Location: Horticultural Crops Production and Genetic Improvement Research Unit
2023 Annual Report
Objectives
Objective 1: Characterize important genetic traits in blueberry, blackberry, and raspberry to improve selection efficiency and identify novel sources of genetic resistance to disease.
Objective 2: Breed improved blueberry, blackberry, and raspberry cultivars for the commercial fruit industry including high yielding, virus tolerant, high-quality fruits for the fresh and processing markets.
Approach
For each crop, a modified recurrent mass selection system will be used. Individuals that are selected in a given generation will be intercrossed to produce the next generation. For Rubus spp. and strawberry 4000-6000 seedlings, and 2500-4000 blueberry seedlings from 30-100 crosses will be evaluated annually. Approximately 0.5 to 1.0% of the seedlings are selected based on subjectively evaluated fruit quality, plant performance, ripening period, and yield. Frozen samples will be evaluated for processing characteristics. Selections identified as being superior will be propagated for commercial trial and release. For nursery production, the ARS virology program in Corvallis, OR will help produce virus-tested propagation material. To broaden the germplasm base, superior individuals or representatives of superior populations of small fruit species will be crossed among themselves or with advanced selections or cultivars. Selections from these crosses will be used in our breeding program and distributed to other breeders. Emphasis will be on aphid resistance, disease resistance, fruit quality, thornlessness and tolerance to abiotic stresses associated with growing these crops in regions with more diverse climates.
This program collaborates with molecular geneticists in efforts to bridge the gap between genomics and applied plant breeding in berry crops. Our program helps to determine the mapping populations to develop or genotypes to include and how the various phenotypic traits (phenological, reproductive, and vegetative) will be evaluated. The phenotyping for each project is being coordinated across multiple locations with different climatic conditions. For raspberry leaf curl disease, suspect raspberry samples will be collected and their virome analyzed using Next Generation Sequencing. This approach will also be used to examine two novel diseases of grapevines in Oregon. Diagnostic assays will be developed and used for epidemiology studies, certification and quarantine purposes. Virus vectors will be identified and strategies for vector control developed as a means to manage virus diseases. Total genomic sequencing of five Rubus cultivars will be used to determine if the inserted RYNV sequences represent full-length or partial RYNV and if all insertions are at the same site. If the RYNV insertions are at the same site in each of these cultivars it would indicate that the insertion may have happened once and been passed on in breeding programs. Several approaches will be tested for applying gene silencing as a tool to eliminate viruses from growing points of plants (meristematic dome and several leaf primordia): 1. Virus specific dsRNA will be produced and provided to plants in tissue culture as an additive to the media; 2. dsRNA will be attached to positively charged clay nanoparticles and sprayed on plants in tissue culture or growth chambers; and 3. RBDV infected plants will be grafted onto transgenic plants (already developed red raspberry) that are producing RNAi silencing of RBDV. Meristems will be collected at various times after treatments, plants regenerated and tested for RBDV.
Progress Report
This is a final report for project 2072-21000-058-000D, entitled, “Genetic Improvement of Blackberry, Red and Black Raspberry, and Blueberry”, which expired on February 12, 2023, and has been replaced by new project 2072-21000-060-000D, entitled, “Genetic Improvement of Blackberry, Red and Black Raspberry, and Blueberry”. For additional information, please review the report for the new project.
In support of Objective 1, we made new plant crosses, germinated new seedling populations, and evaluated advanced selections for commercially important horticultural and fruit quality traits. The breeding programs continued to engage with stakeholders through commission meetings, field days, and industry reports and distributed clean plant material of cultivars and promising new advanced selections to nurseries and grower-cooperators by working with the National Clean Plant Network. The breeding program continued its cooperation with Oregon State University (OSU) to host on-farm trials of advanced breeding lines at the OSU North Willamette Research and Extension Center (OSU-NWREC). The breeders established multiple new Material Transfer Agreements (MTAs) to support propagation of advanced breeding lines in U.S. nurseries and subsequent commercial trials to identify new potential cultivars. Substantial commercial plantings of the most recent trailing blackberry release, ‘Columbia Star’, were established in Oregon.
