Geographical distribution and hosts of citrus chlorotic dwarf associated virus
Citrus chlorotic dwarf disease was first observed in the mid-1990s in Turkey, in citrus orchards along the southern coast (Mersin province, Eastern Mediterranean region). In the field, the first symptoms appeared on young leaves during spring. The most obvious one was the formation of a typical ‘V’ shaped notch on the leaves, in addition to deformation (curling, boat-shapes), chlorosis and narrowing of the leaves. Affected young trees displayed a bushy vegetation and stunted appearance, due to shortened internodes. Flowering and fruit production were also reduced. This disease has been observed on several citrus species, in particular on lemon (Citrus limon), pomelo (C. maxima), sour orange (C. aurantium), mandarin (C. reticulata), tangelo (C. reticulata x C. paradisi). Sweet orange (C. sinensis) and grapefruit (C. paradisi) can be affected, but symptoms seem to be less severe. Initial studies showed that the disease was graft-transmissible and possibly vectored by Parabemisia myricae (Homoptera: Aleyrodidae). However, the transmission of the disease by P. myricae could not be confirmed in later studies using molecular methods. In 2012, the causal agent of this disease was identified as a new virus possibly belonging to Geminiviridae and tentatively called citrus chlorotic dwarf associated virus (CCDaV). Following its initial discovery in Mersin province, CCDaV was then also found in other provinces in Turkey, as well as in China and Thailand. The origin of these new findings remains unknown, but the use of infected planting material is suspected to be the main pathway for spreading the disease between continents. At field level, it is suspected that vectors probably spread the virus, but their identity could not be ascertained.
- Turkey
Following the initial record of CCDaV in Mersin province, further studies conducted in 2016-2017 in 4 major citrus-growing regions (Western Mediterranean region, coastal Aegean region, Southern Marmara region and Eastern Black Sea region) showed that CCDaV has spread to new areas in the Eastern Mediterranean region (Adana, and Hatay provinces). CCDaV was also found in a few citrus trees growing in the garden of a hotel in Belek (Antalya province, Mediterranean region).
- China
In 2015, CCDaV was reported for the first time from Dehong prefecture (Yunnan province). It was noted that symptoms of leaf mosaic, distortion, shortened internodes, and reduced fruit production had been observed since 2008 on Eureka lemon (C. limon). During further studies conducted from 2017 to 2019 in 145 citrus orchards located in 11 major citrus-growing provinces, CCDaV was found in Yunnan (73 positive samples out of 704), Guangxi (60/195) and Guangdong (1/136), but not in the other studied provinces. The virus was detected in Eureka lemon (C. limon), Tahiti lime (C. latifolia) and pomelo (C. maxima).
- Thailand
In 2019, symptoms of the disease were first observed in Nakhon on pomelo (C. maxima (=C. grandis) cv. Ruby Green). Molecular tests confirmed the presence of CCDaV.
A geographical distribution and a list of host plants of CCDaV are now stored in the EPPO Global Database: https://gd.eppo.int/taxon/CCDAV0
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