft transmissible dwarfing (GTD) agent #225 T, which is used for experimental dwarfing of grapefruit and Oroblanco trees in Israel was found to contain at least five citrus viroids (CVds) with estimated sizes of 284, 295, 299, 318 and 371 nts. Segregation and exclusion of one or more of these CVds from GTD#225 T inoculated trees was found to cause an inconsistent dwarfing effect, often observed in the field trials. This review summarizes sequence information of four CVds that were recently separated and cloned from the GTD#225 T complex. Two of the viroids of 371 and 299 nts were found to be sequence variants of citrus exocortis viroid and hop stunt viroid respectively. The others CVds of 284 and 318 nts respectively were found to be natural mosaic type chimeric viroids, composed from the genomic parts of previously characterized viroids belonging to similar or different viroid groups. Each of these viroids was found to represent a different CVd group. The history of dwarfing with GTD agents and the horticultural merits of this practice both for the intensive and sustainable citrus farming is presented. | |
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