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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetic Improvement and Virus Management of Small Fruit Crops

Location: Horticultural Crops Research

2013 Annual Report


1a.Objectives (from AD-416):
Objective 1: Develop improved small fruit cultivars, including thornless, machine harvestable virus tolerant blackberries with excellent flavor; high yielding, high quality, virus tolerant, strawberries with outstanding processing characteristics; and virus tolerant, high yielding black raspberries with flavor and color characteristics similar to the current standard cultivars.

Objective 2: Collect, evaluate, and incorporate into the breeding programs new sources of genetic variability for Rubus, Vaccinium, Fragaria, and other berry crops. Sub-objective 2a. Incorporate new/novel germplasm into breeding material, with particular emphasis on biotic stress resistance. Sub-objective 2b. Determine whether trait-associated markers can be developed and, if developed, can identify genotypes that express a phenotype of interest.

Objective 3: Characterize viruses and virus complexes that infect berry crops (blackberry yellow vein, blueberry necrotic ring blotch, funky spot, raspberry crumbly fruit disease, and grape red leaf diseases) and develop management strategies to minimize the impact of these diseases on berry crops. Sub-objective 3a. Sequence novel viruses of small fruit crops and develop assays for their rapid detection. Sub-objective 3b. Characterize natural host range, reservoirs and vectors of these viruses and develop strategies to minimize their impact on production.

Objective 4: Apply thermal-, cryo- and chemotherapy to develop virus-tested planting stocks of berry cultivars for fruit production.


1b.Approach (from AD-416):
For each crop, a modified recurrent mass selection system that is very effective for perennial, asexually propagated plants will be followed. Individuals that are selected in a given generation will be intercrossed to produce the next generation. Additional sources of variation (e.g., current cultivars, selections from other breeding programs, or wild selections) will be introduced to the parental pool as needed. Anywhere from 4000-6000 seedlings of Rubus spp. and strawberry, and 3000-4000 blueberry seedlings, all produced from 30-100 crosses, will be evaluated annually. While the primary focus is on cultivars for commercial fruit production, in the process of conducting a breeding program you inevitably identify selections that would be useful for the commercial nursery industry as landscape plants. Since our evaluations system is not geared towards ornamental plants, we try to get these promising selections into commercial nurseries for evaluation. For broadening 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 climate change. Viruses that have significant impact on yield and fruit quality will be sequenced using dsRNAs, small RNAs or Rolling Circle Amplification products as template for sequencing using Nexgen sequencing. Virus diversity will be characterized to ensure diagnostic assays are broad spectrum and useful 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 in commercial plantings.


3.Progress Report:
This report documents progress for this new project which started March of 2013 and continues research from project 5358-21000-037-00D, "Physiology and Genetic Improvement of Small Fruit Crops".

Work has begun on meeting the objectives of this new project. New seedling field were planted, germplasm was evaluated, and identified genotypes that express a phenotype of interest.

We initiated experiments to detect viruses in several berry crops. Set-up plots for virus spread studies and used thermal therapy to eliminate viruses on blueberry and elderberry.


Last Modified: 10/21/2014
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