Viruses and virus-like diseases liable to be carried by strawberry germplasm material
In the FAO/IPGRI Technical guidelines for the safe movement of small fruit germplasm, in particular, viruses and virus-like diseases liable to be carried by strawberry germplasm are described. The main quarantine diseases of strawberry listed by EPPO are included, but some more unusual ones are also mentioned (marked with an asterisk and briefly described below).
arabis mosaic nepovirus (EU Annex II/A2)
aster yellows MLO
fragaria chiloensis ilarvirus*
raspberry ringspot nepovirus (EPPO A2 quarantine pest)
strawberry crinkle rhabdovirus (EU Annex II/A2)
strawberry green petal MLO
strawberry latent C disease (EPPO A1 quarantine pest)
strawberry latent ringspot nepovirus (EU Annex II/A2)
strawberry mild yellow-edge disease (EU Annex II/A2)
strawberry mottle virus
strawberry pseudo mild yellow-edge carlavirus
strawberry vein banding caulimovirus (EPPO A2 quarantine pest)
strawberry witches' broom MLO (EPPO A1 quarantine pest)
tobacco streak ilarvirus
tomato black ring nepovirus (EU Annex II/A2)
tomato ringspot nepovirus (EPPO A2 quarantine pest)
Chlorotic fleck: This disease is probably caused by a virus and is latent in most cultivars. It induces chlorotic fleck symptoms on the indicator Fragaria vesca. It has been reported only in Louisiana in USA. It can be experimentally transmitted to F. vesca and F. virginiana by leaflet grafting and Aphis gossypii, but not by mechanical transmission.
Fragaria chiloensis ilarvirus: This virus was isolated from wild Fragaria chiloensis plants imported into USA from Chile, and described in 1993. Fragaria chiloensis ilarvirus is symptomless on F. chiloensis. The virus has quasi-isometric particles of 21.4 nm in diameter and bacilliform particles (up to 57 nm long) have also been reported. This virus seems to be limited to Chile, in the Andes and coastal mountain areas. It can be transmitted through pollen and seed. However, its host range and vectors are currently unknown and it is not clear whether the virus is a potentially important pathogen of cultivated strawberry.
June yellows: This strawberry disorder is not graft-transmissible. The causal agent is still unknown but groups of dsRNA have been associated with symptoms of June yellows. Diseased strawberry plants develop clearly delimited, unusually sectorial, chlorotic areas. Symptoms diminish in warm weather. Usually, affected plants become stunted over a few seasons and die prematurely. This disorder is observed world-wide and transmitted by seeds and vegetative propagation, but not by grafting, sap inoculation or vectors. In addition, June yellows has not been eliminated by thermotherapy or meristem tip culture. However, the EPPO Panel on certification of pathogen-tested fruit crops has considered that June yellows was a genetic disorder.
Leaf roll: In cultivated strawberries, the symptoms are characterized by downward rolling of leaflet margins. Leaves are chlorotic, rugose with vein clearing. This disorder of unknown etiology has only been observed in the northeastern part of North America and Kazakhstan. The disease can be transmitted by grafting but not by mechanical inoculation, and is not eliminated by thermotherapy.
Pallidosis disease: The causal agent of this disease has not been characterized but is thought to be a virus. The disease is associated with several high molecular weight dsRNA bands. The pathogen is either latent or causes very mild symptoms on strawberry. It causes epinasty, distortion, chlorosis and dwarfing in graft-inoculated F. virginiana clones UC 10 and UC 11. Pallidosis has been reported from Australia, Canada and USA. This disease is seed borne in F. vesca.
Vein yellowing: This disease is thought to be caused by a virus and induces in cultivated strawberries very striking symptoms of vein yellowing. Symptoms are obvious in spring and autumn but are masked in summer. Apparently, the disease is not damaging to infected plants. It has only been reported in Japan. The disease can be transmitted by leaflet grafting but not by mechanical means.
Diekmann, M.; Frison, E.A.; Putter, T. (eds) (1994) FAO/IPGRI Technical Guidelines for the safe movement of small fruit germplasm, FAO/IPGRI, Rome, 13-45.