Mlo Gene Research Articles

Gene markers generating polygenic resistance in melon-Fusarium wilt-FOM1.2 interaction pathosystem.

Developing melon genotypes with resistance to Fusarium oxysporum f. sp. Melonis-(FOM) race1.2 is a major goal in any breeding program. In this study, we identified the role of 11 gene markers that contribute to polygenic resistance during the FOM1.2-melon interaction. qRT-PCR analysis elucidated upregulation of candidate marker genes AMT, DXPR, Fom-2, GLUC, GalS, GRF3, MLO, PRK, RuBlsCo, TLP and WRKY in resistant 'Shante-F1' and 'Khatouni', and susceptible 'Shante-T' and 'Shahabadi' at 7, 14 and 21 days post-inoculation (dpi). We also studied changes in defence-related enzyme activity: chitinase (CHI), β-1,3-glucanase (GLU) and peroxidase (POX) in melon roots. AMT, GLUC and DXPR transcripts were upregulatied in leaf and root tissues of the resistant 'Shante-F1' and 'Shahabadi'. Transcript levels for GalS and GRF3 increased 6.77- and 6.83-fold in roots of 'Shante-F1' at 7 dpi, whereas in PRK, TLP and WRKY theye increased by 7.84-, 5.15- and 12.26-fold at 14 dpi, respectively. However, transcript levels increased by 5.18-fold for Fom-2 and 8.46-fold for MLO at 21 dpi. Also, RBC transcript level peaked at 14 dpi with 4.9-fold increase in leaves of resistant genotypes, whereas AMT increased 2.94-fold at 21 dpi, and GLUC and DXPR increased 7.11- and 2.91-fold at 14 dpi in 'Shante-F', respectively. Defence-related-enzyme activity was also upregulated three-fold in resistant varieties. The dynamic shifts in the melon transcriptome induced by FOM1.2 emphasize that resistance mechanisms are predominantly regulated through signalling pathways involving CHI, GLU, and POX defence response. Surprisingly, the AMT gene, basically resistant to downy mildew, Pseudoperonospora cubensis; GLUC, MLO and PRK resistant to powdery mildew (Sphaerotheca fusca); TLP and WRKY resistant to Phytophthora blight (Phytophthora capsici); and GRF3 and RBC resistant to root knot nematodes (Meloidogyne spp.) were upregulated in resistant genotypes, indicating a dual role of these genes in resistance to more than one disease at a time.

Application of bulk segregant RNA-Seq (BSR-Seq) and allele-specific primers to study soybean powdery mildew resistance

BackgroundPowdery mildew (PM) is one of the important soybean diseases, and host resistance could practically contribute to soybean PM management. To date, only the Rmd locus on chromosome (Chr) 16 was identified through traditional QTL mapping and GWAS, and it remains unclear if the bulk segregant RNA-Seq (BSR-Seq) methodology is feasible to explore additional PM resistance that might exist in other varieties.ResultsBSR-Seq was applied to contrast genotypes and gene expressions between the resistant bulk (R bulk) and the susceptible bulk (S bulk), as well as the parents. The ∆(SNP-index) and G’ value identified several QTL and significant SNPs/Indels on Chr06, Chr15, and Chr16. Differentially expressed genes (DEGs) located within these QTL were identified using HISAT2 and Kallisto, and allele-specific primers (AS-primers) were designed to validate the accuracy of phenotypic prediction. While the AS-primers on Chr06 or Chr15 cannot distinguish the resistant and susceptible phenotypes, AS-primers on Chr16 exhibited 82% accuracy prediction with an additive effect, similar to the SSR marker Satt431.ConclusionsEvaluation of additional AS-primers in the linkage disequilibrium (LD) block on Chr16 further confirmed the resistant locus, derived from the resistant parental variety ‘Kaohsiung 11’ (‘KS11’), not only overlaps with the Rmd locus with unique up-regulated LRR genes (Glyma.16G213700 and Glyma.16G215100), but also harbors a down-regulated MLO gene (Glyma.16G145600). Accordingly, this study exemplified the feasibility of BSR-Seq in studying biotrophic disease resistance in soybean, and showed the genetic makeup of soybean variety ‘KS11’ comprising the Rmd locus and one MLO gene.

