Yoon-Jung Hwang

Exploitation of induced 2n -gametes for plant breeding

Key MessageEfficient induction of unreduced gamete in different crops and its genetic consequences will open new avenues for plant breeding.AbstractUnreduced gamete formation derived via abnormal meiotic cell division is an important approach to polyploidy breeding. This process is considered the main driving force in spontaneous polyploids formation in nature, but the potential application of these gametes to plant breeding has not been fully exploited. An effective mechanism for their artificial induction is needed to attain greater genetic variation and enable efficient use of unreduced gametes in breeding programs. Different approaches have been employed for 2n-pollen production including interspecific hybridization, manipulation of environmental factors and treatment with nitrous oxide, trifluralin, colchicine, oryzalin and other chemicals. These chemicals can act as a stimulus to produce viable 2n pollen; however, their exact mode of action, optimum concentration and developmental stages are still not known. Identification of efficient methods of inducing 2n-gamete formation will help increase pollen germination of sterile interspecific hybrids for inter-genomic recombination and introgression breeding to develop new polyploid cultivars and increase heterozygosity among plant populations. Additionally, the application of genomic tools and identification and isolation of genes and mechanisms involved in the induction of 2n-gamete will enable increased exploitation in different plant species, which will open new avenues for plant breeding.

FISH and GISH: molecular cytogenetic tools and their applications in ornamental plants.

Key messageThe innovations in chromosome engineering have improved the efficiency of interrogation breeding, and the identification and transfer of resistance genes from alien to native species.AbstractRecent advances in molecular biology and cytogenetics have brought revolutionary, conceptual developments in mitosis and meiosis research, chromosome structure and manipulation, gene expression and regulation, and gene silencing. Cytogenetic studies offer integrative tools for imaging, genetics, epigenetics, and cytological information that can be employed to enhance chromosome and molecular genomic research in plant taxa. In situ hybridization techniques, such as fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH), can identify chromosome morphologies and sequences, amount and distribution of various types of chromatin in chromosomes, and genome organization during the metaphase stage of meiosis. Over the past few decades, various new molecular cytogenetic applications have been developed. The FISH and GISH techniques present an authentic model for analyzing the individual chromosome, chromosomal segments, or the genomes of natural and artificial hybrid plants. These have become the most reliable techniques for studying allopolyploids, because most cultivated plants have been developed through hybridization or polyploidization. Moreover, introgression of the genes and chromatin from the wild types into cultivated species can also be analyzed. Since hybrid derivatives may have variable alien chromosome numbers or chromosome arms, the use of these approaches opens new avenues for accurately identifying genome differences.

Different Day and Night Temperature Responses in Lilium hansonii in Relation to Growth and Flower Development

Temperature is one of the most important factors that directly affect the possibility and the rate of flower differentiation in many geophytes such as Lilium. In this experiment, different day and night temperatures were used to determine the required day and night temperature for flower bud development in Lilium hansonii. After low temperature exposure for breaking bulb dormancy, the bulbs were planted in pots, and placed in designated growth chambers each with a specific temperature. The plants were exposed to different temperatures for 30 days, and 15 days after planting sample plants were collected in each treatment for observation of flower bud development using the scanning electron microscope (SEM). Responses of plant height, number of leaves, and stem diameter were also measured as affected by difference between day and night temperature (DIF) and average daily temperature (ADT). The results showed that average daily temperature and high day temperature had a direct effect on the quality, quantity, and time required for flower bud development. They also affected the stem elongation, number of leaves, and stem diameter. Higher ADT and DT (25°C) promoted stem elongation and increased leaf unfolding rate (LUR), but with less number of leaves produced. As ADT and DT increased, stem diameter decreases. In lower ADT and DT (15°C) treatment, greater stem diameter and higher number of flower buds (2–7 buds) were produced. Higher ADT and DT promoted early flower bud initiation, but lower number of flower buds with higher possibilities of flower bud abortion, while lower ADT and DT showed slower flower bud initiation and development with higher flower bud formation.

The complete chloroplast genome of Lilium distichum Nakai (Liliaceae)

Abstract Lilium distichum is a native lily species in Korea, northeastern China and far eastern Russia. The complete chloroplast genome sequence of L. distichum was generated by de novo assembly using whole genome next generation sequences. The chloroplast genome of L. distichum was 152 598 bp in length and divided into four distinct regions, such as large single copy region (82 031 bp), small single copy region (17 487 bp) and a pair of inverted repeat regions (26 540 bp). The genome annotation predicted a total of 112 genes, including 78 protein-coding genes, 30 tRNA genes,and 4 rRNA genes. Phylogenetic analysis with the reported chloroplast genomes revealed that L. distichum is most closely related to L. superbum (Turk’s-cap lily).

