3.4 Seed Quality
Control
3.4.1 Environmental Data
Analysis
The environmental data that is collected should be analyzed during
the growth period. This allows for correction of abnormal growth
conditions that could lead to poor seed quality. Data should fit a
normal distribution curve if environmental conditions are being
properly maintained. To determine whether temperature and RH
have normal distribution, perform a normality test. If there is
environmental data from multiple locations in a growth area,
check for normal distribution of temperature and RH at each
location. If data does not fit a normal distribution curve, work to
correct the conditions in the growth area to prevent poor seed
quality. If data from the multiple locations has normal distribution,
the data should be tested to determine if there is significant difference in conditions among the various locations. Start by testing
whether the variances are equal (see Note 45). The results of the
variance test will determine which test should be used to determine
whether there are significant differences between the multiple locations (see Note 46). If there are significant differences in temperature or RH between the locations, work to correct the conditions in
the growth area.
3.4.2 Microscopy
The purity, physical integrity of seeds, and the presence of pests and
seed-borne diseases can be detected by visual examination with the
naked eye, magnifying lenses or a dissecting microscope. To assess
the seed sample, spread the seeds on white paper under a well-lit
microscope. Take note of shriveled, small, irregular shaped and
different colored seeds. Differences in size, shape, and color of
seeds may indicate that the seeds were not produced under optimal
conditions, or may correspond to specific mutations. Generally,
gray or white coloration on the seed surface indicates fungal contamination. Discard contaminated seeds if possible; otherwise sterilize seeds with fungicides before planting.
3.4.3 Germination
Testing
Seed viability should be monitored at regular intervals by conducting germination tests under a standard set of conditions. It is
recommended that seeds in long-term storage should be monitored at least every 10 years while seeds in short-term storage
should be monitored at least every 5 years [13, 15]. It is also
good practice to test seeds prior to storage, so that poor quality
samples can be recognized and regenerated if necessary.
Low germination may be the result of dormancy, or because
seeds are nonviable. Dormant seeds can be distinguished because
they remain firm and in good condition after imbibition, while
nonviable seeds soften and are attacked by fungi. Extended stratification is a method that can usually break dormancy.
Initial germination rates should exceed 80%, but may be lower
for some lines. Mutations in a significant number of genes, mostly
involved in biosynthesis and signaling pathways of certain
14
Christopher Calhoun et al.
Control
3.4.1 Environmental Data
Analysis
The environmental data that is collected should be analyzed during
the growth period. This allows for correction of abnormal growth
conditions that could lead to poor seed quality. Data should fit a
normal distribution curve if environmental conditions are being
properly maintained. To determine whether temperature and RH
have normal distribution, perform a normality test. If there is
environmental data from multiple locations in a growth area,
check for normal distribution of temperature and RH at each
location. If data does not fit a normal distribution curve, work to
correct the conditions in the growth area to prevent poor seed
quality. If data from the multiple locations has normal distribution,
the data should be tested to determine if there is significant difference in conditions among the various locations. Start by testing
whether the variances are equal (see Note 45). The results of the
variance test will determine which test should be used to determine
whether there are significant differences between the multiple locations (see Note 46). If there are significant differences in temperature or RH between the locations, work to correct the conditions in
the growth area.
3.4.2 Microscopy
The purity, physical integrity of seeds, and the presence of pests and
seed-borne diseases can be detected by visual examination with the
naked eye, magnifying lenses or a dissecting microscope. To assess
the seed sample, spread the seeds on white paper under a well-lit
microscope. Take note of shriveled, small, irregular shaped and
different colored seeds. Differences in size, shape, and color of
seeds may indicate that the seeds were not produced under optimal
conditions, or may correspond to specific mutations. Generally,
gray or white coloration on the seed surface indicates fungal contamination. Discard contaminated seeds if possible; otherwise sterilize seeds with fungicides before planting.
3.4.3 Germination
Testing
Seed viability should be monitored at regular intervals by conducting germination tests under a standard set of conditions. It is
recommended that seeds in long-term storage should be monitored at least every 10 years while seeds in short-term storage
should be monitored at least every 5 years [13, 15]. It is also
good practice to test seeds prior to storage, so that poor quality
samples can be recognized and regenerated if necessary.
Low germination may be the result of dormancy, or because
seeds are nonviable. Dormant seeds can be distinguished because
they remain firm and in good condition after imbibition, while
nonviable seeds soften and are attacked by fungi. Extended stratification is a method that can usually break dormancy.
Initial germination rates should exceed 80%, but may be lower
for some lines. Mutations in a significant number of genes, mostly
involved in biosynthesis and signaling pathways of certain
14
Christopher Calhoun et al.