Septoria Tritici Research Articles

The molecular dialogue between Zymoseptoria tritici and wheat.

Zymoseptoria tritici is a highly damaging pathogen that causes high wheat yield losses in temperate climates. Z. tritici emerged during the domestication of wheat in the Fertile Crescent and has been extensively used as a model system for population genetic and genomic studies. New genetic tools and resources have provided a better understanding of the molecular components involved in the wheat-Z. tritici interaction, highlighted by the cloning of three wheat resistance genes and four Z. tritici avirulence genes. Despite the considerable progress made in the last few years, the mechanisms that mediate Z. tritici colonization remain largely unknown. In this review, we summarize the latest advances in understanding the molecular components mediating wheat-Z. tritici interactions and we discuss future research lines to close current knowledge gaps.

DMI fungicide resistance in Zymoseptoria tritici is unlinked to geographical origin and genetic background: a case study in Europe.

The hemibiotrophic fungus Zymoseptoria tritici causing Septoria tritici blotch (STB), is a devastating foliar pathogen of wheat worldwide. A common group of fungicides used to control STB are the demethylation inhibitors (DMIs). DMI fungicides restrict fungal growth by inhibiting the sterol 14-α-demethylase, a protein encoded by CYP51 gene and essential for maintaining fungal cell permeability. However, the adaptation of Z. tritici populations in response to intensive and prolonged DMI usage has resulted in a gradual shift towards reduced sensitivity to this group of fungicides. In this study, 311 isolates were collected pre-treatment from nine wheat-growing regions in Europe in 2019. These isolates were analysed by high-throughput amplicon-based sequencing of nine housekeeping genes and the CYP51 gene. Analyses based on housekeeping genes and the CYP51 gene revealed a lack of population structure in Z. tritici samples irrespective of geographical origin. Minimum spanning network (MSN) analysis showed clustering of multilocus genotypes (MLGs) based on CYP51 haplotypes, indicating an effect of selection due to DMI fungicide use. The majority of the haplotypes identified in this study have been reported previously. The diversity and frequencies of mutations varied across regions. Using a high-throughput amplicon-sequencing approach, we found several mutations in the CYP51 gene combined in different haplotypes that are likely to cause fungicide resistance. These mutations occurred irrespective of genetic background or geographical origin. Overall, these results contribute to the development of effective and sustainable risk monitoring for DMI fungicide resistance. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Appropriate sampling to aid on-farm assessments of the haplotype composition of Zymoseptoria tritici populations.

Zymoseptoria tritici causes Septoria tritici blotch (STB), which is the biggest threat to wheat in the UK. Azole fungicides have been used since the 1980s to control STB, but resistance to these chemicals is now widespread. The main resistance mechanism is based on the accumulation of CYP51 mutations, with 33 mutations reported. Hence, farmers need an accurate estimate of the haplotype composition of Z. tritici populations to develop effective fungicide treatments and resistance management. Isolates from Z. tritici lesions were collected from three fields across three commercial farms using two sampling approaches. Analysis of the isolate sequences revealed that the number of distinct haplotypes and the haplotype composition of the most dominant haplotypes varied only between and not within farms. Conventional W-shaped and point sampling both found the same percentage of distinct haplotypes and frequencies of the six most dominant haplotypes. The results from this survey suggest that farm-resistance-management strategies should be based on farm-specific rather than national data, and that sampling within a single field is sufficient. W-shaped sampling is often recommended in sampling approaches, but this survey finds no evidence of this approach being more appropriate for detecting a greater percentage of distinct haplotypes which may aid the discovery of potential new resistance threats. © 2024 Fera Science Ltd. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

5'-Methoxyarmillane, a Bioactive Sesquiterpenoid Aryl Ester from the Fungus Armillaria ostoyae.