Computational identification, characterization, and expression analysis of MLO genes in two powdery mildew resistant and susceptible lines of sunflower

Sunflower is one of the major oilseeds producing crops in the world. However, the crop production is affected by powdery mildew in the tropics, caused by a fungal pathogen Golovinomyces latisporus. A step towards developing genetic resistance is by identifying potential genes involved. The MLO genes when silenced provide durable and broad-spectrum resistance. In this study, we identified the MLO gene family in the genome of Sunflower using computational methods. We analyzed the chromosomal distribution, gene structure conserved motifs, and phylogenetic relationship of sunflower MLO genes with MLO genes of other species. A total of 38 MLO genes were identified which are distributed unevenly on the chromosomes with varied intron/exon gene structures. These were phylogenetically distributed into six different groups. The cis elements identified in the promoter region had hormone responsive, stress responsive, development related elements along with transcription factors. We developed recombinant inbred lines by crossing H. annuus and H. praecox (F7 generation). Further, we performed RNAseq analysis of transcriptomes sequenced from powdery mildew infected leaf samples of PMR-16 (resistant) and PMS-27 (susceptible) varieties of the recombinant inbred lines. Expression analysis revealed 12 differentially expressed genes between both varieties. Our results can be used as a reference for future functional studies.

Highly effective mlo-based powdery mildew resistance in hexaploid wheat without pleiotropic effects

Application of the mlo-based resistance in barley against powdery mildew attacks is a major success in crop breeding, since it confers durable disease resistance. Resistance caused by mutations in the Mlo gene seems to be ubiquitous across a range of species. This work addresses the introduction of mlo-based resistance into hexaploid wheat, which is complicated by the occurrence of three homoeologous genes: Mlo-A1, Mlo-B1 and Mlo-D1. EMS-generated mutant plants were screened for mutations in the three homoeologues. We selected and combined 6, 8, and 4 mutations, respectively, to obtain triple homozygous mlo mutant lines. Twenty-four mutant lines showed highly effective resistance towards attack by the powdery mildew pathogen under field conditions. All 18 mutations appeared to contribute to resistance; however, they had different effects on the occurrence of symptoms such as chlorotic and necrotic spots, which are pleiotropic to the mlo-based powdery mildew resistance. We conclude that to obtain highly effective powdery mildew resistance in wheat and to avoid detrimental pleiotropic effects, all three Mlo homoeologues should be mutated; however, at least one of the mutations should be of the weaker type in order to alleviate strong pleiotropic effects from the other mutations.

Functional and evolutionary study of MLO gene family in the regulation of Sclerotinia stem rot resistance in Brassica napus L.

BackgroundOilseed rape (Brassica napus L.) is known as one of the most important oilseed crops cultivated around the world. However, its production continuously faces a huge challenge of Sclerotinia stem rot (SSR), a destructive disease caused by the fungus Sclerotinia sclerotiorum, resulting in huge yield loss annually. The SSR resistance in B. napus is quantitative and controlled by a set of minor genes. Identification of these genes and pyramiding them into a variety are a major strategy for SSR resistance breeding in B. napus.ResultsHere, we performed a genome-wide association study (GWAS) using a natural population of B. napus consisting of 222 accessions to identify BnaA08g25340D (BnMLO2_2) as a candidate gene that regulates the SSR resistance. BnMLO2_2 was a member of seven homolog genes of Arabidopsis Mildew Locus O 2 (MLO2) and the significantly SNPs were mainly distributed in the promoter of BnMLO2_2, suggesting a role of BnMLO2_2 expression level in the regulation of SSR resistance. We expressed BnMLO2_2 in Arabidopsis and the transgenic plants displayed an enhanced SSR resistance. Transcriptome profiling of different tissues of B. napus revealed that BnMLO2_2 had the most expression level in leaf and silique tissues among all the 7 BnMLO2 members and also expressed higher in the SSR resistant accession than in the susceptible accession. In Arabidopsis, mlo2 plants displayed reduced resistance to SSR, whereas overexpression of MLO2 conferred plants an enhanced SSR resistance. Moreover, a higher expression level of MLO2 showed a stronger SSR resistance in the transgenic plants. The regulation of MLO2 in SSR resistance may be associated with the cell death. Collinearity and phylogenetic analysis revealed a large expansion of MLO family in Brassica crops.ConclusionOur study revealed an important role of BnMLO2 in the regulation of SSR resistance and provided a new gene candidate for future improvement of SSR resistance in B. napus and also new insights into understanding of MLO family evolution in Brassica crops.

