Fibroblast function recovery through rejuvenation effect of nanovesicles extracted from human adipose-derived stem cells irradiated with red light.

Fibroblasts (hDFs) are widely employed for skin regeneration and the treatment of various skin disorders, yet research were rarely investigated about restoration of diminished therapeutic efficacy due to cell senescence. The application of stem cell and stem cell-derived materials, exosomes, were drawn attention for the restoration functionality of fibroblasts, but still have limitation for unintended side effect or low yield. To advance, stem cell-derived nanovesicle (NV) have developed for effective therapeutic reagents with high yield and low risk. In this study, we have developed a method using red light irradiated human adipose-derived stem cells (hADSCs) derived NV (R-NVs) for enhancing the therapeutic efficacy and rejuvenating hDFs. Through red light irradiation, we were able to significantly increase the content of stemness factors and angiogenic biomolecules in R-NVs. Treatment with these R-NVs was found to enhance the migration ability and leading to rejuvenation of old hDFs to levels similar to those of young hDFs. In subsequent in vivo experiments, the treatment of old hDFs with R-NVs demonstrated a superior skin wound healing effect, surpassing that of young hDFs. In summary, this study successfully induced rejuvenation and leading to increased therapeutic efficacy to R-NVs treated old hDFs previously considered as biowaste.

Enhancing viability and angiogenic efficacy of mesenchymal stem cells via HSP90α and HSP27 regulation based on ROS stimulation for wound healing.

Light-based therapy has been reported as a potential preconditioning strategy to induce intracellular reactive oxygen species (ROS) signaling and improve the angiogenic properties of various types of cells. However, bio-stimulation mechanisms of light therapy in terms of ROS-heat shock proteins (HSPs) mediated anti-apoptotic and angiogenic pathways in human adult stem cells have not been fully delineated yet. Commonly used light sources such as light-emitting diode (LED) and laser are accompanied by drawbacks, such as phototoxicity, thermal damage, and excessive ROS induction, so the role and clinical implications of light-induced HSPs need to be investigated using a heat-independent light source. Here, we introduced organic LED (OLED) at 610 nm wavelength as a new light source to prevent thermal effects from interfering with the expression of HSPs. Our results showed that light therapy using OLED significantly upregulated anti-apoptotic and angiogenic factors in human bone marrow mesenchymal stem cells (hMSCs) at both gene and protein levels via the activation of HSP90α and HSP27, which were stimulated by ROS. In a mouse wound-closing model, rapid recovery and improved re-epithelization were observed in the light-treated hMSCs transplant group. This study demonstrates that the upregulation of Akt (protein kinase B)-nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling, caused by HSP90α and HSP27 expression, is the mechanism behind the anti-apoptotic and angiogenic effects of OLED treatment on stem cells.

QTL mapping and improvement of pre-harvest sprouting resistance using japonica weedy rice.

The stability of cultivation and production in terms of crop yield has been threatened by climate change due to global warming. Pre-harvest sprouting (PHS) is a threat to crops, especially staple foods, including rice, because of reductions in yield and quality. To address the problem of precocious germination before harvest, we performed quantitative trait loci (QTL) analysis for PHS using F8 RILs populations derived from japonica weedy rice in Korea. QTL analysis revealed that two stable QTLs, qPH7 and qPH2, associated with PHS resistance were identified on chromosomes 7 and 2, respectively, explaining approximately 38% of the phenotypic variation. The QTL effect in the tested lines significantly decreased the degree of PHS, based on the number of QTLs included. Through fine mapping for main QTL qPH7, the region for the PHS was found to be anchored within 23.575-23.785 Mbp on chromosome 7 using 13 cleaved amplified sequence (CAPS) markers. Among 15 open reading frames (ORFs) within the detected region, one ORF, Os07g0584366, exhibited upregulated expression in the resistant donor, which was approximately nine times higher than that of susceptible japonica cultivars under PHS-inducing conditions. Japonica lines with QTLs related to PHS resistance were developed to improve the characteristics of PHS and design practical PCR-based DNA markers for marker-assisted backcrosses of many other PHS-susceptible japonica cultivars.

Various Three-Dimensional Culture Methods and Cell Types for Exosome Production.

