Species crosses using Cucurbifa pepo var. “Nishikikanro" as the staminate parent did not produce F
1 hybnds when the usual open flowver pollinations were made at 7 a.m. on the day of anthesis, probably because pollen germination in this variety is low after anthesis, while the receptivity of the pistillate species is maximum after anthesis The author succeded in making these difficult crosses by storing at lO°C the staminate flowers that harvested at 10 p.m. the day prior to anthesis. All characteristics of these two F
1 hybrids are similar to those of their reciprocal hybrids except for a peculiar fact. From the same fruit of C. maxima x C. pepo two types of fruit shape appeared, differing in the region of blossom-end. Cross-compatiblity of C. pepo var. "Connecticut Field" is high, judging from the successful results of species crosses by several earlier workers, while that of "Nishikikanro" is low in the usual open flower pollination. One of the main causes may be the remarkable physiological changes that occur with different flower age m "Nishikikanro" The production of F
1 hybrids between "Nishikikanro" and two other species was not successful in the usual open flower pollinations at 7 a.m. of the flowering day, but was successful in the following combinations of different ages. 1. Early open flower pollination at 4 a.m.of the flowering day ; C. pepo x C. moschata. 2. Bud pollination at at 7 a.m. of the day before anthesis ; C. pepo x C. maxima. 3. Open flower pollination at 7 a.m. of the flowering day with pollen from male flowers stored at 1O°C from 10 p.m. of the day before anthesis ; C. maxima x C. pepo and C. moschata x C. papo.
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