Resistant Sunflower Research Articles

Pangenome Data Analysis Reveals Characteristics of Resistance Gene Analogs Associated with Sclerotinia sclerotiorum Resistance in Sunflower

The sunflower, an important oilseed crop and food source across the world, is susceptible to several pathogens, which cause severe losses in sunflower production. The utilization of genetic resistance is the most economical, effective measure to prevent infectious diseases. Based on the sunflower pangenome, in this study, we explored the variability of resistance gene analogs (RGAs) within the species. According to a comparative analysis of RGA candidates in the sunflower pangenome using the RGAugury pipeline, a total of 1344 RGAs were identified, comprising 1107 conserved, 199 varied, and 38 rare RGAs. We also identified RGAs associated with resistance against Sclerotinia sclerotiorum (S. sclerotiorum) in sunflower at the quantitative trait locus (QTL). A total of 61 RGAs were found to be located at four quantitative trait loci (QTLs). Through a detailed expression analysis of RGAs in one susceptible and two tolerant sunflower inbred lines (ILs) across various time points post inoculation, we discovered that 348 RGAs exhibited differential expression in response to Sclerotinia head rot (SHR), with 17 of these differentially expressed RGAs being situated within the QTL regions. In addition, 15 RGA candidates had gene introgression. Our data provide a better understanding of RGAs, which facilitate genomics-based improvements in disease resistance in sunflower.

Genomic Insights into Disease Resistance in Sunflower (Helianthus annuus): Identifying Key Regions and Candidate Genes for Verticillium dahliae Resistance.

Sunflower (Helianthus annuus) is a globally significant field crop, and disease resistance is crucial for ensuring yield stability and crop quality. Verticillium dahliae is a notorious soilborne pathogen that causes Verticillium Wilt (VW) and threatens sunflower production worldwide. In this study, we conducted a comprehensive assessment of sunflower resistance to V. dahliae across 231 sunflower cultivar lines, from the Sunflower Association Mapping (SAM) population. We employed EMMAX and ridge regression best linear unbiased prediction (rrBLUP) and identified 148 quantitative trait loci (QTLs) and 23 putative genes associated with V. dahliae resistance, including receptor like kinases, cell wall modification, transcriptional regulation, plant stress signalling and defense regulation genes. Our enrichment and quantitative real-time PCR validation results highlight the importance of membrane vesicle trafficking in the sunflower immune system for efficient signaling and defense upon activation by V. dahliae. This study also reveals the polygenic architecture of V. dahliae resistance in sunflowers and provides insights for breeding sunflower cultivars resistant to VW. This research contributes to ongoing efforts to enhance crop resilience and reduce yield losses due to VW, ultimately benefiting sunflower growers and the agricultural sector.

Genome-wide identification and evolution of the SAP gene family in sunflower (Helianthus annuus L.) and expression analysis under salt and drought stress.

Stress-associated proteins (SAPs) are known to play an important role in plant responses to abiotic stresses. This study systematically identified members of the sunflower SAP gene family using sunflower genome data. The genes of the sunflower SAP gene family were analyzed using bioinformatic methods, and gene expression was assessed through fluorescence quantification (qRT-PCR) under salt and drought stress. A comprehensive analysis was also performed on the number, structure, collinearity, and phylogeny of seven Compositae species and eight other plant SAP gene families. The sunflower genome was found to have 27 SAP genes, distributed across 14 chromosomes. The evolutionary analysis revealed that the SAP family genes could be divided into three subgroups. Notably, the annuus variety exhibited amplification of the SAP gene for Group 3. Among the Compositae species, C. morifolium demonstrated the highest number of collinearity gene pairs and the closest distance on the phylogenetic tree, suggesting relative conservation in the evolutionary process. An analysis of gene structure revealed that Group 1 exhibited the most complex gene structure, while the majority of HaSAP genes in Group 2 and Group 3 lacked introns. The promoter analysis revealed the presence of cis-acting elements related to ABA, indicating their involvement in stress responses. The expression analysis indicated the potential involvement of 10 genes (HaSAP1, HaSAP3, HaSAP8, HaSAP10, HaSAP15, HaSAP16, HaSAP21, HaSAP22, HaSAP23, and HaSAP26) in sunflower salt tolerance. The expression of these 10 genes were then examined under salt and drought stress using qRT-PCR, and the tissue-specific expression patterns of these 10 genes were also analyzed. HaSAP1, HaSAP21, and HaSAP23 exhibited consistent expression patterns under both salt and drought stress, indicating these genes play a role in both salt tolerance and drought resistance in sunflower. The findings of this study highlight the significant contribution of the SAP gene family to salt tolerance and drought resistance in sunflower.