Cell-based therapies have been used as promising treatments for several untreatable diseases. However, cell-based therapies have side effects such as tumorigenesis and immune responses. To overcome these side effects, therapeutic effects of exosomes have been researched as replacements for cell-based therapies. In addition, exosomes reduced the risk that can be induced by cell-based therapies. Exosomes contain biomolecules such as proteins, lipids, and nucleic acids that play an essential role in cell-cell and cell-matrix interactions during biological processes. Since the introduction of exosomes, those have been proven perpetually as one of the most effective and therapeutic methods for incurable diseases. Much research has been conducted to enhance the properties of exosomes, including immune regulation, tissue repair, and regeneration. However, yield rate of exosomes is the critical obstacle that should be overcome for practical cell-free therapy. Three-dimensional (3D) culture methods are introduced as a breakthrough to get higher production yields of exosomes. For example, hanging drop and microwell were well known 3D culture methods and easy to use without invasiveness. However, these methods have limitation in mass production of exosomes. Therefore, a scaffold, spinner flask, and fiber bioreactor were introduced for mass production of exosomes isolated from various cell types. Furthermore, exosomes treatments derived from 3D cultured cells showed enhanced cell proliferation, angiogenesis, and immunosuppressive properties. This review provides therapeutic applications of exosomes using 3D culture methods.

Identification of Potential QTLs Related to Grain Size in Rice.

Rice is a major crop, providing calories and food for most of the world's population. Currently, the global population is rapidly increasing, and securing a yield of rice that can satisfy everyone is an ongoing challenge. The yield of rice can be increased by controlling 1000-grain weight as one of the important determining factors. Grain length, grain width, grain thickness, and 1000-grain weight, which determine grain size, are controlled by QTLs. To identify QTLs related to grain size, we screened and then mapped 88 RIL individuals derived from a cross between JJ625LG, which has a long grain size, long spindle-shaped grains, and low 1000-grain weight, and Namchan, which has short grains with round shape and heavy 1000-grain weight. In 2021 and 2022, 511 SNP markers were used to map QTLs related to grain size to a physical map. The QTLs found to be related to grain size are evenly distributed on chromosomes 2, 3, 5, 10, and 11. The mapping results also show that the QTLs qGl3-2, qRlw3, and qRlw3-2 of chromosome 3, and qGt5 and qRlw5 of chromosome 5 are, respectively, associated with GS3 and qSW5, which are the major genes previously cloned and found to be related to grain size. In addition, qGw10 and qGw10-1, which were additionally detected in this study, were found to be associated with Os10g0525200 (OsCPq10), a potential candidate gene involved in controlling grain size. This gene codes for a cytochrome P450 family protein and is reported to have a positive effect on grain size by interacting with proteins related to mechanisms determining grain size. In particular, OsCPq10 was screened in the same identified QTL region for 2 consecutive years, which is expected to have a positive effect on grain size. These results will be helpful for breeding elite rice cultivars with high yields through additional fine mapping related to grain size.

Subaqueous 3D stem cell spheroid levitation culture using anti-gravity bioreactor based on sound wave superposition.

BACKGROUND: Recently, various studies have revealed that 3D cell spheroids have several advantages over 2D cells in stem cell culture. However, conventional 3D spheroid culture methods have some disadvantages and limitations such as time required for spheroid formation and complexity of the experimental process. Here, we used acoustic levitation as cell culture platform to overcome the limitation of conventional 3D culture methods. METHODS: In our anti-gravity bioreactor, continuous standing sonic waves created pressure field for 3D culture of human mesenchymal stem cells (hMSCs). hMSCs were trapped and aggerated in pressure field and consequently formed spheroids. The structure, viability, gene and protein expression of spheroids formed in the anti-gravity bioreactor were analyzed by electron microscope, immunostaining, polymerase chain reaction, and western blot. We injected hMSC spheroids fabricated by anti-gravity bioreactor into the mouse hindlimb ischemia model. Limb salvage was quantified to evaluate therapeutic efficacy of hMSC spheroids. RESULTS: The acoustic levitation in anti-gravity bioreactor made spheroids faster and more compact compared to the conventional hanging drop method, which resulted in the upregulation of angiogenic paracrine factors of hMSCs, such as vascular endothelial growth factor and angiopoietin 2. Injected hMSCs spheroids cultured in the anti-gravity bioreactor exhibited improved therapeutic efficacy, including the degree of limb salvage, capillary formation, and attenuation of fibrosis and inflammation, for mouse hindlimb ischemia model compared to spheroids formed by the conventional hanging drop method. CONCLUSION: Our stem cell culture system using acoustic levitation will be proposed as a new platform for the future 3D cell culture system.

Application of a Novel Quantitative Trait Locus Combination to Improve Grain Shape without Yield Loss in Rice (Oryza sativa L. spp. japonica).

