Cucurbit Genetics Cooperative Report 4:12-13 (article 6) 1981
An Estimate of the Heritability of Low Temperature Seed
Germination in Cucumber
James Nienhuis and R. L. Lower
University of Wisconsin,
Madison, WI 53706
Reduced germination in low temperature spring soils often
results in erratic stands and reduced yield potential in
many agronomic and horticultural crops. For this reason,
numerous breeding programs and genetic studies have been
initiated with the objective of developing cultivars with
improved germination, emergence and seedling vigor under
adverse conditions of low soil temperatures (3,4). Low temperature
tolerance in cucumbers and other vegetable crops is necessary,
as uniform and rapid emergence is essential for successful
mechanization of the crop. In addition, the establishment
of vigorous plants under low temperature conditions would
allow the extension of processing and marketing seasons
(2).
The objective of this initial study was to estimate the
heritability of low temperature germination, and to develop
a selection procedure for population improvement.
Seeds of 210 half-sib families derived from a random mating
heterogenous population of adapted cucumber lines were evaluated
for percent germination at 13°C under controlled environment
conditions at the University of Wisconsin Biotron. We chose
a family structure (half-sibs) for evaluation of low temperature
germination for several reason.
- selection among family means would be more effective
with traits of low heritability.
- a family structure provides a continuous distribution
of family means, as opposed to a discrete distribution
among individuals.
- a family structure allows evaluation of performance
at optimal as well as suboptimal temperatures. Performance
of a family at optimal temperatures can be used as a check
of seed viability, as well as a method to adjust family
performance at suboptimal temperatures for non-genetic
effects such as poorly filled or damaged seed.
Two replicated of 20 seeds from each family were placed
on moist filter paper in petri dishes and evaluated for
percent germination at both 13 and 25°C. Germination
was defined as radicle emergence of 5 mm or longer. Narrow
sense heritability among half-sib family means for germination
at 13°C was estimated as 0.17 ± 0.06 (Table 1).
A recurrent selection procedure adapted from Lonnquist's
(2) modified ear-to-row selection was also initiated. The
first 10 germinated seeds from each of 20 selected families
(selection intensity 10%) were transplanted to the greenhouse
and grown to maturity. Individuals within each family were
random mated by using four randomly selected staminate flowers
to pollinated each pistillate flower. This provided approximately
150 new families for evaluation in the next cycle of selection.
Using this method, two cycles of recurrent selection can
be completed per year. Seed from the first three cycles
of recurrent selection are currently being increased under
uniform environmental conditions to minimize the confounding
effects of processing and storage time on progress from
selection. We hope to evaluate progress from selection,
as well as look at correlated responses to selection, in
the fall of 1981.
Table 1. Analysis of variance for percent germination of cucumber at 13°C 10 days after seeding (arcsin transformed data).
| Source |
df |
Mean squares |
Expected mean squares |
Abbreviation |
Replication |
1 |
- |
- |
- |
Family |
209 |
0.0187 |
s2e + 2s2f |
m1 |
Error |
209 |
0.0155 |
s2e |
m2 |
s2f = 1/4 s2A = (m1 - m2)/2
Literature Cited
- Lonnquist, J. H. 1964. A modification of the ear-to-row
procedure for the improvement of corn populations.
Crop Sci. 4:227-228.
- Lower, R. L. 1974. Measurement and selections for cold
tolerance in cucumber. Pickle Pak Science IV:
8-11.
- McConnell, R. L. and C. O. Gardner. 1979. Selection for
cold temperature germination in two corn population. Crop.
Sci. 19: 765-768.
- Pesev, N. V. 1970. Genetic factors affecting maize tolerance
to low temperature emergence and germination. Theor.
Appl. Genetics 40:351-356.
