Natural infection with raspberry bushy dwarf virus (RBDV) of the putatively RBDV‐resistant red raspberry cultivar Glen Moy, and the demonstration that it does not contain the RBDV resistance gene, Bu

Abstract

Summary.When released to commerce in 1981, the red raspberry cv. Glen Moy was reported to be immune to the Scottish type isolate of raspberry bushy dwarf virus (RBDV‐D200). Field observations of this cultivar in localities where RBDV was prevalent tended to support this claim of its resistance, but in the past 6–10 yr, RBDV infection has been reported in this cultivar in Australasia, USA and in several commercial crops in England. Therefore, experiments were made to investigate the reason(s) for this apparent anomaly using RBDV‐infected material, putatively of cv. Glen Moy, from two locations in southern England and one each from Australia, New Zealand (NZ) and the USA. Genetic fingerprinting of genomic DNA from samples of these five RBDV‐infected raspberry sources confirmed their identity as cv. Glen Moy. Comparisons of some serological and genomic properties of the five Glen Moy RBDV isolates indicated that, whilst they shared many properties with previously well characterised isolates of this virus, they were distinguishable from them. Characterisation of the isolate from NZ maintained in raspberry showed that it did not have a Rubus host range characteristic of resistance‐breaking (RB) isolates, indicating that for this location, and probably also for those of Australia and the USA, RB isolates were not the cause of infection in cv. Glen Moy. When virus‐tested plants of cv. Glen Moy and 45 progeny seedlings from the cross between cv. Glen Moy and the RBDV‐susceptible cv. Autumn Bliss were graft inoculated with RBDV‐D200, all grafted plants became infected indicating that cv. Glen Moy does not contain the RBDV resistance gene, Bu. Possible reasons for the previously reported resistance of cv. Glen Moy to RBDV are discussed.