Molecular cytogenetic analysis and phylogenetic relationship of 5S and 45S ribosomal DNA in sinomartagon Lilium species by fluorescence in situ hybridization (FISH)

This study was conducted to elucidate the evolution of chromosomal diversification in eight species of Lilium by fluorescence in situ hybridization (FISH) technique using ribosomal DNA probes for the 5S rDNA and 45S rDNA. A phylogenic tree was reconstructed based on the results of the sequence analysis of the non-transcribed spacer (NTS) and inter-transcribed spacer (ITS) regions. The FISH analysis showed Lilium lancifolium (2x) were composed of 3 pairs of 45S rDNA genes on short arms of chromosome # 1, 2, and 7, and 3 pairs on long arms of chromosome # 4, 6, and 11. L. callosum and L. concolor showed the same pattern with L. lancifolium. However, L. dauricum showed 3 pairs of signals on the short arm of chromosome # 1, 2, and 7, and a pair of 45S rDNA signals was detected on the long arms of chromosome # 6 by FISH. The sequence length of the ITS1 and ITS2 regions were 229 bp and 233 bp, respectively. The length of the NTS region, including 5S rDNA segment, was within the range of 474 to 678 bp. According to the phylogenic analysis, L. concolor, L. amabile and L. callosum were closely related, whereas L. lancifolium, diploid and triploid were distantly related.

Ecological analysis of Lilium tsingtauense native in Korea

Korea has large diversity in Lilium germplasm and approximately 15 different species of lilies grow naturally. In present study, a comprehensive evaluation of habitat associations and distribution patterns of Lilium tsingtauense in Korea was carried out. A total of 26 natural habitats of L. tsingtauense were investigated and data regarding its ecological and morphological characteristics under different geological and environmental conditions were collected. During survey it was observed that this species was well distributed nationwide with highly variable altitudes such as Jindo Island (82 m) and Mt. Jiri (1182 m). Most (84%) of natural habitats of this species were found in the northern slopes of mountains and the remainder (15%) habitats were present in the southern regions. Flowers with upward facing had no fragrance and flowering time of this species was in between early July to mid-July. Colonies of Larix leptolepis, as well as 106 other plant species, were mainly found in these natural habitats. The soil was strongly acidic, within the pH range of 4.3-5.3. EC, organic content, total-nitrogen content, and CEC varied among natural habitats. Most of the soils of the natural habitats were sandy loam with low clay ratios. This study can provide baseline information regarding the effective exploitation and use of L. tsingtauense resources for breeding research.

Morphological characterization under different ecological habitats and physical mapping of 5S and 45S rDNA in Lilium distichum with fluorescence in situ hybridization

BackgroundThis study was performed to investigate the phenotypic, karyomorphological, and habitat environment characteristics of Lilium distichum that grows naturally in South Korea. Currently, this species follows limited distribution areas and its natural populations are at the brink of extinction mainly due to fragmentation or destruction its natural habitat.ResultsThis species was distributed between approximately 1,000 and 1,500 m above sea level with an average temperature of 22°C. The soil characteristics surrounding the natural habitats included loamy and silt loam soils having organic matter content (10.82%), pH (5.22), electrical conductivity (EC) (0.37 dS/m), total nitrogen (0.45%), and cation exchange capacity (34.3 cmol+/kg). The peak period of blossoming was between 27 July and 1 August. The maximum number of flowers was observed in Mount Deogyu (2.8), whereas the minimum number of flowers was observed in Mount Jiri (1.3) and Mount Seorak (1.2). Results regarding the number of verticillate leaf, bract counts, and verticillate leaf length and width were highest in Mount Odae, while lowest in the Mount Seorak region. The chromosome complement of L. distichum is 2n = 2x = 24; the length of somatic metaphase chromosomes ranges from 17.01 ± 0.32 μm (chromosome 10) to 32.06 ± 0.35 μm (chromosome 1) with a total length/genome of 261.92 μm. In L. distichum, the presence of 1 pair (two loci) of 5S ribosomal DNA (rDNA) and 8 pairs (16 loci) of 45S rDNA was revealed on metaphase chromosomes. One pair of 5S rDNA signal was observed in interstitial region of long arm of chromosome 3 which co-occurred with 45S rDNA. Among the eight pairs of 45SrDNA, three pairs of 45S rDNA signals were observed in short arm of chromosome (chromosome 2, 6, and 7) which were located close to centromere. The other five pairs of 45S rDNA signals were positioned in the interstitial region of long arm (chromosome 3, 4, 5, 10, and 11).ConclusionsThis study provides baseline information regarding the effective exploitation and use of L. distichum resources for breeding research to be used as cut flower and potted plants.