Grain shape is one of the key factors deciding the yield product and the market value as appearance quality in rice (Oryza sativa L.). The grain shape of japonica cultivars in Korea is quite monotonous because the selection pressure of rice breeding programs works in consideration of consumer preference. In this study, we identified QTLs associated with grain shape to improve the variety of grain shapes in Korean cultivars. QTL analysis revealed that eight QTLs related to five tested traits were detected on chromosomes 2, 5, and 10. Among them, three QTLs-qGL2 (33.9% of PEV for grain length), qGW5 (64.42% for grain width), and qGT10 (49.2% for grain thickness)-were regarded as the main effect QTLs. Using the three QTLs, an ideal QTL combination (qGL2P + qGW5P + qGT10B) could be constructed on the basis of the accumulated QTL effect without yield loss caused by the change in grain shape in the population. In addition, three promising lines with a slender grain type were selected as a breeding resource with a japonica genetic background based on the QTL combination. The application of QTLs detected in this study could improve the grain shape of japonica cultivars without any linkage drag or yield loss.

Silica-Based Advanced Nanoparticles For Treating Ischemic Disease.

Recently, various attempts have been made to apply diverse types of nanoparticles in biotechnology. Silica nanoparticles (SNPs) have been highlighted and studied for their selective accumulation in diseased parts, strong physical and chemical stability, and low cytotoxicity. SNPs, in particular, are very suitable for use in drug delivery and bioimaging, and have been sought as a treatment for ischemic diseases. In addition, mesoporous silica nanoparticles have been confirmed to efficiently deliver various types of drugs owing to their porous structure. Moreover, there have been innovative attempts to treat ischemic diseases using SNPs, which utilize the effects of Si ions on cells to improve cell viability, migration enhancement, and phenotype modulation. Recently, external stimulus-responsive treatments that control the movement of magnetic SNPs using external magnetic fields have been studied. This review addresses several original attempts to treat ischemic diseases using SNPs, including particle synthesis methods, and presents perspectives on future research directions.

Characterization and QTL Mapping of a Major Field Resistance Locus for Bacterial Blight in Rice.

Bacterial blight (BB) disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), is among the major factors that can cause rice yields to decrease. To address BB disease, researchers have been looking for ways to change pesticides and cultivation methods, but developing resistant cultivars is the most effective method. However, the resistance and genetic factors of cultivars may be destroyed due to the emergence of new Xoo species caused by recent and rapid climate changes. Therefore, breeders need to identify resistance genes that can be sustained during unpredictable climate changes and utilized for breeding. Here, qBBR11, a quantitative trait locus (QTL) for resistance to BB disease, was detected in KJ (Korea Japonica varieties) 11_067 to KJ11_068 on chromosome 11 in a population derived by crossing JJ (Jeonju) 623 and HR(High resistant)27,195, which possess similar genetic backgrounds but different degrees of resistance to BB disease. qBBR11 was reduced from 18.49-18.69 Mbp of chromosome 11 to 200 kbp segment franked. In this region, 16 candidate genes were detected, and we identified 24 moderate-impact variations and four high-impact variations. In particular, high-impact variations were detected in Os11g0517800 which encode the domain region of GCN2 which is the eIF-2-alpha kinase associated with the resistance of abiotic/biotic stress in rice. In JJ623, which is moderately resistant to BB disease, a stop codon was created due to single nucleotide polymorphism (SNP). Therefore, compared with HR27195, JJ623 has weaker resistance to BB disease, though the two have similar genetic backgrounds. The results suggest that variation in the qBBR11 region regulates an important role in improving resistance to BB diseases, and qBBR11 is useful in providing an important resource for marker-assisted selection to improve mechanisms of resistance to BB disease.

Effect of polystyrene nanoplastics and their degraded forms on stem cell fate.

