Cucurbit Genetics Cooperative Report 17:38-39 (article 11) 1994
Todd C. Wehner and Zohair M. Mirdad
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
Genetic resistance to chilling in cucurbits would be useful for protection of seedlings against spring frost. Previous research on cucumber (Cucumis sativus L.) indicated that it is chilling susceptible, but that there are genetic differences for response to low temperature. We were interested in the relative resistance of other cucurbits, and whether they had the same response to the test method developed for cucumber (Smeets et al., 1991; Smeets and Wehner, 1988, 1989, 1990,. 1991 a.b; Wehner and Bunch, 1989) using the Phytotron controlled environment facility (Downs and Thomas, 1983) at North Carolina State University.
The objective of this study was to determine the general range of resistance of five cucurbit species using methods developed for testing cucumber seedlings. This preliminary survey will be used to design a more informative and larger study.
Plants of five species were tested: Cucumis melo ‘Cordele’, Cucumis sativus ‘Gy 14’, Citrullus lanatus ‘Crimson Sweet’, Cucurbita pepo ‘Autumn Gold’, and Luffa aegyptiaca ‘Fletcher’. Seeds were planted in 57 x 57 mm peat pots on 4 August, 1993. They were grown for 16 days under 9 hour daylength in growth chambers at 30/260C. On 20 August (2nd to 3rd true leaf stage) the seedlings were subjected to a chilling treatment of 3, 5, 7 or 9 hours at 4C at a light intensity of approximately 500 μ mol ● M-2 ● s-1 PPFD400 to 700 nm. Plants were rated on 25 August using a 0 to 9 scale ( 0 = no damage, 1-2 = trace, 3-4 = slight, 5-6 = moderate, 7-8 = advanced, 9 = dead). The experiment design was a single replication of 9 plants per species.
The 3 hour duration produced little or no damage on the five species tested except for cucumber and luffa, which had moderate damage (Table 1). At 5 hours, melon also had moderate damage, and foliar damage ratings increased with chilling duration as expected. With 7 hours of chilling, the mean was closest to the midpoint of the 0 to 9 scale, and the range from susceptible to resistant species was as large as it got. Thus, the 7 hour chilling treatment is probably the best for screening for genetic differences in the five cucurbit species. The 7 hour duration also provided the best test conditions for evaluation of cucumber cultivars.
Based on this preliminary test, ‘Crimson Sweet’ watermelon and ‘Autumn Gold’ squash were most resistant, and ‘Cordele’ melon, ‘Fletcher’ luffa and ‘Gy 14’ cucumber were most susceptible. Future studies could be run to identify chilling resistant accessions using the test methods described here with a 7 hour chilling duration.
Table 1. Chilling damage in five cucurbit speciesz
Chilling damage (rating) |
|||||
Crop (species) |
3 hours |
5 hours |
7 hours |
9 hours |
Mean |
| Watermelon (Citrullus lanatus) | 0 | 1 | 3 | 3 | 1.8 |
| Squash (Cucurbita pepo) | 0 | 1 | 2 | 6 | 2.2 |
| Melon (Cucumis melo) | 2 | 5 | 6 | 7 | 5.0 |
| Luffa (Luffa aegyptiaca) | 5 | 4 | 6 | 7 | 5.5 |
| Cucumber (Cucumis sativus) | 4 | 6 | 7 | 7 | 6.0 |
| Mean | 2.2 | 3.4 | 4.8 | 6.0 | 4.1 |
| Range | 5 | 5 | 5 | 4 | 4.8 |
zDamage rated on a single replication of 9 plants per chilling duration. Rating was 0-9 (0 = none, 1-2 = trace, 3-4 = slight, 5-6 = moderate, 7-8 = severe, 9 = dead).
Literature Cited
- Downs, R.J. and J.F. Thomas. 1983. Phytotron Procedural Manual for Controlled Environment Research at the Southeastern Plant Environment Laboratory. NCARS Tech. Bul. 244 (revised), 44 p.
- Smeets, L., R. J. Downs and T.C. Wehner. 1991. Air velocity and chilling damage in cucumber cultigens. Phytotron Rpt-1991; 87-88. N.C. State Univ. Raleigh, N.C.
- Smeets, L. and T.C. Wehner. 1988. Chilling sensitivity in cucumber genotypes as affected by duration of chilling, growing temperature, and watering. Phytotron Rpt-1988; 73-74. N.C. State Univ. Raleigh, N.C.
- Smeets, L. and T.C. Wehner. 1989. Further research on the development of a method for screening chilling sensitivity in cucumber genotypes. Phytotron Rpt-1989; 95-96. N.C. State Univ., Raleigh, N.C.
- Smeets, L. and T.C. Wehner. 1990. Screening for genetic variation in chilling sensitivity in cucumber. Phytotron Rpt-1990; 96-97, N.C. State Univ. Raleigh, N.C.
- Smeets, L. and T.C. Wehner. 1991a. Inheritance of chilling resistance in cucumber. Phytotron Rpt. 1991:61. N.C. State Univ. Raleigh, N.C.
- Smeets, L. and T.C. Wehner. 1991b/ Evaluation of the cucumber germplasm collection for chilling sensitivity. Phytotron Rpt-1991; 89-90. N.C. State Univ. Raleigh, N.C.
- Wehner, T.C. and T. Bunch. 1989. Screening the cucumber germplasm collection for chilling resistance. Phytotron Rpt.-1989: 104-105. N.C. State Univ. Raleigh, N.C.