Graft-Transmissible Diseases of Ribes - Pathogens, Impact, and Control

Analysis of R Genes Related to Blackcurrant Reversion Virus Resistance in the Comparative Transcriptome of Ribes nigrum cv. Aldoniai

Blackcurrant reversion virus (BRV) is the most destructive mite-transmitted pathogen in blackcurrants. The understanding of the resistance to BRV is limited, hindering and delaying the selection process. To identify the resistance (R) gene for BRV resistance, a gene expression analysis based on de novo blackcurrant cv. Aldoniai comparative transcriptome analysis (mock- and BRV-inoculated samples at 2 and 4 days post-inoculation (dpi)) was performed. In this study, 111 annotated clusters associated with pathogenesis according to conservative R gene domains were identified. In virus-infected samples, only Cluster-12591.33361 showed significant expression at 4 dpi. The expression profiles of this cluster were significantly associated with the presence of BRV particles in plant tissues, making it a putative R gene in the dominant resistance strategy in the BRV-Ribes nigrum interaction. The newly identified gene R.nigrum_R belongs to the CC-NBS-LRR class and has 63.9% identity with RPM1 in Populus spp. This study provides new insights on dominant putative R genes related to resistance to BRV in R. nigrum, which could aid targeted research and genetic improvement in breeding programs of blackcurrants.

Mixed Infection of Blackcurrant with a Novel Cytorhabdovirus and Black Currant-Associated Nucleorhabdovirus

A virome screen was performed on a new breeding line, KB1, of blackcurrant. Rhabdovirus-like particles were observed by electron microscopy in ultrathin sections of flower stalks, and the complete genome sequence of a novel virus, provisionally named blackcurrant rhabdovirus 2 (BCRV2), was determined and verified using high-throughput sequencing. The genomic organization of BCRV2 was characteristic of cytorhabdoviruses (family Rhabdoviridae) and included seven genes: 3 ́- N-P´-P-P3-M-G-L -5 ́. BLASTP analysis revealed that the putative L protein had the highest amino acid sequence identity (75 %) with strawberry virus 2. BCRV2 was detected in Cryptomyzusgaleopsidis, but efficient transmission by this aphid was not confirmed. Of note, we observed coinfection of the KB1 line with blackcurrant-associated rhabdovirus (BCaRV) by RT-PCR. This is likely the first evidence of the presence of a cyto- and a nucleorhabdovirus in a single host.

Creation and Use of Highly Adaptive Productive and Technological Red Currant Genotypes to Improve the Assortment and Introduction into Different Ecological and Geographical Zones

Global climate change with the cyclicity of natural and climatic processes in the growing season of berry plants, causes weakening at the defense system to (a)biotic stressors, which actualize the need for accelerated cultivar-improving breeding. A new hybrid red currant material was obtained and studied by the method of interspecific hybridization. Correlation analysis was used to assess the relationship between adaptively significant and economical and biological traits. To assess intergenotypic variability, hierarchical clustering was used according to the studied features, which allowed combining three standard methods of multidimensional data analysis. Genotypes adapted to different stressors were identified. The genotypes 271-58-24, 44-5-2, 261-65-19, and ‘Jonkheer van Tets’ were found to have a higher ratio of bound water to free water as compared with the others. Moreover, the genotypes of 271-58-24, 261-65-19, 77-1-47, and ‘Jonkheer van Tets’ were found to have less cold damage during the cold periods. The two most productive genotypes were found to be the genotypes 44-5-2, 143-23-35, and 1426-21-80. A dependence of yield on the beginning of differentiation of flower buds, which led to the abundance of flower inflorescences, was revealed. Rapid restoration of leaf hydration ensured successful adaptation of genotypes to the “temperature shock” of the growing season. The genotypes 271-58-24 and ‘Jonkheer van Tets’ were then observed to be far from the test traits and none of these traits were observed to characterize these two genotypes. The genotypes of 261-65-19 and 77-1-47 were then observed to be characterized by their high stability to Cecidophyopsis ribis scores. Genotypes 261-65-19 and 271-58-24, obtained with the participation of ‘Jonkheer van Tets’ as the maternal form, showed sufficient resistance to Pseudopeziza ribis and Cecidophyopsis ribis. Overall results suggested that the hydration recovery of red currant plants is significantly important for a yield improvement. A new cultivar ’Podarok Pobediteliam (genotype 44-5-2) was obtained that meets the requirements of intensive gardening and is characterized by high adaptability, productivity, and technological effectiveness.