Prunus necrotic ringspot virus

Prunus necrotic ringspot virus (PNRSV) is a plant pathogenic virus causing ring spot diseases affecting species of the genus Prunus, as well as other species such as rose (Rosa spp.) and hops (Humulus lupulus).[1][2] PNRSV is found worldwide due to easy transmission through plant propagation methods and infected seed.[3] The virus is in the family Bromoviridae and genus Ilarvirus. Synonyms of PNRSV include European plum line pattern virus, hop B virus, hop C virus, plum line pattern virus, sour cherry necrotic ringspot virus, and peach ringspot virus.[4]

Prunus necrotic ringspot virus
Mosaic virus can appear as subtle blotches on the leaves of the plant, or more extreme discolouration.
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Kitrinoviricota
Class: Alsuviricetes
Order: Martellivirales
Family: Bromoviridae
Genus: Ilarvirus
Species:
Prunus necrotic ringspot virus
Synonyms

European plum line pattern virus
hop B virus
hop C virus
peach ringspot virus
plum line pattern virus
Prunus ringspot virus
red currant necrotic ringspot virus
rose chlorotic mottle virus
rose line pattern virus
rose vein banding virus
rose yellow vein mosaic virus

Hosts and symptoms
More subtle patterning indicating rose mosaic virus.

All cultivated species of the genus Prunus, which includes plums, cherries, apricots, almonds, and peaches, are susceptible to one or more strains of PNRSV. Hops and rose are also susceptible to infection by the virus.[5][6] Other susceptible hosts used for diagnosis include Chenopodium quinoa Willd.,[7] sunflower (Helianthus annus), and Momordica balsamina.[6]

Symptoms on orchard trees can include death of buds and roots, reduced tree survival and uniformity,[8] and increased susceptibility to winter injury.[2] Some common symptoms also include necrotic “shot holes” in leaves or rugosity and mosaic symptoms.[9] In sweet cherries, PNRSV causes reduced leaf size and produces diffused chlorotic rings and/or spots.[10] Generally, symptoms of PNRSV appear in the year following infection, and then becomes symptomless,[11] although some strains cause recurrent symptoms annually. Although adult trees can show recovery from initial symptoms, keeping young trees virus-free is important because the virus can cause long-lasting stunting compared to healthy trees.[11] It is important to note that symptom severity varies due to host cultivar and viral isolate.

Transmission and epidemiology

PNRSV can be transmitted through plant propagation methods, making spread through tree nursery stock and root grafting in orchards problematic.[2] The virus also has been shown to infect and transmit through pollen and seeds.[12][13] PNRSV has been shown to be transmitted by bees carrying infected pollen into orchards.[14] PNRSV infects all seed parts, therefore infection of seed can occur from an infected pollen grain, ovule, or both.[13] Seed transmission incidence can be different among different species or varieties of hosts;[9] host factors that control viral seed transmission, however, are unknown. Cross pollination with PNRSV infected pollen to healthy plants has shown that the virus can also infect the fruit and not just seeds. The virus can also be transmitted by thrips,[15] however the contribution and importance of thrips transmission is unknown.

Management and control

The most important measure in controlling PNRSV is through planting of certified virus-free trees.[9] Tree nurseries producing propagative material can use thermotherapy (keeping cultures at 38˚ C for at least 20 days), and/or apical meristem cultures to eliminate PNRSV.[16] Prompt removal of infected trees is often recommended as a control strategy, but is not practical for most growers. Field studies have shown that planting of same or similar cultivars near an infected orchard favored earlier infection than when different cultivars were grown,[17] indicating that planting of unrelated cultivars could help slow spread of the virus and allow healthy trees to bear fruit before infection. Genetically engineered resistance may be a possibility for control in the future using RNA interference silencing.[18]

