Cucurbit Genetics Cooperative Report 13:49 (Article 20) 1990

Availability and Use of Interspecific Populations Involving Cucurbita moschata and C. pepo

Henry M. Munger

Department of Plant Breeding, 252 Emerson Hall, Cornell University, Ithaca, NY 14853

In view of increasing interest in the transfer of traits between species of Cucurbita, it may be relevant to call attention to the existence of interspecific populations that we have maintained and found useful. These are derived from the work of Wall and York (1960) and have been maintained by periodic increases in isolated plantings which allow natural intercrossing within each population. All populations started with several F₁ plants obtained through embryo culture from 'Yankee Hybrid' (YH, a yellow straightneck summer squash, C. pepo) pollinated by 'Butternut' (BN, C. moschata). Wall and York (2) created the following three populations:

1. YH X BN F₂ obtained by selfing the F₁. Increases in 1960, 1973, 1979, and 1989 consisted of isolated plantings of 50-75 plants each.
2. (YH X BN) X BN. Four increases were made as for the F₂. Plants most closely approaching bush habit were backcrossed several times to Butternut to get 'Butternut 77'. This has not so far been useful as a variety because of a strong tendency to produce dimorphic crookneck plants. With correction of this defect nearly accomplished, it may be possible to take advantage of the slightly earlier maturity, more concentrated fruit set, and shorter vines derived from C. pepo.
3. (YH X BN) X C. pepo. This population is highly variable because backcrosses to several summer squash varieties were combined for increases in 1960. Three additional increases have been made. It was used as a bridge for the transfer of resistance to powdery mildew and cucumber mosaic from C. martinezii to C. pepo. Contin (1) obtained several viable seeds after pollinating this backcross population with the F₁ of Butternut X C. martinezii. The resulting plants were selected for PMR and were readily crossable with various C. pepo varieties. We have also found in this population plants with resistance to the squash vine borer, Melittia cucurbitae (Harris) and have used them to start incorporating this insect resistance into C. pepo.

Some of the recent increases of these 3 populations will be sent to the National Seed Storage Laboratory. For the near future, seeds may be obtained from the author.

Literature Cited

1. Contin, M. E. 1978. Interspecific transfer of powdery mildew resistance in the genus Cucurbita. Ph.D. Thesis. Cornell University.
2. Wall, J. R. and T. L. York. 1960. Gametic diversity as an aid to inter-specific hybridization in Phaseolus and in Cucurbita. Proc. Amer. Soc. Hort. Sci. 75:419-428.