Haeyoung Na

The effects of plant growth regulators, activated charcoal, and AgNO3 on microspore derived embryo formation in broccoli (Brassica oleracea L. var. italica)

Embryos derived from isolated microspore culture are of great importance for producing homozygous plants for breeding. Microspore culture can reduce time and laborious effort in the breeding of Brassica plants. Microspore derived embryos (MDE) formation in broccoli (Brassica oleracea L. var. italica Plenck) was studied with different plant growth regulators (PGRs), activated charcoal, and silver nitrate (AgNO3) to determine the optimal chemical conditions in the microspore culture. A 6-benzylaminopurine (BA) concentration of 0.05 mg L−1 resulted in increased MDE formation compared to those at other BA concentrations. Compared to the 0.05 mg L−1 BA concentration, fewer MDEs were formed in BA concentrations exceeding 0.1 mg L−1, similar to those cultured on medium without BA. However, 0.5× Nitsch & Nitsch (NLN) liquid medium supplemented with 0.05 mg L−1 napthalene acetic acid (NAA) and BA was more effective in inducing MDE formation than was BA alone. The higher MDE formation rate was observed in 0.5× NLN liquid culture medium containing 0.05 mg L−1 NAA and 0.01 mg L−1 BA. The MDE yield was significantly higher in all concentrations when activated charcoal was added to the microspore culture media. The optimal concentration of activated charcoal was 1.0 mg per petri dish, and the optimum AgNO3 concentration was 0.1 mg L−1, which induced MDE formation to 26.2 embryos, compared to 11.6 embryos without AgNO3.

Changes in physicochemical characteristics during fruit development in June-bearing strawberry cultivars

Changes in physicochemical characteristics were investigated during fruit development in ‘Maehyang’, ‘Seolhyang’, ‘Keumhyang’, ‘Akihime’, and ‘Red Pearl’ strawberries. Fresh weights and color parameters of strawberry fruits changed significantly during the fruit development in all cultivars. Fruit shapes of ‘Maehyang’ and ‘Akihime’ were conical, with an index of length to width being 1.5 and that of ‘Seolhyang’, ‘Keumhyang’, and ‘Red Pearl’ were cordate, the index being 1.3. Firmness decreased as the fruit developed in all cultivars. Contents of sugars, organic acids, ascorbic acid, and anthocyanin increased as the fruits developed while the ellagic acid content decreased. Sugars, ascorbic acid, and anthocyanin contents of ‘Maehyang’, ‘Seolhyang’, and ‘Keumhyang’ were higher than those of ‘Akihime’ and ‘Red Pearl’. Results indicate that newly-bred Korean strawberry cultivars containing high levels of bioactive compounds were superior to major Japanese cultivars that have been broadly cultivated in East Asian countries.

Comparative anatomy of embryogenic and non-embryogenic calli frompimpinella brachycarpa

Anatomical differences between embryogenic and non-embryogenic calli ofPimpinella brachycarpa were investigated by light microscopy and electron microscopy. Initial callus tissue emerged from expiants after 14 d of culturing. The embryogenie calli (EC) were firm, rather opaque, and light yellow in color. The cells usually formed small, compact clusters. Nonembryogenic calli (NEC), however, were friable, semitransparent, and yellow or gray. These formed relatively larger and loosely held clusters. Scanning electron microscopy showed that EC were composed of individual compact and spherical cells that were rather regular in size and approximately 20 µm long. All were tightly held together and appeared to organize globular embryos. In contrast, the NEC comprised elongated and loosely held cells that were approximately 50 µm long. Tubular and u-shaped NEC cells protruded irregularly, and were of varying heights along the cell aggregates. Transmission electron microscopy of the EC revealed typical eukaryotic cytoplasmic components, including nuclei, mitochondria, and vacuoles in the cytoplasm enclosed by an electron-transparent cell wall. Based on the numerous ribosomes within the cytoplasm, these cells appeared to be well-organized and metabolically active. The NEC cells were much larger and more highly vacuolated than those of the EC. In ultrathin sections, the former seemed to be almost devoid of other cellular contents except for plastids and nuclei. Furthermore, EC and NEC showed different regeneration capacities in their somatic embryo formation. Most EC produced hyperhydric somatic embryos, followed by normal somatic embryos; whereas only a few shooted or rooted somatic embryos arose from the NEC.

Microspore derived embryo formation and doubled haploid plant production in broccoli ( Brassica oleracea L. var italica ) according to nutritional and environmental conditions

In cell culture, the maintenance of proper growing conditions is a key approach for improving the formation of embryos, and is useful in the production of doubled haploid (DH) plants. Optimal nutritional and environmental conditions for the microspore culture of Brassica oleracea L. var italica were determined in order to reduce time and effort in breeding. The optimal conditions for microspore embryo formation differed depending on genotype. Microspore-derived embryos (MDE) formation was influenced by the strength of the NLN medium, the microelement and sugar concentration, and the heat shock temperature and period. The 0.5XNLN liquid medium was the most favorable for MDE formation. The most efficient formation of MDE was observed in the 0.5X NLN liquid medium, without the addition of microelements. When 13 or 15% sucrose was added to the 0.5X NLN liquid medium, the amount of normal MDE formation increased. The optimum heat shock temperature and period for MDE formation was 32.5°C and 24 h, respectively. A polyploidy test indicated that 30% of the microspore derived plants were diploid throughout the embryogenesis process.

Microspore-derived embryo formation in radish (Raphanus sativus L.) according to nutritional and environmental conditions

Composition of nutrient media, flower bud size, sucrose concentration, heat shock stress, and ethylene inhibitor could have marked effects on microspore embryogenesis. No microspore-derived embryos (MDE) were formed when the microspores were isolated from radish (Raphanus sativus L.) flower buds of 1.0–2.5 mm in size, whereas MDE were formed with microspores isolated from 2.5–4.5 and 4.5–6.5 mm flower buds. The microspores isolated from 2.5–4.5 mm flower buds showed high embryo yields. MDE formation was highest when 150 g·L−1 sucrose was added to the half strength Nitsch & Nitsch (NLN) liquid medium, but at sucrose concentrations less than 100 g·L−1 there was no MDE formation. Microspores cultured on half strength NLN liquid medium containing 0.05 mg·L−1 silver nitrate (AgNO3) produced the most MDE, showing more than two-fold increase in yield compared to those cultured on medium without AgNO3. A heat shock pretreatment of microspores at 32°C for 24 h gave high-frequency production of MDE when compare to higher or lower temperatures; no MDE were formed at 42.5°C. The highest yield of MDE was observed when microspores were derived from 2.5–4.5 mm flower buds cultured on half strength NLN medium containing 150 g·L −1 sucrose, 0.05 mg·L−1 AgNO3, and precultured with heat shock pretreatment of microspores at 32°C for 24 h, followed by incubation 25°C for 30 days. A polyploidy test indicated that 19.7% of the microspore-derived plants were doubled haploid, other plants were haploid, and chimeras were haploid and diploid.