Phenotypic analysis of parents and their reciprocal F1 hybrids in Phalaenopsis

In this study, we studied the phenotypic and breeding efficiency of Phalaenopsis reciprocal hybrids and their parents. For reciprocal hybridization, Phalaenopsis ‘KS Little Gem’ and ‘1747’ from Taiwan were used as parents. After crossing ‘KS Little Gem’ × ‘1747’ in 2010, 34 individuals from ‘KS 1059’ hybrids were developed. The crossing between ‘1747’ × ‘KS Little Gem’ resulted in the development of 63 individuals from ‘KS 1076’ hybrids. Detailed morphological characteristics of newly developed hybrids; ‘KS 1059’, ‘KS 1076’ and their parents were collected according to guidelines determined by the Korea Seed and Variety Service (KSVS). The leaf characteristics were similar in reciprocal hybrids and their parents, except in number of leaves, which as were maximal in ‘KS 1059’. In terms of flower characteristics including number of flowers, inflorescence length, pedicel length and pedicel diameter, features of the parents were combined in the hybrids. By contrast in case of flower length, both hybrids showed similarity to ‘KS Little Gem’, and a similar pattern was observed in flower width. The petal length in hybrids and parents were similar, but the petal width of hybrids was more closer to that of ‘KS Little Gem’. The length of whiskers was long in both parents, but very short whiskers were recorded in hybrids. The length and width of the apical lobe were similar in parents and hybrids, but hybrids were closer to ‘1747’. In the case of duration of of flowering, the maximum value of 123 days was recorded in ‘KS Little Gem’ similar to ‘KS 1059’, whereas ‘1747’ and ‘KS 1076’ had almost identical values. It can be concluded that to generate Phalaenopsis with a longer shelf life, ‘KS Little Gem’ might be selected as the female parent during hybridization.

The complete chloroplast genomes of Lilium tsingtauense Gilg (Liliaceae)

Abstract Lilium tsingtauense, known as ‘Korean wheel lily’ and ‘Twilight lily’, is a lily species naturally distributed in Korea. The complete chloroplast genome sequences of L. tsingtauense was obtained by de novo assembly using whole-genome next-generation sequencing data. The chloroplast genome of L. tsingtauense was 152,710 bp in length and consisted of four distinct regions, such as large single-copy region (82,059 bp), small single-copy region (17,619 bp) and a pair of inverted repeat regions (26,516 bp). The genome contained a total of 113 genes, including 79 protein-coding genes, 30 tRNA genes and 4 rRNA genes. Phylogenetic analysis with the reported chloroplast genomes revealed that L. tsingtauense is most closely related to Lilium hansonii, a lily species native to Korea.

Distribution of various types of repetitive DNAs in Allium cepa L. based on dual color FISH

Fluorescence in situ hybridization (FISH) is a powerful tool for the detection of DNA sequences in a specific region of a chromosome as well as for integrated physical mapping. The detailed karyotypes of two onion cultivars (‘Eumjinara’ and ‘Sinseonhwang’), which are resources for the onion genome sequencing project were constructed based on dual color FISH using 5S and 45S rDNAs, telomeric tandem repeats, and Cot-1 DNA. All materials showed 2n = 2x = 16. Four loci of 5S rDNAs were located on the interstitial regions of the short arms of one pair of chromosomes in both onion cultivars. One loci of 45S rDNA signal was distally detected on each short arm of the two pairs of chromosomes in ‘Eumjinara’ and ‘Sinseonhwang’, but the latter possessed another locus of 45S rDNA on the distal part of the long arm in one homolog of a chromosome pair. Co-localization of telomeric tandem repeats and 45S rDNA signals was observed in ‘Eumjinara’ and ‘Sinseonhwang’. A difference in the distribution of 45S rDNA sites and the co-localization of signals observed between the two cultivars are indicators of recent activities in the nuclear genome that may involve homologous recombination or transposition of certain repeats. Cot-1 DNA signals are distributed throughout the chromosomes and show stronger signals in the terminal regions. The elucidation of Cot-1 DNA through in-situ hybridization would only show a large amount of tandemly repeating, non-coding and dispersedly repetitive DNAs in onion genome.