Introgression of bacterial leaf blight (BLB) resistant gene, Xa7 into MARDI elite variety, MR219 by marker assisted backcrossing (MABC) approach / Introdução do gene resistente à ferragem da folha bacteriana (BLB), xa7 na variedade MARDI elite, MR219 por abordagem de backcrossing assistida por marcador (MABC)

Abstract Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. This disease causes substantial yield loss as high as 70%. Development of rice varieties which inherited BLB resistant traits is a crucial approach to promote and sustain rice industry in Malaysia. Hence, this study aims were to enhance BLB disease resistant characters of high yielding commercial variety MR219 through backcross breeding approach with supporting tool of marker-assisted selection (MAS). Broad spectrum BLB resistance gene, Xa7 from donor parent IRBB7 were introgressed into the susceptible MR219 (recurrent parent) using two flanking markers ID7 and ID15. At BC3F4, we managed to generate 19 introgressed lines with homozygous Xa7 gene and showed resistant characteristics as donor parent when it was challenged with Xanthomonas oryzae pv. oryzae through artificial inoculation. Recurrent parent MR219 and control variety, MR263 were found to be severely infected by the disease. The improved lines exhibited similar morphological and yield performance characters as to the elite variety, MR219. Two lines, PB-2-107 and PB-2-34 were chosen to be potential lines because of their outstanding performances compared to parent, MR219. This study demonstrates a success story of MAS application in development of improved disease resistance lines of rice against BLB disease.

Resumo A mancha bacteriana das folhas (BLB) é uma das principais doenças do arroz na Malásia. Essa doença causa perdas substanciais de rendimento de até 70%. O desenvolvimento de variedades de arroz que herdaram características de resistência ao BLB é uma abordagem crucial para promover e sustentar a indústria do arroz na Malásia. Portanto, o objetivo deste estudo foi aumentar os caracteres BLB resistentes a doenças da variedade comercial MR219 de alto rendimento por meio de uma abordagem de cruzamento retrocruzamento com ferramenta de apoio de seleção assistida por marcador (MAS). O gene de resistência a BLB de amplo espectro, Xa7 do pai doador IRBB7, foi introgressado no MR219 suscetível (pai recorrente) usando dois marcadores flanqueadores ID7 e ID15. No BC3F4, conseguimos gerar 19 linhagens introgressadas com o gene Xa7 homozigoto e apresentamos características de resistência como genitor doador quando desafiado com Xanthomonas oryzae pv. oryzae por inoculação artificial. O pai recorrente MR219 e a variedade controle, MR263, estavam gravemente infectados pela doença. As linhas melhoradas exibiram características morfológicas e de desempenho de rendimento semelhantes às da variedade elite, MR219. Duas linhas, PB-2-107 e PB-2-34, foram escolhidas como linhas potenciais por causa de seus desempenhos excelentes em comparação com a mãe, MR219. Este estudo demonstra uma história de sucesso de aplicação de MAS no desenvolvimento de linhas de arroz melhoradas com resistência a doenças contra a doença BLB.

A Genome-Wide Analysis of the Pentatricopeptide Repeat Protein Gene Family in Two Kiwifruit Species with an Emphasis on the Role of RNA Editing in Pathogen Stress.

Kiwifruit is a perennial fruit tree with high nutritional and economic value; however, various pathogen stresses have resulted in reductions in its yield and quality. Pentatricopeptide repeat proteins (PPRs), characterized by tandem repetitions of 35 amino acid motifs, play roles in RNA editing, mRNA stability, and splicing. They may also regulate plant development and growth. Nevertheless, the roles of PPRs in plant development and disease resistance remain unclear. In this study, we focused on the roles of PPRs in the fruit development and pathogen stress of kiwifruit and conducted a series of analyses of the PPR gene family in two representative kiwifruit species (Actinidia chinensis (Ach) and Actinidia eriantha (Ace)) with markedly different degrees of disease resistance. A total of 497 and 499 PPRs were identified in Ach and Ace, respectively. All the kiwifruit PPRs could be phylogenetically divided into four subfamilies. There were about 40.68% PPRs predicted to be localized to mitochondria or chloroplasts. A synteny analysis showed that the expansion of the kiwifruit PPRs mainly originated from segmental duplication. Based on RNA-seq data from the fruit over 12 periods of development and maturity, a weighted correlation network analysis suggested that two PPRs, Actinidia20495.t1 and Actinidia15159.t1, may be involved in fruit development and maturation. In addition, we observed different responses with respect to the expression of PPRs and RNA editing between resistant and susceptible kiwifruits following infection with pathogenic bacteria, indicating the regulatory role of PPRs in the stress response via the modulation of RNA editing. The differentially expressed upstream transcription factors of the PPRs were further identified; they may regulate resistance adaption by modulating the expression of the PPRs. Collectively, these results suggest that PPRs play roles in the development and disease resistance of kiwifruit and provide candidate genes for further clarifying the resistance mechanisms in kiwifruits.