Higher fungi of the genus Armillaria belonging to the phylum Basidiomycota produce bioactive sesquiterpenoid aryl esters called melleolides. A bioactivity-guided discovery process led to the identification of the new melleolide 5'-methoxyarmillane (1) in organic extracts from the mycelium of Armillaria ostoyae. Remarkably, supplementation of rapeseed oil to the culture medium potato dextrose broth increased the production of 1 by a factor of six during the course of the 35 days fermentation. Compound 1 was isolated and its structure elucidated by UHPLC-QTOF-HR-MS/MS and NMR spectroscopy. It showed toxicity against Madin-Darby canine kidney II (MDCK II, IC50 19.2 μg/mL, 44.1 μM) and human lung cancer Calu-3 cells (IC50 15.2 μg/mL, 34.9 μM) as well as moderate bioactivity against Mycobacterium tuberculosis (MIC 8 mg/mL, 18.4 μM) and Mycobacterium smegmatis (MIC 16 mg/mL, 36.8 μM), but not against Staphylococcus aureus, Escherichia coli, Candida albicans, and Septoria tritici. No inhibitory effects of 1 against the influenza viruses H3N2, H1N1pdm, B/Malaysia, and B/Massachusetts were observed.

An array of Zymoseptoria tritici effectors suppress plant immune responses.

Zymoseptoria tritici is the most economically significant fungal pathogen of wheat in Europe. However, despite the importance of this pathogen, the molecular interactions between pathogen and host during infection are not well understood. Herein, we describe the use of two libraries of cloned Z. tritici effectors that were screened to identify effector candidates with putative pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI)-suppressing activity. The effectors from each library were transiently expressed in Nicotiana benthamiana, and expressing leaves were treated with bacterial or fungal PAMPs to assess the effectors' ability to suppress reactive oxygen species (ROS) production. From these screens, numerous effectors were identified with PTI-suppressing activity. In addition, some effectors were able to suppress cell death responses induced by other Z. tritici secreted proteins. We used structural prediction tools to predict the putative structures of all of the Z. tritici effectors and used these predictions to examine whether there was enrichment of specific structural signatures among the PTI-suppressing effectors. From among the libraries, multiple members of the killer protein-like 4 (KP4) and killer protein-like 6 (KP6) effector families were identified as PTI suppressors. This observation is intriguing, as these protein families were previously associated with antimicrobial activity rather than virulence or host manipulation. This data provides mechanistic insight into immune suppression by Z. tritici during infection and suggests that, similar to biotrophic pathogens, this fungus relies on a battery of secreted effectors to suppress host immunity during early phases of colonization.

Functional characterization of extracellular and intracellular catalase-peroxidases involved in virulence of the fungal wheat pathogen Zymoseptoria tritici.

Understanding how pathogens defend themselves against host defence mechanisms, such as hydrogen peroxide (H2O2) production, is crucial for comprehending fungal infections. H2O2 poses a significant threat to invading fungi due to its potent oxidizing properties. Our research focuses on the hemibiotrophic fungal wheat pathogen Zymoseptoria tritici, enabling us to investigate host-pathogen interactions. We examined two catalase-peroxidase (CP) genes, ZtCpx1 and ZtCpx2, to elucidate how Z. tritici deals with host-generated H2O2 during infection. Our analysis revealed that ZtCpx1 was up-regulated during biotrophic growth and asexual spore formation invitro, while ZtCpx2 showed increased expression during the transition from biotrophic to necrotrophic growth and in-vitro vegetative growth. Deleting ZtCpx1 increased the mutant's sensitivity to exogenously added H2O2 and significantly reduced virulence, as evidenced by decreased Septoria tritici blotch symptom severity and fungal biomass production. Reintroducing the wild-type ZtCpx1 allele with its native promoter into the mutant strain restored the observed phenotypes. While ZtCpx2 was not essential for full virulence, the ZtCpx2 mutants exhibited reduced fungal biomass development during the transition from biotrophic to necrotrophic growth. Moreover, both CP genes act synergistically, as the double knock-out mutant displayed a more pronounced reduced virulence compared to ΔZtCpx1. Microscopic analysis using fluorescent proteins revealed that ZtCpx1 was localized in the peroxisome, indicating its potential role in managing host-generated reactive oxygen species during infection. In conclusion, our research sheds light on the crucial roles of CP genes ZtCpx1 and ZtCpx2 in the defence mechanism of Z. tritici against host-generated hydrogen peroxide.

ZymoSoups: A high-throughput forward genetics method for rapid identification of virulence genes in Zymoseptoria tritici.