Diversity of sunflower rust pathogen biotypes (<i>Puccinia helianthi</i> Schwein.) in the Rostov region

In the last decade there has been established an increase in the prevalence of Puccinia helianthi in sunflower crops in Russia. In the Rostov region, on the territory of the Don Experimental Station (the Azov region), severe damage by the sunflower rust pathogen was established in 2020. In this regard, there was a need to study the race of the fungus on sunflower crops in the Rostov region. The purpose of the study was to identify rust pathogen isolates collected from sunflower crops in accordance with the accepted international triplet nomenclature in different areas of the Rostov region in the period 2021–2023. As testers, there was used a set of differentiating lines of sunflower resistance to the pathogen, containing SM 90, SM 29, P-386, HA-R1, HA-R2, HA-R3, HA-R4, HA-R5 and the line ‘ED 47’, susceptible to all biotypes of the fungus. The total sample consisted of 237 parasite urediniospore isolates collected from infected leaves of sunflower plants. There were differentiated 34 biotypes of P. helianthi. The most virulent pathotype 777 was identified among isolates from the Tatsinsky, Morozovsky and Konstantinovsky districts of the region in 2023. The race with code number 700 was identified in almost all represented areas of the region and accounted for 52.7% of the studied sample of sunflower rust pathogen isolates. In the current work the racial composition of the pathogen in the Rostov region was studied for the first time. The study results have indicated the need to continue monitoring new biotypes of P. helianthi, as well as expand and accelerate work on the development of sunflower hybrids resistant to the predominant race with code 700 in the sample.

Новый гербицидоустойчивый сорт подсолнечника масличного типа Бузулук сур

Early maturing herbicide resistant sunflower variety of oil type Buzuluk sur (elite number 875) was developed as a result of the breeding and genetic program on development of sulfonylurea resistant plants at the V.S. Pustovoit All-Russian Research Institute of Oil Crops. This variety was developed using a complex of hybridization methods, backcrosses, and group repollination. A line VK1-sur was a donor of a resistance gen to tribenuron methyl (Sur), early maturing variety of oil type was a recipient. Subsequent individual selection with progeny estimation of the best by its morphological and economically valuable traits families and a control of herbicide resistance on the all stages of a breeding process allowed creating a population resistant to tribenuron methyl. The new variety is designed for cultivation in the production system Sumo and ExpressSun.

Multiple Forms of Resistance to the Phomopsis Stem Canker Pathogens Diaporthe helianthi and D. gulyae in Sunflower.

Phomopsis stem canker of cultivated sunflower (Helianthus annuus L.) can be caused by multiple necrotrophic fungi in the genus Diaporthe, with Diaporthe helianthi and D. gulyae being the most common causal agents in the United States. Infection begins at the leaf margins and proceeds primarily through the vasculature, progressing from the leaf through the petiole to the stem, resulting in formation of brown stem lesions centered around the petiole. Sunflower resistance to Phomopsis stem canker is quantitative and genetically complex. Due to the intricate disease process, resistance is possible at different stages of infection, and multiple forms of defense may contribute to the overall level of quantitative resistance. In this study, sunflower lines exhibiting field resistance to Phomopsis stem canker were evaluated for stem and leaf resistance to multiple isolates of D. helianthi and D. gulyae in greenhouse experiments, and responses to the two species were compared. Additionally, selected resistant and susceptible lines were evaluated for petiole transmission resistance to D. helianthi. Lines with distinct forms of resistance were identified, and results indicated that responses to stem inoculation were strongly correlated (Spearman's coefficient 0.598, P < 0.001) for the two fungal species, while leaf responses were not (Spearman's coefficient 0.396, P = 0.076). These results provide a basis for genetic dissection of distinct forms of sunflower resistance to Phomopsis stem canker and will facilitate combining different forms of resistance to potentially achieve durable control of this disease in sunflower hybrids.

