First report of hop stunt viroid from sweet cherry with dapple apple fruit symptoms in China

Authors: XU, LI - Shangdong Institute Of Pomology; WANG, JIAWEI - Shangdong Institute Of Pomology; ZHU, DONGZI - Shangdong Institute Of Pomology; ZONG, XIAOJUAN - Shangdong Institute Of Pomology; WEI, HAIRONG - Shangdong Institute Of Pomology; CHEN, XIN - Shangdong Institute Of Pomology; Hammond, Rosemarie; LIU, QINGZHONG - Shangdong Institute Of Pomology

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2016
Publication Date: 11/21/2016
Citation: Xu, L., Wang, J., Zhu, D., Zong, X., Wei, H., Chen, X., Hammond, R., Liu, Q. 2016. First report of hop stunt viroid from sweet cherry with dapple apple fruit symptoms in China. Plant Disease. 101(2):94: doi: 10.1094/PDIS-08-16-1086-PDN.

Interpretive Summary: Viroids are small nucleic acid molecules that cause serious diseases in crop plants worldwide. They are spread through infected seed and mechanically through grafting and handling of infected plants. Hop stunt viroid has been found in a wide range of plant hosts that includes hop, cucumber, citrus, grapevine, plum, pear, peach, apricot and almond and is the causal agent of serious diseases, such as hop stunt of hop and dapple fruit disease of plum and peach. In a study of the phytosanitary status of stone fruit trees in China, we identified two strains of hop stunt viroid in sweet cherry trees showing symptoms of dapple fruit disease. The presence of hop stunt viroid represents a serious threat for the stone fruit industry in China and a potential source of inoculum for propagation materials. This report expands our knowledge of the presence of viroids in sweet cherry trees in China and has implications for movement of plant material between continents and will be of use to an international audience of researchers in academia, industry, and government organizations with an interest in plant pathology and control of fruit tree diseases.

Technical Abstract: Hop stunt viroid (HSVd), the type member of the genus Hostuviroid, family Pospiviroidae, was first described from hops with stunt disease in Japan. HSVd has a wide host range that includes hop, cucumber, citrus, grapevine, plum, pear, peach, apricot and almond and is the causal agent of serious diseases, such as hop stunt of hop and dapple fruit disease of plum and peach. HSVd has also been isolated from sweet and sour cherry trees where infection appeared to be latent. Sweet cherry (Prunus avium L.) is an important economic fruit and widely grown in China, however, HSVd infection in this host has never been reported in China. In May 2010, sweet cherry trees (P. avium L. cultivar Red-lamp) exhibiting dapple fruit disease were observed in a suburban orchard in Tai’an, Shandong Province, China. Following grafting of scions from the diseased trees onto healthy trees, dapple fruit symptoms developed in fruits of grafted trees. Samples were collected from fifteen dapple fruit and ten symptomless fruit trees. Total RNAs extracted from leaf tissues were used for reverse transcription polymerase chain assays (RT-PCR) and biological indexing for HSVd was performed using the indicator host cucumber (Cucumis sativus L.cv. Suyo). Amplicons of the expected size of were obtained from fifteen cherry samples exhibiting dapple fruit disease symptoms and ten cucumbers. Sequence analysis of cloned amplicons revealed the presence of two different variants of HSVd which were deposited in GenBank as Accession Nos. KX355199 and KX355200. Phylogenetic analysis of these sequences and additional HSVd sequences showed that the isolates obtained from sweet cherry in China were closely related to HSVd isolates from peach and almond. To our knowledge, this is the first report of HSVd infecting sweet cherry trees in China. Further work on field surveys in sweet cherry to assess the incidence of HSVd in the main sweet cherry growing regions will be performed.