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Cucurbit Genetics Cooperative Report 18:5-6 (article 3) 1995

Selection for Multiple Lateral Determinate Cucumber Genotypes

J.E. Staub and L. Crubaugh

Vegetable Crops Research, USDA/ARS, Department of Horticulture, University of Wisconsin-Madison, WI 53706 U.S.A.

Introduction. Manipulation of plant architecture with concomitant adjustments in plant population density can be utilized to increase the yield potential of cucumber. Determinate plants are homozygous recessive for a gene, de, which causes the premature termination of plant growth as a consequence of the conversion of the sympodial bud into floral tissue (2). This plant type has a more concentrated fruit set than indeterminate types and so allows for easy determination of optimal harvest time (1, 3). We are using the determinate, G421 (provided by R.L. Lower, University of Wisconsin) in our breeding program to increase once-over harvest yield potential in the U.S. processing cucumber.

A little leaf, multiple branching mutant genotype (H-19) has been recovered at the University of Arkansas. It possesses a sequential fruiting habit, and thus may also be a potential source for increasing the yield in cucumber (4). We have used G421 and H-19 in an inbred back-crossing program (recurrent parent - G421) to develop multiple lateral, sequential fruiting determinate lines for once-over machine harvest. We now report the progress in the development of this plant type.

Materials and Methods. The initial G421 x H-19 cross has been carried to the F2 , BC1S2 and BC2S2. F2 progeny were evaluated [randomized complete block design (RCBD) with 4 replications] in 1991 for several economically important characteristics on 1.5 m row centers and 0.76 m between plants (Table 1). Measurements of plant traits were also taken on BC1 plants in a greenhouse and these data were compared to BC1 S1 progeny in a field nursery (Table 2). Data from these evaluations indicated that adequate variation was present in the progeny for continued selection to be imposed. Therefore, BC1 S2 and BC2 S2 progeny were evaluated in a 1994 field nursery at Hancock, WI for determinate habit, multilateral character, and sex expression. Approximately 194 families were examined in a RCBD with four replications. Approximately 25 to 50 plants of each family derived from each of 194 families were evaluated in 25 plant family plot rows at 0.76 m plant spacing (1.5 m row centers) at Hancock, WI.

Results and discussion. Multiple lateral plants were identified which possessed 2 to 7 laterals depending on the cross (data not presented). Plants of UW G421 in the same field had between 0 and 2 laterals. the average number of laterals ranged between 2 and 4 depending upon the family examined. The determinate nature of many multiple lateral plants could not be confirmed because the branch length of determinate plants can vary greatly (12 to 48"; Table 2). Plants were selected, self-pollinated and these progeny will be re-evaluated in subsequent generations to confirm their genotype.

Approximately 144 selections were made from the approximately 4,800 BC1 S2 and BC2 S2 plants examined (3% selection intensity). Attempts were made to self pollinate these selected plants. About 66 (47%) of the pollinations produced fruit. The low pollination percentage of selected plants was in large part due to the time of pollination. Final selections were made late in the season after several harvests had been made and plants were senescing.

Several potential determinate, multilateral, gynoecious and monoecious plants were identified in the various families. Depending upon family, the fruit length (L): diameter (D) ratio of fruit harvested from these plants ranged between 2.8 to 3.4. Therefore, it is likely that the determinate, multiple lateral types resulting from this project will have adequate L/D ratios for commercial production. These BC1 S3 and BC2 S3 families will be evaluated at replicated close spacing (~ 7 cm between plants on 1.5 row centers) in 1995 to confirm their genotype and determine their yield potential.

Table 1. Plant and fruit characteristics of parental germplasm (dede and DeDe), F1 and F2 generations in cucumber (Cucumis sativus L.).

Mean yield (fruits/plant) Harvestx
Parent/generation
Mean days to flower
Mean lateral numberz
Mean node length (cm)y
1
3
Mean length: diameter ratio (L/D)w
UW G421 (dede)
45.8
1.9
5.0
2.3
7.4
3.0
H-19 (DeDe)
48.8
10.2
4.3
3.1
15.2
3.1
F1
46.0
3.0
5.3
2.1
10.5
2.9
F2
46.6
3.8
5.2
2.3
9.0
3.0
LSD (0.05)
5.7
3.9
2.5
2.9
8.7
0.2

zLaterals on the main stem.
yLength between nodes on the main stem.
xCumulative average yield over 3 harvests.
w20 randomly sampled fruit.

Table 2. A comparison of plant and fruit characteristics of BC1 parents and their BC1 S1progeny derived from an initial dede x DeDe mating in cucumber (Cucumis sativus L.)

BC1parents
BC1S1 progeny
Main stem
Main Stem
Lateral number
Lateral length
cm
inch
Mean
SD
Mean
SD
Mean
SD
29
12
65
15
1.8
1.2
11
12
58
24
78
23
1.3
1.0
21
15
87
36
100
42
3.9
3.3
44
39
101
42
115
61
4.7
3.0
54
48
116
48
117
40
4.4
2.7
44
41
130
54
177
27
6.9
4.5
44
36

Literature Cited

  1. George, W.L. 1970. Genetic and environmental modification of determinate plant habit in cucumbers. J. Amer. Soc. Hort. Sci. 95:583-586.
  2. Hutchins, A.E. 1940. Inheritance in the cucumber. J. Agr. Res. 60:117-128.
  3. Kaufmann, C.S. and R.L. Lower. 1976. Inheritance of an extreme dwarf plant type in the cucumber. J. Amer. Soc. Hort. Sci. 101:150-151.
  4. Staub, J.E., L.D. Knerr and H.J. Hopen. 1992. Effects of plant density and herbicides on cucumber productivity. J., Amer. Soc. Hort. Sci. 117:48-53.
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