Pangenome characterization and analysis of the NAC gene family reveals genes for Sclerotinia sclerotiorum resistance in sunflower (Helianthus annuus).

Sunflower (Helianthus annuus) is one of the most important economic crops in oilseed production worldwide. The different cultivars exhibit variability in their resistance genes. The NAC transcription factor (TF) family plays diverse roles in plant development and stress responses. With the completion of the H. annuus genome sequence, the entire complement of genes coding for NACs has been identified. However, the reference genome of a single individual cannot cover all the genetic information of the species. Considering only a single reference genome to study gene families will miss many meaningful genes. Apangenome-wide surveyand characterization of the NAC genes in sunflower species were conducted. In total, 139 HaNAC genes are identified, of which 114 are core and 25 are variable. Phylogenetic analysis of sunflower NAC proteins categorizes these proteins into 16 subgroups. 138 HaNACs are randomly distributed on 17 chromosomes. SNP-based haplotype analysis shows haplotype diversity of the HaNAC genes in wild accessions is richer than in landraces and modern cultivars. Ten HaNAC genes in the basal stalk rot (BSR) resistance quantitative trait loci (QTL) are found. A total of 26 HaNAC genes are differentially expressed in response to Sclerotinia head rot (SHR). A total of 137 HaNAC genes are annotated in Gene Ontology (GO) and are classified into 24 functional groups. GO functional enrichment analysis reveals that HaNAC genes are involved in various functions of the biological process. We identified NAC genes in H. annuus (HaNAC) on a pangenome-wide scale and analyzed S. sclerotiorum resistance-related NACs. This study provided a theoretical basis for further genomic improvement targeting resistance-related NAC genes in sunflowers.

Seed pretreatment with brassinosteroids stimulates sunflower immunity against parasitic weed (Orobanche cumana) infection.

Broomrape (Orobanche cumana) negatively affects sunflower, causing severe yield losses, and thus, there is a need to control O. cumana infestation. Brassinosteroids (BRs) play key roles in plant growth and provide resilience to weed infection. This study aims to evaluate the mechanisms by which BRs ameliorate O. cumana infection in sunflower (Helianthus annuus). Seeds were pretreated with BRs (1, 10, and 100 nM) and O. cumana inoculation for 4 weeks under soil conditions. O. cumana infection significantly reduced plant growth traits, photosynthesis, endogenous BRs and regulated the plant defence (POX, GST), BRs signalling (BAK1, BSK1 to BSK4) and synthesis (BRI1, BR6OX2) genes. O. cumana also elevated the levels of malondialdehyde (MDA), hydroxyl radical (OH-), hydrogen peroxide (H2O2) and superoxide (O2 •-) in leaves/roots by 77/112, 63/103, 56/97 and 54/89%, as well as caused ultrastructural cellular damages in both leaves and roots. In response, plants activated a few enzymes, superoxide dismutase (SOD), peroxidase (POD) and reduced glutathione but were unable to stimulate the activity of ascorbate peroxidase (APX) and catalase (CAT) enzymes. The addition of BRs (especially at 10 nM) notably recovered the ultrastructural cellular damages, lowered the production of oxidative stress, activated the key enzymatic antioxidants and induced the phenolic and lignin contents. The downregulation in the particular genes by BRs is attributed to the increased resilience of sunflower via a susceptible reaction. In a nutshell, BRs notably enhanced the sunflower resistance to O. cumana infection by escalating the plant immunity responses, inducing systemic acquired resistance, reducing oxidative or cellular damages, and modulating the expression of BR synthesis or signalling genes.

Identification and validation of novel QTL associated with powdery mildew (Golovinomyces cichoracearum (DC.) V.P. Heluta.) resistance in sunflower (Helianthus annuus L.)