Overexpression of the First Peanut-Susceptible Gene, AhS5H1 or AhS5H2, Enhanced Susceptibility to Pst DC3000 in Arabidopsis.

Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (S genes). Here, we characterized two SA hydroxylase genes (AhS5H1 and AhS5H2) as the first S genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of AhS5H1 or AhS5H2 decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each AhS5H gene increased susceptibility to Pst DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of AhS5H genes, AhNPR1 and AhPR10 was simultaneously induced by chitin. Overexpression of each AhS5H in Arabidopsis abolished the induction of AtPR1 or AtPR2 upon chitin treatment. Eventually, AhS5H2 expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of AhS5H1 and AhS5H2 was tissue-specific.

Resistant and Susceptible Pinus thunbergii ParL. Show Highly Divergent Patterns of Differentially Expressed Genes during the Process of Infection by Bursaphelenchus xylophilus.

Pine wilt disease (PWD) is a devastating disease that threatens pine forests worldwide, and breeding resistant pines is an important management strategy used to reduce its impact. A batch of resistant seeds of P. thunbergii was introduced from Japan. Based on the resistant materials, we obtained somatic plants through somatic embryogenesis. In this study, we performed transcriptome analysis to further understand the defense response of resistant somatic plants of P. thunbergii to PWD. The results showed that, after pine wood nematode (PWN) infection, resistant P. thunbergii stimulated more differential expression genes (DEGs) and involved more regulatory pathways than did susceptible P. thunbergii. For the first time, the alpha-linolenic acid metabolism and linoleic acid metabolism were intensively observed in pines resisting PWN infection. The related genes disease resistance protein RPS2 (SUMM2) and pathogenesis-related genes (PR1), as well as reactive oxygen species (ROS)-related genes were significantly up-expressed in order to contribute to protection against PWN inoculation in P. thunbergii. In addition, the diterpenoid biosynthesis pathway was significantly enriched only in resistant P. thunbergii. These findings provided valuable genetic information for future breeding of resistant conifers, and could contribute to the development of new diagnostic tools for early screening of resistant pine seedlings based on specific PWN-tolerance-related markers.

The Detection of Yr Genes in Xinjiang Wheat Cultivars Using Different Molecular Markers.

Wheat stripe rust is a fungal disease caused by Puccinia striiformis f. sp. Tritici (Pst). It significantly impacts wheat yields in Xinjiang, China. Breeding and promoting disease-resistant cultivars carrying disease-resistance genes remains the most cost-effective strategy with which to control the disease. In this study, 17 molecular markers were used to identify Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, Yr26, Yr41, Yr44, and Yr50 in 82 wheat cultivars from Xinjiang. According to the differences in SNP loci, the KASP markers for Yr30, Yr52, Yr78, Yr80, and Yr81 were designed and detected in the same set of 82 wheat cultivars. The results showed that there was a diverse distribution of Yr genes across all wheat cultivars in Xinjiang, and the detection rates of Yr5, Yr15, Yr17, Yr26, Yr41, and Yr50 were the highest, ranging from 74.39% to 98.78%. In addition, Yr5 and Yr15 were prevalent in spring wheat cultivars, with detection rates of 100% and 97.56%, respectively. A substantial 85.37% of wheat cultivars carried at least six or more different combinations of Yr genes. The cultivar Xindong No.15 exhibited the remarkable presence of 11 targeted Yr genes. The pedigree analysis results showed that 33.33% of Xinjiang wheat cultivars shared similar parentage, potentially leading to a loss of resistance against Pst. The results clarified the Yr gene distribution of the Xinjiang wheat cultivars and screened out varieties with a high resistance against Pst.