Septoria tritici blotch is caused by the fungus Zymoseptoria tritici and poses a major threat to wheat productivity. There are over twenty mapped loci in wheat that confer strong (gene-for-gene) resistance against this pathogen, however the corresponding genes in Z. tritici that confer virulence against distinct R genes remain largely unknown. In this study, we developed a rapid forward genetics methodology to identify genes that enable Z. tritici to gain virulence on previously resistant wheat varieties. We used the known gene-for-gene interaction between Stb6 and AvrStb6 as a proof-of-concept that this method could quickly recover single candidate virulence genes. We subjected the avirulent Z. tritici strain IPO323, which carries the recognized AvrStb6 allele, to UV mutagenesis and generated a library of over 66,000 mutants. We screened these mutants on leaves of the resistant wheat variety Cadenza, in mixtures (soups) ranging from 100-500 mutants per soup. We identified five soups with a gain-of-virulence (GoV) phenotype relative to the IPO323 parental strain and re-sequenced 18 individual isolates, including four control isolates and two mutants lacking virulence, when screened individually. Of the 12 confirmed GoV mutants, one had a single nucleotide polymorphism (SNP) in the AvrStb6 coding region. The other 11 GoV mutants exhibited large (~70Kb) deletions at the end of chromosome 5, including the AvrStb6 locus. Our findings demonstrate the efficiency of this forward genetic approach in elucidating the genetic basis of qualitative resistance to Z. tritici and the potential to rapidly identify other, currently unknown, Avr genes in this pathogen.

Colchicine, Caffeine, Gramine, and Their Derivatives as Potential Herbicides, Fungicides, and Insecticides.

A preliminary in silico screening of 94 compounds, including colchicine, caffeine, gramine, and their derivatives, was conducted to identify potential herbicides, insecticides, and fungicides. Among the compounds tested, only gramine and its 13 derivatives exhibited potential activity. These compounds were further tested against eight species of insects, three species of weeds, and four species of fungi. All of the tested alkaloids were found to be ineffective as herbicides and insecticides, but they did exhibit some fungicidal activity. Four gramine derivatives showed some activity against Phytophthora infestans, Botrytis cinerea, Zymoseptoria tritici, and Fusarium culmorum.

Virulence variation and pathotypes of Zymoseptoria tritici isolates causing wheat leaf blotch in Oromia, Ethiopia

Leaf blotch, caused by Zymoseptoria tritici, is a fungal disease that poses a severe threat to wheat production worldwide. Knowledge of virulence variability is crucial in choosing effective control measures. However, there have only been a few studies of the pathogenic variability and pathotypes within Ethiopian isolates. Hence, the objective of this study was to assess the virulence spectrum and variability of Z. tritici isolates. Forty-three isolates were tested for their virulence and pathotype against 7 wheat differential lines that have different resistance genes. A pathogenicity assay detected 41 differential line-specific virulent isolates among 301 interactions between a host and pathogen based on the percentage coverage of the leaf area by pycnidia. Some isolates were virulent against 50 %–60 % of the resistant genes, but most of them were virulent against some differential lines. Isolates such as EtA-11, EtSh-1, EtSh-2, EtSh-4, and EtA-19 expressed broad-spectrum virulence, highlighting that such isolates are useful for germplasm screening. The isolates were classified into 25 pathotypes, defined by their differential virulence responses. They were also assigned to two clusters according to their mean pycnidia percent. Pathotypes and principal component analysis detected 58.1 % and 62.2 % pathogenic diversity in Ethiopian isolates, respectively. The current findings provide information that breeders can use to identify and select more resistant varieties for farmers.

Novel resistance loci for quantitative resistance to Septoria tritici blotch in Asian wheat (Triticum aestivum) via genome-wide association study

