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  • Author or Editor: J.D. Chung x
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Somatic embryogenesis was initiated from in vitro-grown leaf explants of rose using an induction period of 4 weeks on MS basal medium supplemented with auxin followed by several subcultures on MS basal medium with cytokinin. `4th of July' showed the highest regeneration frequency (24.4%) on 5.3 μm NAA followed by culture on medium containing 18.2 μm zeatin. `Tournament of Roses' produced somatic embryos when cultured for 4 weeks on medium containing dicamba, 2.3 μm followed by three subcultures on medium containing 18.2 μm zeatin. Embryogenic callus matured on MS media containing 0.5 μm NAA, 6.8 μm zeatin, and 2.9 μm GA3. Long-term cultures were established for both cultivars. Somatic embryos germinated on MS medium containing IBA and BA. Silver nitrate (58.8 μm) enhanced shoot formation and germination of somatic embryos. Plants derived from somatic embryos were acclimatized and successfully established in the greenhouse.

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Lettuce (Lactuca sativa L.) were transformed using microparticle bombardment with two different genes, alpha-glucuronidase (GUS) gene and Chinese cabbage Glutathione Reductase (GR) gene. The adventitious shoots of cotyledonary explant from 4-day-old seedlings were formed (46.7%) in MS basal media supplemented with 5.0 μm IAA and 1.0 μm 2ip. When 1100 psi helium pressure, 9 target distance, and coating with tungsten 10 microparticles were used and explants were treated with osmoticum-conditioning medium (0.6M sorbitol/mannitol), 4 h prior to and 16 h after bombardment, it was identified by GUS assay that these conditions were the most efficient for transformation of foreign genes into cotyledon tissue of lettuce with particle bombardment. PCR confirmed that the band observed in the transgenic plants were originated from T-DNA tranfer with strong hybridization. The genomic Southern analysis showed that the 1.5-kbp fragment was hybridized with radiolabeled 1.5-kbp GR probe. To know whether the expression of the GR gene can be stably maintained in the next generation, when T2 selfing seeds that were obtained from the transformed mother plants were sowed on MS medium supplemented with 200 μm kanamycin, 70% of seedlings were revealed resistance to kanamycin.

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This experiment was conducted to identify the effect of various growth retardants on the growth of Aerides japonicum in vitro. Paclobutrazol was found the most effective retardant for reducing the leaf growth of seedling. Ancymidol and uniconazole also showed retarding effects on leaf growth of one, whereas Daminozide didn't. When growth retardants were added to culture medium, leaf length of seedlings was gradually shortened and leaf width became wider than that of control. However, root length was shorter and number of roots and root diameter were greatly increased. On the contrary, at 0.05 and 0.1 ppm uniconazole, growth of leaf and root were enhanced. It was showed that the possibility of using as an additive for good growth of Aerides japonicum seedling in vitro. The activity of GA-like substances was higher in the portion in which growth of seedlings were promoted. It was identified by anatomical observations that the number of stomata and thickness of cell layer in leaf were increased by treatment of retardants.

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