RNA-Seq and Comparative Transcriptomic Analyses of Asian Soybean Rust Resistant and Susceptible Soybean Genotypes Provide Insights into Identifying Disease Resistance Genes.

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is one of the most destructive foliar diseases that affect soybeans. Developing resistant cultivars is the most cost-effective, environmentally friendly, and easy strategy for controlling the disease. However, the current understanding of the mechanisms underlying soybean resistance to P. pachyrhizi remains limited, which poses a significant challenge in devising effective control strategies. In this study, comparative transcriptomic profiling using one resistant genotype and one susceptible genotype was performed under infected and control conditions to understand the regulatory network operating between soybean and P. pachyrhizi. RNA-Seq analysis identified a total of 6540 differentially expressed genes (DEGs), which were shared by all four genotypes. The DEGs are involved in defense responses, stress responses, stimulus responses, flavonoid metabolism, and biosynthesis after infection with P. pachyrhizi. A total of 25,377 genes were divided into 33 modules using weighted gene co-expression network analysis (WGCNA). Two modules were significantly associated with pathogen defense. The DEGs were mainly enriched in RNA processing, plant-type hypersensitive response, negative regulation of cell growth, and a programmed cell death process. In conclusion, these results will provide an important resource for mining resistant genes to P. pachyrhizi infection and valuable resources to potentially pyramid quantitative resistance loci for improving soybean germplasm.

Activated Expression of Rice DMR6-like Gene OsS3H Partially Explores the Susceptibility to Bacterial Leaf Streak Mediated by Knock-Out OsF3H04g.

Downy Mildew Resistance 6-like (DMR6-like) genes are identified as salicylic acid (SA) hydroxylases and negative regulators of plant immunity. Previously, we identified two rice DMR6-like genes, OsF3H03g, and OsF3H04g, that act as susceptible targets of transcription activator-like effectors (TALEs) from Xanthomonas oryzae pv. oryzicola (Xoc), which causes bacterial leaf streak (BLS) in rice. Furthermore, all four homologs of rice DMR6-like proteins were identified to predominantly carry the enzyme activity of SA 5-hydroxylase (S5H), negatively regulate rice broad-spectrum resistance, and cause the loss of function of these OsDMR6s, leading to increased resistance to rice blast and bacterial blight (BB). Here, we curiously found that an OsF3H04g knock-out mutant created by T-DNA insertion, osf3h04g, was remarkedly susceptible to BLS and BB and showed an extreme reduction in SA content. OsF3H04g knock-out rice lines produced by gene-editing were mildly susceptible to BLS and reduced content of SA. To explore the susceptibility mechanism in OsF3H04g loss-of-function rice lines, transcriptome sequencing revealed that another homolog, OsS3H, had induced expression in the loss-of-function OsF3H04g rice lines. Furthermore, we confirmed that a great induction of OsS3H downstream and genomically adjacent to OsF3H04g in osf3h04g was primarily related to the inserted T-DNA carrying quadruple enhancer elements of 35S, while a slight induction was caused by an unknown mechanism in gene-editing lines. Then, we found that the overexpression of OsS3H increased rice susceptibility to BLS, while gene-editing mediated the loss-of-function OsS3H enhanced rice resistance to BLS. However, the knock-out of both OsF3H04g and OsS3H by gene-editing only neutralized rice resistance to BLS. Thus, we concluded that the knock-out of OsF3H04g activated the expression of the OsS3H, partially participating in the susceptibility to BLS in rice.

Loss of a Premature Stop Codon in the Rice Wall-Associated Kinase 91 (WAK91) Gene Is a Candidate for Improving Leaf Sheath Blight Disease Resistance.

Leaf sheath blight disease (SB) of rice caused by the soil-borne fungus Rhizoctonia solani results in 10-30% global yield loss annually and can reach 50% under severe outbreaks. Many disease resistance genes and receptor-like kinases (RLKs) are recruited early on by the host plant to respond to pathogens. Wall-associated receptor kinases (WAKs), a subfamily of receptor-like kinases, have been shown to play a role in fungal defense. The rice gene WAK91 (OsWAK91), co-located in the major SB resistance QTL region on chromosome 9, was identified by us as a candidate in defense against rice sheath blight. An SNP mutation T/C in the WAK91 gene was identified in the susceptible rice variety Cocodrie (CCDR) and the resistant line MCR010277 (MCR). The consequence of the resistant allele C is a stop codon loss, resulting in an open reading frame with extra 62 amino acid carrying a longer protein kinase domain and additional phosphorylation sites. Our genotype and phenotype analysis of the parents CCDR and MCR and the top 20 individuals of the double haploid SB population strongly correlate with the SNP. The susceptible allele T is present in the japonica subspecies and most tropical and temperate japonica lines. Multiple US commercial rice varieties with a japonica background carry the susceptible allele and are known for SB susceptibility. This discovery opens the possibility of introducing resistance alleles into high-yielding commercial varieties to reduce yield losses incurred by the sheath blight disease.