BackgroundSeptoria tritici blotch (STB) disease causes yield losses of up to 50 per cent in susceptible wheat cultivars and can reduce wheat production. In this study, genomic architecture for adult-plant STB resistance in a Septoria Association Mapping Panel (SAMP) having 181 accessions and genomic regions governing STB resistance in a South Asian wheat panel were looked for.ResultsField experiments during the period from 2019 to 2021 revealed those certain accessions, namely BGD52 (CHIR7/ANB//CHIR1), BGD54 (CHIR7/ANB//CHIR1), IND92 (WH 1218), IND8 (DBW 168), and IND75 (PBW 800), exhibited a high level of resistance. Genetic analysis revealed the presence of 21 stable quantitative trait nucleotides (QTNs) associated with resistance to STB (Septoria tritici blotch) on all wheat chromosomes, except for 2D, 3A, 3D, 4A, 4D, 5D, 6B, 6D, and 7A. These QTNs were predominantly located in chromosome regions previously identified as associated with STB resistance. Three Quantitative Trait Loci (QTNs) were found to have significant phenotypic effects in field evaluations. These QTNs are Q.STB.5A.1, Q.STB.5B.1, and Q.STB.5B.3. Furthermore, it is possible that the QTNs located on chromosomes 1A (Q.STB.1A.1), 2A (Q.STB_DH.2A.1, Q.STB.2A.3), 2B (Q.STB.2B.4), 5A (Q.STB.5A.1, Q.STB.5A.2), and 7B (Q.STB.7B.2) could potentially be new genetic regions associated with resistance.ConclusionOur findings demonstrate the importance of Asian bread wheat as a source of STB resistance alleles and novel stable QTNs for wheat breeding programs aiming to develop long-lasting and wide-ranging resistance to Zymoseptoria tritici in wheat cultivars.

Embracing Biological Control of Septoria Tritici Blotch for Sustainable Wheat Protection

ABSTRACTWheat, one of the top‐produced cereals worldwide, is affected by many abiotic and biotic stresses, such as the ascomycete fungus Zymoseptoria tritici, the causal agent of Septoria tritici blotch (STB). STB has historically been managed with fungicides, but the pathogen readily overcomes chemical control because of its rapid genetic evolution. In addition, many fungicides are now being banned or limited by governments aiming for more environment‐friendly methods for pest management. This scenario gave rise to thinking about alternative control means such as biological control agents (BCAs) and organism‐derived biomolecules (ODBs). In this work, we review microbial BCA candidates and ODBs currently studied for the control of STB. Key studies have identified successful candidates including bacterial strains of the genera Pseudomonas and Bacillus, and fungal strains such as Trichoderma harzianum, Penicillium olsonii and Acremonium alternatum. In addition, lesser‐studied fungi, bacteria and compounds have been tested. Despite promising research, no BCA or ODB has been registered or commercially used against STB, and field trials are notably lacking, with existing studies being limited in scale. Further understanding of the interactions between Z. tritici and the wheat microbiome may uncover new potential candidates for STB biocontrol.

Multiple routes to fungicide resistance: Interaction of Cyp51 gene sequences, copy number and expression.

We examined the molecular basis of triazole resistance in Blumeria graminis f. sp. tritici (wheat mildew, Bgt), a model organism among powdery mildews. Four genetic models for responses to triazole fungicides were identified among US and UK isolates, involving multiple genetic mechanisms. Firstly, only two amino acid substitutions in CYP51B lanosterol demethylase, the target of triazoles, were associated with resistance, Y136F and S509T (homologous to Y137F and S524T in the reference fungus Zymoseptoria tritici). As sequence variation did not explain the wide range of resistance, we also investigated Cyp51B copy number and expression, the latter using both reverse transcription-quantitative PCR and RNA-seq. The second model for resistance involved higher copy number and expression in isolates with a resistance allele; thirdly, however, moderate resistance was associated with higher copy number of wild-type Cyp51B in some US isolates. A fourth mechanism was heteroallelism with multiple alleles of Cyp51B. UK isolates, with significantly higher mean resistance than their US counterparts, had higher mean copy number, a high frequency of the S509T substitution, which was absent from the United States, and in the most resistant isolates, heteroallelism involving both sensitivity residues Y136+S509 and resistance residues F136+T509. Some US isolates were heteroallelic for Y136+S509 and F136+S509, but this was not associated with higher resistance. The obligate biotrophy of Bgt may constrain the tertiary structure and thus the sequence of CYP51B, so other variation that increases resistance may have a selective advantage. We describe a process by which heteroallelism may be adaptive when Bgt is intermittently exposed to triazoles.

