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First report of tomato leaf curl New Delhi virus in the Zhejiang province of China

A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

Date: November 2022
Source: European Plant Protection Organisation (EPPO) Reporting Service 11/2022/243 [summ. Mod.DHA, edited]
https://gd.eppo.int/reporting/article-7474

_Tomato leaf curl New Delhi virus_ (_Begomovirus_, ToLCNDV - EPPO A2 List) is reported for the 1st time from China. In August 2021, virus-like symptoms were observed on tomato (_Solanum lycopersicum_) plants grown in a glasshouse (ca. 0.5 ha) in Zhejiang province.

Laboratory analysis (PCR tests, sequencing) confirmed the presence of ToLCNDV in a symptomatic sample. ToLCNDV was confirmed by PCR in additional 8 tomato plants showing upward leaf curling and leaf distortion. Considering the widespread occurrence of the vector _Bemisia tabaci_ in China, ToLCNDV may represent a potential threat to vegetable crops in the country.

[Source publication: https://doi.org/10.1094/PDIS-06-22-1427-PDN]

--
Communicated by:
ProMED

[_Tomato leaf curl New Delhi virus_ (ToLCNDV; genus _Begomovirus_) was first identified as causing severe yield losses on tomato and watermelon crops on the Indian subcontinent. It belongs to the tomato leaf curl and yellow leaf curl clades of the genus. Known species in these clades cause similar diseases on solanaceous and other hosts and are considered to be the biggest constraint to solanaceous and cucurbit crops, both in terms of yield losses (up to 100% in tomato) and loss of fruit quality.

Begomoviruses are transmitted by different whitefly vectors (such as _Bemisia tabaci_ biotypes). Many can also be transmitted by mechanical means and grafting, but they are generally not considered to be seed transmitted. Whiteflies in themselves are serious pests of many vegetable crops. If virus sources are available locally, high vector numbers are often reflected in high levels of the viral diseases they transmit. Begomovirus control is particularly difficult in open field crops due to the widespread presence and wide host range of whiteflies. Disease management may include pathogen exclusion, vector control, as well as elimination of possible pathogen and/or vector reservoir plants. In some cases, crop cultivars with increased virus resistance are available.

ToLCNDV was limited to Asia until it was reported from Europe for the 1st time in 2013 on cucurbits in Spain (ProMED post 20131223.2131729). It has since also been reported from several other countries in the Mediterranean region. Severe potato leaf curl disease caused by a ToLCNDV is currently emerging as a global threat.

Novel viruses have been shown to emerge from recombination events during co-infections of ToLCNDV and other begomoviruses (see links below).The recombinant viruses are often more aggressive and have a widened host range, compared to each of the partners. Examples are new viruses identified in the Mediterranean region causing severe damage to cucurbit crops but poorly infecting tomatoes; or the new potato strain of ToLCNDV having acquired an extraneous betasatellite (small circular DNA in addition to the viral genome), which is considered responsible for its host preference and severity of symptoms. Such new hybrid viruses pose an increased risk to solanaceous, cucurbit, and potentially other crops worldwide.

Maps
China:
http://travelsmaps.com/wp-content/uploads/2016/09/map-of-china_7.gif
China provinces:
http://www.chinadiscovery.com/assets/images/customer-support/maps/china-provinces-map-600.jpg

Pictures
Leaf curl disease on tomato:
https://www.agric.wa.gov.au/sites/gateway/files/TYLCV%203%20bush.jpg,
https://c8.alamy.com/comp/ACGAME/tomato-yellow-leaf-curl-virus-symptoms-on-tomato-leaves-on-plants-ACGAME.jpg,
https://www.plantmanagementnetwork.org/pub/php/research/2008/TYLCV/image/TYLCV2.jpg and
https://vegcropshotline.org/wp-content/uploads/2018/06/IMG_20180616_103634.jpg
ToLCNDV symptoms:
http://cienciacebas.files.wordpress.com/2013/09/aranda-1.jpg (zucchini) and
http://cienciacebas.files.wordpress.com/2013/09/aranda-2.jpg (cucumber & melon)
Photo gallery of symptoms of different begomoviruses:
http://www.forestryimages.org/browse/TaxImages.cfm?fam=651&genus=Begomovirus
Whiteflies:
https://www.planetnatural.com/wp-content/uploads/2012/12/whitefly.jpg and
https://www.pinpointpestcontrol.com/images/whitefly-on-plant.jpg

Links
Additional news story:
https://www.hortidaily.com/article/9481686/tolcndv-emerges-in-china/
Information on ToLCNDV:
https://gd.eppo.int/taxon/TOLCND (with distribution),
https://doi.org/10.1079/cabicompendium.118179,
https://doi.org/10.2903/j.efsa.2020.6179,
https://doi.org/10.1111/ppa.12978,
https://doi.org/10.3389/fmicb.2019.00140,
https://doi.org/10.1007/s41348-021-00463-w (potato strain) and
https://doi.org/10.3390/v9100264 (review)
Novel ToLCNDV recombinant viruses:
https://doi.org/10.3390/v8110307 and
https://doi.org/10.1007/s10327-019-00849-7
Information on viral betasatellites:
https://doi.org/10.1007/s11262-019-01716-5,
https://viralzone.expasy.org/7777,
https://www.ncbi.nlm.nih.gov/genomes/GenomesGroup.cgi?taxid=190729 and via
https://www.sciencedirect.com/topics/immunology-and-microbiology/betasatellite
Information on leaf curl viral diseases on different hosts:
http://www.oisat.org/pests/diseases/viral/leaf_curl__virus.html and via
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/tomato-leaf-curl-virus
Virus & betasatellite taxonomy via:
https://ictv.global/taxonomy
_B. tabaci_ whiteflies, taxonomy, and biotypes:
http://www.iucngisd.org/gisd/species.php?sc=106 (with pictures)
EPPO A2 quarantine list:
https://www.eppo.int/ACTIVITIES/plant_quarantine/A2_list
- Mod.DHA

ProMED map:
Zhejiang Province, China: https://promedmail.org/promed-post?place=8707219,352]