Sensitivity of Species and Hybrids of the Genus Citrus and Relatives to Citrus Psorosis Virus

Abstract

Citrus psorosis virus (CPsV), genus Ophiovirus, causes an important disease in many countries. In growing regions where natural disease spread occurs, damage caused by the virus can be controlled using resistant or tolerant cultivars, but sensitivity of many species and hybrids of Citrus and related genera is presently unknown. To find potential sources of CPsV resistance, we first propagated 61 species (or cultivars) and hybrids of Citrus and related genera [Citrus (37), Microcitrus (5), Fortunella (6), Eremocitrus (1), Pleiospermium (1), Atalantia (1), Severinia (1), Clausena (1), Poncirus (1) and hybrids (7)] on Rough lemon seedlings inoculated with the CPsV isolate PB 143. Out of the 61 accessions tested 54 showed symptoms and reacted by ELISA with a CPsV-specific antibody, 2 (M. inodora and F. hindsii) were symptomless but gave high ELISA values, suggesting tolerance to CPsV, 5 (C. depresa, Cleopatra mandarin, C. excavata, Carrizo citrange and CPB 4475 citrumelo) showed symptoms in the first flush but gave a negative ELISA reaction, and 1 (Poncirus trifoliata) was ELISA negative and symptomless. We then examined CPsV infection by ELISA and RT-PCR in Cleopatra mandarin, P. trifoliata and Citrumelo seedlings inoculated with CPsV isolates P 121, PB 108 and PB 143. While P 121 was detected in all Cleopatra and citrumelo plants, the other isolates were detected in only 50% of the inoculated plants, with all plants indexed as CPsV positive displaying symptoms. All P. trifoliata plants inoculated with either isolate indexed negative for CPsV and remained symptomless. Our results suggest CPsV resistance in P. trifoliata and partial isolate-specific resistance in some accessions.