Cucurbit Genetics Cooperative Report 6:45 (article 21) 1983
J. D. McCreight
U. S. Department of Agriculture, Agricultural Research Service, P. O. Box 5098, Salinas, CA 93915
Abnormally long veined plants occurred in 7 of 10 F2 sib progenies from the 11th backcross generation of a cross of ‘PMR 45’ with aphid resistant 90234, derived from PI 371795 (1). The 7 progenies segregated 109 normal:31 long vine plants (X2=0.6095, P=0.3–0.5). The mutant plants were characterized by longer internodes compared with the normal segregates.
Greenhouse data from two of these families confirmed the field data and clarified some of the other phenotypic differences between the long vine and normal segregates. Progenies 48763 and 48764 segregated 73 normal:27 long vine plants (X2=0.2133, P=0.5–0.7). Mean first internode lengths of 2.3 cm for normal and 8.4 cm for long vine segregates of 48764 at 19 days after planting were significantly different at t0.001. Progeny 48763 showed that the effect of this mutant on internode length persisted beyond the first internode of the main stem (Table 1). There was no significant difference for number of nodes on the main stem or vine fresh weight between normal and long vine 48763 segregates.
| Table 1. Mean internode lengths (cm) of normal and long internode segregates of progeny 48763 at 30 days after planting.z
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| Phenotype | Main stem | Lateral branches
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| 1st | 2nd | 3rd | ||
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| Normal | 4.2** | 4.1 | 5.4* | 3.4 |
| Long internode | 7.7 | 5.0 | 4.8 | 4.2 |
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| z Significant differences within columns at the t0.005 (*) and t0.001 (**) levels. | ||||
Internode length of the lateral branches appears to be unaffected by this mutation, although the mean internode length of the 2nd lateral of the normal segregates was significantly, but not greatly longer than that of the long vine segregates (Table 1). Number of nodes on the 1st and 3rd lateral branches were not significantly different between the two phenotypes, but they were significantly different at the t0.001 level on the 2nd lateral branch: 7.3 nodes on the normal segregates versus 3.4 on the long vine segregates. This may be due to random variation in development of lateral branches (some appear to be determinate while others are indeterminate), or it could be an artifact of greenhouse culture.
Thus, this mutant affects the internode length of the main stem, but not of the lateral branches. The name long mainstem internode and symbol lmi are proposed for this gene.
Literature Cited
- Kishaba, A. N., G. W. Bohn, and H. H. Toba. 1971. Resistance to Aphis gossypii in muskmelon, Cucumis melo. J. Econ. Entomol. 64:935–937.