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United States Department of Agriculture

Agricultural Research Service

Research Project: Strawberry, Raspberry, Blackberry: Crop Improvement Through Genomics and Genetics

Location: Genetic Improvement of Fruits and Vegetables

Project Number: 1245-21220-254-00
Project Type: Appropriated

Start Date: Aug 08, 2013
End Date: Aug 07, 2018

Objective:
The overall goal of this project is to improve strawberry, raspberry and blackberry crops by better understanding and utilizing phenotypic traits. These include traits that will improve crop efficiency through increased production of marketable fruit and/or decreased requirement of inputs such as labor or pesticides. They also include traits that will negatively affect crop efficiency and have no immediate apparent commercial utility, but which will eventually have significant broader impact through increased understanding of basic function for these important fruit crops and other plants. The specific objectives of this project are: Objective 1: Identify or generate and characterize raspberry, diploid and octoploid strawberry, and tetraploid blackberry genotypes with beneficial or deleterious traits that affect repeat flowering and fruiting, resistance to abiotic stresses and diseases, or plant architecture. [NP301, C1, PS1A PS1B]. Objective 2: Develop and evaluate once-fruiting strawberry germplasm with high yield, excellent fruit quality, and resistance to Colletotrichum and Botrytis for performance under Mid-Atlantic growing conditions. [NP301, C1, PS1A] Objective 3: Develop and evaluate multiple-fruiting strawberry germplasm with open plant architecture, adequate runner production, high yield, and resistance to foliar and fruit rot diseases such as Colletotrichum and Botrytis for performance in the novel Beltsville low-tunnel production system. [NP301, C1, PS1A] Objective 4: Elucidate the functions or regulation of genes affecting traits that will improve strawberry production efficiency, such as flowering, fruiting, plant organ and flower development, or plant architecture. [NP301, C1, PS1B]

Approach:
The diploid strawberry will be used as a model to better understand the genetic control of key production traits in the cultivated octoploid. Existing diploid germplasm will be evaluated, and novel diploid germplasm will be generated and characterized and compared with a few reference octoploid genotypes. Existing germplasm will be evaluated in growth chambers, under both ideal temperatures and higher stressful temperatures, primarily for the repeat-fruiting trait. The mutagen, ethyl methanesulfonate, will be used to generate plants with novel production phenotypes for further genetic study. The inheritance of selected novel traits with potential to affect crop productivity will be determined through testcrosses and segregation traits and molecular markers among progeny. Candidate genes will be identified by using whole-genome sequencing of bulked mutant DNAs and comparing the genome sequences of the mutant and the genotype from which the mutant was derived. The expression of candidate genes will be examined for developmental patterns and tissue localization. Transformed F. vesca plants will be produced that over-express the gene, or knock out gene expression, and promoter-reporter transformants also will be made and analyzed. Genes determined to be specifically induced at milestone developmental stages will be used as markers for which tissues and stages of reproductive development are susceptible to heat stress. Expression in specific cell types within an organ will be examined using RNA obtained using Laser Capture Microdissection. Traditional breeding methods will be used to develop improved octoploid strawberry cultivars. Cross-pollinations will be made that will result in seedlings that fruit once a year and others that will fruit multiple times a year. The genetics of repeat fruiting will be determined using the segregation ratios of these annually produced seedlings. Seedlings will be selected that have potential as cultivars and will be further evaluated in production systems appropriate for each type of fruiting pattern. Breeding goals will include improving yield, fruit quality and flavor, and disease resistance both in the field and after refrigerated storage. For the repeat-fruiting selections, additional emphasis will be placed on length of season and harvest efficiency. A novel low-tunnel production system will be used to evaluate these selections’ potential as cultivars while simultaneously providing a test environment to study the response of octoploid strawberries to environmental conditions including heat stress. Repeat-fruiting selections and cultivars will be evaluated weekly in the low-tunnel system for yield, fruit quality, and disease resistance from late winter to late fall. Environmental measurements, such as air and soil temperature, humidity, light, soil moisture, wind speed, and leaf wetness, will be made every 10 to 30 seconds and recorded throughout the year. Fruit production and environmental data will be analyzed through crop modeling to determine which environmental factors and what time period before harvest most strongly affect total fruit yield and the proportion of decayed fruit.

Last Modified: 8/22/2014
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