References
  1. Nemeth, M (1986). Virus, Mycoplasma, and Rickettsia Diseases of Fruit Trees. Norwell, MA: Marianus Nijhoff Publishers.
  2. Mink, G. I. (1992). "Prunus necrotic ringspot virus". Diseases of Fruit Crops. 3: 335–356.
  3. Kryczynski, S.; et al. (1992). "Prunus necrotic ringspot virus spread in sour cherry orchard and in rootstock production". Acta Horticulturae. 309: 105–110. doi:10.17660/ActaHortic.1992.309.12.
  4. Hammond, R. W. (2011). Prunus necrotic ringspot virus in Virus and Virus-like Diseases of Pome and Stone Fruits. St. Paul, MN: APS Press. pp. 207–213.
  5. Bock, K. R. (1967). "Strains of Prunus necrotic ringspot virus in hop (Humulus lupulus L.)". Annals of Applied Biology. 59 (3): 437–446. doi:10.1111/j.1744-7348.1967.tb04460.x.
  6. Fulton, R. W. (1970). "Prunus necrotic ringspot virus". CMI/ABB Descriptions of Plant Viruses. 5.
  7. Crosslin, J. M.; et al. (1992). "Biophysical differences among Prunus necrotic ringspot ilarviruses". Phytopathology. 82 (2): 200. doi:10.1094/phyto-82-200.
  8. Topchiiska, M. (1983). "Effect of Prunus necrotic ringspot virus and prune dwarf virus on some biological properties of peach". Acta Horticulturae. 130: 307–312. doi:10.17660/ActaHortic.1983.130.53.
  9. Pallas, V.; et al. (2012). "Ilarviruses of Prunus spp.: A continued concern for fruit trees". Phytopathology. 102 (12): 1108–1120. doi:10.1094/phyto-02-12-0023-rvw. PMID 23148725.
  10. Jones, A. L.; et al. (1996). Prunus necrotic ringspot in Diseases of Tree Fruits in the East. MI: Michigan State University. pp. 92–93.
  11. Davidson, T. R. and George, J. A. (1965). "Effects of necrotic ring spot and sour cherry yellows on the growth and yield of young sour cherry trees". Canadian Journal of Plant Science. 45 (6): 525–535. doi:10.4141/cjps65-103.
  12. Amari, K.; et al. (2007). "Prunus necrotic ringspot virus early invasion and its effects on apricot pollen grains performance". Phytopathology. 97 (8): 892–899. doi:10.1094/phyto-97-8-0892. PMID 18943628.
  13. Amari, K.; et al. (2009). "Vertical transmission of Prunus necrotic ringspot virus: Hitch-hiking from gametes to seedling". Journal of General Virology. 90 (7): 1767–1774. doi:10.1099/vir.0.009647-0. PMID 19282434.
  14. Howell, W. E.; et al. (1998). "Natural spread of cherry rugose mosaic disease in two Prunus necrotic ringspot virus biotypes in a central Washington sweet cherry orchard". Plant Disease. 72 (7): 636–640. doi:10.1094/pd-72-0636.
  15. Greber, R. S.; et al. (1992). "Thrips-facilitated transmission of Prune dwarf and Prunus necrotic ringspot virus"es from cherry pollen to cucumber". Plant Disease. 76 (10): 1039–1040. doi:10.1094/pd-76-1039.
  16. Manganaris, G. A.; et al. (2003). "Elimination of PPV and PNRSV through thermotherapy and meristem-tip culture". Plant Cell Reports. 22 (3): 195–200. doi:10.1007/s00299-003-0681-y. PMID 12898177. S2CID 22544618.
  17. Uyemoto, J. K.; et al. (2003). "Horizontal spread of ilarviruses in young trees of several peach cultivars". Plant Disease. 87 (1): 75–77. doi:10.1094/pdis.2003.87.1.75. PMID 30812704.
  18. Song, G.; et al. (2013). "Engineering cherry rootstocks with resistance to Prunus necrotic ringspot virus through RNAi-mediated silencing". Plant Biotechnology Journal. 11 (6): 702–708. doi:10.1111/pbi.12060. PMID 23521804.
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