Cucurbit Genetics Cooperative Report 2:37 (article 22) 1979
J. D. Graham and W. P. Bemis
University of Arizona, Tucson, AZ 85721
A fertile interspecific trisomic of Cucurbita moschata was first reported by Bemis, who added a single chromosome from the wild, perennial, xerophytic species, C. palmata, to disomic C. moschata cv, ‘Butternut’ (1). Repeating the procedure of crossing the autoallotriploid, containing two C. moschata genomes and one C. palmata genome, with diploid C. moschataresulted in sixteen interspecific trisomic lines, seven of which were morphologically similar to the original interspecific trisomic. The remaining nine lines represented five additional phenotypically distinctive groups, suggesting that a total of six different C. palmata were recovered. One primary trisomic of C. moschata was obtained from a triploid ‘Butternut’ plant.
Since the trisomic progeny of the aneuploids were morphologically distinguishable from their disomic sibs, an accurate determination of transmission rates of the extra chromosome through the female and male was possible (Table 1). Transmission through the female ranged from 15% to 32% for the C. palmata chromosomes and was 44% for the extra chromosome in the primary trisomic. None of the extra chromosomes were transmitted through the male.
Considering the diploid nature of Cucurbita and the distant relationship between C. moschata and C. palmata, there was surprisingly little effect of the C. palmata chromosomes on the gross morphology of the C. moschata recipient. Fruit from one of the interspecific trisomics exhibited the hard rind of C. palmata showing that this dominant trait is carried on one chromosome. In only two of the interspecific trisomics was the vigor of the plants visibly less than that of disomic C. moschata. Reduction in tendril length and the occurrence of male buds at the branches of the early tendrils were common to most of the trisomics, including the primary trisomic, suggesting a chromosomal effect due to genic imbalance of trisomics.
Table 1. Transmission of the extra chromosome in C. moschata trisomics.
Phenotypic Group |
Female transmission |
Male transmission |
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Interspecific Trisomics |
No. lines |
Total plants |
% 2n +1 |
Total plants |
% 2n +1 |
| Pl restricted neck fruit | 8 | 677 | 26 | 505 | 0 |
| P2 hard rind | 2 | 100 | 26 | 95 | 0 |
| P3 sticky leaves | 3 | 259 | 32 | 143 | 0 |
| P4 slightly restricted neck | 2 | 88 | 31 | 97 | 0 |
| P5 pale staminate flowers | 1 | 47 | 21 | 42 | 0 |
| P6 club shaped fruit | 1 | 73 | 15 | 89 | 0 |
| Primary Trisomic | 1 | 57 | 44 | 70 | 0 |
Literature Cited
- Bemis, W. P. 1973. Interspecific aneuploidy in Cucurbita. Genet. Res. 21:221-228.