The cotton miR171a-SCL6 module mediates plant resistance through regulating GhPR1 expression.

Plants have developed intricate defense mechanisms in response to fluctuating environmental cues, including the use of microRNA (miRNA) as post-transcriptional regulators. However, the specific mechanisms through which miRNA contributes to disease resistance remain largely elusive. While the miR171-SCLs have been investigated in an eclectic array of plants, there has been a notable scarcity of research specifically focused on cotton (Gossypium hirsutum). In our previous miRNA-sequencing analysis, we found that ghr-miR171a displayed a differential response to infections by Verticillium dahliae. In this study, we further investigated the function of the miR171a-SCL6 module in cotton during V. dahliae infection. The ghr-miR171a was confirmed to direct the cleavage of GhSCL6 mRNA in the post-transcriptional process, as evidenced by 5' RLM-RACE, ß-glucuronidase (GUS) histochemical staining and enzyme activity assay. Interestingly, we found that overexpressing ghr-miR171a reduced cotton plants' resistance to V. dahliae, while suppressing ghr-miR171a increased the plants' defense capacity. The GhSCL6 protein, when fused with green fluorescent protein (GFP), localizes in the cell nucleus, indicating its potential role in gene regulation. This was further corroborated by yeast two-hybrid assays, which verified GhSCL6's transcriptional activation ability. Through quantitative reverse transcriptase PCR (qRT-PCR), luciferase (LUC) fluorescence, and yeast one-hybrid assays, we found that GhSCL6 binds to the GT-box element of the GhPR1 promoter, activating its expression and thereby enhancing plant disease resistance. Taken together, our findings demonstrate that the cotton miR171a-SCL6 module regulates Verticillium wilt resistance in plants through the post-transcriptional process. This insight may offer new perspectives for disease resistance strategies in cotton.

Uncovering genomic and transcriptional variations facilitates utilization of wild resources in cotton disease resistance improvement.

BACKGROUND: Upland cotton wild/landraces represent a valuable resource for disease resistance alleles. Genetic differentiation between genotypes, as well as variation in Verticillium wilt (VW) resistance, has been poorly characterized for upland cotton accessions on the domestication spectrum (from wild/landraces to elite lines). RESULTS: To illustrate the effects of modern breeding on VW resistance in upland cotton, 37 wild/landraces were resequenced and phenotyped for VW resistance. Genomic patterns of differentiation were identified between wild/landraces and improved upland cotton, and a significant decline in VW resistance was observed in association with improvement. Four genotypes representing different degrees of improvement were used in a full-length transcriptome analysis to study the genetic basis of VW resistance. ROS signaling was highly conserved at the transcriptional level, likely providing the basis for VW resistance in upland cotton. ASN biosynthesis and HSP90-mediated resistance moderated the response to VW in wild/landraces, and loss of induction activity of these genes resulted in VW susceptibility. The observed genomic differentiation contributed to the loss of induction of some important VW resistance genes such as HSP90.4 and PR16. CONCLUSIONS: Besides providing new insights into the evolution of upland cotton VW resistance, this study also identifies important resistance pathways and genes for both fundamental research and cotton breeding.

BrMYB108 confers resistance to Verticillium wilt by activating ROS generation in Brassica rapa.

Increasing plant resistance to Verticillium wilt (VW), which causes massive losses of Brassica rapa crops, is a challenge worldwide. However, few causal genes for VW resistance have been identified by forward genetic approaches, resulting in limited application in breeding. We combine a genome-wide association study in a natural population and quantitative trait locus mapping in an F2 population and identify that the MYB transcription factor BrMYB108 regulates plant resistance to VW. A 179 bp insertion in the BrMYB108 promoter alters its expression pattern during Verticillium longisporum (VL) infection. High BrMYB108 expression leads to high VL resistance, which is confirmed by disease resistance tests using BrMYB108 overexpression and loss-of-function mutants. Furthermore, we verify that BrMYB108 confers VL resistance by regulating reactive oxygen species (ROS) generation through binding to the promoters of respiratory burst oxidase genes (Rboh). A loss-of-function mutant of AtRbohF in Arabidopsis shows significant susceptibility to VL. Thus, BrMYB108 and its target ROS genes could be used as targets for genetic engineering for VL resistance of B. rapa.