Genome-wide identification, evolution, and expression analysis of MLO gene family in melon (Cucumis melo L.).

Powdery mildew (PM) is one of the main fungal diseases that appear during the cultivation of the melon fruit crop. Mildew Resistance Locus "O" (MLO) is known as a gene family and has seven conserved transmembrane domains. An induced functional loss of a specific MLO gene could mainly confer PM resistance to melons. However, the genomic structure of MLO genes and its main role in PM resistance still remain unclear in melon. In this study, bioinformatic analysis identified a total of 14 MLO gene family members in the melon genome sequence, and these genes were distributed in an uneven manner on eight chromosomes. The phylogenetic analysis divided the CmMLO genes into five different clades, and gene structural analysis showed that genes in the same clade had similar intron and exon distribution patterns. In addition, by cloning the CmMLO gene sequence in four melon lines, analyzing the CmMLO gene expression pattern after infection, and making microscopic observations of the infection pattern of PM, we concluded that the CmMLO5 (MELO3C012438) gene plays a negative role in regulating PM-resistance in the susceptible melon line (Topmark), and the critical time point for gene function was noticed at 24 and 72 hours after PM infection. The mutational analysis exhibited a single base mutation at 572 bp, which further results in loss of protein function, thus conferring PM resistance in melon. In summary, our research evidence provides a thorough understanding of the CmMLO gene family and demonstrates their potential role in disease resistance, as well as a theoretical foundation for melon disease resistance breeding.

Advances in Durable Resistance to Diseases in Staple Food Crops: A Review

Background: At all stages of their development, plants are in permanent contact with causative agents of various diseases. Mechanisms of disease resistance and its durability in crops largely depend on the pathogen’s lifestyle, namely the nutrition mode and host range. Objective: The objective of this review is to consider the main advances in the production of genotypes with durable disease resistance in the globally important food crops, wheat, rice, and potato, as well as barley. Results: In wheat, durable resistance could be provided by the employment of various adult plant resistance genes against biotrophic pathogens, whose action commonly does not involve hypersensitivity response, as well as major quantitative genes, including mutants of susceptibility alleles, against necrotrophs via marker assisted selection (MAS). In barley, the most prominent example is the gene mlo conferring durable powdery mildew resistance, but it is compromised by higher susceptibility to some necrotrophic fungi. A few genes for broad-spectrum resistance against the rice blast and bacterial blight pathogens confirmed their effectiveness for decades, and they could be combined with effective R genes via MAS. Resistance to late blight of potato is mainly provided by R genes introgressed from wild potato species, which could be pyramided with quantitative trait loci. Genes for extreme resistance to potato viruses derived from related species provide durable and broad-spectrum resistance and could be effectively deployed in potato breeding using MAS. Silencing susceptibility genes by genome editing technologies is the most promising approach to produce plants with durable resistance to many pathogens in the crop species. Genetic transformation with genes for resistance-associated proteins or constructs providing silencing via RNA interference is an effective biotechnological method to generate plants with durable resistance against pathogens, especially viruses. Conclusion: Main advances in the production of crop plants with durable resistance are based on studies of molecular mechanisms of plant immunity and its special features for pathogens with different lifestyles via the use of biotechnological approaches such as MAS for pyramiding of monogenic quantitative resistance genes or qualitative R genes, changes in expression of certain genes associated with resistance, the introduction of transgenes, mutagenesis and genome editing aimed at silencing susceptibility genes.

Barley Ror1 encodes a class XI myosin required for mlo-based broad-spectrum resistance to the fungal powdery mildew pathogen.