Sunflower (Helianthus annuus L.; 2n=2x=34) is an important annual oilseed crop cultivated worldwide. In the recent past, powdery mildew disease has evolved as a significant constraint for yield and quality production in sunflower crop. Hence, a F2 mapping population was developed from a cross COSF 15B x IR6 to identify quantitative trait loci (QTL) associated with powdery mildew resistance in sunflower. F2:4 recombinant lines of this population were screened along with parents and scored for powdery mildew resistance during Dec-Feb 2021-22. Per cent disease index (PDI) was calculated from the data taken 75 days after sowing (DAS) using a 0-9 score scale. Genetic linkage map was constructed with 92 SSR markers which covered 1053.3 cM. The QTL analysis resulted in the detection of one QTL in LG10 for PDI. It has 2.54 LOD and accounted for 12.25 per cent phenotypic variation. The flanking markers viz., ORS684 and ORS1110 have a flanking distance of 1.7 cM and validated with a set ofpopulation revealed that 24% and 28% PVE respectively. Hence, it may be concluded that markers ORS684 and ORS1110 can be effectively utilized for marker assisted breeding programme to develop the sunflower lines resistant to powdery mildew.

Genetic diversity of broomrape (Orobanche cumana Wallr.) populations from different geographical origins assessed by ISSR markers

Abstract The present study was focused on the assessment of genetic diversity in twenty-three populations of Orobanche cumana parasitizing on sunflower in Bulgaria, Turkey, Moldova and Romania using 13 ISSR markers. The obtained results on the genetic diversity parameters showed that the broomrape populations were characterised by a significant level of the intrapopulation diversity. In addition, descriptive population genetic statistics revealed that Turkish populations had a higher level of genetic diversity indices than populations from several areas of the northeast and east of the Balkan Peninsula included in Eastern Europe. The analysis of molecular variance showed that 38 % of the genetic variability was due to differences within populations, 34 % was due to differences among populations and the lowest molecular variation was among countries (28 %). According to clustering and PCA methods, Moldavian, Bulgarian and Romanian broomrapes shared more genetic traits with each other than with Turkish populations within a main gene pool. As a whole, all results of this study showed that there is a high intrapopulation diversity of the O. cumana gene pool in the Black Sea basin. From the clustering and PCA analyses, it can be concluded that the grouping of broomrape populations is partly determined by their geographical origin, as well as by the genetic differences and similarities accumulated over time, and is not related to virulence. The information obtained from this study may be highly relevant in contributing to the development of sustainable control strategies of the pathogen and breeding programmes for sunflower resistance to broomrape.

Inheriting the resistance of sunflower to tribenuron methyl under insufficient humidification in the southern Steppe of Ukraine

Aim. This study aimed to investigate the inheritance of resistance to sulfonylurea herbicides in sunflower under conditions of insufficient humidification in the southern Steppe of Ukraine. Methods. Isolation, castration, hybridization, herbicide application (Granstar Pro 75 % w.g., containing tribenuron methyl as the active substance (a.s.)), evaluation of herbicide resistance, and statistical analysis of the acquired data. Results. The investigation into the inheritance of resistance to sulfonylurea herbicides involved the utilization of both resistant (SURES-1, OS 1099 V, OS 2017 V) and non-resistant (Od 1002 B, Od 1318 V, OS 1295 V) sunflower genotypes. Through crossing, four F1 hybrid combinations were generated, namely OS 2017 V × OS 1099 V, SURES-1 × Od 1002 B, SURES-1 × Od 1318 V, and Od 1318 V x OS 1295 V. Subsequent treatment of F1 plants with the herbicide Granstar Pro 75 % w.g. revealed that three combinations (OS 2017 V × OS 1099 V, SURES-1 × Od 1002 B, SURES-1 × Od 1318 V) exhibited complete resistance to the herbicide. In the second generation, following herbicide treatment, the hybrid combinations SURES-1 × Od 1002 B and SURES-1 × Od 1318 V displayed segregation into resistant and non-resistant plants. Conversely, the plants in the combination OS 2017 V × OS 1099 V maintained complete resistance to the herbicidal effects. Conclusions. The investigation, conducted in the challenging climatic conditions of the southern Steppe of Ukraine, demonstrated complete resistance to sulfonylurea herbicides in three hybrid combinations of both F1 and F2 generations. Notably, the combination OS 2017 V × OS 1099 V exhibited uniform resistance throughout the second generation, devoid of segregation. Moreover, the results of F2 segregation analysis in the SURES-1 × Od 1002 B and SURES-1 × Od 1318 V populations indicated that resistance to tribenuron methyl is primarily governed by the presence of a dominant gene allele. These findings offer valuable insights for the development of sunflower hybrids with enhanced herbicide resistance, particularly in regions with adverse climatic conditions.

