Biological characteristics of Citrus cachexia viroid isolates in local tangerine orchards (Citrus unshiu Marcovitch) in East Mazandaran

In recent years symptoms of viroid diseases, include stem pitting and gumming have highly incidenced in citrus orchards of Mazandaran. This study was conducted for determining the biological characteristics of Citrus cachexia viroid strains in local tangerine orchards. 150 samples were collected from three important infected districts. Purification was carried out in CF-11 column. Presence of viroid was confirmed with RT-PCR using specific primers. For differentiation of Cachexia viroid isolates, 13 types of citrus were bark grafted on rootstock and symptoms were observed. RT-PCR data showed that 6% of samples were infected only with cachexia, while other samples showed mix infection with exocortis, tristeza and psorosis. According to the assay, the best indicator plant is the Mexican lime (Citrus aurantifolia. Swing.), which could express the typical symptoms of mild to severe infection. Also it is possible to separate severe strains from mild strains based on the symptoms on the local tangerine trees and gumming on the branches can be the primary basis for differentiation.