Occurrence of the T36 genotype of Citrus tristeza virus in citrus orchards in Sicily, Italy.
In 2014, during a large survey covering more than 25 000 ha in eastern Sicily, Italy, a subset of 249 alemow (Citrus macrophylla) seedlings was tested for the presence of viruses by DAS-ELISA. A subset of 57 infected alemow seedlings, randomly selected, was transferred in a safe climate controlled greenhouse and grown to observe symptoms. Tissues from these alemow source plants were then used to bark-inoculate sour orange seedlings. Within 6 months, all alemow seedlings showed vein clearing and different degrees of stem pitting, whereas 36 sour orange seedlings were symptomless and 21 displayed a shortening of internodes and seedling yellows leaf discolouration typical of seedlings yellows phenotype (SY), associated with poor root systems. The causal pathogen was identified as Citrus tristeza virus (CTV) T36 genotype based on various molecular analyses. This is thought to be the first report of a T36 CTV infection in Italy.