In support of Objective 2, we screened small fruit germplasm that included diverse wild crop relatives of blueberry, raspberry, and blackberry, and applied genetic markers for mapping of horticultural traits, such as firmness, in blueberry. The raspberry breeding program made selections and evaluated germplasm containing wild introgressions from native R. idaeus, R. parvifolius, R. coreanus, and R. innominatus. The blackberry breeding program made selections and evaluated germplasm containing wild introgressions from R. georgicus or R. caucasicus. The blueberry breeding program made selections and evaluated germplasm based on crosses using parents which showed greater resistance to infection from blueberry shock virus (BlShV) and heat tolerance.
We initiated or continued collaborative projects involving the development and deployment of new genetic marker technologies for small fruit crops. These included starting work toward development of genetic marker panels with Diversity Arrays Technology (DArT) for the USDA-ARS Breeding Insight initiative for strawberries, participating in the testing of Breeding Insight database tools and phenotype collection software, testing genetic marker technologies developed for blueberry by the Breeding Insight team, collaborating with the Vaccinium Coordinated Agriculture Project (VacCAP) team for blueberry genomic prediction, and developing the first set of genetic markers for mapping a trailing blackberry population. The caneberry research program worked with researchers in Corvallis, Oregon, to implement genetic markers in black raspberry for marker-assisted prediction aphid resistance in new seedling populations. We made significant progress in the characterization of Rubus yellow net virus (RYNV), a virus which infects raspberry genomes. This included sequencing and detection of RYNV in raspberry, discovery of evidence of RYNV integration into the raspberry genome and comparing standard methods for virus detection to high-throughput sequencing (HTS)-based methods. In addition to RYNV studies, the virologist published a report on viruses impacting blueberry in North America and the implications for production and nursery propagation, as well as characterizing and publishing a novel variant of Grapevine leafroll-associated virus-3 (GLRaV-3) infecting Idaho grapevines. The project also generated publications in collaboration with other National Clean Plant Network members which discussed improved methods for propagation of disease-free plant materials. We developed and propagated a diversity panel of red raspberry selections to use for experiments to screen for resistance to raspberry bushy dwarf virus (RBDV) in support of genetic experiments for mapping sources of resistance.
We collaborated with other research groups to develop cost-effective methods for producing and isolating high quality double-stranded RNA (dsRNA) in microbial systems (Escherichia coli). Production of large quantities of non-contaminated dsRNA is currently a major hurdle for the future viability of RNAi therapy treatments, and this work contributed to progress in that field.
Accomplishments
1. Explored measurement tools and genetic basis for fruit texture in northern and southern highbush blueberries. Fruit texture and firmness is a critical component of post-harvest quality and consumer acceptance. Predicting these traits as early as possible is important because blueberry is a long-lived perennial that takes years to reach fruiting potential. ARS researchers in Corvallis, Oregon, collaborated with the Vaccinium Coordinated Agriculture Project (VacCAP) working group to measure various internal fruit and skin texture traits for blueberry and generate molecular marker genotypes. The markers were used to identify genetic variants associated with texture traits. These markers can be used to predict texture and firmness at the seedling stage, which may improve breeding efficiency and lead to development of new, firm-fruited varieties more quickly.
Review Publications
Luby, C.H., Doane, S., Mackey, T.A., Yang, W. 2023. A comparison of two firmness-testing machines for measuring blueberry firmness and size. HortTechnology. 33(1):98-102. https://doi.org/10.21273/HORTTECH05060-22.
Iorizzo, M., Lila, M., Perkins-Veazie, P., Luby, C.H., Vorsa, N., Edger, P., Bassil, N.V., Munoz, P., Zalapa, J.E., Gallardo, R.K., Atucha, A., Main, D., Giongo, L., Li, C., Polashock, J.J., Sims, C., Canales, E., DeVetter, L., Coe, M., Chagne, D., Colonna, A., Espley, R. 2023. VacciniumCAP, a community-based project to develop advanced genetic tools to improve fruit quality in blueberry and cranberry. Acta Horticulturae. 1362:71-80. https://doi.org/10.17660/ActaHortic.2023.1362.11.
Strik, B.C., Davis, A.J., Jones, P.A., Finn, C.E. 2022. Reduced-input pruning methods are a viable option for machine-harvested 'Mini Blues' highbush blueberry. HortScience. 57(10):1313–1320. https://doi.org/10.21273/HORTSCI16703-22.
