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Cucurbit Genetics Cooperative Report 5:16-17 (article 8) 1982

Genetic Variation for Low-Temperature Germination Ability in Cucumber

Todd C. Wehner

North Carolina State University, Raleigh, NC 27650

Low-temperature germination ability in cucumber varieties may be useful in establishing earlier and more uniform stands for spring plantings. Previous research showed that there were differences in germination speed at temperature below 17°C (1). Also % germination at 13°C had a narrow-sense heritability of 0.17 (2). The objective of this study was to identify lines with superior low-temperature germination ability, and to measure the heritability of that trait.

Cucumber lines were tested for germination speed at 15°C and 20°C in a randomized complete block design with 2 replications and 203 lines (19 cultivars, 8 breeding lines, and 176 plant introduction lines). The treatment unit was a 60 mm diameter petri plate. Each plate had 20 seeds placed on 2 layers of filter paper to which 1.5 ml of distilled water was added. The test was run for 30 days, and the number of seeds germinating each day was counted. Seeds were considered germinated when the radicle reached 6 mm in length. Average days to germination and percent germination were calculated for each treatment unit. All lines had at least 70% germination at 20°C.

Heritability of low-temperature germination was measured using parent-progeny regression. Crosses were made at random among 68 lines from the screening study, and the F1 tested as described above. Progeny means were regressed on maternal and paternal parent performance, and the narrow-sense heritability estimated as twice the regression coefficient.

The fastest 15 lines to germinate at 15°C included 7 plant introduction lines from Turkey, and 5 cultivars (Table 1). The slowest 15 lines to germinate at 15°C (excluding the 16 that did not germinate at all) were plant introduction lines, and included one Cucumis sativus var. hardwickii accession (PI 215589).

Table 1. The fastest and slowest 15 lines to germinate at 15°C (excluding 16 lines that failed to germinate).

Rank
Cultivar or Line
Seed Source
Germination at 15°C
Germination at 20°C
Days
Percent
Days
Percent
1
PI 109484
Turkey
3.5
98
2.0
100
2
PI 222985
Iran
3.6
100
2.0
100
3
PI 174166
Turkey
3.8
90
2.0
100
4
Green Star
Harris Seed
3.9
100
2.0
90
5
PI 169392
Turkey
4.0
93
2.0
100
6
PI 222860
Korea
4.0
73
2.0
90
7
Dasher
PetoSeed
4.1
98
2.0
100
8
PI 174173
Turkey
4.1
80
2.0
100
9
Greenpak
Harris Seed
4.2
90
2.2
90
10
PI 293923
South Carolina
4.2
80
2.0
100
11
PI 164950
Turkey
4.2
50
2.2
100
12
Ashley
PetoSeed
4.3
100
2.0
100
13
PI 338236
Turkey
4.3
83
2.0
100
14
SMR 58
Petoseed
4.4
95
2.1
100
15
PI 169397
Turkey
4.5
100
2.0
100
173
PI 390252
Japan
9.0
50
2.0
100
174
PI 321009
Taiwan
9.0
43
2.0
100
175
PI 385967
Kenya
9.2
73
2.1
100
176
PI 215589
India
9.6
15
2.9
90
177
PI 401732
Puerto Rico
9.7
18
2.0
100
178
PI 390254
Japan
9.7
78
2.1
100
179
PI 390240
Japan
9.9
63
2.0
100
180
PI 306785
Canada
10.6
38
2.2
100
181
PI 206952
Israel
11.5
5
3.0
70
182
PI 357838
Turkey
11.5
3
2.0
100
183
PI 206952
Yugoslavia
11.5
23
6.1
70
184
PI 390253
Japan
13.1
58
2.0
100
185
PI 321010
Taiwan
13.5
3
4.0
90
186
PI 344435
Iran
13.6
48
2.2
100
187
PI 176953
Turkey
17.3
33
2.5
100
 
LSD (5%)
3.6
45
   
CV (%)
21
47

Parent-progeny correlation coefficients indicate that there is no material effect for a low-temperature germination ability (Table 2). If anything, there is a slight paternal effect, since the correlation is slightly higher between progeny and paternal parent. Narrow-sense heritability would be approximated as twice the regression of offspring on parent if the genotypes were not inbred. However, since many of the parents were inbred, heritability is closer to b than to 2b (in the range of .15 to .20). Thus, the heritability estimated by Nienhuis and Lower (2) is fairly close to the one estimated here. The low heritability may be due in part to the small standard deviation in the parents as compared to their progeny (s = 1.7 and 10.9 days, respectively).

Table 2. Parent-progeny correlation and regression estimates for days to germination at 15°C.

Parent

r

b mean s

2b

Maternal

0.16

0.14 mean 0.11

0.28

Paternal

0.18

0.15 mean 0.10

0.30

It appears that sufficient genetic variability exists for low-temperature germination ability that progress could be made by selection. The low heritability for the trait indicates that selection should be based on families rather than on individuals.

Literature Cited

  1. Lower, R. L. 1974. Measurement and selection for cold tolerance in cucumber. Pickle Pak Sci. 4:8-11.
  2. Nienhuis, J. and R. L. Lower1981. An estimate of the heritability of low temperature and seed germination in cucumber. Cucurbit Genet. Coop. Rpt. 4:12-13.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 23 October, 2009