TilhanTec-SUNH-1 (IIOSH-15-20): A new high seed and oil yielding and downy mildew resistant sunflower hybrid suitable for rainfed condition of India

Aim: To develop more heterotic hybrids for seed and oil yield coupled with resistant or tolerant to major disease (downy mildew) and insect pests (leafhoppers) for commercial cultivation in rainfed conditions and DNA profiling of the newly developed hybrid (TilhanTec-SUNH-1) along with 2 female lines, 4 male lines and 3 hybrids using sunflower specific simple sequence repeat (SSR) markers. Methodology: Two parentages (ARM-243A and RGP-100) were utilized for the development of a new promising sunflower hybrid, TilhanTec-SUNH-1 (IIOSH-15-20). Performance of entry was assessed at 29 and 14 locations, respectively, during the kharif and rabi seasons over three years through All India Coordinated Trials (IHT, AHT-I &amp; II) and a state multilocation trial at three locations. A total of nine quantitative observations were recorded. A total of 80 SSR primers were used on the 4 hybrids for DNA fingerprinting. Results: Considerable seed yield superiority (28.7% and 10.5%) was observed in AICRP trials over DRSH-1 and KBSH-44, respectively. Oil yield superiority was 27.1% and 27.3% compared to national checks DRSH-1 and KBSH-44. TilhanTec-SUNH-1 was found resistant (0%) to downy mildew and leafhoppers (1.1 grade) while tolerant to Alternariaster leaf spot. Four SSR markers, viz., ORS-57, ORS-203, ORS-1028 and ORS-598 can be confidently used for the identification of TilhanTec-SUNH-1 as well as for genetic purity tests. Interpretation: The results of this investigation revealed that TilhanTec-SUNH-1 is superior in terms of seed and oil yield and resistance to downy mildew and moderately resistant to leafhoppers and tolerant to Alternariaster leaf spot. It is notified and released by CVRC for commercial cultivation in rainfed conditions of the sunflower growing states of India. Key words: Downy mildew, Heterosis breeding, Molecular markers, Oil yield, Seed yield

Genetic analysis of basal stalk rot resistance introgressed from wild Helianthus petiolaris into cultivated sunflower (Helianthus annuus L.) using an advanced backcross population.

Sclerotinia sclerotiorum is a serious pathogen causing severe basal stalk rot (BSR) disease on cultivated sunflower (Helianthus annuus L.) that leads to significant yield losses due to insufficient resistance. The wild annual sunflower species H. petiolaris, commonly known as prairie sunflower is known for its resistance against this pathogen. Sunflower resistance to BSR is quantitative and determined by many genes with small effects on the resistance phenotype. The objective of this study was to identify loci governing BSR resistance derived from H. petiolaris using a quantitative trait loci (QTL) mapping approach. BSR resistance among lines of an advanced backcross population (AB-QTL) with 174 lines developed from a cross of inbred line HA 89 with H. petiolaris PI 435843 was determined in the field during 2017-2019, and in the greenhouse in 2019. AB-QTL lines and the HA 89 parent were genotyped using genotyping-by-sequencing and a genetic linkage map was developed spanning 997.51 cM and using 1,150 SNP markers mapped on 17 sunflower chromosomes. Highly significant differences (p<0.001) for BSR response among AB-QTL lines were observed disease incidence (DI) in all field seasons, as well as disease rating (DR) and area under the disease progress curve (AUDPC) in the greenhouse with a moderately high broad-sense heritability (H 2) of 0.61 for the tested resistance parameters. A total of 14 QTL associated with BSR resistance were identified on nine chromosomes, each explaining a proportion of the phenotypic variation ranging from 3.5% to 28.1%. Of the 14 QTL, eight were detected for BSR resistance in the field and six were detected under greenhouse conditions. Alleles conferring increased BSR resistance were contributed by the H. petiolaris parent at 11 of the 14 QTL.

