IN VITRO "REJUVENATION" OF WOODY SPECIES IS TEMPORARY

Using “rejuvenated” mature explants we micropropagated hazelnut (Corylus sp.), chestnut (Castanea sp.) and grape (Vitis sp.) plants. We have continuously subcultured explants of hybrid hazelnut for more than three years, explants of grape for ca. five years, and explants of hybrid American chestnut for ca. eight years in vitro. In vitro micropropagated hazelnut plants that were grown in the greenhouse developed both male and female flowers and set nuts in 15 months. Hazelnut plants that were transplanted in the field set normal male flowers in one year after been taken out of culture, and set nuts in their second growth year. In vitro produced chestnut plants produced male flowers in their second growth year, and following the second dormancy, they developed both male and female flowers and set nuts in the greenhouse. Micropropagated grape plants grown in the greenhouse formed tendrils, a characteristic of mature plants, within two to three months after been taken out of the culture. These results suggest that in vitro “rejuvenated” and micropropagated plants of mature origin may retain their physiologic maturity during long-term in vitro culture or regain it soon after they are taken out of the culture. They may set fruit earlier then seedling plants, similar to conventionally (asexually) propagated plants.

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