The Citrus Exocortis Disease: A Complex of Viroid-RNAs

Abstract

Citrons inoculated with different field sources, displayed a variety of symptoms ranging from very mild leaf bending and necrosis to the severe reaction normally associated with exocortis disease. Nucleic acid preparations from shoot samples were analyzed by sequential polyacrylamide gel electrophoresis. All source from both California and Spain contained one to four viroids with distinct physical and biological properties. The size range was estimated from 371 nucleotides for the citrus exocortis viroid (CEV) to 275 for the smallest viroid. The recovery of single viroids suggested a relationship between the distinct viroids and the symptom reaction expressed in citron.