Molecular-genetic machanisms of resistance to broomrape in sunflower

Sunflower broomrape (Orobanche cumana Wallr.) is an obligate parasitic plant that specifically infects sunflower and can cause significant yield losses. In this regard, obtaining sunflower varieties resistant to broomrape is an important task for agriculture. Sunflower breeding for resistance to broomrape was initiated in the beginning of the 20th century in USSR. However, the production of new resistant sunflower varieties was accompanied by the emergence of new virulent broomrape races that overcame the effect of resistance genes. For a number of sunflower genetic loci that determine resistance to broomrape, the location on the genetic map was determined, but only for some of them probable candidate genes were identified and the possible molecular mechanism of their action was described. In addition, transcriptomic data have recently been obtained for broomrape-resistant and susceptible sunflower varieties, which also makes it possible to get closer to understanding the molecular basis of resistance formation. This review focuses on molecular genetic mechanisms of sunflower resistance to broomrape, identified on the basis of genetic mapping of resistance loci, determination of probable candidate genes, as well as available transcriptomic data.

ВАЛИДАЦИЯ ДНК-МАРКЕРА УСТОЙЧИВОСТИ ПОДСОЛНЕЧНИКА К РАСЕ G ЗАРАЗИХИ НА МАЛЫХ ВЫБОРКАХ

The genotypic and phenotypic segregation of 57 plants of a progeny of two heterozygous F1 sunflower hybrids was analyzed (by DNA-marker) by a trait of resistance to a broomrape race G. The observed segregation by a genotype corresponded reliably to the theoretically expected ones in monohybrid crosses due to models 3:1 and 1:2:1. The segregation by a phenotype corresponded completely to the segregation by a marker of a model 3:1. A developed marker allows selecting by a trait of sunflower resistance to the broomrape race G.

Insights into physiological and metabolic modulations instigated by exogenous sodium nitroprusside and spermidine reveals drought tolerance in Helianthus annuus L.

Drought is the most critical climatic factor instigating severe threats to crop production worldwide. As stress ameliorants, exogenous sodium nitroprusside (SNP) or spermidine (Spd) supply has positive responses in alleviating the drought adversities in crops, however, reports regarding their combined effects is still elusive. Here, the protective role of SNP and Spd to confer drought resistance in sunflower (Helianthus annuus L.) through up-regulation of physiological and metabolic processes was investigated. Plants were foliar sprayed with individual or combined SNP (100 μM) or Spd (100 μM). Drought was induced by keeping the soil at 100% (normal) and 60% (drought stress) field capacity levels. Drought exposure caused a marked decline in relative water content (RWC), excised leaf water retention (ELWR), net photosynthesis (PN), transpiration rate (E), stomatal conductance (gs), and sub-stomatal conductance (Ci) with substantial increase in catalase (CAT), superoxide dismutase (SOD), and peroxidase (POX). SNP plus Spd exhibited a considerable increase in CAT, SOD, and POX activities under drought, and helped the plants to retain optimum water status and gas exchange attributes. Similarly, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents were increased significantly to drought; however, a notable decline was recorded in drought prone plants treated with exogenous SNP plus Spd. Moreover, addition of SNP plus Spd under drought caused a remarkable increase in chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll total (Chl t), carotenoids (Car), and growth traits like shoot length (SL), root length (RL), shoot fresh weight (SFW), shoot dry weight (SDW), root dry weight (RDW). Combined SNP and Spd application could potentially alleviate the drought-induced damages in sunflower through increased water status (8–10%), antioxidant enzymes (17–28%), chlorophyll pigments (14–21%), and growth performance (12–22%) under drought stress.

Co-Expression Networks in Sunflower: Harnessing the Power of Multi-Study Transcriptomic Public Data to Identify and Categorize Candidate Genes for Fungal Resistance.

Fungal plant diseases are a major threat to food security worldwide. Current efforts to identify and list loci involved in different biological processes are more complicated than originally thought, even when complete genome assemblies are available. Despite numerous experimental and computational efforts to characterize gene functions in plants, about ~40% of protein-coding genes in the model plant Arabidopsis thaliana L. are still not categorized in the Gene Ontology (GO) Biological Process (BP) annotation. In non-model organisms, such as sunflower (Helianthus annuus L.), the number of BP term annotations is far fewer, ~22%. In the current study, we performed gene co-expression network analysis using eight terabytes of public transcriptome datasets and expression-based functional prediction to categorize and identify loci involved in the response to fungal pathogens. We were able to construct a reference gene network of healthy green tissue (GreenGCN) and a gene network of healthy and stressed root tissues (RootGCN). Both networks achieved robust, high-quality scores on the metrics of guilt-by-association and selective constraints versus gene connectivity. We were able to identify eight modules enriched in defense functions, of which two out of the three modules in the RootGCN were also conserved in the GreenGCN, suggesting similar defense-related expression patterns. We identified 16 WRKY genes involved in defense related functions and 65 previously uncharacterized loci now linked to defense response. In addition, we identified and classified 122 loci previously identified within QTLs or near candidate loci reported in GWAS studies of disease resistance in sunflower linked to defense response. All in all, we have implemented a valuable strategy to better describe genes within specific biological processes.

