Cucurbit Genetics Cooperative Report 11:9-12 (article 5) 1988
Todd C. Wehner
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
In 1987, I surveyed public (state university and U.S. Dept. Agric.) and private (seed or processing companies) plant breeders assigned to the improvement of cucumber. The survey included questions on breeding objectives, selection methods, type of germplasm released, and traits of interest in the breeding program. See (1) for definitions of breeding methods and germplasm types. The traits of interest was an expanded versions of a survey run in 1985. The information is summarized here in order that plant breeders can determine what resources need to be developed in the future for germplasm collections, and what research is needed to support efforts to improve cucumbers for the consumer.
Of the surveys sent out, 6 public and 11 private cucumber breeders responded. The public breeders were from New York, North Carolina, South Carolina, Texas, and Wisconsin.The private breeders represented Abbott& Cobb, Asgrow Seed, Campbell Inst. Res. Tech., Ferry-Morse, Harris-Moran, Musser Seed, Nickerson-Zwann, Northrup King, Petoseed, and Sunseeds.
As expected, most cucumber breeders were using the pedigree and backcross methods (Table 1). Inbred-backcross and single-seed descent were also used in breeding programs, Methods such as recurrent selection and pure-line family (bulk breeding) were rarely used, especially among private breeders. Breeding objectives for public researchers were to develop inbred lines (germplasm or cultivar) or hybrid cultivars, and for private breeders were to develop hybrid or inbred cultivars. There was some confusion about the definition of inbred vs. open-pollnated cultivars, since inbred cultivars are sub-mated in isolation to produce certified seed, often referred to as open pollination. Generally, open-pollinated cultivars are developed by mass selection from an open-pollinated population, and have an inbreeding coefficient (F near 0 (vs. F near 1 for inbred cultivars).
Most public cucumber breeders in the U.S.A. were involved in the improvement of pickling types or on more basic research in genetics and population improvement (Table 2). Private breeders emphasized pickling and slicing types about equally. Secondary emphasis included wok on Middle-Eastern slicers (so called Beit Alpha types), and a small emphasis on trellis (Japanese burpless) slicers.
Most programs emphasized disease resistance, fruit yield, and fruit quality as primary considerations in selection, with earliness and sex expression nearly as important (Table 2). The traits that cucumber breeders wanted evaluated most in the U.S. germplasm, collection were resistance to gummy stem blight (caused by Didymella bryoniae), root-knot nematode (caused by Meloidogyne spp.), Alternaria cucumerina, and fruit rot (caused by Rhizoctonia solani). Heat tolerance, combining ability for yield, and seedcell size were the only traits in the top 10 that did not involve disease resistance (Table 3). Most of the traits of high interest are being evaluated currently.
Table 1. Survey responses of 6 public and 11 private cucumber breeders working in the U.S.A. in 1987 for importance of breeding methods and germplasm typesz .
Ranking of responses |
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Question / Answer |
Public |
Private |
|
Average ranking of breeding methods: |
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| Pedigree (cross, select. self) | 1.2 | 1.4 | |
| Backcross (cross, select, backcross) | 1.3 | 1.6 | |
| Inbred-backcross (cross, BC, self, sel.) | 2.0 | 2.0 | |
| Single-seed descent (cross, self, self, sel.) | 2.3 | 2.4 | |
| Recurrent selection (RS)) – half sib | 3.2 | 3.3 | |
| – full sib | 2.7 | 3.1 | |
| – S1 line | 3.2 | 3.3 | |
| – S2 line | 2.5 | 3.5 | |
| Mass selection (single-plant RS) | 3.0 | 3.1 | |
| Pure-line family (cross, bulk, self, sel.) | 2.8 | 3.3 | |
| Reciprocal recurrent selection | 3.3 | 3.6 | |
Objective for release of germplasm types: |
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| Inbred line (germplasm) | 2.0 | 2.8 | |
| Population (germplasm) | 2.7 | 3.6 | |
| Hybrid cultivar (2-4 inbreds crossed) | 2.0 | 1.1 | |
| Inbred or line cultivar (from selfing) | 2.5 | 2.6 | |
| Open-pollinated cultivar (from mass sel.) | 3.5 | 3.3 | |
| Multiline cultivar (mixture of isolines) | 3.5 | 3.7 | |
| Synthetic cultivar (>3 inbreds intercrossed) | 3.8 | 3.6 | |
zImportance was rated 1 to 4 (1 = frequent, 2 =occasional, 3 = rare, 4 = never).