Several studies have examined the effects of micro- and nanoplastics on microbes, cells, and the environment. However, only a few studies have examined their effects-especially, those of their reduced cohesiveness-on cell viability and physiology. We synthesized surfactant-free amine-functionalized polystyrene (PS) nanoparticles (NPs) and PS-NPs with decreased crosslinking density (DPS-NPs) without changing other factors, such as size, shape, and zeta potential and examined their effects on cell viability and physiology. PS- and DPS-NPs exhibited reactive oxygen species (ROS) scavenging activity by upregulating GPX3 expression and downregulating HSP70 (ROS-related gene) and XBP1 (endoplasmic reticulum stress-related gene) expression in human bone marrow-derived mesenchymal stem cells (hBM-MSCs). Additionally, they led to upregulation of MFN2 (mitochondrial fusion related gene) expression and downregulation of FIS1 (mitochondrial fission related gene) expression, indicating enhanced mitochondrial fusion in hBM-MSCs. Cell-cycle analysis revealed that PS- and DPS-NPs increased the proportion of cells in the S phase, indicating that they promoted cell proliferation and, specifically, the adipogenic differentiation of hBM-MSCs. However, the cytotoxicity of DPS-NPs against hBM-MSCs was higher than that of PS-NPs after long-term treatment under adipogenic conditions.

Identification of QTL Combinations that Cause Spikelet Sterility in Rice Derived from Interspecific Crosses.

BACKGROUND: The exploitation of useful genes through interspecific and intersubspecific crosses has been an important strategy for the genetic improvement of rice. Postzygotic reproductive isolation routinely occurs to hinder the growth of pollen or embryo sacs during the reproductive development of the wide crosses. RESULT: In this study, we investigated the genetic relationship between the hybrid breakdown of the population and transferred resistance genes derived from wide crosses using a near-isogenic population composed of 225 lines. Five loci (qSS12, qSS8, qSS11, ePS6-1, and ePS6-2) associated with spikelet fertility (SF) were identified by QTL and epistatic analysis, and two out of five epistasis interactions were found between the three QTLs (qSS12, qSS8 and qSS11) and background marker loci (ePS6-1 and ePS6-2) on chromosome 6. The results of the QTL combinations suggested a genetic model that explains most of the interactions between spikelet fertility and the detected loci with positive or negative effects. Moreover, the major-effect QTLs, qSS12 and qSS8, which exhibited additive gene effects, were narrowed down to 82- and 200-kb regions on chromosomes 12 and 8, respectively. Of the 13 ORFs present in the target regions, Os12g0589400 and Os12g0589898 for qSS12 and OS8g0298700 for qSS8 induced significantly different expression levels of the candidate genes in rice at the young panicle stage. CONCLUSION: The results will be useful for obtaining a further understanding of the mechanism causing the hybrid breakdown of a wide cross and will provide new information for developing rice cultivars with wide compatibility.

Bulk Nanoencapsulation of Phase Change Materials (PCMs) via Spontaneous Spreading of a UV-Curable Prepolymer.

Phase change materials (PCMs) have received considerable attention for various latent heat storage systems for efficient thermal energy utilization. Herein, a facile and fast method for the bulk nanoencapsulation of organic PCMs is proposed, based on the thermodynamically spontaneous spreading phenomenon of three immiscible liquid phases. In this approach, a complete engulfing of PCM nanodroplets (core phase) by immiscible prepolymer droplets (coating phase), both of which are bulk-dispersed in another immiscible medium (continuous phase), is thermodynamically driven by the relation between the surface energies of the core, coating, and continuous phases. To demonstrate the proposed method, melted n-docosane (PCM, core phase) nanodroplets are completely engulfed within a couple of minutes by immiscible polyethylene glycol diacrylate (PEGDA, coating phase) in an aqueous poly(vinyl alcohol) solution (continuous phase), and the PEGDA layer quickly cross-linked upon UV irradiation to form a rigid shell protecting the PCM core. As-produced PCM nanocapsules display promising heat storage and release performances as well as high durability in repeated heating-cooling cycles in both dry and wet states. The proposed process may serve as a useful platform for bulk production of PCM nanocapsules with various core and shell compositions in a facile, fast, and scalable way.

Yield Stress Enhancement of a Ternary Colloidal Suspension via the Addition of Minute Amounts of Sodium Alginate to the Interparticle Capillary Bridges.