Molecular and Genetic Bases for Sunflower Resistance to Broomrape

Molecular and Genetic Bases for Sunflower Resistance to Broomrape

Разработка ДНК-маркеров признака устойчивости подсолнечника к расе G заразихи (Orobanche cumana Wallr.)

Broomrape (Orobanche cumana Wallr.) is an obligatory parasite which is able to decrease significantly sunflower yields. The race G is the most spread and virulence broomrape race in the Russian Federation. Cultivation of genetically resistance sunflower varieties and hybrids is the most ecologic and economically efficient method to control this parasite plant. Usage of DNA-markers when selecting the resistant plants increases significantly the effectiveness of a breeding process. To mark the sunflower resistance to broomrape race G, using bioinformative approaches, we developed new DNA-markers: four SCAR (sequence characterized amplified region) and ten SSR (simple sequence repeat). These markers were tested on 20 lines and hybrids of sunflower. Due to the results of this testing, all SSR- and two SCAR-markers were eliminated by steps. SCAR-marker RORS1 was characterized with the presence of an amplified DNA fragment with a length ≈ 168 bps and showed association with a trait of resistance, and SORS1 with a fragment length ≈ 322 bps had a relation with a sus-ceptible phenotype. These markers composed a marker system for a multiplex PCR, which allowed distinguishing resistant and susceptible lines and hybrids, except a line VK678 and F1 hybrids developed using this line as parental one. To eliminate faults of the marker system, seven SCAR-markers analogous to SORS1 were created. Due to estimation result, we selected a marker SORS9 characterized with the presence an amplified DNA fragment with a length ≈ 217 bps in susceptible phenotypes. The new system of markers RORS1/SORS9 for a multiplex PCR was validated on 70 sunflower lines and hybrids. The susceptible lines and hybrids were characterized with amplification of only marker SORS9, resistant lines – only marker RORS1, and resistant hybrids – both markers. The developed marker system allowed distinguishing all susceptible lines and hybrids from the resistant sunflower genotypes.

Assessment of parental lines, F1 and F2 sunflower hybrids to Septoria leaf spot infection and some inheritance patterns

Abstract The foliar fungal disease Septoria leaf spot is economically important for sunflowers. It develops most intensively during the wet and warm season. However, the genetic nature of sunflower resistance to Septoria leaf spot is still not clear. The purpose of our work was to identify some inheritance patterns of sunflower resistance to this disease based on the assessment of lines and hybrids of the first and second generations. The studied material was sown in 2020 and 2021 and subsequently grown on a stationary artificial infectious plot enriched with Septoria helianthi pathogen. The frequency of infection and the severity of infection of each sample were taken into account. The two-factor variance analysis revealed a significant influence of genotype on the frequency of infection in six sunflower lines and confirmed the effect of individuality of the response of individual genotypes to disease damage. It was shown that about 65 % of the total variation of the trait is due to the genetic nature of the line, and only a little more than 20 % and about 11 % – to the influence of the environment and the “genotype × environment” interaction respectively. Based on disease damage data in 2020 and 2021, the lines were classified as susceptible, moderately susceptible, moderately resistant and resistant. Differentiation of lines according to sensitivity to Septoria leaf spot made it possible to obtain hybrids with different manifestations of the trait in their parents. The nature of inheritance of infection frequency in F1 sunflower hybrids was determined by the degree of dominance. As a result, it was revealed intermediate inheritance, as well as positive and negative overdominance of the trait. The severity of infection by S. helianthi pathogen in F1 hybrids was inherited according to the type of parental form with greater resistance to the disease. F2 populations were found to inherit infection frequency from the more resistant parent, showing a proportion of infected plants similar to that of the more resistant line from a given cross combination. It has been shown that the frequency of infection of the F2 population with Septoria leaf spot can be affected by the severity of infection of F1 plant with the pathogen S. helianthi.