Bacterial phytopathogen Pectobacterium causes soft rot disease in several vegetable crops globally, resulting in heavy agricultural losses at both the pre and postharvest stages. The present work was carried out to screen Kimchi cabbage genetic resources conserved at the National Agrobiodiversity Center, Rural Development Administration, Korea, for resistance against the soft rot pathogen Pectobacterium carotovorum subsp. carotovorum KACC 21701 over a period of three years (from 2020 to 2022). Infection of the phytopathogen was carried out at four-leaf stage and for each accession, twenty-five plants per germplasm were infected with KACC 21701. Kimchi cabbage cultivars Wangmatbaechu, Seoulbaechu, and CR Kiyoshi were used as control. Seven-days post-infection, the Disease Index (DI) values were manually recorded from zero to four, zero matched perfectly heathy plants and four completely dead plants. The 682 accessions of Kimchi cabbage exhibited varying degrees of disease resistance to KACC 21701 and thirty accessions, exhibiting a DI≤2, were considered for replication studies. During the replication studies, four landrace germplasms (IT102883, IT120036, IT120044, and IT120048) and one cultivar (IT187919) were confirmed to be moderately susceptible to KACC 21701. Results of the preliminary screening as well as replication studies were documented for the all the 682 germplasms. Addition of such information to the passport data of stored germplasms might serve as potential bio-resource for future breeders and researchers to develop resistant varieties or study the mechanisms involved in resistance of plants to such phytopathogen.

Fusarium crown root rot (FCRR) is a severe fungal disease caused by Fusarium oxysporum f. sp. radicis-lycopersici (FORL) in tomato. Resistance to FORL is conferred by single dominant locus Frl on chromosome 9, but its precise genomic location is not clearly determined. In this study, detailed location of Frl was assessed by using a set of molecular markers physically anchored on Chr.9 and F2 and RIL population derived from FORL-resistant inbred AV107-4 (S.lycopersicum) x susceptible L3708 (S. pimpinellifolium). Bioassay of the two populations with a FORL strain isolated from Korea resulted in single dominant heritance of the resistance. Two SCAR and 11 CAPS markers encompassing 3.6Mb~72Mb of Chr.9 were developed from the Tomato-EXPEN 2000 map and SolCAP SNP-array analysis. These markers were genotyped on 345 F2 plants. A high level of cosegregation with the resistance were observed for 5 markers which were mapped at a large physical interval of 5.1Mb (T1212) to 46.4Mb (SSR237), indicating that genetic recombination was highly suppressed in this region. Cosegregation of these markers with Frl was confirmed by using 126 RILs. The results implied that, in contrast with the previously reported long arm, Frl is present on a pericentromeric region of short arm of Chr. 9, in which crossing-over is severely suppressed. The marker set was further tested on 12 FORL-resistance or susceptibility commercial cultivars. Unlike the biparental populations, frequent linkage break was observed for T1212 and D4 in commercial cultivars. T1212 and D4 showed 50% and 100% match with the phenotype, respectively. D4, a CAPS, was converted to a high resolution melting (HRM) marker and tested on 55 breeding lines from private seed companies (Fig.3). All breeding lines showed the HRM genotype for resistance allele, indicating that D4 can be useful for selecting FORL-resistance tomato plants.

Fresh market tomato cultivars are divided largely based on fruit color appearance (red or pink), which is attributed by the trait of peel. It had been reported that mutation of the Slmyb12 gene suppresses synthesis of yellow-colored flavonoid (naringenin chalcone) in peel and causes pinkish tomato fruit. Whereas wild-type tomato plants synthesizing naringenin chalcone produce yellow-colored peel, which resulting in the fruit appearance to be red. The present study was performed to investigate the association between the Slmyb12 and fruit color of domestic tomato inbreed lines. A SCAR marker was developed from an Indel mutation site (72bp insertion in exon3) of the Slmyb12, and tested on 22 and 18 red and pink-fruited inbred lines, respectively. Unexpectedly, the results showed that all inbred lines tested had wild-type Slmyb12. The full length sequences of the Slmyb12 were cloned from two inbred lines (FCR1 and FCP1), but the sequence alignment did not identify any nucleotide variations within this gene. Furthermore, scanning of SNPs between FCR1 and FCP1 using SolCAP Tomato SNP array) found no SNPs for Slmyb12. To delimit the genomic region of the gene conferring fruit color of domestic tomato lines, we are analyzing SNPs in the genes adjacent to the Slmyb12 using an F2 population derived from FCR1 x FCP1. So far, one SNP located at 1,750kbp downstream from the stop codon of Slmyb12 was mapped using 54 F2 plants and 83% of phenotype-marker association was revealed, demonstrating that the fruit color is controlled bySlmyb12 indeed, or other neighboring gene(s) involved in the pathway of naringenin chalcone synthesis. Further study with more SNPs will clear up this question.

Most of the melon(Cucumis melo L.) breeding lines in Korea show andromonoecious (male-perfect flowers) sex expression, which requires laborious hand emasculation to produce the F1 seeds. There is a high demand for developing monoecious (male-female flowers) elite germplasm. The present study was carried out to develop molecular markers for selecting monoecious plants based on the CmACS-7 gene [a locus with 1-aminocyclopropane-1-carboxylic acid synthase(ACS) activity] responsible for ethylene synthesis and sex determination in melon. The full length sequences of the CmACS-7 were cloned from a monoecious inbred ‘Mo23’ and an andromonoecious inbred ‘Am24’. Sequence alignment revealed a major SNP(C170T) in exon1 and 18bp indel in intron4 of the CmACS-7, and a CAPS (SNP-C170T) and SCAR (ID4-18) were developed from the SNP and indel, respectively. A total of 453 F2 plants derived from ‘Mo23’ x ‘Am24’ were determined for their sex expression and genotyped using the SCAR marker. A Mendelian ratio of 3(monoecy): 1(andromonoecy) was observed from the F2 population, and sex type of 449 plants (except for four plants that showed incomplete monoecy) cosegregated with the SCAR marker, demonstrating that CmACS-7 is a single dominant gene conferring monoecy of ‘Mo23’. Allele variation of the CmACS-7 was evaluated by genotyping 114 melon accessions with diverse geographical origins using the CAPS and SCAR. C170T-SNP in exon1 of the CmACS-7 was highly conserved in melon germplasm and perfectly matched with the phenotype, whereas the 18bp-indel mutation in intron4 existed in various forms. The results demonstrated that CAPS marker SNP-C170T can be useful for marker-assisted selection(MAS) of monoecious melon plants