Preliminary investigations on the occurrence of Citrus Tristeza Virus (CTV)in central-western Sicilian orchards and on the mycorrhizal status in citranges (Citrus sinensis (L.) Osb. x Poncirus trifoliata (L.) Raf.)

Abstract

In the last decade, since the first outbreak of Citrus tristeza virus (CTV) in the province of Catania (2002), several new CTV foci were found in Sicily. In order to determine CTV occurrence in centra-lwestern Sicily, identify and characterize viral strains and verify the mycorrhizal status of citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliate (L.) Raf.]. one of the most utilized tollerant rootstock, an epidemiological survey was carried out in 2011. Symptomless samples from citrus groves from different Sicilian provinces (Agrigento, Palermo, Trapani, Caltanissetta) were collected and submitted to serological assay. Only samples from Agrigento and Palermo provinces were ELISA-positive. Moreover, RT-PCRs of p18, p20 and p23 genes and single strand conformation polymorphism (SSCP) assays, showed two CTV strain variants in the infected samples from Palermo. Cloning and sequencing of the detected CTV variants for phylogenic study are in progress. Citrange root samples taken from rootstocks of field-grown plants and seedlings were collected and submitted to an optimized staining technique aimed at visualizing the endomycorrhizal fungal structures. Seedling and micro-propagated plants, kept under laboratory conditions, were also inoculated with both endemic and commercial endomycorrhizal inoculum. First results indicate a limited root colonization. The lack of the mycorrhizal advantage could play a role on the wellknown susceptibility of citrange to common soil pathogens.