Capillary suspensions are ternary solid-liquid-liquid systems produced via the addition of a small amount of secondary fluid to the bulk fluid that contained the dispersed solid particles. The secondary fluid could exert strong capillary forces between the particles and dramatically change the rheological properties of the suspension. So far, research has focused on capillary suspensions that consist of additive-free fluids, whereas capillary suspensions with additives, particularly those of large molecular weight that are highly relevant for industrial purposes, have been relatively less studied. In this study, we performed a systematic analysis of the properties of capillary suspensions that consist of paraffin oil (bulk phase), water (secondary phase), and α-Al2O3 microparticles (particle phase), in which the aqueous secondary phase contained an important eco-friendly polymeric binder, sodium alginate (SA). It was determined that the yield stress of the suspension increased significantly with the increase in the SA content in the aqueous secondary phase, which was attributed to the synergistic effect of the capillary force and hydrogen bonding force that may be related to the increase in the number of capillary bridges. The amounts of SA used to induce a significant change in the yield stress in this study were very small (<0.02% of the total sample volume). The addition of Ca2+ ions to the SA-containing secondary phase further increased the yield stress with possible gelation of the SA chains-in the presence of excess Ca2+ ions, however, the yield stress decreased because of the microscopic phase separation that occurred in the aqueous secondary phase. The microstructures of the sintered porous materials that were produced by using capillary suspensions as precursors were qualitatively well correlated to the rheological behavior of the precursor suspensions, suggesting a new method for the subtle control of the microstructures of porous materials using the addition of minute amounts of polymeric additives.

QTL mapping for pre-harvest sprouting resistance in japonica rice varieties utilizing genome re-sequencing.

Pre-harvest sprouting (PHS) leads to serious economic losses because of reductions in yield and quality. To analyze the quantitative trait loci (QTLs) for PHS resistance in japonica rice, PHS rates on panicles were measured in 160 recombinant inbred lines (RILs) derived from a cross between the temperate japonica varieties Odae (PHS resistant) and Unbong40 (PHS susceptible) under two different environmental conditions-field (summer) and greenhouse (winter) environments. Genome re-sequencing of the parental varieties detected 266,773 DNA polymorphisms including 248,255 single nucleotide polymorphisms and 18,518 insertions/deletions. We constructed a genetic map comprising 239 kompetitive allele-specific PCR and 49 cleaved amplified polymorphic sequence markers. In the field environment, two major QTLs, qPHS-3FD and qPHS-11FD, were identified on chromosomes 3 and 11, respectively, whereas three major QTLs, qPHS-3GH, qPHS-4GH, and qPHS-11GH, were identified on chromosomes 3, 4, and 11, respectively, in the greenhouse environment. qPHS-11GH and qPHS-11FD had similar locations on chromosome 11, suggesting the existence of a gene conferring stable PHS resistance effects under different environmental conditions. The QTLs identified in this study can be used to improve the PHS resistance of japonica varieties, and they may improve our understanding of the genetic basis of PHS resistance.

Improving the Glossiness of Cooked Rice, an Important Component of Visual Rice Grain Quality.

BACKGROUND: Rice is one of the few cereals consumed as a whole grain, and therefore the appearance of the final milled product, both before and after cooking, strongly influences the consumer's perception of product quality. Matching consumer preference for rice grain quality is a key component of rice variety development programs, as the quality drives demand, which in turn drives variety adoption, market price, and profitability. The quality of cooked rice is normally evaluated indirectly, through measurement of key elements driving quality as well as more directly by sensory evaluation, but remains a complex trait conditioned by the genetic complexity of factors driving quality, changes wrought by environment, and the complexity of consumer preferences. RESULT: In this study, we evaluated 17 traits, including the taste value obtained by glossiness of cooked rice (TV), to explain rice eating quality by statistical methods and identified QTLs associated with TV. To explain the correlation among traits, exploratory factor analysis was performed for 2 years. The overall eating quality (OE) was correlated with TV and protein content loading at the same factor (PA1) in 2017, and there was a relationship between the OE (PA1) and the TV (PA2) in 2018 (PA1:PA2, r = 0.3). In QTL analysis using 174 RILs, three QTLs for TV derived from Wandoaengmi6 were detected on chromosomes 4, 6, and 9. The QTL qTV9 delimited within Id9007180 and 9,851,330 on chromosome 9 was detected in both years, explaining approximately 17% of the variation, on average. Through the use of fine mapping, qTV9 was delimited to an approximately 34-Kbp segment flanked by the DNA markers CTV9_9 and CTV9_13, and nine ORFs were listed in the target region as candidate genes associated with TV. In the evaluation of qTV9's effect on OE, the lines with qTV9 showed a significant increase in correlation coefficiency compared to the negative lines. These data will apply to functional analysis on the glossiness and the MAS breeding program to improve the eating quality of japonica as a donor line. CONCLUSION: In this paper we report a number of QTL associated with changes in glossiness of cooked rice, and these may have utility in the development of MAS in breeding programs with a specific focus on cooked grain quality.

Gold Binding Peptide Identified from Microfluidic Biopanning: An Experimental and Molecular Dynamics Study.

