Seung Gyun Yang

Transgenic watermelon rootstock resistant to CGMMV (cucumber green mottle mosaic virus) infection

In watermelon, grafting of seedlings to rootstocks is necessary because watermelon roots are less viable than the rootstock. Moreover, commercially important watermelon varieties require disease-resistant rootstocks to reduce total watermelon yield losses due to infection with viruses such as cucumber green mottle mosaic virus (CGMMV). Therefore, we undertook to develop a CGMMV-resistant watermelon rootstock using a cDNA encoding the CGMMV coat protein gene (CGMMV-CP), and successfully transformed a watermelon rootstock named ‘gongdae’. The transformation rate was as low as 0.1–0.3%, depending on the transformation method used (ordinary co-culture vs injection, respectively). However, watermelon transformation was reproducibly and reliably achieved using these two methods. Southern blot analysis confirmed that the CGMMV-CP gene was inserted into different locations in the genome either singly or multiple copies. Resistance testing against CGMMV showed that 10 plants among 140 T1 plants were resistant to CGMMV infection. This is the first report of the development by genetic engineering of watermelons resistant to CGMMV infection.

High frequency somatic embryogenesis and plant regeneration in tissue cultures of Codonopsis lanceolata

Culture conditions for high frequency somatic embryogenesis and plant regeneration from cotyledonary explants of Codonopsis lanceolata are described. The maximum induction frequency of somatic embryos from cotyledonary explants was 80% on Murashige and Skoog (MS) medium containing 6% sucrose with 1 mg/l 2,4-dichlorophenoxyacetic acid and 10% coconut water. Upon transfer onto MS basal medium containing 3% sucrose, most somatic embryos developed into plantlets.

Dry type of carrot (Daucus carota L.) artificial seeds

Abstract Somatic embryos from cell suspension cultures of carrot were singly encapsulated with alginic acid to be used as artificial seeds. Most of the freshly encapsulated embryos germinated after being stored at 4°C. A hydrated capsule retained enough water for the encapsulated embryo to germinate. However, germination was effectively blocked when hydrated capsules were subjected to air-blowing dehydration, to the level of over 80% water loss. Ninety-seven percent of the capsules dehydrated by 88% water loss were capable of germination on subsequent rehydration. Pretreatment of embryos with abscisic acid (ABA) for 10 days prior to encapsulation, enhanced the germination percentage of capsules which were dehydrated by 95% water loss following rehydration: as the concentration of ABA increased to 0.13 mg l−1, the germination percentage also increased by up to 31%. Sixty-eight percent of the capsules, dehydrated by 92%, germinated after 10 days of storage at 4°C on subsequent rehydration. These results indicate that the dehydrated capsule containing a somatic embryo has greater similarity to the natural seed in form and function than the hydrated capsule.