Immature embryo rescue of grapevine (Vitis vinifera L.) after an extended period of seed trace culture

In this work the effect of time on in vitro culture of seed traces is evaluated. Without changing media, there was no decline in the number of rescued embryos for any cross within and up to 210 d of culture. After that period a decline was shown for varieties producing abundant callus from the external tegument. Direct germination of embryos increased in all crosses except for Blush Seedless x 73049, which stopped direct germination after 90 d. The polyembryony was advantageous for the cross Superior Seedless x Dawn Seedless, because it increased the percentage of normal plantlets. Multiple embryos showed a higher capacity to germinate in all cases. More embryos were obtained by excision and they presented a higher percentage of normal plantlets in comparison to plantlets obtained by embryos germinated directly. Embryos from the varieties Ruby Seedless, Blush Seedless and Bronx Seedless mainly produced normal plantlets while Crimson Seedless, Superior Seedless and Fantasy Seedless embryos mostly produced abnormal plantlets.