Loss-of-function alleles of plant MLO genes confer broad-spectrum resistance to powdery mildews in many eudicot and monocot species. Although barley (Hordeum vulgare) mlo mutants have been used in agriculture for more than 40 years, understanding of the molecular principles underlying this type of disease resistance remains fragmentary. Forward genetic screens in barley have revealed mutations in two Required for mlo resistance (Ror) genes that partially impair immunity conferred by mlo mutants. While Ror2 encodes a soluble N-ethylmaleimide-sensitive factor-attached protein receptor (SNARE), the identity of Ror1, located at the pericentromeric region of barley chromosome 1H, remained elusive. We report the identification of Ror1 based on combined barley genomic sequence information and transcriptomic data from ror1 mutant plants. Ror1 encodes the barley class XI myosin Myo11A (HORVU.MOREX.r3.1HG0046420). Single amino acid substitutions of this myosin, deduced from non-functional ror1 mutant alleles, map to the nucleotide-binding region and the interface between the relay-helix and the converter domain of the motor protein. Ror1 myosin accumulates transiently in the course of powdery mildew infection. Functional fluorophore-labeled Ror1 variants associate with mobile intracellular compartments that partially colocalize with peroxisomes. Single-cell expression of the Ror1 tail region causes a dominant-negative effect that phenocopies ror1 loss-of-function mutants. We define a myosin motor for the establishment of mlo-mediated resistance, suggesting that motor protein-driven intracellular transport processes are critical for extracellular immunity, possibly through the targeted transfer of antifungal and/or cell wall cargoes to pathogen contact sites.

Drought Stress Interacts With Powdery Mildew Infection in Tomato.

Under field conditions, plants are often exposed to more than one stress factor at the same time, and therefore need to adapt to different combinations of stresses. Crosstalk between responses to abiotic and biotic stresses is known to occur, and the interaction between stress responses can be positive or negative. We studied the interaction of drought stress and powdery mildew (PM) infection in tomatoes using near-isogenic tomato lines (NILs) carrying the Ol-1, ol-2, or Ol-4 gene that confers resistance to tomato PM caused by Oidium neolycopersici. Our study demonstrated that drought-induced growth reduction was not further reduced by powdery mildew infection. Drought stress, however, decreased fungal infection in the susceptible genotype Moneymaker (MM) with fungal biomass tending to decrease further as the drought severity increased. Drought stress did not affect PM resistance levels of resistant NIL carrying ol-2 (a mutant of the tomato susceptibility Mlo gene) and Ol-4 an NLR (nucleotide-binding site-LRR) R gene associated with a fast hypersensitivity response (HR) but tended to slightly decrease disease levels of NIL-Ol-1 (no gene characterized yet, associated with a slow HR following PM infection). At the molecular level, genes involved in abscisic acid (ABA), salicylic acid (SA), and ethylene pathways were highly induced under combined stress indicating the involvement of ABA, SA, and ethylene in the crosstalk between abiotic and biotic stress. Messenger RNA expression of the ABA-responsive dehydrin SlTAS14 was induced under drought and combined stress with the highest induction under combined stress, and resistant NIL lines showed higher expression levels than MM. The expression of SlNCED (involved in ABA synthesis) was also upregulated under drought and highly induced under combined stress. Expression levels of pathogen responsive gene SlPR1 (an indicator of the SA pathway) and SlACS (involved in ethylene synthesis) were highly induced under powdery mildew infection in MM and the Ol-1 and were induced the most under combined stress in these lines. Taken together, these findings indicate that drought stress can interact with and influence PM infection in tomatoes in a resistance type-dependent manner. The role of hormonal signaling pathways in the crosstalk between drought stress and PM infection is further discussed.

Identification of barley accessions from the VIR collection carrying the <i>mlo11(cnv2)</i> powdery mildew resistance allele

