The response of different genotypes of citrus and relatives to Citrus psorosis virus inoculation

Damage caused by Citrus psorosis virus (CPsV) could be avoided obtaining resistant cultivars by breeding, but the sensitivity of most citrus hosts to CPsV is unknown. To find potential sources of resistance we inoculated 63 cultivars and hybrids of Citrus and related genera [ Citrus (36), Microcitrus (5), Fortunella (6), Eremocitrus (1), Pleiospermium (1), Atalantia (2), Severinia (1), Clausena (1), Swinglea (1), Afraegle (1), Poncirus (1) and hybrids (7)] with the CPsV isolate PB-143 and monitored symptoms and CPsV infection by ELISA. Microcitrus inodora and Fortunella hindsii were symptomless but gave high ELISA values, suggesting tolerance to CPsV, whereas Citrus depresa , Clausena excavata , Cleopatra mandarin, sour orange, Carrizo citrange and CPB4475 citrumelo were ELISA negative, suggesting resistance. Further examination of CPsV infection by reverse transcription quantitative real time PCR (RT-qPCR) in Cleopatra mandarin, Poncirus trifoliata and Carrizo citrange seedlings inoculated with CPsV isolates P-121, PB-102 and PB-143, revealed different infection rates and CPsV accumulation, depending on the isolate and citrus genotype. Bud propagation of these genotypes on CPsV-inoculated sweet orange plants incited a bud union disorder that hindered flushing and scion growth, suggesting that the high viral load in the rootstock induced a hypersensitive-like reaction in the partially resistant scion.