New geographic distribution and molecular diversity of Citrus chlorotic dwarf-associated virus in China

In 2009, an emerging citrus viral disease caused by Citrus chlorotic dwarf-associated virus (CCDaV) was discovered in Yunnan Province of China. However, the occurrence and spread of CCDaV in other citrus-growing provinces in China is unknown to date. To better understand the distribution and molecular diversity of CCDaV in China, a total of 1 772 citrus samples were collected from 11 major citrus-growing provinces and were tested for CCDaV by PCR. Among these, 134 citrus samples from Guangxi, Yunnan and Guangdong were tested positive for CCDaV, demonstrating that the occurrence and spread of CCDaV are increasing in China. The complete genome sequences of 17 CCDaV isolates from different provinces and hosts were sequenced. Comparisons of the whole-genome sequences of the 17 CCDaV isolates as well as the 15 isolates available in GenBank revealed that the sequence identity was about 99–100%, showing that the CCDaV isolates were highly conserved. Phylogenetic studies showed that the 32 CCDaV isolates belonged to four different groups based on geographical origins and host species, and that CCDaV isolates from China and Turkey were clustered into different groups. The results provide important information for clarifying the distribution and genetic diversity of CCDaV in China.