Cucurbit Genetics Cooperative Report 4:2-4 (article 1) 1981
Investigations into the Characteristics of Seeds From Compact
Cucumber Plants
M.D. Edwards and R. L. Lower
University of Wisconsin,
Madison, WI 53706
Seeds from compact (cp cp) cucumber plants often germinate
poorly when compared to those from normal vining-type (Cp Cp)
plants, particularly in adverse environments."Compact"
seeds also appear somewhat unlike "vining" cucumber
seeds. The average seed weight is about 35% that of normal
seeds. Also, seeds are often more cylindrical than the flat,
ellipsoidal shape characteristic of cucumber seeds.
This study was conducted to gain insight into the variability
present for a number of seed characteristics in a heterogeneous
population of compact genotypes and to determine if visually
apparent seed characteristics were associated with poor
germinability. Initially, a random sample of 62 open-pollinated,
mature fruit was selected from a population of compact genotypes
at Hancock Experimental Farm in September 1979. Fruit length
and diameter were measured, then seed were extracted and
fermented at room temperature for three days to facilitate
cleaning. Washed seed were air-dried for thee days, then
evaluated for total seed number and percentage of "flat"
seeds prior to packaging. Seeds of three fruit were discarded
at this time due to failure of seed development.
Three months later two samples each of 10 "flat"
and 10 "cylindrical" seeds were taken from each
of the remaining 59 seed lots and evaluated for sample weight.
There samples were then planted 1.5 cm deep in vermiculite
in wooden flats on a greenhouse bench and overhead irrigated
until germination occurred. Experimental design was a randomized
complete block with two replications. Emergence percentage
and rate (mean number of days to emergence) were recorded
for each sample. In addition, visual ratings were recorded
for severity of cotyledonary abnormalities and vigor at
the time the second true leaf was beginning to expand.
A wide range of variability was observed for fruit and
seed characteristics among 59 randomly-sampled fruit as
indicated in Table 1. Partitioning of the observed variability
for emergence percentage is shown in Table 2. Most of the
variability was observed between fruit samples, but highly
significant components were also attributable to replicates
and "seed types" within each fruit. Phenotypic
correlations between seed and fruit characteristics are
presented in Table 3. Emergence percentage is significantly
and positively correlated with percentage flat seeds, total
seed number, and seed weight.
Several multiple regression models were fitted in an attempt
to predict emergence percentage from seed characteristics.
Although a number of seed characteristics are correlated
with emergence percentage, these characteristics are significantly
intercorrelated and as a result account for some of the
same variability in emergence percentage. The best model
accounted for only 24% of the variability observed for emergence
percentage in this sample of fruit. Presumably, factors
other than visually apparent seed characteristics are important
in determining seed quality in compact cucumbers.
Table 1. Distribution of fruit and seed characteristics
for 59 randomly-sampled fruit.
Characteristic |
Mean |
S. D. |
Minimum |
Maximum |
Fruit length (cm) |
14.5 |
2.9 |
9.0 |
22.0 |
Fruit width (cm) |
6.7 |
0.62 |
5.5 |
8.0 |
Seed number |
162.0 |
65.0 |
28.0 |
313.0 |
Percent flat seeds |
58.0 |
22.0 |
0.0 |
97.0 |
Seed weight (g/seed) |
0.011 |
0.002 |
0.007 |
0.016 |
- Flat seeds |
0.011 |
|
|
|
- Cylindrical seeds |
0.011 |
|
|
|
Emergence percentage |
42.0 |
30.0 |
0.0 |
98.0 |
- Flat seeds |
48.0 |
|
|
|
- Cylindrical seeds |
35.0 |
|
|
|
Days to emergence |
7.6 |
1.6 |
5.8 |
12.3 |
- Flat seeds |
7.6 |
|
|
|
- Cylindrical seeds |
7.6 |
|
|
|
Table 2. Analysis of variance for emergence percentage
among 59 random fruit.
Source |
df |
Mean squares for emergence |
Fruit |
25 |
0.354** |
Replication |
1 |
0.183** |
Error 1 |
59 |
0.015 |
Seed type within fruit |
59 |
0.043** |
Error 2 |
59 |
0.009 |
|
|
R2 = 0.94 |
** significant at the 0.01 level.
Table 3. Phenotypic correlations between fruit and seed
characteristics among 59 random fruit.
Trait |
Fruit diameter |
% flat seeds |
Seed number |
Seed weight |
Emergence % |
Days to emergence |
Fruit length |
0.21 |
0.16 |
0.50** |
0.32** |
0.01 |
-0.19 |
Fruit diameter |
|
-0.04 |
0.06 |
0.49** |
-0.16 |
0.14 |
% flat seeds |
|
|
0.40** |
0.27** |
0.45** |
-0.45** |
Total seed number |
|
|
|
0.06 |
0.34** |
-0.47** |
| Mean seed weight |
|
|
|
|
0.31* |
-0.13 |
Emergence % |
|
|
|
|
|
-0.60** |
*,** significant at the 0.05 and 0.01 levels, respectively.