Stomatal penetration: the cornerstone of plant resistance to the fungal pathogen Zymoseptoria tritici

BackgroundSeptoria tritici blotch (STB), caused by the foliar fungus Zymoseptoria tritici, is one of the most damaging disease of wheat in Europe. Genetic resistance against this fungus relies on different types of resistance from non-host resistance (NHR) and host species specific resistance (HSSR) to host resistance mediated by quantitative trait loci (QTLs) or major resistance genes (Stb). Characterizing the diversity of theses resistances is of great importance for breeding wheat cultivars with efficient and durable resistance. While the functional mechanisms underlying these resistance types are not well understood, increasing piece of evidence suggest that fungus stomatal penetration and early establishment in the apoplast are both crucial for the outcome of some interactions between Z. tritici and plants. To validate and extend these previous observations, we conducted quantitative comparative phenotypical and cytological analyses of the infection process corresponding to 22 different interactions between plant species and Z. tritici isolates. These interactions included four major bread wheat Stb genes, four bread wheat accessions with contrasting quantitative resistance, two species resistant to Z. tritici isolates from bread wheat (HSSR) and four plant species resistant to all Z. tritici isolates (NHR).ResultsInfiltration of Z. tritici spores into plant leaves allowed the partial bypass of all bread wheat resistances and durum wheat resistance, but not resistances from other plants species. Quantitative comparative cytological analysis showed that in the non-grass plant Nicotiana benthamiana, Z. tritici was stopped before stomatal penetration. By contrast, in all resistant grass plants, Z. tritici was stopped, at least partly, during stomatal penetration. The intensity of this early plant control process varied depending on resistance types, quantitative resistances being the least effective. These analyses also demonstrated that Stb-mediated resistances, HSSR and NHR, but not quantitative resistances, relied on the strong growth inhibition of the few Z. tritici penetrating hyphae at their entry point in the sub-stomatal cavity.ConclusionsIn addition to furnishing a robust quantitative cytological assessment system, our study uncovered three stopping patterns of Z. tritici by plant resistances. Stomatal resistance was found important for most resistances to Z. tritici, independently of its type (Stb, HSSR, NHR). These results provided a basis for the functional analysis of wheat resistance to Z. tritici and its improvement.

Influence of crop management on stability rye yield and some grain quality traits

AbstractThe study explored the performance of hybrid and population rye (Secale cereale) cultivars under two different crop management intensities in Poland: moderate‐intensity and high‐intensity management. The focus was grain yield, grain quality, yield components, and variety stability in two growing seasons (2018/2019 and 2019/2020) at three locations. Hybrid cultivars consistently yielded higher grain yields (9.81 t ha−1) than population cultivars (7.90 t ha−1), with increase of 24.9%. However, hybrid cultivars had lower protein content (8.94%) than population cultivars (9.77%). Spike number was the most influential factor on yield, followed by 1000‐grain weight and grains per spike, regardless of cultivar type. Hybrid cultivars displayed a lower degree of stability as assessed using the ranking sum of the Shukla variance and the multi‐trait stability index. Hybrid cultivars were strongly dependent on resistance to fungal diseases, including Septoria (Mycosphaerella graminicola), and increased stability under moderate‐intensity management. Resistance to soil acidification became more important for cultivar stability under high‐intensity management.

Development and characterisation of novel durum wheat-H. chilense 4Hch chromosome lines as a source for resistance to Septoria tritici blotch.

The use of wild species as a source of genetic variability is a valued tool in the framework of crop breeding. Hordeum chilense Roem. et Schult is a wild barley species that can be a useful genetic donor for sustainable wheat breeding which carries genes conferring resistance to some diseases or increasing grain quality, among others. Septoria tritici blotch (STB), caused by the Zymoseptoria tritici fungus, is one of the most important wheat diseases worldwide, affecting both bread and durum wheat and having a high economic impact. Resistance to STB has been previously described in H. chilense chromosome 4Hch. In this study, we have developed introgression lines for H. chilense chromosome 4Hch in durum wheat using interspecific crosses, advanced backcrosses, and consecutive selfing strategies. Alien H. chilense chromosome segments have been reduced in size by genetic crosses between H. chilense disomic substitution lines in durum wheat and durum wheat lines carrying the Ph1 deletion. Hordeum chilense genetic introgressions were identified in the wheat background through several plant generations by fluorescence in situ hybridisation (FISH) and simple sequence repeat (SSR) markers. An STB infection analysis has also been developed to assess STB resistance to a specific H. chilense chromosome region. The development of these H. chilense introgression lines with moderate to high resistance to STB represents an important advance in the framework of durum breeding and can be a valuable tool for plant breeders.

