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[1]
Date: Fri 4 May 2018 11:56 CEST
Source: Julius Kuehn Institute [in German, trans. & summ. Mod.DHA, edited] <https://www.mz-web.de/quedlinburg/julius-kuehn-institut-quedlinburg-dem-spargelvirus-auf-den-leib-gerueckt-30118122>
Scientists at the Julius Kühn Institute (JKI) in Quedlinburg want to make asparagus plants resistant to a virus that is robbing them of their strength. A nationwide survey in Germany has shown that asparagus from all growing regions is infected, said JKI's Thomas Nothnagel.
The virus is transmitted by aphids, but also by harvesting of spears.
Root growth of plants is reduced, biochemical components change, spears become thinner and yields decrease.
The research strategy is to cross resistant wild asparagus strains from southern Europe and South Africa with cultivated asparagus to make it resistant to the virus. The JKI scientists then pass on their results to commercial growers to develop new marketable varieties.
They expect that it could be at least 6 to 7 years before resistant plants can be grown in the field. The scientists have been working on the cross-pollination programme for around 5 years.
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communicated by: ProMED-mail <promed@promedmail.org>
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[2]
Date: December 2017
Source: Genetic Resources and Crop Evolution [edited] <https://link.springer.com/article/10.1007%2Fs10722-016-0476-y>
[ref: Nothnagel T, Budahn H, Krämer I, et al. Evaluation of genetic resources in the genus _Asparagus_ for resistance to _Asparagus virus 1_ (AV-1). Genet Resour Crop Evol. 2017; 64(8): 1873-87; doi:
10.1007/s10722-016-0476-y]
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The potyvirus _Asparagus virus 1_ (AV-1) is the most important virus attacking garden asparagus worldwide. While the damage caused by AV-1 is often underestimated because of no visible symptoms on shoots or cladophylls, yield losses between 30 to 70 per cent have been reported. Furthermore, influence of virus infection on spear quality and susceptibility to other pathogens such as _Fusarium_ spp. was discussed intensively. It is currently estimated that European asparagus plantations have an infestation of 90 to 100 per cent. The reason might be the ease of virus transmission by aphids (non-persistent mode of transmission) or mechanical transmission.
Furthermore a high concentration of the production areas and the immediate replanting of asparagus fields as result of limited acreage also support the rapid AV-1 spread. For example, asparagus production areas in Germany increased from 6399 ha in 1991 to 25 700 ha in 2015 and are concentrated in only 5 regions. Additionally, there is a strong limitation or even absence of crop rotation. More recently, some authors have reported a high AV-1 infestation of nursery plants and marketable crowns, too, which additionally promote the infestation of new plantations.
Worldwide comprehensive studies have shown that there are no AV-1 resistant cultivars in the garden asparagus _A. officinalis_. The genus _Asparagus_ is very complex and its evolution is not completely understood, number of listed species varies (100-300). The main focus of our study was _A. officinalis_ and the near relative Eurasian wild asparagus, but a number of species from the main center of species diversity in Southern Africa was also used.
44 _A. officinalis_ cultivars, gene bank accessions and breeding lines as well as 34 accessions of wild relatives of _Asparagus_ were evaluated for resistance to AV-1. All tested 660 individual plants of _A. officinalis_ germplasm were susceptible to AV-1 infection. In contrast, in 276 plants of 29 Asparagus wild accessions, no virus infection could be detected. These resistant accessions comprised of
19 diploid, tetraploid, and hexaploid species of both the Eurasian and the African clades of the asparagus germplasm.
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communicated by: ProMED-mail <promed@promedmail.org>
[No viruses were known in asparagus until the crop was introduced into China in the early 1980s where yields were noted to decline without clear symptoms. Subsequently, 9 viruses have been reported on asparagus to date. For several, including _Asparagus virus 1_ (AV-1; genus _Potyvirus_), asparagus is the only natural host, although AV-1 can also infect some experimental hosts such as _Nicotiana_ and _Chenopodium_ species after mechanical inoculation.
Asparagus viruses are spread with infected plant material (such as propagative crowns and tissue cultures) and during harvest on contaminated cutting tools. Species in the large genus _Potyvirus_ are also transmitted by aphids and mechanical means. Unlike some of the other asparagus viruses, AV-1 is not seed transmitted.
The survey data above reporting an extraordinarily high level of overall AV-1 incidence in commercial asparagus cultures in Germany illustrate the dangers of monocultures and the risks of lacking screening of germplasm and propagation material. Both virus species and strains of individual species can accumulate over successive host generations in a predominantly vegetatively propagated crop, such as asparagus. This may lead to an overall gradual decline of crop vigour and productivity over time which is not readily recognised, as illustrated by the case of asparagus reported here.
Maps
Germany:
<http://healthmap.org/promed/p/101> and
<http://www.lib.utexas.edu/maps/europe/germany.jpg> (with states) Europe, overview:
<http://www.edinphoto.org.uk/0_MAPS/0_map_europe_political_2001_enlarged.jpg>
Pictures
AV-1 infected experimental asparagus plants at JKI:
<https://bit.ly/2M24N1g>
Healthy _A. officinalis_ plant with fruits:
<https://weeds.brisbane.qld.gov.au/sites/default/files/styles/large/public/images/asparagus_officinalis1_-_jm.jpg>
Aphids (_Myzus persicae_):
<http://bit.ly/NnIFsS>
Links
Additional news story (in German):
<https://www.proplanta.de/Agrar-Nachrichten/Wissenschaft/Spargel-sollen-resistent-gegen-Viren-werden_article1525594746.html>
Information on AV-1:
<https://web.archive.org/web/20070803182847/http://phene.cpmc.columbia.edu/ICTVdB//00.057.0.01.006.htm>,
<https://www.ncbi.nlm.nih.gov/pubmed/25216774>,
<https://www.genome.jp/virushostdb/443746>,
<https://apsjournals.apsnet.org/doi/full/10.1094/PDIS-07-16-1075-PDN>,
(in China) and
<https://onlinelibrary.wiley.com/doi/abs/10.1111/jph.12169> (resistant _Asparagus_ species) Information on asparagus viruses, including AV-1:
<https://www.ncbi.nlm.nih.gov/pubmed/22682173> (review), <http://ipm.ucanr.edu/PMG/r7100511.html>,
<https://bit.ly/2LZ8i8K>,
<https://link.springer.com/article/10.1007/BF00043472> (in tissue cultures), and via <http://www.apsnet.org/publications/apsnetfeatures/Pages/DiseasesofAsparagus.aspx>
Virus taxonomy via:
<https://talk.ictvonline.org/taxonomy/>
Information on aphids:
<https://bugguide.net/node/view/147/tree/all>,
<https://www.britannica.com/animal/aphid>, and via <https://projects.ncsu.edu/cals/course/ent425/text18/plantvectors.html>
(as plant virus vectors)
Genus _Asparagus_ taxonomy and species lists:
<http://www.theplantlist.org/browse/A/Asparagaceae/Asparagus/> and <https://www.cabi.org/isc/datasheet/7408>
Julius Kuehn Institute:
<https://www.julius-kuehn.de/en/>
- Mod.DHA]
Topics
Species
