Interference of Citrus Viroids with Cachexia Symptoms on Parson's Special Mandarin

Abstract

In the routine indexing of cachexia on Parson's special mandarin, irregularities and inconsistencies of symptom expression were found. In most cases these seemed to be associated with co-infection of the original explant with exocortis. Therefore the hypothesis of an interaction between exocortis and cachexia agents was considered. An experiment was carried out by co-inoculating on Parson's special mandarin a pure cachexia isolate (X-701) and three different exocortis sources, previously characterized as severe (E-117), moderate (E-111) and mild (E-140) according to their reaction on Etrog citron. The results indicated that E-117 and E-111 interfered with cachexia symptom expression. None of the plants inoculated with X-701 and E-117 or E-111 showed cachexia symptoms, whereas all plants inoculated with X-701 alone or in combination with E-140 gave positive reactions. These results indicate that certain citrus viroids or viroid combinations may mask symptom expression of cachexia