Biopanning refers to the processes of screening peptides with a high affinity to a target material. Microfluidic biopanning has advantages compared to conventional biopanning which requires large amounts of the target material and involves inefficient multiple pipetting steps to remove nonspecific or low-affinity peptides. Here, we fabricate a microfluidic biopanning system to identify a new gold-binding peptide (GBP). A polydimethylsiloxane microfluidic device is fabricated and bonded to a glass slide with a gold pattern that is deposited by electron-beam evaporation. The microfluidic biopanning system can provide high adjustability in the washing step during the biopanning process because the liquid flow rate and the resulting shear stress can be precisely controlled. The surface plasmon resonance analysis shows that the binding affinity of the identified GBP is comparable to previously reported GBPs. Moreover, molecular dynamics simulations are performed to understand its binding affinity against the gold surface in detail. Theoretical calculations suggest that the association and dissociation rates of the GBPs depend on their sequence-dependent conformations and interactions with the gold surface. These findings provide insight into designing efficient biopanning tools and peptides with a high affinity for various target materials.

Pyramiding of two rice bacterial blight resistance genes, Xa3 and Xa4, and a closely linked cold-tolerance QTL on chromosome 11.

KEY MESSAGE: We fine mapped the Xa4 locus and developed a pyramided rice line containing Xa3 and Xa4 R - alleles and a cold-tolerance QTL. This line will be valuable in rice breeding. Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a destructive disease of cultivated rice. Pyramiding BB resistance genes is an essential approach for increasing the resistance level of rice varieties. We selected an advanced backcross recombinant inbred line 132 (ABL132) from the BC3F7 population derived from a cross between cultivars Junam and IR72 by K3a inoculation and constructed the mapping population (BC4F6) to locate the Xa4 locus. The Xa4 locus was found to be delimited within a 60-kb interval between InDel markers InDel1 and InDel2 and tightly linked with the Xa3 gene on chromosome 11. After cold (4 °C) treatment, ABL132 with introgressions of IR72 in chromosome 11 showed lower survival rate, chlorophyll content, and relative water content compared to Junam. Genetic analysis showed that the cold stress-related quantitative trait locus (QTL) qCT11 was located in a 1.3-Mb interval close to the Xa4 locus. One line, ABL132-36, containing the Xa3 resistance allele from Junam, the Xa4 resistance allele from IR72, and the cold-tolerance QTL from Junam (qCT11), was developed from a BC4F6 population of 250 plants. This is the first report on the pyramiding of Xa3 and Xa4 genes with a cold-tolerance QTL. This region could provide a potential tool for improving resistance against BB and low-temperature stress in rice-breeding programs.

Development of breeding lines with three pyramided resistance genes that confer broad-spectrum bacterial blight resistance and their molecular analysis in rice.

BACKGROUND: The development of resistant cultivars has been the most effective and economical strategy to control bacterial leaf blight (BB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). Molecular markers have made it possible to identify and pyramid valuable genes of agronomic importance in resistance rice breeding. In this study, three resistance genes (Xa4 + xa5 + Xa21) were transferred from an indica donor (IRBB57), using a marker-assisted backcrossing (MAB) breeding strategy, into a BB-susceptible elite japonica rice cultivar, Mangeumbyeo, which is high yielding with good grain quality. RESULTS: Our analysis led to the development of three elite advanced backcross breeding lines (ABL) with three resistance genes by foreground and phenotypic selection in a japonica genetic background without linkage drag. The background genome recovery of the ABL expressed more than 92.1% using genome-wide SSR marker analysis. The pathogenicity assays of three resistance-gene-derived ABL were conducted under glasshouse conditions with the 18 isolates of Xoo prevalent in Korea. The ABL exhibited very small lesion lengths, indicating a hypersensitive reaction to all 18 isolates of Xoo, with agronomic and grain quality traits similar to those of the recurrent parent. Pyramiding the resistance genes Xa4, xa5 and Xa21 provided a higher resistance to Xoo than the introduction of the individual resistance genes. Additionally, the combination of two dominant and one recessive BB resistance gene did not express any negative effect on agronomic traits in the ABL. CONCLUSIONS: The strategy of simultaneous foreground and phenotypic selection to introduce multiple R genes is very useful to reduce the cost and the time required for the isolation of desirable recombinants with target resistance genes in rice. The resistance-gene-derived ABL have practical breeding value without a yield penalty by providing broad-spectrum resistance against most of the existing isolates of BB in South Korea and will have a high impact on the yield stability and sustainability of rice productivity.