Article from
VSCNews, Vegetable and Specialty Crop News
by Seonghee Lee
Advanced Technologies Speed Up Strawberry Breeding
Strawberry is a genetically complex fruit crop. The use of
conventional breeding approaches to combine many important
characteristics in a single variety is difficult and takes a long time.
These characteristics can include disease resistance, fruit quality
attributes such as sugar content or aroma, or any other trait that
naturally occurs in cultivated strawberry.
Traditionally,
University of Florida Institute of Food and Agricultural Sciences
(UF/IFAS) strawberry breeders cross plants with desired breeding
characteristics and select the best offspring over multiple generations
in the field. Recently, the UF/IFAS strawberry breeding program has
integrated advanced breeding technologies into conventional breeding.
The use of the advanced breeding technologies can create superior
strawberry varieties faster and more efficiently.
A DNA test is used to select superior strawberry
seedlings that contain target genes for disease
resistance and fruit quality.
DNA MARKER TECHNOLOGY
For
the last five years, the breeding program has identified several
important genes controlling strawberry flavor, sweetness and disease
resistance that are directly relevant to Florida growers. Researchers
successfully established a system for DNA tests that can detect target
genes and precisely transfer them to new varieties. Using the DNA
marker technology, researchers are now able to quickly screen tens of
thousands of seedlings for target breeding characteristics. This
process of marker-assisted seedling selection can “stack the deck” for
desirable traits prior to field evaluation and makes it possible to
combine high levels of disease resistance with good fruit quality in a
single variety.
In 2018, a total of 55,000 seedlings were
screened by DNA tests for a combination of characteristics (multiple
disease resistance, flavor and earliness of fruit). About 12,500
seedlings were retained for field evaluation in the 2018–2019 season.
These tests can predict seedling traits with greater than 90 percent
accuracy. Many important traits can be quickly combined together for
fruit quality and disease resistance in future varieties.
One tiny leaf disc from each seedling is collected
for rapid DNA extraction.
CRISPR GENE EDITING
In
addition to DNA marker technology, UF researchers recently adopted the
CRISPR gene-editing technique in their breeding program. This method
has been applied in many agronomic crops and is poised to make
contributions in strawberry. CRISPR technology can speed up crop
improvement and development of new varieties.
 | 1) Tissue culture petri dish of Sweet Sensation
FL127, 2) somaclones growing in a greenhouse |
3) somaclones tested in the field
Researchers
anticipate that, over the next decade, CRISPR gene-editing techniques
will be used to rapidly develop elite strawberry varieties with
improved disease resistance and fruit quality along with other valuable
attributes. To utilize the CRISPR gene-editing technology in cultivated
strawberry, breeders successfully developed the system of tissue
culture and transformation for the main UF/IFAS breeding varieties such
as Sweet Sensation® FL127, Florida Radiance and Florida Brilliance.
These tools will be extremely valuable in the long-term efforts of the
strawberry breeding program.
SOMACLONAL VARIATION
The
strawberry breeding team recently established another new technique,
somaclonal variation, to speed up the breeding process. Throughout the
strawberry tissue culture, natural variation occurs because of genetic
mutation developed by in vitro condition or by plant growth hormones in
media. This technique has been used for many other horticulture crops
and cultivar development.
It only takes 40 minutes to get the DNA test results of 384 seedling samples.
The
plants generated by somaclonal variation are cisgenic (genes from other
species are not involved) and are similar to traditionally bred plants.
Breeders use this technique to improve Sweet Sensation® Florida 127 and
Florida Radiance for crown root rot diseases, fruit quality, and plant
shape and size.
Seonghee Lee is a research assistant professor at the UF/IFAS Gulf Coast Research and Education Center in Wimauma.
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