Breeding strategies for late blight resistance in potato crop: recent developments.

Late blight (LB) is a serious disease that affects potato crop and is caused by Phytophthora infestans. Fungicides are commonly used to manage this disease, but this practice has led to the development of resistant strains and it also poses serious environmental and health risks. Therefore, breeding for resistance development can be the most effective strategies to control late blight. Various Solanum species have been utilized as a source of resistance genes to combat late blight disease. Several potential resistance genes and quantitative resistance loci (QRLs) have been identified and mapped through the application of molecular techniques. Furthermore, molecular markers closely linked to resistance genes or QRLs have been utilized to hasten the breeding process. However, the use of single-gene resistance can lead to the breakdown of resistance within a short period. To address this, breeding programs are now being focused on development of durable and broad-spectrum resistant cultivars by combining multiple resistant genes and QRLs using advanced molecular breeding tools such as marker-assisted selection (MAS) and cis-genic approaches. In addition to the strategies mentioned earlier, somatic hybridization has been utilized for the development and characterization of interspecific somatic hybrids. To further broaden the scope of late blight resistance breeding, approaches such as genomic selection, RNAi silencing, and various genome editing techniques can be employed. This study provides an overview of recent advances in various breeding strategies and their applications in improving the late blight resistance breeding program.

Development of novel wheat-rye 6RS small fragment translocation lines with powdery mildew resistance and physical mapping of the resistance gene PmW6RS.

KEY MESSAGE: Novel wheat-rye 6RS small fragment translocation lines with powdery mildew resistance were developed, and the resistance gene PmW6RS was physically mapped onto 6RS-0.58-0.66-bin corresponding to 18.38 Mb in Weining rye. Rye (Secale cereale L., RR) contains valuable genes for wheat improvement. However, most of the rye resistance genes have not been successfully used in wheat cultivars. Identification of new rye resistance genes and transfer of these genes to wheat by developing small fragment translocation lines will make these genes more usable for wheat breeding. In this study, a broad-spectrum powdery mildew resistance gene PmW6RS was localized on rye chromosome arm 6RS using a new set of wheat-rye disomic and telosomic addition lines. To further study and use PmW6RS, 164 wheat-rye 6RS translocation lines were developed by 60Coγ-ray irradiation. Seedling and adult stage powdery mildew resistance analysis showed that 106 of the translocation lines were resistant. A physical map of 6RS was constructed using the 6RS translocation and deletion lines, and PmW6RS was localized in the 6RS-0.58-0.66-bin, flanked by markers X6RS-3 and X6RS-10 corresponding to the physical interval of 50.23-68.61 Mb in Weining rye genome. A total of 23 resistance-related genes were annotated. Nine markers co-segregate with the 6RS-0.58-0.66-bin, which can be used to rapidly trace the 6RS fragment carrying PmW6RS. Small fragment translocation lines with powdery mildew resistance were backcrossed with wheat cultivars, and 39 agronomically acceptable homozygous 6RS small fragment translocation lines were obtained. In conclusion, this study not only provides novel gene source and germplasms for wheat resistance breeding, but also laid a solid foundation for cloning of PmW6RS.

The secret password: Cell death-inducing proteins in filamentous phytopathogens - As versatile tools to develop disease-resistant crops.

