The procedures for biological and biochemical indexing were studied in an experiment to evaluate the use of viroids as dwarfing agents for 'Marsh Seedless' grapefruit. In some plots there was viroids segregation. In two plots the segregation was of CEVd (Citrus exocortis viroid) and in other two the presence of CVd-II (Citrus viroid II) was not detected. As a consequence of the segregation, there were no typical citron exocortis symptoms in the portions in which there was segregation of CEVd. Symptoms occurred in the portions, which there was the segregation was of CVd-II, indicating that the presence of CEV is necessary for the manifestation of typical symptoms of exocortis in citron. Viroids were not detected in a fifth plot, probably due to their absence in the inoculation material of the biological test (escapes), since the field plants showed normal vegetative development and absence of symptoms in the trunk. Finally, a drastic segregation, not referred to in the literature, occurred in a sixth plot, since the field plant showed canopy reduction and symptoms in the trunk. As a conclusion budwood sampling for viroid indexing must be more accurate.
citron; exocortis; Citrus paradisi; grapefruit; inoculation; Citrus medica