Background. The search for barley (Hordeum vulgare L.) genotypes that carry effective genes for resistance to powdery mildew agent Blumeria graminis f. sp. hordei is a present-day issue for Russian plant breeding. The mlo11 allele that confers long-term protection of barley against the pathogen is rarely found among the varieties, approved for cultivation in the territory of Russia. There is no information on the occurrence among Russian varieties of another effective allele, mlo11 (cnv2), therefore, the search for its source is a current necessity. Materials and methods. Seven barley accessions from Ethiopia and 7 accessions from Japan have been tested for resistance to the northwestern population of the powdery mildew agent in the field and in laboratory conditions. To identify of the Mlo gene alleles, nucleotide sequences of the Stowaway-MITE (Miniature Inverted-repeat Transposable Elements) and the adjacent promoter fragments were determined. Results. Phytopathological tests in the field and greenhouse conditions, as well as molecular markers were used to study 14 barley accessions from Ethiopia and Japan. According to the preliminary tests, plants were resistant to powdery mildew. The highly effective allele of powdery mildew resistance mlo11 (cnv2) was for the first time identified in four barley accessions from Ethiopia, k-20087, k-20523, k-20524 and k-28126. Under field conditions, adult plants were resistant, and in the greenhouse they were moderately damaged by powdery mildew (1-2 points). The disease symptoms were similar to those described for the sample Eth295, a carrier of the mlo11(cnv2) allele variant: single pustules and the absence of necrotic spots on the leaves. The fragments of Stowaway-MITE and adjacent Mlo 5' promoter sequences were amplified in all 14 accessions. The amplicons were cloned and sequenced. The unique marker SNPs within the MITE and Mlo 5’ promoter sequences, i.e. the substitutions of cytosine by thymine in positions 262 and 452, were found only in k-20087, k-20523, k-20524 and k-28126. These accessions belong to different botanical varieties and differ from each other in a number of morphological features, i.e. they are not duplicates. Conclusions. The genotypes selected as a result of the study can serve as a source of the mlo11(cnv2) allele in breeding powdery mildew-resistant barley varieties.

RACE1, a Japanese Blumeria graminis f. sp. hordei isolate, is capable of overcoming partially mlo-mediated penetration resistance in barley in an allele-specific manner.

Loss-of-function mutation of the MILDEW RESISTANCE LOCUS O (Mlo) gene confers durable and broad-spectrum resistance to powdery mildew fungi in various plants, including barley. In combination with the intracellular nucleotide-binding domain and leucine-rich repeat receptor (NLR) genes, which confer the race-specific resistance, the mlo alleles have long been used in barley breeding as genetic resources that confer robust non-race-specific resistance. However, a Japanese Blumeria graminis f. sp. hordei isolate, RACE1, has been reported to have the potential to overcome partially the mlo-mediated penetration resistance, although this is yet uncertain because the putative effects of NLR genes in the tested accessions have not been ruled out. In this study, we examined the reproducibility of the earlier report and found that the infectious ability of RACE1, which partially overcomes the mlo-mediated resistance, is only exerted in the absence of NLR genes recognizing RACE1. Furthermore, using the transient-induced gene silencing technique, we demonstrated that RACE1 can partially overcome the resistance in the host cells with suppressed MLO expression but not in plants possessing the null mutant allele mlo-5.

Adult resistance genes to barley powdery mildew confer basal penetration resistance associated with broad-spectrum resistance.

Powdery mildew isa major disease of barley (Hordeum vulgare L.) for which breeders have traditionally relied on dominant, pathogen race-specific resistance genes for genetic control. Directional selection pressures in extensive monocultures invariably result in such genes being overcome as the pathogen mutates to evade recognition. This has led to a widespread reliance on fungicides and a single broad-spectrum recessive resistance provided by the mlo gene. The range of resistance genes and alleles found in wild crop relatives and landraces has been reduced in agricultural cultivars through an erosion of genetic diversity during domestication and selective breeding. Three novel major-effect adult plant resistance (APR) genes from landraces, designated Resistance to Blumeria graminis f. sp. hordei (Rbgh1 to Rbgh3), were identified in the terminal regions of barley chromosomes 5HL, 7HS, and 1HS, respectively. The phenotype of the new APR genes showed neither pronounced penetration resistance, nor the spontaneous necrosis and mesophyll cell death typical of mlo resistance, nor a whole epidermal cell hypersensitive response, typical of race-specific resistance. Instead, resistance was localized to the site of attempted penetration in an epidermal cell and was associated with cell wall appositions and cytosolic vesicle-like bodies, and lacked strong induction of reactive oxygen species. The APR genes exhibited differences in vesicle-like body sizes, their distribution, and the extent of localized 3,3-diaminobenzidine staining in individual doubled haploid lines. The results revealed a set of unique basal penetration resistance genes that offer opportunities for combining different resistance mechanisms in breeding programs for robust mildew resistance.

