Replication/Accumulation and Symptom Expression of Citrus Viroids on Some Species of Citrus and Related Genera

Abstract

Plants of 32 species of Citrus and related genera grafted on rough lemon root- stock were inoculated with an artificial mixture of citrus viroids containing Citrus exocortis viroid , Citrus viroid I, Citrus viroid II, Citrus viroid III and Citrus viroid IV . Infection and viroid titers were determined by sPAGE and molecular hybridization analysis. Plants in which viroid infection could not be detected were further indexed by inoculation on Etrog citron 861 S1. Under the conditions of this assay most of the species were symptomless carriers. Only Citrus excelsa, C. ichangensis, C. karna, C. latifolia , C. meyeri and C. pyriformis developed symptoms as a result of viroid infection. Comparative analysis of nucleic acid extracts from bark versus leaf blade tis- sues indicated that in 10 species, viroid that were readily detectable from bark were undetectable from leaf blade tissues by sPAGE.