 Measurement of Single-seed Respiration Rates
Seeds vary in quality or vigor, and a number of
vigor tests have been devised to assay seeds
and provide relative rankings of seed lots. Seed
respiration following imbibition is an indication of
metabolic activity and is correlated with seed vigor.
A new approach to respiration measurements called
the Q2Technology (www.astec-global.com) allows the
respiration rates of individual seeds to be measured.
The respiratory activity of each seed is recorded over
time, and Q2 software determines several parameters
that characterize the respiratory patterns and the
variation among seeds in these patterns.
The Bradford lab has been working with the Q2 since
2006, funded by a grant from the Vegetable and Flower
Seed Permanent Research Fund of the American Seed
Trade Association and in-kind support from ASTEC.
They have tested seeds of a number of species in the
Q2 and conducted comparisons of Q2 values and other
measures of seed vigor. Various aspects of the oxygen
consumption curves provide information on seed
quality, as characteristic patterns of respiratory activity
are associated with seed vigor, priming and aging. The
values characterizing these patterns are associated with
the time of initiation of rapid respiration, the rate of
respiration and the minimum oxygen level and were
related significantly to seed vigor. The measurement
of individual seeds also provides insight into the
variability that can exist within seed lots that may not
be evident in germination uniformity. Results from
the studies were recently reported at the International
Workshop on Seeds in Olsztyn, Poland and are being
prepared for publication.
 Genetic Basis of Lettuce Seed Thermoinhibition
Lettuce seeds are susceptible to thermoinhibition when planted at high
temperatures, leading to failures or delays in germination and seedling
emergence and resulting in yield losses and higher costs. The Bradford lab
has been working to identify the genetic basis of this seed dormancy trait
and to develop germplasm with reduced susceptibility to thermodormancy.
The lab previously identified a quantitative trait locus (QTL) and an associated
gene that regulates the temperature sensitivity of germination.
The gene is involved in the biosynthesis of abscisic acid (ABA), which is a
germination inhibitor. The lab also has shown that this gene (LsNCED4) is
up-regulated during seed development and in response to high temperature.
Global gene expression studies using the microarrays mentioned above have
identified networks of genes whose expression is altered in lettuce seeds by
high temperature. A second genetic population is also being developed to
map and study other QTLs and genes that are involved in seed germination
and quality traits. This work is supported by the USDA-CSREES National
Research Initiative and by the National Science Foundation through the
Compositae Genome Project.
DNA Extraction from Seeds
The SBC worked with seed industry partners to develop and verify high-throughput protocols for DNA extraction from seeds of a wide range of crops and seed types. The SBC developed an efficient system to grind and extract DNA from vegetable seeds. Protocols were developed to extract high-quality DNA from 11 seed types in a high-throughput format. The DNA can be used for variety identification, hybridity screening, marker- assisted selection, or other purposes. This project was funded jointly by a consortium of vegetable seed companies including Rijk Zwaan Breeding BV, DeRuiter Seeds Inc., Harris Moran, Hazera Genetics LTD., Sakata Seeds America, Seminis Vegetable Seeds, Sunseeds and Syngenta AG.
High-throughput DNA Extraction from Seeds
Seed Science & Technology, Volume 34, 741-745
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