Analysis of allelic variants of RhMLO genes in rose and functional studies on susceptibility to powdery mildew related to clade V homologs

Key messageRose has 19 MLO genes. Of these, RhMLO1 and RhMLO2 were shown to be required for powdery mildew infection, which suggests their potential as susceptibility targets towards disease resistance.Powdery mildew, caused by Podosphaera pannosa, is one of the most serious and widespread fungal diseases for roses, especially in greenhouse-grown cut roses. It has been shown that certain MLO genes are involved in powdery mildew susceptibility and that loss of function in these genes in various crops leads to broad-spectrum, long-lasting resistance against this fungal disease. For this reason, these MLO genes are called susceptibility genes. We carried out a genome-wide identification of the MLO gene family in the Rosa chinensis genome, and screened for allelic variants among 22 accessions from seven different Rosa species using re-sequencing and transcriptome data. We identified 19 MLO genes in rose, of which four are candidate genes for functional homologs in clade V, which is the clade containing all dicot MLO susceptibility genes. We detected a total of 198 different allelic variants in the set of Rosa species and accessions, corresponding to 5–15 different alleles for each of the genes. Some diploid Rosa species shared alleles with tetraploid rose cultivars, consistent with the notion that diploid species have contributed to the formation of tetraploid roses. Among the four RhMLO genes in clade V, we demonstrated using expression study, virus-induced gene silencing as well as transient RNAi silencing that two of them, RhMLO1 and RhMLO2, are required for infection by P. pannosa and suggest their potential as susceptibility targets for powdery mildew resistance breeding in rose.

Europe's Farm to Fork Strategy and Its Commitment to Biotechnology and Organic Farming: Conflicting or Complementary Goals?

The European Commission's Farm to Fork (F2F) strategy, under the European Green Deal, acknowledges that innovative techniques, including biotechnology, may play a role in increasing sustainability. At the same time, organic farming will be promoted, and at least 25% of the EU's agricultural land shall be under organic farming by 2030. How can both biotechnology and organic farming be developed and promoted simultaneously to contribute to achieving the Sustainable Development Goals (SDGs)? We illustrate that achieving the SDGs benefits from the inclusion of recent innovations in biotechnology in organic farming. This requires a change in the law. Otherwise, the planned increase of organic production in the F2F strategy may result in less sustainable, not more sustainable, food systems.

Genome\u2010wide identification of mlo genes in the cultivated peanut (Arachis hypogaea L.)

Powdery mildew disease caused by Oidium arachidis poses a threat to peanut production in Africa. Loss of function mutants of specific Mlo (Mildew Locus O) genes have provided broad-spectrum and durable resistance against pathogen in many crop species. Since there is huge potential to utilize susceptibility gene-mediated resistance in crop improvement, genome-wide mining of susceptibility genes is required for further researches. However, the susceptibility genes have not been characterized in peanut genome. In this research study, the genome of the cultivated peanut was used as reference to identify the AhMlo loci. Our results revealed that 25 AhMlo loci were identified and distributed on the chromosomes of the cultivated peanut. Eleven AhMlo loci were located on the A-genome while the remaining 14 on the B-genome. Variable number of inserted intron sequences (4–14) and transmembrane helix (4–8) were observed in the coding sequence of the AhMlo loci. Furthermore, phylogenetic analysis of the AhMlo loci along with homologs from other species has clustered the AhMlo loci into six clades. Three AhMlo loci were clustered in the clade V known to regroup the powdery susceptibility loci in dicots. Additionally, four core promoters were predicted on the promoter region of the specific AhMlo along with cis-regulatory elements related to PM susceptibility. These results provided strong evidence of the identification and distribution of the Mlo loci in the cultivated peanut genome and the identified specific AhMlo loci can be used for loss of susceptibility study.

Specific Resistance of Barley to Powdery Mildew, Its Use and Beyond. A Concise Critical Review.

