Cucurbit Genetics Cooperative Report 14:22-24 (article 9) 1991
J. Staub, L. Crubaugh, H. Baumgartner and H. Hopen
Vegetable Crops Research, U. S. D. A. / A. R. S., Department of Horticulture, University of Wisconsin, Madison 53706 and Department of Horticulture, University of Wisconsin, Madison 53706
Weed competition is a major factor which limits yield in commercial cucumber production. Average estimated annual loss in value of the pickling cucumber crop in the United States due to weeds is $17,359,000 (1). Herbicides currently registered for cucumber production include bensulide, ethalfluralin, DCPA, glyphosate, naptalam, sethoxydin and paraquat (2).
Clomazone (2-[2-chlorophenyl)methyl]-4, 4-dimethyl-3-isoxazolidinone) (2) herbicide is currently in the experimental stage for use in cucumber. It provides excellent weed control as a preemergence herbicide, but can cause injury to cucumber plants at or above the potential use rate depending on environmental conditions during germination. Since it shows potential for weed control in cucumber, we felt it appropriate to determine whether tolerance to this herbicide exists in the U. S. cucumber germplasm collection. If such resistance could be found and its genetic basis determined, then clomazone tolerant lines might be developed.
Seeds of each of 794 accessions in the U. S. germplasm collection were sown in a three replicate study. Replications (30 cm long) were arranged in a randomized complete block design at the University of Wisconsin experimental farm, Hancock, Wis. in 1990. Clomazone at 1.1 kg/ha was preplant incorporated in rows 153 cm apart, and 25 seeds per replication were planted approximately 25 mm apart within rows, The use rate for this soil (Typic Udipsamment; sandy, mixed, mesic) will probably be 0.28 kg/ha.
Phytotoxicity was rated visually to measure herbicide damage 2 and 3 weeks after planting (1 = green, no damage; 2 = marginal chlorosis, 25% damage; 3 = 50% of leaf surface chlorotic; 4 = 75% chlorotic; 5 = 100% chlorotic).
PI 165029 (Turkey), PI 212985 (India), PI 249562 (Thailand), PI 279466 (Japan), PI 390245 (Japan), and PI 504813 (Japan) were rated tolerant to clomazone injury (1.5 or below) in all replications. Reaction of all other germplasm accessions was either inconsistent, segregation or susceptible (>25% damage; Fig 1; panel a). Two to 5 plants of each tolerant germplasm accession were selected, transplanted to a greenhouse, and self- pollinated.
An experiment was designed to reevaluate these field tolerant selections in a greenhouse herbicide test. Clomazone was incorporated at 0, 0.28, 0.55, and 1.1 kg/ha in soil media (unsterilized field soil used above) and deposited in 12 cm diameter pots which were arranged in a randomized complete block design with 3 replications. Five to 10 seeds of each selection and three susceptible cultigens (PI 390257, PI 391571, and WI 2870) were sown in each replicate and phytotoxicity ratings (as above) were taken at the cotyledon, and first and second true leaf stages.
The various clomazone concentrations elicited distinctive plant responses and cultigens displayed differing clomazone phytotoxicity (Table 1). A linear concentration dependent phytotoxic response to clomazone was recorded in all rating times. Although the cultigens responded differently at the cotyledon and first true leaf stage, no differences were detected at the third leaf stage. In the cotyledon stage PI 249562 and PI 279466 were less affected by clomazone treatment than controls (field susceptible). By the appearance of the second true leaf, response of these germplasm accessions was similar to controls. In contrast, PI 249561 (which was similar to the controls at the cotyledon stage) outperformed the controls at the second leaf stage. Tolerant plant responses recorded in the field were not observed in the greenhouse. Differing environmental conditions during growth and development may explain the lack of association between field and greenhouse response to clomazone.
Figure 1. Clomazone injury on cucumber plants 3 weeks after preplant incorporation under field conditions (top: 1.1 kg/ha, rating = 4.5) and in the greenhouse (bottom: from left to right 0, 0.28, and 1.1 kg/ha, rating = 1.25, and 4, respectively).
Table 1. Analysis of Variance and means of phytotoxicity ratings of greenhouse grown plants subjected to clomazone herbicide (preplant incorporated) at 0, 0.28, 0.55, and 1.1 kg/ha.
Mean Square |
For stage of development |
|||
Source of variation |
df |
Cotyledon |
1st Leaf |
2nd Leaf |
| Cultigen (C) | 8 | 1.70** | 4.41** | 0.52 |
| Replication (R) | 2 | 0.50 | 0.70 | 0.53 |
| Error a | 16 | 0.56 | 0.35 | 0.24 |
| Treatment (T) | 3 | 35.19** | 38.56** | 61.84** |
| C x T | 24 | 0.50 | 0.75 | 0.16 |
| Error b | 6 | 0.23 | 0.32 | 0.36 |
Mean |
For stage of development |
|||
Cultigen |
Cotyledon |
1st Leaf |
2nd Leaf |
|
Field Tolerant |
||||
| PI 249561 | 2.58 | 1.79 | 2.75 | |
| PI 249562 | 1.94 | 3.18 | 3.33 | |
| PI 279466 | 1.85 | 3.33 | 3.46 | |
| PI 279467 | 2.35 | 2.48 | 3.17 | |
| PI 390245 | 2.35 | 2.48 | 3.17 | |
| PI 212985 | 2.37 | 1.42 | 2.94 | |
Field Susceptible |
||||
| PI 390257 | 2.96 | 2.69 | 3.06 | |
| PI 391571 | 2.83 | 2.35 | 3.17 | |
| WI 2870 | 2.71 | 2.21 | 3.04 | |
Mean |
For stage of development |
|||
Treatment (kg/ha) |
Cotyledon |
1st Leaf |
2nd Leaf |
|
| 0.0 | 1.0 | 1.0 | 1.0 | |
| 0.28 | 2.13 | 2.04 | 3.09 | |
| 0.55 | 2.99 | 2.85 | 4.01 | |
| 1.10 | 3.63 | 3.81 | 4.38 | |
| LSD (5%) | 0.35 | 0.35 | 0.22 | |
**Indicates significant at 1% level.
Literature Cited
- Crop losses due to weeds in Canada and the United States. 1984. Weed Science Society of America, Champaign, IL. pp. 102.
- Herbicide Handbook of the Weed Science Society of America. 1989. Sixth Edition. Weed Science Society of America, Champaign, IL. pp. 65-66.