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First reports of Liberibacter solanacearum om Tunisia, Finland

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

In this post:

[1] Tunisia: Lso D & E, carrot

[2] Finland: Lso C, potato

******

[1] Tunisia: Lso D & E, carrot

Date: January 2019

Source: European Plant Protection Organisation (EPPO) Reporting Service 01/2019/020 [edited] <https://gd.eppo.int/reporting/article-6450>

1st report of '_Candidatus_ Liberibacter solanacearum' and its vectors _Bactericera trigonica_ and _B. nigricornis_ in Tunisia

----------------------------------------------------------------------

In 2014-2016 symptoms similar to those associated with the presence of 'Ca. L. solanacearum' [Lso] (EPPO A1 List, Solanaceae haplotypes) were observed in [several] governorates. Symptoms including leaf curling, yellowing, bronze and purplish discoloration, stunting of plants and roots, and proliferation of secondary roots, affected 20 to 40% of the carrots in some plots and caused significant yield losses. Symptoms were observed both in fields sown with locally produced seed and imported seed.

Laboratory analyses on samples from carrot fields in Kairouan [governorate] detected Lso haplotypes D and E. This is the 1st time haplotypes D and E were detected co-infecting a carrot plant. 3 samples taken from [a] field for carrot seed production tested positive for haplotype D.

Surveys on vectors were conducted between May 2014 and April 2015 showed that _Bactericera trigonica_ and _B. nigricornis_ (both

Hemiptera: Triozidae) were present in all symptomatic fields. The authors note that both species were not previously known to be present in Tunisia and consider that they are likely to be the vectors of Lso as reported in other Mediterranean countries. _B. trigonica_ and _B.

nigricornis_ were also observed on other crops from the Apiaceae family as well as on tomato and potato.

Communicated by:ProMED-mail <promed@promedmail.org>

******

[2] Finland: Lso C, potato

Date: January 2019

Source: European Plant Protection Organisation (EPPO) Reporting Service 01/2019/021 [edited] <https://gd.eppo.int/reporting/article-6451>

1st report of '_Candidatus_ Liberibacter solanacearum' haplotype C in a symptomless potato plant in Finland

----------------------------------------------------------------------

In Finland, Lso haplotype C is transmitted by the carrot psyllid _Trioza apicalis_ (Hemiptera: Triozidae) and causes yield losses (see EPPO RS 2012/118 and 2017/129). Because Lso haplotypes A and B (EPPO

A1 List) cause the damaging zebra chip disease in potato in the USA and New Zealand, the occurrence of Lso in cultivated and volunteer potatoes in Tavastia Proper and Satakunta regions of Finland was studied.

A total of 8 volunteer potato plants and one cultivated potato plant grown at the edge of a carrot field were tested by PCR and found to be positive for Lso haplotype C but did not show symptoms of zebra chip disease. This is the 1st observation of haplotype C in field grown potatoes. It may be noted that haplotype E was also detected in potato stores in Spain (see EPPO RS 2017/134) [ProMED-mail post http://promedmail.org/post/20170802.5222241].

Transmission experiments were performed. Attempts to transmit Lso into potato with _T. apicalis_ were not successful. Lso haplotype C was transmitted from infected carrots to potato plants by leaf grafting and by phloem connection formed by dodder but daughter tubers produced by the infected potato plants all tested negative.

Communicated by: ProMED-mail <promed@promedmail.org>

[Only a few members of _Candidatus_ Liberibacter have been characterised so far, including the pathogens causing citrus greening (see previous ProMED-mail posts in the archives) which is limited to these crops due to the host specificity of the psyllid vectors.

_Ca._ Liberibacter solanacearum (Lso) was found to be associated with zebra chip (ZC) of potato, as well as a yellowing disease of tomato and capsicum in New Zealand. Lso has since also been associated with yellowing diseases of other solanaceous crops and some crops in the family Apiaceae. Main vectors of Lso are the potato psyllid (_Bactericera cockerelli_) in solanaceous host and carrot psyllids (_Trioza apicalis_, _Bactericera trigonica_) in Apiaceae. These vectors have a much wider host range than the greening vectors and additional vector species are also being identified, further extending potential host range and economic impact of Lso.