Powdery mildew caused by the airborne ascomycete fungus Blumeria graminis f. sp. hordei (Bgh) is one of most common diseases of barley (Hordeum vulgare). This, as with many other plant pathogens, can be efficiently controlled by inexpensive and environmentally-friendly genetic resistance. General requirements for resistance to the pathogens are effectiveness and durability. Resistance of barley to Bgh has been studied intensively, and this review describes recent research and summarizes the specific resistance genes found in barley varieties since the last conspectus. Bgh is extraordinarily adaptable, and some commonly recommended strategies for using genetic resistance, including pyramiding of specific genes, may not be effective because they can only contribute to a limited extent to obtain sufficient resistance durability of widely-grown cultivars. In spring barley, breeding the nonspecific mlo gene is a valuable source of durable resistance. Pyramiding of nonspecific quantitative resistance genes or using introgressions derived from bulbous barley (Hordeum bulbosum) are promising ways for breeding future winter barley cultivars. The utilization of a wide spectrum of nonhost resistances can also be adopted once practical methods have been developed.

Phylogenetic Relationship of Plant MLO Genes and Transcriptional Response of MLO Genes to Ralstonia solanacearum in Tomato.

As a broad-spectrum disease resistance factor, MLO is involved in a variety of biotic and abiotic stress responses in plants. To figure out the structural features, phylogenetic relationships, and expression patterns of MLO genes, we investigated the genome and transcriptome sequencing data of 28 plant species using bioinformatics tools. A total of 197 MLO genes were identified. They possessed 5–7 transmembrane domains, but only partially contained a calmodulin-binding domain. A total of 359 polymorphic sites and 142 haplotypes were found in 143 sequences, indicating the rich nucleotide diversity of MLO genes. The MLO genes were unevenly distributed on chromosomes or scaffolds and were mainly located at the ends, forming clusters (24.1% genes), tandem duplicates (5.7%), and segment duplicates (36.2%). The MLO genes could be classified into three groups by phylogenetic analysis. The angiosperm genes were mainly in subgroup IA, Selaginella moellendorffii genes were in subgroup IA and IIIB, Physcomitrella patens genes were in subgroup IB and IIIA, and almost all algae genes were in group II. About half of the MLO genes had homologs within and across species. The Ka/Ks values were all less than 1, varying 0.01–0.78, suggesting that purifying selection had occurred in MLO gene evolution. In tomato, RNA-seq data indicated that SlMLO genes were highly expressed in roots, followed by flowers, buds, and leaves, and also regulated by different biotic stresses. qRT–PCR analysis revealed that SlMLO genes could respond to tomato bacterial wilt, with SlMLO1, SlMLO2, SlMLO4, and SlMLO6 probably involved in the susceptibility response, whereas SlMLO14 and SlMLO16 being the opposite. These results lay a foundation for the isolation and application of related genes in plant disease resistance breeding.

Genetic diversity of cereal crops for powdery mildew resistance

Powdery mildew (causal agent Blumeria graminis) is a widespread and harmful fungi disease of cereal crops especially in the regions with humid climate. The pathogen is differentially interacting with plant host genotypes. Growing cereal crop varieties protected with different resistance genes is the most rational, costly and ecologically safe way of combating powdery mildew. The supply of effective genes can be increased due to studies of crop genetic resources collection, introgression of resistance from wild relatives, and also at the expense of mutant forms created with the use of traditional (induced mutagenesis) and biotechnological methods including genome editing. This causes the increasing interest to searching and identifying resistance genes, elucidation of their structural and functional organization, and analysis of molecular mechanisms of the character development. The review summarizes modern information on the identified genes of powdery mildew resistance of the main cereal crops wheat, barley and oat. The list of wheat and barley genes identified at the molecular level is presented. It includes genes encoding NLR and CNL proteins (Pm2, Pm3, TaMla2, TaMla3 genes of wheat, rye Pm8 gene, barley Mla gene), receptor-like proteins (barley Mlo gene), transport proteins and receptor-like kinases (Lr34, Lr67, Pm21 of wheat).