Cell death-inducing proteins (CDIPs) are some of the secreted effector proteins manifested by filamentous oomycetes and fungal pathogens to invade the plant tissue and facilitate infection. Along with their involvement in different developmental processes and virulence, CDIPs play a crucial role in plant-pathogen interactions. As the name implies, CDIPs cause necrosis and trigger localised cell death in the infected host tissues by the accumulation of higher concentrations of hydrogen peroxide (H2O2), oxidative burst, accumulation of nitric oxide (NO), and electrolyte leakage. They also stimulate the biosynthesis of defense-related phytohormones such as salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), and ethylene (ET), as well as the expression of pathogenesis-related (PR) genes that are important in disease resistance. Altogether, the interactions result in the hypersensitive response (HR) in the host plant, which might confer systemic acquired resistance (SAR) in some cases against a vast array of related and unrelated pathogens. The CDIPs, due to their capability of inducing host resistance, are thus unique among the array of proteins secreted by filamentous plant pathogens. More interestingly, a few transgenic plant lines have also been developed expressing the CDIPs with added resistance. Thus, CDIPs have opened an interesting hot area of research. The present study critically reviews the current knowledge of major types of CDIPs identified across filamentous phytopathogens and their modes of action in the last couple of years. This review also highlights the recent breakthrough technologies in studying plant-pathogen interactions as well as crop improvement by enhancing disease resistance through CDIPs.

An ERAD-related ubiquitin-conjugating enzyme boosts broad-spectrum disease resistance and yield in rice.

Rice is a staple crop for over half of the global population. However, blast disease caused by Magnaporthe orzae can result in more than a 30% loss in rice yield in epidemic years. Although some major resistance genes bolstering blast resistance have been identified in rice, their stacking in elite cultivars usually leads to yield penalties. Here we report that OsUBC45, a ubiquitin-conjugating enzyme functioning in the endoplasmic reticulum-associated protein degradation system, promotes broad-spectrum disease resistance and yield in rice. OsUBC45 is induced upon infection by M. oryzae, and its overexpression enhances resistance to blast disease and bacterial leaf blight by elevating pathogen-associated molecular pattern-triggered immunity (PTI) while nullifying the gene-attenuated PTI. The OsUBC45 overexpression also increases grain yield by over 10%. Further, OsUBC45 enhances the degradation of glycogen synthase kinase 3 OsGSK3 and aquaporin OsPIP2;1, which negatively regulate the grain size and PTI, respectively. The OsUBC45 reported in our study has the potential for improving yield and disease resistance for sustainable rice production.

Genetic analysis of stripe rust resistance in the common wheat line Kfa/2*Kachu under a Chinese rust environment.

KEY MESSAGE: We mapped a new race-specific seedling stripe rust resistance gene on wheat chromosome 5BL and a new APR locus QYr.hazu-2BS from CIMMYT wheat line Kfa/2*Kachu. Breeding resistant wheat (Triticum aestivum) varieties is the most economical and efficient way to manage wheat stripe rust, but requires the prior identification of new resistance genes and development of associated molecular markers for marker-assisted selection. To map stripe rust resistance loci in wheat, we used a recombinant inbred line population generated by crossing the stripe rust-resistant parent 'Kfa/2*Kachu' and the susceptible parent 'Apav#1'. We employed genotyping-by-sequencing and bulked segregant RNA sequencing to map a new race-specific seedling stripe rust resistance gene, which we designated YrK, to wheat chromosome arm 5BL. TraesCS5B02G330700 encodes a receptor-like kinase and is a high-confidence candidate gene for YrK based on virus-induced gene silencing results and the significant induction of its expression 24 h after inoculation with wheat stripe rust. To assist breeding, we developed functional molecular markers based on the polymorphic single nucleotide polymorphisms in the coding sequence region of YrK. We also mapped four adult plant resistance (APR) loci to wheat chromosome arms 1BL, 2AS, 2BS and 4AL. Among these APR loci, we determined that QYr.hazu-1BL and QYr.hazu-2AS are allelic to the known pleiotropic resistance gene Lr46/Yr29/Pm39 and the race-specific gene Yr17, respectively. However, QYr.hazu-2BS is likely a new APR locus, for which we converted closely linked SNP polymorphisms into breeder-friendly Kompetitive allele-specific PCR (KASP) markers. In the present study, we provided new stripe rust resistance locus/gene and molecular markers for wheat breeder to develop rust-resistant wheat variety.

Functional study of BpCOI1 reveals its role in affecting disease resistance in birch.

