In Vitro Culture of Embryos Obtained by Crossing Tetraploid Grape Cultivar 'Kyoho' with Diploid Cultivars

Abstract

Zygotic embryos from crosses between tetraploid grape cultivar 'Kyoho' and diploid cultivars 'Rizamat' and 'Sekirei' were rescued at different developmental stages 60 to 70 days after pollination. The immature, mature and abnormal embryos were aseptically excised from the ovules and culture on MS medium without phytohormones in an effort to obtain triploid seedlings.
1. Most zygotes which advanced to and beyond the torpedo-shaped germinated on MS basal medium, whereas immature and abnormal ones failed to develop. However, the germination of both immature and abnormal embryo improved when they were cultured on a modified MS medium without ammonium salts but supplemented instead with 250, 500, or 1000 mg•liter^-1 of casein hydrolysate.
2. Although most of the germinated embryos stopped growing on these germination media, they initiated to leaf-out or multiple leaf buds after being transferred to a MS medium supplemented with 0.2, 2, or 5 mg•liter^-1 of BA; they then formed shoots. When shoots were transferred to MS medium without phytohormones, roots were initiated. Sub-sequently, plantlets were successfully acclimated and established.
Almost 100% of the mature embryos developed into plantlets, whereas only 10% of the immature ones could be rescued. Therefore, an embryo rescue and culture methods developed by this study would be successfully utilized for obtaining triploid grape seedlings from crosses between tetraploid and diploid cultivars.