Evaluation of collection spring barley varieties for valuable economic features for breeding in the central forest-steppe of Ukraine

Aim. To conduct immunological monitoring of collection spring barley varieties against pathogens of the most common diseases. To select starting material with a set of valuable features for in breeding for pathogen resistance and productivity in the central forest-steppe of Ukraine. Results and Discussion. The Erysiphe graminis f. sp. hordei, Bipolaris sorokiniana and Drechslera teres populations were found to be the most widespread in the Central Forest-Steppe of Ukraine. Drechslera graminea, Pyrenophora tritici-repentis Drechsler and Puccinia hordei were not common, and in only waterlogged years their damage intensity amounted to 10-15%. Complex resistance (damage 10.0 %) to three diseases – E. graminis f. sp. hordei, B. sorokiniana and D. teres was identified in the following varieties: Dokaz, Aspekt, Kuburas, Hanka, and STN 115. The recessive genes mlo were shown to be extensively and highly effective against E. graminis f. sp. hordei. Varieties Adonis, Bojos, Aspen, Barke, Class, Eunova, Josefin, Danuta, Breemar, and Madeira were resistant to these genes. Structural analysis performed with varieties of spring barley, which were resistant to disease. The following varieties were superior to the check variety in terms of length, grain number and weight from the main ear: Kuburas, Troychan, Sanktrum, and Yevroprestyzh. Conclusions. We selected sources of complex resistance to diseases (damage  10.0%): Aspekt, Dokaz, Hanka, Kuburas, and STN 115. The donors of resistance to E. graminis f. sp. hordei (damage  3.5%) are Adonis, Barke, Bojos, Aspen, Сlass, Danuta, Eunova, Josefin, Breemar, and Madeira. The sources of valuable economic features are: by the ear length (9.7-10.2 cm) - varieties Kuburas, Vivaldi, Troychan, Sanktrum, Yevroprestyzh; by the grain number from the main ear (25.5-27.8) - varieties Kuburas, Troychan, Sanktrum, Koloryt, Yevroprestyzh, Danuta, and Eunova; by grain weight from the main ear (1.5-2.0 g) - varieties Kuburas, Vivaldi, Troychan, Sanktrum, Hanka, Koloryt, Yevroprestyzh, Barke, Danuta, Pivdennyi,and Eunova.

Sources of valuable crop features of spring barley varieties for breeding in the central forest-steppe of Ukraine

The population of Erysiphe graminis f. sp. hordei Em. Marchal, Bipolaris sorokiniana Shoem. and Drechslera teres Ito. was found to be the most widespread in the central forest-steppe of Ukraine. Drechslera graminea Ito and Puccinia hordei Otth. were not common. For an average of 7 years of research, the sources of the disease complex have been identified on a provocative background. Resistance (lesions up to 10.0 %) to two diseases – Erysiphe graminis and Drechslera teres were characterized by the following varieties: Etyket, Obolon, Parnas, Khadar, Edem, Pivdennyi, Koloryt (Ukraine), Josefin (France), Ebson, Malz, Aspen (Czech Republic), Barke, Bojos, Breemar, Brenda, Landora, Madeira, Danuta, Adonis, Сlass (Germany), Vivaldi, Eunova, Secuva (Austria). Complex resistance (lesions up to 10.0 %) to three diseases – Erysiphe graminis, Bipolaris sorokiniana and Drechslera teres were characterized by the following varieties: Aspekt, Dokaz (Ukraine), Hanka, Kuburas (Germany), STN 115 (Poland). The recessive genes mlo: mlo9, mlo11 and the combination of genes: mlo + Mla13 + Ml (La), mlo + Mla1 and mlo + Mla12 have been shown to be highly effective for Erysiphe graminis for a long time. High resistance and resistance were characterized by varieties protected by these resistance genes: Adonis, Barke, Bojos, Aspen, Сlass, Danuta, Eunova, Josefin, Breemar і Madeira. In spring barley varieties that showed disease resistance, structural analysis was performed by plant height, number of stems, spike length, number of grains, and weight of spikelets. In terms of length, number of grains and weight of grain of the main ear, the following varieties were better than the standard: Kuburas, Koloryt, Troichan, Barke, Danuta, Hanka, Ievroprestyzh, Sanktrum and others. Dedicated sources and donors of resistant varieties of spring barley to common pathogens can be used for immunity selection. Selected varieties by yield are the material for the selection of spring barley as a source of valuable features. These varieties are involved in hybridization. Key words: varieties, immunological monitoring, resistance, Erysiphe graminis, Bipolaris sorokiniana і Drechslera teres, valuable crop features, sources, donors.