Vol. 72 No: 4

Title:
Application of Selected Viroids for Dwarfing and Enhancement of Production of ‘Valencia’ Orange

Authors:
J.S. SEMANCIK, A.G. RAKOWSKI, J.A. BASH and D.J. GUMPF

pp: 563-570

Abstract:
Citrus viroids, CVd-Ia, CVd-IIa, and CVd-IIIb, representative of three distinct Citrus Viroid Groups, resulted in a statistically significant reduction of 20–50% in tree size of Valencia orange, Citrus sinensis (L.) Osb., on Poncirus trifoliata (L.) Raf. rootstock. Reduction in canopy volume was accompanied by an increase in yield per tree in the presence of CVd-IIa, whereas a net decreases in yield resulted with either CVd-Ia or CVd-IIIb. Nevertheless, the yield per canopy volume was significantly enhanced in all viroid-containing trees when compared with the viroid-free trees. Analyses of "dwarfing factors" from different citrus growing countries indicated that single viroid isolates with nucleotide sequences similar to CVd-IIIb have been independently selected. Although pathogenic agents in some hosts, selected viroids may also be viewed as transmissible, small, nuclear ribonucleic acids (Tsn-RNAs) in those specific hosts which do not express a disease syndrome.

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