Cucurbit Genetics Cooperative
Other Crop Genetics Cooperatives
Home About Membership Reports Gene Lists Conferences Links Search NCSU
Cucurbit Genetics Cooperative Report 10:87 (article 46) 1987

Downy Mildew Resistance in Cucurbita

R. W. Robinson

Horticultural Sciences Department, New York State Agricultural Experiment Station, Geneva, NY

C. A. John 1

Castle Seed Co., Homestead, Florida 33031

Cucurbita ecuadorensis and C. okeechobeensis are generally considered to be not very closely related. They were placed in different groups, when Cucurbita species were classified for similarity by numerical taxonomy (1), isozymes (4), and gourd bee relationships (3). Thus, it is surprising that they can be crossed easily. The cross was first made by Cutler and Whitaker (2). We obtained good fruit set for the interspecific cross, and each fruit had many plump seed with good germination.

Both species are late to flower, but they produced both pistillate and staminate flowers by September at Geneva, NY. The interspecific hybrid, however, was still vegetative and had no floral buds when frost occurred a month later. Cuttings were therefore sent to Homestead, Florida, where the F1 plants finally flowered., in April, 11 months after the seed was sown.

Downy mildew occurred in the planting at Florida, devastating all squash plants in the field, except those of C. ecuadorensis x C. okeechobeensis. Since the parents of this cross were not included in the planting, it was not possible to determine which species contributed resistance to Pseudoperonospora cubensis. If only one of the parental species is resistant, then downy mildew resistance must be dominant.

The interspecific F1 was crossed with C. maxima cv. Buttercup, C. moschata cv Calabaza, and with breeding lines of C. pepo. Each 3-way cross produced viable seed that germinated without embryo culture, although the seed was thin, due to poorly developed cotyledonary tissue. There was a high degree of sterility in the next generation of each cross, but selfs, sibs, and backcrosses to the cultivated species were obtained, producing germplasm useful for breeding mildew and virus resistant squash.

Literature Cited

  1. Bemis., W. P., A. M. Rhoades, T. W. Whitaker, and S. G. Carmer. 1970. Numerical taxonomy applied to Cucurbita relationships. Amer. J. Bot. 57:404-412.
  2. Cutler, H. C. and T. W. Whitaker. 1969. A new species of Cucurbita from Ecuador. Ann. Missouri Bot. Gard. 55:392-396.
  3. Hurd, P. D. Jr. and E. G. Linsley. 1970. A classification of the squash and gourd bees Peponapsis and Xenoglossa (Hymenoptera: Apoidea). Univ. Calif. Publ. Entom. 62:1-39.
  4. Puchalski, J. T. and R. W. Robinson. 1978. Comparative analysis of isozymes of Cucurbita species. Cucurbit Genetics Coop. Rpt. 1:28.

1 Deceased

Home About Membership Reports Gene Lists Conferences Links Search NCSU
Department of Horticultural Science Box 7609North Carolina State UniversityRaleigh, NC 27695-7609919-515-5363
Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 3 August, 2007