The Lso species is divided into haplotypes: A and B affecting Solanaceae; C, D and E affecting Apiaceae. Both groups of haplotypes have been reported from the Americas and New Zealand. Carrot haplotypes have been reported from Europe (ProMED-mail posts http://promedmail.org/post/20120713.1199961,

http://promedmail.org/post/20151009.3702151,

http://promedmail.org/post/20161130.4666613), northern Africa (ProMED-mail post http://promedmail.org/post/20141121.2978030) and the Middle East (ProMED-mail post http://promedmail.org/post/20170130.4803773). However, haplotype E was recently also detected in potatoes in Spain [ProMED-mail post http://promedmail.org/post/20170802.5222241], representing the 1st report of a haplotype being able to infect both Apiaceae and Solanaceae. This suggests that a lot more research is needed on epidemiology, biology and distribution of Lso worldwide.

Potato haplotypes A & B are still considered absent from the European/Mediterranean region. The first report of potatoes being affected by Lso in Europe was from Spain with haplotype E, but the report did not state whether typical zebra chip symptoms were observed (ProMED-mail post http://promedmail.org/post/20170802.5222241). Item [2] above specifies that potatoes infected with haplotype C were symptomless. It would remain to be clarified whether the different Apiaceae haplotypes affect potatoes in different ways, or whether all the Apiaceae haplotypes are symptomless in solanaceous hosts. A lot more research is needed on epidemiology, biology and distribution of Lso worldwide.

Maps

Tunisia:

<http://ontheworldmap.com/tunisia/tunisia-road-map-max.jpg>,

<http://healthmap.org/promed/p/71>, and

<https://www.mapsofworld.com/tunisia/maps/tunisia-political-map.jpg>

(governorates)

Finland:

<http://www.worldatlas.com/webimage/countrys/europe/lgcolor/ficolor.gif>,

<http://healthmap.org/promed/p/118>, and <https://www.mapsofworld.com/finland/maps/finland-political-map.jpg>

(regions)

Europe, overview:

<https://mapofeurope.com/wp-content/uploads/2018/03/europe-political-map.jpg>

Pictures

Lso affected carrot:

<http://journals.plos.org/plosone/article/figure/image?size=medium&id=info:doi/10.1371/journal.pone.0161016.g002>

and

<https://gd.eppo.int/media/data/taxon/L/LIBEPS/pics/1024x0/1939.jpg>

(compared with healthy)

Lso symptoms on tomato:

<http://nwdistrict.ifas.ufl.edu/phag/files/2014/10/Fig-7-PY-Dufault.jpg>

and

<http://tinyurl.com/y5zcfqvm> (Western Australia Department of Primary Industries and Regional Development, Agriculture and Food) Zebra chip of potato:

<http://www.agriculture.gov.au/SiteCollectionImages/pests-diseases-weeds/zebra-chip-1.jpg>,

<http://www.digitaljournal.com/img/4/2/9/0/i/4/1/7/o/8ab1aa702fece1872973ac17aec85b6f.jpg>

(processed infected tuber, compared with healthy), <http://tinyurl.com/y4yhtdna> (Western Australia Department of Primary Industries and Regional Development, Agriculture and Food), and <http://bit.ly/2lVfcQ6> Lso, microscopy:

<http://bacmap.wishartlab.com/system/images/1223/medium/Candidatus_Liberibacter.jpg?1319706599>

Lso photo gallery:

<https://gd.eppo.int/taxon/LIBEPS/photos>

Carrot psyllid:

<https://www.britishbugs.org.uk/homoptera/Psylloidea/Psyllidae_images/Trioza_apicalis_2.jpg>

Links

Information on _Ca._ Liberibacter solanacearum:

<https://gd.eppo.int/taxon/LIBEPS>,

<http://onlinelibrary.wiley.com/doi/10.1111/epp.12043/pdf>,

<http://www.cabi.org/isc/datasheet/109434>,

<http://www.rhizobia.co.nz/downloads/Weir_CS23.pdf>

Lso haplotypes: