Fundamental and practical bases for creating a blackcurrant field repository in Russia

Creating a virus-free repository of blackcurrant will allow an assessment of productivity, other qualitative characteristics and the use of pollen from healthy plants for breeding. The aim of the research was to reveal the most promising varieties and hybrids of blackcurrant, test plants for viruses and obtain nuclear stock plants for laying the repository. The studies were carried out in 2018-2020 using generally accepted methods of variety study, virus diagnosis and plants reproduction. Valuable blackcurrant varieties and hybrids of the All-Russian Horticultural Institute for Breeding, Agrotechnology and Nursery breeding were studied; the most productive clones were selected and tested by ELISA and PCR. The species composition of harmful viruses in the fruiting stands of blackcurrant under ex situ conditions is diverse. The total prevalence of Arabis mosaic virus (ArMV), Raspberry ringspot virus (RpRSV), Strawberry latent ringspot virus (SLRSV), Tomato black ring virus (TBRV) on blackcurrant plants was 31.5 %. The prevalence of SLRSV and RpRSV was about 15 %, TBRV – 14 %, ArMV – 7 %. Blackcurrant reversion virus (BRV) was absent. As a result of the monitoring carried out in 2018, blackcurrant plants of 8 varieties free from harmful viruses were identified and, after PCR, will be used to establish the repository and base mother nursery.

Elucidation of the Roles of Blackcurrant reversion virus and Phytoplasma in the Etiology of Full Blossom Disease in Currants

To determine the roles of phytoplasmas and Blackcurrant reversion virus (BRV) in the etiology of full blossom disease (FBD), we conducted graft and dodder transmission experiments. Scions from FBD-affected Ribes rubrum were grafted onto red currants, white currants, and black currants. Red and white cultivars revealed symptoms of FBD, whereas blackcurrant displayed symptoms of BRV. No differences in symptoms were observed between plants infected with BRV only and those infected with BRV and phytoplasma. Aster yellows phytoplasma subgroup 16SrI-C was transferred from FBD-infected red currants to periwinkle, where symptoms of green and yellow petal were observed. Back-transmission of phytoplasma to currant seedlings of red and black currant was not successful. Scions of periwinkle infected with aster yellows phytoplasmas of subgroup 16SrI-C and 16SrI-B, which were bottle-, bark-, and approach-grafted onto seedlings of red and black currant, resulted in positive but symptomless transmission of phytoplasma to red currant. We conclude that FBD symptoms are induced by BRV rather than by phytoplasma, which was originally described as the causal agent of FBD.