ISHS Acta Horticulturae 662: VII International Symposium on Temperate Zone Fruits in the Tropics and Subtropics
IN OVULO HYBRID EMBRYO CULTURE IN CONTROLLED GRAPE CROSSES INVOLVING STENOSPERMOCARPIC PARENTS |
| Authors: | L. Sahijram, V.C. Kanamadi |
| Keywords: | seedless grapes, breeding, in ovulo/ex ovulo embryo culture, hybrid plantlets |
| Abstract:
Using conventional breeding procedures, it is not possible to obtain hybrid progeny in grape crosses involving seedless (‘stenospermocarpic’) female parents. Such crosses can, however, be salvaged using embryo rescue, as embryos are shown to exist in the aborted seeds of mature berries. Two types of crosses were effected: (i) Seedless X Seedless and (ii) Seedless X Seeded. In ovulo embryo culture was carried out beginning 4 weeks post-pollination (wpp). The percentage recovery of plantlets was found to be very low. In one experiment, out of 128 ovules cultured, only one plantlet could be regenerated. To study factors responsible for the low rate of regeneration, ovules were subjected to histological and micrometric analysis on a daily basis beginning 24 hours post-pollination. Zygote formation was seen up to 4 dpp in all the crosses studied there was endosperm formation, indicating successful double fertilization. Since the rate of hybrid plantlet recovery was very low, recently another experiment was set up using controlled grape crosses wherein in ovulo embryo culture was followed by embryo excision and culture. In all the crosses in the latter study, cv. Thompson Seedless was used as the female parent and 15 lines of grape variously resistant to the Downy mildew disease served as the pollen donor parent. Of the 6455 buds crossed, 48.13% (3107) set berries which yielded 1353 (43.55%) excisable/culturable ovules at 6-10 wpp. At 8 weeks from in vitro incubation of excised ovules, hybrid embryos were dissected out and subcultured. 18.85% (255) of the ovules dissected contained an apparently viable embryo. Most of these embryos developed into plantlets. So far, 294 hybrid plantlets have been transplanted successfully into soil. | |
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