Occurrence and genetic diversity ofRaspberry leaf blotch virus(RLBV) infecting cultivated and wildRubusspecies in Finland

Abstract

Raspberry leaf blotch virus (RLBV) is a recently described (−)ssRNA virus (genus Emaravirus) associated with the long-known, severe raspberry leaf blotch disorder (RLBD). The virus is presumably transmitted by the raspberry leaf and bud mite (Phyllocoptes gracilis; Eriophyidae). Cultivated and wild raspberries (Rubus idaeus) displaying RLBD or yellowing symptoms were sampled in 14 districts in Finland and tested for RNA3 and RNA5 of RLBV by reverse transcription PCR (RT-PCR) and dot blot hybridization. A total of 59 samples were tested for RLBV, including 36 plants of cultivated raspberry, 20 wild raspberry plants, one ornamental purple flowering raspberry plant (Rubus odoratus), and two samples of P. gracilis (20 mites pooled per sample) collected from RLBD-affected Glen Ample. Fifty-three (93%) of the 57 plants tested were RLBV-positive, including seven raspberry cultivars (Balder, Glen Ample, Jenkka, Malling Minerva, Maurin Makea, Muskoka, Ottawa) and purple flowering raspberry, which is a new host for RLBV. RLBV was also detected by RT-PCR in mites (P. gracilis) collected from buds of RLBV-positive raspberry plants. The partial nucleotide (nt) sequence of the RLBV NP gene (nt 835-1284 of RNA3) was determined for 21 isolates obtained from 10 districts in Finland. Identical isolates were detected in distant districts, and distinctly different isolates were found in the same raspberry cultivation. Furthermore, eight different NP sequence variants were detected in the nine plants of a single raspberry cultivar (Glen Ample) tested from two districts. The nt and deduced amino acid sequences of the 21 isolates were 92.0-100% and 89.3-100% identical, respectively. Phylogenetic analysis revealed two main clusters. One cluster included three isolates, of which two isolates were from one farm in Finland and one isolate was previously characterised in Scotland. The other cluster contained the remaining 19 isolates characterised in this study. The results indicate that RLBV is widely distributed in cultivated and wild raspberries in Finland and shows considerable genetic variability.

The population structure of Rose rosette virus in the USA

“…Similar findings have also been observed in pigeon pea sterility mosaic virus-2 isolates, with 5 % variability seen in the RNA 5 segment [54]. In addition, diversity in RNA 3 and RNA 4 was similar to that previously observed for RRV and other emaraviruses [55][56][57][58][59][60][61].…”

Molecular detection and characterisation of black raspberry necrosis virus and raspberry bushy dwarf virus isolates in wild raspberries

“…These findings are important because BRNV has not been reported previously in Finland and because RBDV has been detected so far only in cultivated raspberries in Finland (Wang et al ., ; Nukari et al ., ). Small interfering RNA deep sequencing was used recently to facilitate the first detection of the mite‐transmitted raspberry leaf blotch virus (genus Emaravirus ) in cultivated and wild raspberries in Finland (Dong et al ., ). These results indicate that monitoring and controlling of wild raspberry populations that are proximal to cultivated raspberries should be encouraged to maintain crop productivity.…”

“…In Finland, RBDV has been reported to infect cultivated raspberries (Wang et al ., ; Nukari et al ., ) and Arctic brambles, Rubus arcticus L. (Kokko et al ., a , b ), but there are few studies available on occurrence of RBDV in wild raspberries. Finally, raspberry leaf blotch virus (genus Emaravirus ) was also recently detected in Finland in both wild and cultivated raspberries as well as the ornamental species Rubus odoratus L. (Bi et al ., ; Dong et al ., ).…”

Variability of Emaravirus Species Associated with Sterility Mosaic Disease of Pigeonpea in India Provides Evidence of Segment Reassortment

“…Some plant RNA viruses evolve rapidly, while others evolve slowly resulting in either genetically diverse or stable virus populations [ 23 , 24 , 25 ]. A thorough understanding of the genetic variability of emaraviruses involved in SMD of pigeonpea may help in the development of reliable and robust diagnostic tools and improved disease management strategies [ 13 , 26 , 27 , 28 , 29 , 30 , 31 ]. The sequence variability among the 23 isolates of PPSMV-1 and PPSMV-2, collected from ten geographic locations across India, was assessed by producing complete/partial sequences of selected RNA segments ( Supplementary Table S1 ).…”