Plants interact with biotic and abiotic environments. Some of these interactions are detrimental including herbivory consumption and infections by microbial pathogens. The COI1 (coronatine insensitive 1) protein is the master controller of JA-regulated plant responses and plays a regulatory role in the plant defense response. However, there is little information on COI1 function in birch (Betula platyphylla × Betula pendula). Herein, we studied the F-box protein BpCOI1 which is located in the nucleus. To validate the function of this protein, we developed transgenic birch plants with overexpression or repression of BpCOI1 gene. Growth traits, such as tree height, ground diameter, number of lateral branches, did not change significantly among transgenic lines. Alternaria alternata treatment experiments indicated that low expression of BpCOI1 reduced disease resistance in birch. Furthermore, our results showed that low expression of BpCOI1 significantly reduced the sensitivity of plants to exogenous MeJA. Co-expression analysis showed gene expression patterns with similar characteristics. These genes may be closely related in function, or members involved in the same signaling pathway or physiological process with BpCOI 1. The results of transcriptome sequencing and co-expression analysis showed that BpCOI1 affects plant defense against Alternaria alternata by regulating jasmonates. This study reveals the role of BpCOI1 in disease resistance and proposes the possibility of controlling diseases through molecular breeding in birch.

Genome-wide association study of resistance to anthracnose in pepper (Capsicum chinense) germplasm.

BACKGROUND: Anthracnose is a fungal disease caused by Colletotrichum spp. that has a significant impact on worldwide pepper production. Colletotrichum scovillei is the most common pathogenic anthracnose-causing species in the Republic of Korea. RESULTS: The resistances of 197 pepper (Capsicum chinense) accessions deposited in Korea's National Agrobiodiversity Center were evaluated for their response against the virulent pathogens Colletotrichum acutatum isolate 'KSCa-1' and C. scovillei isolate 'Hana') in the field and in vitro methods for three consecutive years (2018 to 2020). The severity of the disease was recorded and compared between inoculation methods. Six phenotypically resistant pepper accessions were selected based on three years of disease data. All of the selected resistant pepper accessions outperformed the control resistant pepper in terms of resistance (PI 594,137). A genome-wide association study (GWAS) was carried out to identify single nucleotide polymorphisms (SNPs) associated with anthracnose resistance. An association analysis was performed using 53,518 SNPs and the disease score of the 2020 field and in vitro experiment results. Both field and in vitro experiments revealed 25 and 32 significantly associated SNPs, respectively. These SNPs were found on all chromosomes except Ch06 and Ch07 in the field experiment, whereas in the in vitro experiment they were found on all chromosomes except Ch04 and Ch11. CONCLUSION: In this study, six resistant C. chinense accessions were selected. Additionally, in this study, significantly associated SNPs were found in a gene that codes for a protein kinase receptor, such as serine/threonine-protein kinase, and other genes that are known to be involved in disease resistance. This may strengthen the role of these genes in the development of anthracnose resistance in Capsicum spp. As a result, the SNPs discovered to be strongly linked in this study can be used to identify a potential marker for selecting pepper material resistant to anthracnose, which will assist in the development of resistant varieties.

Mycorrhizal colonization and Streptomyces viridosporus HH1 synergistically up-regulate the polyphenol biosynthesis genes in wheat against stripe rust.

BACKGROUND: Stripe rust is considered one of the most devastating diseases of wheat all over the world, resulting in a high loss in its production. In this study, time-course changes in expression of the polyphenol biosynthesis pathways genes in wheat against stripe rust were investigated. The defense mechanisms triggered by mycorrhizal colonization and/or spraying with Streptomyces viridosporus HH1 against this disease were also investigated. RESULTS: Results obtained revealed that C3H, which is considered the key gene in lignin biosynthesis, was the most expressed gene. Furthermore, most of the chlorogenic acid and flavonoid biosynthesis genes were also overexpressed. Volcano plots of the studied genes reveal that the dual treatment led to a high significant overexpression of 10 out of the 13 studied genes. Heatmap of these genes showed that the most frequent expressed gene in response to all applied treatments along the study period was DFR, the key gene in the biosynthesis of anthocyanidins. Gene co-expression network of the studied genes showed that HQT was the most central gene with respect to the other genes, followed by AN2 and DFR, respectively. Accumulation of different flavonoids and phenolic acids were detected in response to the dual treatment, in particular, cinnamic acid, coumarin, and esculetin, which recorded the highest elevation level recording 1000, 488.23, and 329.5% respectively. Furthermore, results from the greenhouse experiment showed that application of the dual treatment led to an 82.8% reduction in the disease severity, compared with the control treatment. CONCLUSIONS: We can conclude that the biosynthesis of lignin, chlorogenic acid, and flavonoids contributed to the synergistic triggering effect of the dual treatment on wheat resistance to stripe rust.