Cucurbit Genetics Cooperative Report 14:51-52 (article 18) 1991
James D. McCreight
U.S. Department of Agriculture, Agricultural Research Service, U.S. Agricultural Research Station, 1636 East Alisal Street, Salinas, CA 93905
Lettuce infectious yellows (LIY) is a sweetpotato whitefly, Bemesia tabaci (Genn.), transmitted virus disease that occurs in the lower deserts of California, Arizona, and Mexico (1). Foliar symptoms appear approximately eightweeks after innoculation and are characterized by interveinal yelolowing beginning with the older leaves. LIY also reduces yield. The objective in the present study was to compare LIYV susceptible ‘Topmark’ with cultivars and germplasm that have resistance to other virus diseases, insects, or that are from regions where the sweet potato whitefly is endemic throughout the year.
Twenty-three melon cultivars, varieties, breeding lines, and plant introductions (Table 1) were tested for resistance to LIYV in the field at Brawley, California in 1988. The wild species C. prophetarium L. was also included. Seeds were planted into dry soil on 17 August and irrigated by furrow on 18 August. Symptoms were evaluated on 19 October using a 1 (symptomless) to a 9 (dead) scale. At that time plant size was evaluated using a 1 (runt) to 9 (large, completely covering the bed) scale and numbers of fruit were counted. Plots were 8.4 m in length on 2.4 m centers and consisted of 10 hills spaced 0.7 m apart; four seeds were planted per hill. The design was a completely randomized block with two replications. Means separation was done using Duncan’s Multiple Range test (a = 0.05) . LIYV infection was confiemed by ELISA (1).
The 24 entries differed greatly for plant size, number of fruit per plant and LIYV symptom severity (Table 1). The entries varied greatly also for horticultural qualities such as earliness; fruit shape, size and skin color; and flesh color and texture (data not shown). LIY symptom severity was not correlated with plant size (r = -0.06) or number of fruit per plant (r = -0.16).
Sudden wilt-like symptoms may have confounded LIYV symptoms to some extent, but probably did not greatly affect the relative ranking for LIYV symptoms among the entries because interveinal yellowing is not part of the sudden wilt syndrome (data not shown). Wild Melon could not be evaluated for LIYV because the plants had senesced, but the entry was prolific and had set an average of 7.2 fruit per plant (Table 1). The correlation between LIYV and sudden wilt symptoms was small (r = 0.09, p0.05).
Esteva et al. (3) reported that PI 161375 was heterogeneous for resistance to a greenhouse whitefly, Trialeurodes vaporariorum (Westwood) transmitted yellows virus. In this test, PI 161375 was rated 4.5 for LIYV symptom severity and was uniform in its response. Esteva et al. (2) and Soria et al. (4) reported resistance to the greenhouse whitefly-transmitted yellows virus in wild relatives of melon. In this test, Cucumis prophetarum expressed mild LIYV symptoms.
Snake Melon, a local variety from Saudi Arabia had the mildest LIYV symptomsand large vines. PI 124111, 92577 (a different increase of PI 124111), and MR 1, a downy mildew, Pseudoperonopsora cubensis (Berk. & Curt.) (5), resistant inbred of PI 124111 also had relatively mild LIYV symptoms.
Table 1. Mean LIYV symptoms, fruit per plant and plant size.
Entry |
LIYV |
Fruit |
Plant |
| Snake Melon | 2.0 a | 1.7 b | 8.5 ab |
| 92577 | 3.0 ab | 1.8 b | 6.5 b-e |
| C. prophetarum | 3.0 ab | 8.3 a | 3.0 g |
| PI 12411 | 3.0 ab | 2.1 b | 5.5 c-g |
| MR 1 | 3.5 ab | 1.8 b | 6.5 b-e |
| PMR 45 | 3.5 ab | 1.5 b | 5.5 c-g |
| Quantif | 3.5 ab | 1.3 b | 9.5 a |
| WMR 29 | 4.0 a-c | 1.8 b | 5.5 c-g |
| FC (WMR 29 x FC) | 4.5 a-d | 1.8 b | 6.0 b-g |
| PI 161375 | 4.5 a-d | 1.9 b | 6.0 c-g |
| 18236z | 5.0 b-e | 2.0 b | 5.0 d-g |
| PMR 6 | 5.0 b-e | 1.6 b | 6.5 b-e |
| AR Hale’s Best Jumbo | 5.5 b-e | 2.2 b | 7.0 a-d |
| AR Topmark | 5.5 b-e | 2.1 b | 7.0 a-d |
| Juane Canari | 5.5 b-e | 1.4 b | 6.5 b-e |
| Quascem | 6.5 c-f | 1.8 b | 8.0 a-c |
| Topmark | 6.5 c-f | 2.0 b | 6.5 b-e |
| PMR Honeydew | 7.0 de | 1.4 b | 5.5 c-g |
| Local Melon | 7.5 f | 1.6 b | 9.5 a |
| 92516 | 8.5 | 1.8 b | 7.0 a-d |
| Freeman Cucumber | 8.5 | 1.5 b | 3.5 fg |
| PI 1241112 | 8.5 | 1.5 b | 5.5 b-f |
| AR 5 z | 9.0 | 2.1 b | 4.0 e-g |
| Wild Melon | – | 7.2 a | 4.0 e-g |
z Only 1 replication.
Literature Cited
- Duffus, J. E., R. C. Larsen, and H. Y. Liu. 1986. Lettuce infectious yellows virus – a new type of whitefly-transmitted virus. Phytopathology 76:97-100.
- Esteva, J., F. Nuez, and J. Cuartero. 1988. Resistance to yellowing disease in wild relatives of muskmelon. Cucurbit Genet. Coop. Rpt. 11: 52-53.
- Esteva, J., F. Nuez, and M. L. Gomez-Guillamon. 1989. Resistance to yellowing disease in muskmelon. Cucurbit Genet. Coop. Rpt. 12: 44-45.
- Soria, C., M. L. Gomez-Guillamon, J. Esteva, and F. Nuez. 1989. Search for sources of resistance to yellowing disease in Cucumis spp. Cucurbit Genet. Coop. Rpt. 12: 42-43.
- Thomas, C. E. 1986. Downy and powdery mildew resistant muskmelon breeding line MR-1. HortScience 21:329.