Microspore culture is a key method for rapid development of genetically uniform lines. In this study, we aimed to identify the critical factors influencing the efficiency of microspore culture in Chinese cabbage (Brassica rapa), which is an important vegetable crop widely cultivated worldwide for its genetic diversity and nutritional value. To this end, we compared the efficiency of microspore embryogenesis across four different Chinese cabbage genotypes. We selected three accessions representing high, medium, and low efficiencies. Flower buds were harvested to examine pollen developmental stages using a light microscope. Unexpectedly, we found that the genotype with the highest efficiency (Wonkyo20044ho) had abnormally shaped microspores and pollen. In contrast, the genotype with the lowest efficiency (Wonkyo20039ho) had fine, normally shaped pollen. An additional experiment was conducted using the Wonkyo20044ho accession. Different bud sizes were harvested from this accession to observe differences in embryogenesis. The results showed that almost all pollen stages of this genotype were suitable for microspore culture. It can be assumed that the genotype is much more critical for microspore culture efficiency than the developmental stage of the pollen. Our results serve as a valuable reference for improved cabbage breeding methods.

Hypoxia caused by water seeding of rice inhibits germination and often leads to serious problems in seedling establishment and early growth. To solve this problem, it is necessary to develop rice cultivars that can stably germinate and grow under anaerobic environments. In this study, we performed QTL analysis on anaerobic germination (AG) tolerance using 139 recombinant inbred lines (RILs) derived from a cross between Milyang23 and Gihobyeo, and identified two QTLs (qAG2.1, qAG2.2) on chromosome 2. The LOD scores at qAG2.1 and qAG2.2 were 3.30 and 5.31, respectively. The phenotypic variances explained by the QTLs were 9.19% and 14.99%, respectively. The japonica cultivar Gihobyeo provided alleles for AG tolerance at both QTLs. While the chromosomal location of qAG2.2 overlapped with previously identified QTLs for AG tolerance, qAG2.1 was detected in a locus that has not been reported previously. The RILs carrying favorable type alleles for the AG tolerance at both QTLs (qAG2.1 + qAG2.2) expressed 41.0% survival rate under the AG condition, which was significantly higher than those of the RILs carrying single QTL, qAG2.1 (22.0%) or qAG2.2 (26.2%). As the favorable alleles for the two QTLs found in this study derived from the japonica cultivar Gihobyeo, it is expected that they would accompany less linkage drag such as shattering and lodging compared to those derived from indica or landraces. The result of this study would provide useful information for improving AG tolerance of japonica rice cultivars that can be used for water seeding cultivation.

Watermelon (Citrullus lanatus) is an economically important vegetable crop all over the world, which has functional compounds such as lycopene and citrulline. Gummy stem blight caused by Didymella bryoniae is one of the most devastative diseases in watermelon. Single nucleotide polymorphisms (SNPs), which are genetic variations occurring between individuals with respect to a single base, were often used to construct genetic linkage maps and develop molecular markers linked to a variety of horticultural traits and resistance to several diseases. In this study, we developed high-resolution melting (HRM) markers based on SNPs generated from NGS resequencing of two parents in watermelon. Plant materials were C. lanatus ‘920533’ (female and susceptible parent), C. amarus ‘PI 189225’ (male and resistant parent), and their F₁ and F₂ progenies. A total of 13.6 Gbp (‘920533’) and 13.1 Gbp (‘PI 189225’) of genomic sequences were obtained using NGS analysis. A total of 6.09 million SNPs between ‘920533’ and ‘PI 189225’ were detected, and 354,860 SNPs were identified as potential HRM primer sets. From these, a total of 330 primer sets for HRM analysis were designed. As a result, a total of 61 HRM markers that have polymorphic melting curves were developed. These HRM markers can be used for the construction of SNP-based linkage maps and for the analysis of quantitative trait loci (QTLs) related to gummy stem blight resistance.