Heung-Ryul Lee

Construction of an integrated pepper map using RFLP, SSR, CAPS, AFLP, WRKY, rRAMP, and BAC end sequences

Map-based cloning to find genes of interest, markerassisted selection (MAS), and marker-assisted breeding (MAB) all require good genetic maps with high reproducible markers. For map construction as well as chromosome assignment, development of single copy PCR-based markers and map integration process are necessary. In this study, the 132 markers (57 STS from BAC-end sequences, 13 STS from RFLP, and 62 SSR) were newly developed as single copy type PCR-based markers. They were used together with 1830 markers previously developed in our lab to construct an integrated map with the Joinmap 3.0 program. This integrated map contained 169 SSR, 354 RFLP, 23 STS from BAC-end sequences, 6 STS from RFLP, 152 AFLP, 51 WRKY, and 99 rRAMP markers on 12 chromosomes. The integrated map contained four genetic maps of two interspecific (Capsicum annuum ‘TF68’ and C. chinense ‘Habanero’) and two intraspecific (C. annuum ‘CM334’ and C. annuum ‘Chilsungcho’) populations of peppers. This constructed integrated map consisted of 805 markers (map distance of 1858 cM) in interspecific populations and 745 markers (map distance of 1892 cM) in intraspecific populations. The used pepper STS were first developed from end sequences of BAC clones from Capsicum annuum ‘CM334’. This integrated map will provide useful information for construction of future pepper genetic maps and for assignment of linkage groups to pepper chromosomes.

QTL Analysis of Fruit Length Using rRAMP, WRKY, and AFLP Markers in Chili Pepper

A pepper genetic map was constructed from F2 mapping population of 93 individuals from a cross between Capsicum annuum ‘F68’ and C. chinense ‘Habanero’. Surrey was made for the map distribution and polymorphism level of these marker groups; reverse random amplification microsatellite polymorphism (rRAMP), WRKY and amplified fragment length polymorphisms (AFLP). A total of 912 molecular markers [356 rRAMP, 190 WRKY, 305 AFLP, and 61 simple sequence repeats (SSR)] were developed in this study. The rRAMP and WRKY markers were more evenly scattered in the pepper genome than the AFLP and SSR markers, and filled the gaps not populated by the other markers. The interspecific pepper map contained 28 linkage groups with 625 linked markers and covered 3377.2 cM with an average interval of 5.9 cM. On the basis of the map, the fruit length quantitative trait locus (QTL) was analyzed and these QTL regions were detected near rRAMP and WRKY markers on the chromosome 3, 5, 11, and LG3. These marker system, map information, and detected QTLs could be one of basic information for pepper research.

De Novo Transcriptome Analysis of Cucumis melo L. var. makuwa

Oriental melon (Cucumis melo L. var. makuwa) is one of six subspecies of melon and is cultivated widely in East Asia, including China, Japan, and Korea. Although oriental melon is economically valuable in Asia and is genetically distinct from other subspecies, few reports of genome-scale research on oriental melon have been published. We generated 30.5 and 36.8 Gb of raw RNA sequence data from the female and male flowers, leaves, roots, and fruit of two oriental melon varieties, Korean landrace (KM) and Breeding line of NongWoo Bio Co. (NW), respectively. From the raw reads, 64,998 transcripts from KM and 100,234 transcripts from NW were de novo assembled. The assembled transcripts were used to identify molecular markers (e.g., single-nucleotide polymorphisms and simple sequence repeats), detect tissue-specific expressed genes, and construct a genetic linkage map. In total, 234 single-nucleotide polymorphisms and 25 simple sequence repeats were screened from 7,871 and 8,052 candidates, respectively, between the KM and NW varieties and used for construction of a genetic map with 94 F2 population specimens. The genetic linkage map consisted of 12 linkage groups, and 248 markers were assigned. These transcriptome and molecular marker data provide information useful for molecular breeding of oriental melon and further comparative studies of the Cucurbitaceae family.

Isolation of an Rx homolog from C. annuum and the evolution of Rx genes in the Solanaceae family

The well-conserved NBS domain of resistance (R) genes cloned from many plants allows the use of a PCR-based approach to isolate resistance gene analogs (RGAs). In this study, we isolated an RGA (CapRGC) from Capsicum annuum “CM334” using a PCR-based approach. This sequence encodes a protein with very high similarity to Rx genes, the Potato Virus X (PVX) R genes from potato. An evolutionary analysis of the CapRGC gene and its homologs retrieved by an extensive search of a Solanaceae database provided evidence that Rx-like genes (eight ESTs or genes that show very high similarity to Rx) appear to have diverged from R1 [an NBS-LRR R gene against late blight (Phytophthora infestans) from potato]-like genes. Structural comparison of the NBS domains of all the homologs in Solanaceae revealed that one novel motif, 14, is specific to the Rx-like genes, and also indicated that several other novel motifs are characteristic of the R1-like genes. Our results suggest that Rx-like genes are ancient but conserved. Furthermore, the novel conserved motifs can provide a basis for biochemical structural–function analysis and be used for degenerate primer design for the isolation of Rx-like sequences in other plant species. Comparative mapping study revealed that the position of CapRGC is syntenic to the locations of Rx and its homolog genes in the potato and tomato, but cosegregation analysis showed that CapRGC may not be the R gene against PVX in pepper. Our results confirm previous observations that the specificity of R genes is not conserved, while the structure and function of R genes are conserved. It appears that CapRGC may function as a resistance gene to another pathogen, such as the nematode to which the structure of CapRGC is most similar.

Development of a new F1 variety, TY Altorang, with high-quality and multi-disease resistance.

‘TY Altorang’ was developed from a cross between ‘MS-CDE’ and ‘VFR’ in 2009. The cultivar has multi-disease resistances against Tobacco mosaic virus(TMV), Tomato yellow leaf curl virus(TYLCV), Fusarium crown and root rot and Leaf mold disease. Additionally, this cultivar produces larger fruit set resulting in higher fruit harvest. Fruit shape is fair and uniformed ovate type with an average fruit weight of 225 g as a beef-steak type tomato, and the fruit presents longer shelf-life due to higher fruit firmness. The early and medium-maturing variety can be transplanted in February to March, or July to September. Medium-strong plant-vigor and low occurrence of creased stem allow, relativey easy cultivation.