The occurrence of viruses and viroids in ornamental citrus mother plants in Tuscany (Central Italy)

Abstract

Citrus tristeza closterovirus (CTV) has been found several times in the last decades in Italy, and plant protection services are involved in monitoring and surveillance. Although orchards linked to the citrus industry are well monitored, there is an underestimated risk of viruses or virus-like diseases in ornamental nurseries. Our aim was to modify a CTV monitoring program to include other viruses (Citrus variegation virus, CVV; Citrus psorosis virus, CPsV) and viroids (Citrus exocortis viroid, CEVd; Hop stunt viroid, HSVd; Citrus bent leaf viroid, CBLVd; Citrus dwarfing viroid, CDVd; Citrus bark cracking viroid, CBCVd). Ornamental mother plants were monitored for four years in 15 nurseries in two locations in central Italy using inexpensive multiplex RT-PCR protocols. CTV incidence was 1.6â\u80\u9313.5%, with an average distribution of 11.9%. The average incidence of CVV and CPsV was 6.3% and 2.7%, respectively. Higher CTV, CVV and CPsV incidences were observed in C. x paradisi, C. grandis and C. x clementina. The most widespread viroid identified was CEVd (32.9%), frequently observed in C. x limonia and C. limon. HSVd (10.5%), and CDVd (7.1%) were mostly found in C. x limonia. Lower infection rates were observed for CBLVd (2.0%) and CBCVd (1.4%). However, the nurseriesâ\u80\u99 response to the virus alert by the protection services was only partially effective. Although the CTV incidence was lower in nurseries re-checked after the initial detection, it was not eradicated from two nurseries out of three, and the occurrence of viroids was reduced in just one nursery. Given that dangerous viruses along with the concomitant spread of viroids have unfortunately become a fact of every day life, multiplex RT-PCR diagnoses are likely to play an increasing role in warning nursery managers of possible infections

Application of Real Time PCR for the Prevalence Determination of Citrus Exocortis Viroid (CEVd) in Algeria

“…In Italy, results of survey conducted in Campania region showed that CEVd was found to be the most widespread viroids infecting 68% of the tested samples [16]. Rizzo et al [17] found that CEVd was the most widespread viroid in ornamental nurseries in Tuscany (Central Italy), with an incidence reaching almost 50% in three years of monitoring. In Greece, CEVd was shown in high frequency as fourth most prevalent viroids where it was detected in 27.25% of samples collected from different geographical district of the country [18].…”

Advances in citrus propagation in Brazil

“…Mother trees grown in pots or soil should be evaluated annually, and the samples should be sent to a certified laboratory for testing for CVC and HLB (CARVALHO et al, 2005). The occurrence of viruses and viroids in ornamental citrus mother trees was reported by Rizzo et al (2017) in Italy. The possibility of contamination with diseases transmitted by insect vectors from other plants and commercial orchards emphasizes the importance of the health care of citrus plants produced for all uses, not just in the production of nursery trees for use in industrial juice processing and the fresh fruit market.…”

Ornacitrus: Citrus plants (Citrus spp.) as ornamentals

“…This includes the availability of an adequate number of mother plants routinely controlled by the regional plant protection services by means of diagnostic molecular testing (i.e. PCR, RT-PCR, qPCR) for viruses and viroids (Rizzo et al, 2017). On the basis of the current legislation, any finding of quarantine pathogens in a nursery would involve the mandatory destruction of all the plants.…”

“…On the basis of the current legislation, any finding of quarantine pathogens in a nursery would involve the mandatory destruction of all the plants. Currently, the Tristeza virus (CTV -Citrus Tristeza Virus) represents a major concern since its diffusion in commercial fruit production orchards in Sicily (Davino et al, 2003), whereas the most widespread viroid identified in Tuscan ornamental citrus tree nurseries was CEVd (Citrus exocortis viroid), frequently observed in C. × limonia and C. limon together with a high frequency of mixed viroid infections (Rizzo et al, 2017).…”