Table 2. Survey responses of 6 public and 11 private cucumber breeders working in the U.S.A. in 1987z
Number of responses |
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Question / Answer |
Public |
Private |
Total |
|
What are your primary research / breeding objectives? |
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| Breeding pickles | 3 | 7 | 10 | |
| Breeding slicers | 1 | 6 | 7 | |
| Breeding Middle-Eastern slicers | 0 | 1 | 1 | |
| Population development | 1 | 0 | 1 | |
| Genetics research | 1 | 0 | 1 | |
What are your secondary research / breeding objectives? |
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| Breeding pickles | 3 | 2 | 5 | |
| Breeding slicers | 1 | 2 | 3 | |
| Breeding other slicers | 0 | 4 | 4 | |
| Population development | 1 | 0 | 1 | |
| Genetics research | 1 | 0 | 1 | |
What are your minor research / breeding objectives? |
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| Breeding slicers | 2 | 1 | 3 | |
| Breeding other types | 1 | 4 | 5 | |
| Quality research | 1 | 0 | 1 | |
What traits are of primary concern? |
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| Disease resistance | 5 | 9 | 14 | |
| Yield | 3 | 11 | 14 | |
| Fruit quality | 4 | 7 | 11 | |
| Earliness / Sex expression | 3 | 5 | 8 | |
What breeding method do you use most? |
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| Pedigree (cross, select, self) | 5 | 7 | 12 | |
| Backcross (cross, select, backcross) | 4 | 6 | 10 | |
| Inbred-backcross (cross, BC, self, sel.) | 2 | 5 | 7 | |
| Single-seed descent (cross, self, self, sel.) | 3 | 3 | 6 | |
| Recurrent selection (RS) – half-sib | 1 | 0 | 1 | |
| – full sib | 0 | 1 | 1 | |
| S1 line | 0 | 1 | 1 | |
| S2 line | 0 | 0 | 0 | |
| Mass selection (single-plant RS) | 0 | 1 | 1 | |
| Pure-line family (cross, bulk, self, sel) | 0 | 1 | 1 | |
| Reciprocal recurrent selection | 0 | 0 | ||
zNumber of answers are greater than number of people answering where several first-choice responses were given.
Table 3. Traits in the plant introduction collection of cucumber that cucumber breeders would like evaluated (listed in order from a 1987 survey).
Rank in survey |
||
1987 |
1985 |
Trait |
| 1 | 7 | Gummy stem blight resistance* |
| 2 | 5 | Root knot nematode resistance* |
| 3 | 15 | Alternaria leaf blight resistance |
| 4 | 3 | Rhizoctonia fruit rot resistance* |
| 5 | 12 | Heat tolerance |
| 6 | 2 | Anthracnose resistance* |
| 7 | 26 | Pythium cottony leak resistance |
| 8 | 1 | Fruits/plant (combining ability in gynoecious hybrid)* |
| 9 | 8 | Downy mildew resistance* |
| 10 | 6 | Fruit seedcell size |
| 11 | 14 | Cold shock resistance |
| 12 | 11 | Pickleworm resistance* |
| 13 | 17 | CMV resistance |
| 14 | 18 | WMV1 resistance |
| 15 | 19 | WMV2 resistance |
| 16 | 16 | ZYMV resistance |
| 17 | 23 | Drought resistance |
| 18 | 25 | Earliness (no. oversized fruits in single-harvest trial)* |
| 19 | 20 | Angular leafspot resistance |
| 20 | 22 | Cold germination |
| 21 | 21 | Target leafspot resistance |
| 22 | 13 | Salt tolerance* |
| 23 | 4 | Fruit shape (appearance, not length / diameter ratio) |
| 24 | 9 | Powdery mildew resistance |
| 25 | 10 | Fruits / plant (actual) |
| 26 | 28 | Days to first flower |
| 27 | 24 | Branching habit |
| 28 | 27 | Cucumber beetle resistance |
| 29 | 29 | Daylength response |
| 30 | – | Unique character (character not previously documented)* |
| 31 | 33 | Scab resistance |
| 32 | – | Spider mite resistance |
| 33 | 31 | Fusarium wilt resistance |
| 34 | 32 | Bacterial wilt resistance |
| 35 | 30 | Verticillium wilt resistance |
| 36 | – | Nutritional value |
| 37 | – | Parthenocarpic tendency |
| 38 | – | Cold vigor |
| 39 | – | Brinestock quality |
| 40 | – | Sex expression |
| 41 | – | Cold vigor |
| – | – | Beet Pseudo-yellows virus (cucumber yellows) |
| – | – | Rhizoctonia seedling damping-off resistance |
| – | – | Air pollution resistance |
*Trait currently being evaluated, or evaluation completed.
-Not on trait list for survey.
Literature Cited
- Fehr, W.R. 1987. Principles of cultivar development, volume 1. Macmillan Pub Co, New York, N.Y.