Cucurbit Genetics Cooperative Report 3:42 (article 23) 1980
Realization of the Interspecific Hybridization (F1 and BC1) Between Cucurbita pepo
and C. ecuadorensis
R. Dumas de Vaulx and M. Pitrat
Station d'Amelioration
des Plantes Maraicheres, I.N.R.A., Domaine Saint Maurice,
84140 Montfavet-Avignon, France
Cucurbita ecuadorensis is resistant to the most
important and common diseases of C. pepo in France:
powdery mildew, cucumber mosaic virus, watermelon mosaic
virus (1, 2). The interspecific cross between the two species
was attempted only in using C. pepo as pistillate parent
(C. ecuadorensis produced no pistillate flowers
in the conditions of our trials).
Observations of pollen germination of C. ecuadorensis
on C. pepo stigma were made by means of fluorescence.
The results were very different from one flower to the other:
no pollen germination, pollen germination and short pollen
tubes, and, in a few flowers, a small fraction of the pollen
tubes could reach the ovule and the embryo sac.
Only parthenocarpic fruits with empty seed coats were obtained.
However, some very small and white embryos (0 to 10 per fruit)
were observed inside the seed coats one month after pollination.
Without endosperm the embryos could not grow further. These
embryos were put on a culture medium in vitro and
gave rise to plants:15 viable plants were recovered from
ten fruits. These plants had characteristics of the two
parental species and were really F1 hybrids. By selfing the F1 plants,
no fruit set was obtained.
The backcrosses with C. pepo gave fruits but the development
of the embryos inside the seed coats was completely abnormal.
These embryos (10 to 40 per fruit) were transferred on a culture
medium in vitro 40 or 60 days after pollination.
A small fraction (10 of 100) gave rise to normal plants. The
BC1 plants are fertile and some normal
seeds were gathered after selfing.
Literature Cited
- Pitrat, M. and R. Dumas de Vaulx. 1979. Recherche de
geniteurs de resistance a l'Oidium et aux virusde la mosaique
du Concombre et de la mosaique de la Pasteque chez Cucurbita
sp. Ann. Amelior. Plantes 29:4.
- Provvidenti, R., R.W. Robinson and H.M. Munger. 1978.
Resistance in feral species to six viruses infecting Cucurbita.
Plants Dis. Rpt. 62:326-329.
