Distribution of Citrus Exocortis Viroid and Hop Stunt Viroid in Cirtus Orchards of Central Italy as Revealed by One-Tube One-Step RT-PCR

Abstract

A survey was carried out in citrus fields of Lazio and Tuscany in central Italy to determine the presence of Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd), both of which cause economically important diseases in citrus. In order to make pathogen diagnosis easier and more efficient, a one-tube one-step RT-PCR assay was developed and used for the detection of CEVd and HSVd in citrus samples collected from field trees. CEVd and HSVd occurred in 100 and 30% of samples from Lazio respectively, and in 45 and 9% of samples from Tuscany. Specifically, of 21 citrus cultivars belonging to nine citrus species and one hybrid, 12 cultivars and the hybrid were infected with CEVd, one cultivar with HSVd, 3 cultivars with both viroids, and 4 cultivars were free from both viroids. The study revealed a wide distribution of the two viroids in the citrus field samples and showed that one-tube one-step RT-PCR assay is a rapid, sensitive and reliable technique for the detection of these viroids. This diagnostic technique is therefore suitable for the preliminary screening of CEVd and HSVd in routine sanitary and certification programmes because it drastically reduces the number of indicator plants needed for biological indexing of the two viroids.