Haplotype-based association mapping of genomic regions associated with Zymoseptoria tritici resistance using 217 diverse wheat genotypes

BackgroundSeptoria tritici blotch (STB) is considered to be one of the most destructive foliar wheat diseases and is caused by Zymoseptoria tritici. The yield losses are severe and in Northwestern Europe can reach up to 50%. The efficacy of fungicides is diminishing due to changes in the genetic structure of the pathogen. Therefore, resistance breeding is the most effective strategy of disease management. Recently, genome-wide association studies (GWAS) have become more popular due to their robustness in dissecting complex traits, including STB resistance in wheat. This was made possible by the use of large mapping populations and new sequencing technologies. High-resolution mapping benefits from historical recombination and greater allele numbers in GWAS.ResultsIn our study, 217 wheat genotypes of diverse origin were phenotyped against five Z. tritici isolates (IPO323, IPO88004, IPO92004, IPO86036 and St1-03) and genotyped on the DArTseq platform. In polytunnel tests two disease parameters were evaluated: the percentage of leaf area covered by necrotic lesions (NEC) and the percentage of leaf area covered by lesions bearing pycnidia (PYC). The disease escape parameters heading date (Hd) and plant height (Ht) were also measured. Pearson’s correlation showed a positive effect between disease parameters, providing additional information. The Structure analysis indicated four subpopulations which included from 28 (subpopulation 2) to 79 genotypes (subpopulation 3). All of the subpopulations showed a relatively high degree of admixture, which ranged from 60% of genotypes with less than 80% of proportions of the genome attributed to assigned subpopulation for group 2 to 85% for group 4. Haplotype-based GWAS analysis allowed us to identify 27 haploblocks (HBs) significantly associated with analysed traits with a p-value above the genome-wide significance threshold (5%, which was –log10(p) > 3.64) and spread across the wheat genome. The explained phenotypic variation of identified significant HBs ranged from 0.2% to 21.5%. The results of the analysis showed that four haplotypes (HTs) associated with disease parameters cause a reduction in the level of leaf coverage by necrosis and pycnidia, namely: Chr3A_HB98_HT2, Chr5B_HB47_HT1, Chr7B_HB36_HT1 and Chr5D_HB10_HT3.ConclusionsGWAS analysis enabled us to identify four significant chromosomal regions associated with a reduction in STB disease parameters. The list of valuable HBs and wheat varieties possessing them provides promising material for further molecular analysis of resistance loci and development of breeding programmes.

Copy number variation introduced by a massive mobile element facilitates global thermal adaptation in a fungal wheat pathogen

Copy number variation (CNV) can drive rapid evolution in changing environments. In microbial pathogens, such adaptation is a key factor underpinning epidemics and colonization of new niches. However, the genomic determinants of such adaptation remain poorly understood. Here, we systematically investigate CNVs in a large genome sequencing dataset spanning a worldwide collection of 1104 genomes from the major wheat pathogen Zymoseptoria tritici. We found overall strong purifying selection acting on most CNVs. Genomic defense mechanisms likely accelerated gene loss over episodes of continental colonization. Local adaptation along climatic gradients was likely facilitated by CNVs affecting secondary metabolite production and gene loss in general. One of the strongest loci for climatic adaptation is a highly conserved gene of the NAD-dependent Sirtuin family. The Sirtuin CNV locus localizes to an ~68-kb Starship mobile element unique to the species carrying genes highly expressed during plant infection. The element has likely lost the ability to transpose, demonstrating how the ongoing domestication of cargo-carrying selfish elements can contribute to selectable variation within populations. Our work highlights how standing variation in gene copy numbers at the global scale can be a major factor driving climatic and metabolic adaptation in microbial species.

Escuzarmycins A-D, Potent Biofungicides to Control Septoria tritici Blotch.

A study targeting novel antifungal metabolites identified potent in vitro antifungal activity against key plant pathogens in acetone extracts of Streptomyces sp. strain CA-296093. Feature-based molecular networking revealed the presence in this extract of antimycin-related compounds, leading to the isolation of four new compounds: escuzarmycins A-D (1-4). Extensive structural elucidation, employing 1D and 2D NMR, high-resolution mass spectrometry, Marfey's analysis, and NOESY correlations, confirmed their structures. The bioactivity of these compounds was tested against six fungal phytopathogens, and compounds 3 and 4 demonstrated strong efficacy, particularly against Zymoseptoria tritici, with compound 3 exhibiting the highest potency (EC50: 11 nM). Both compounds also displayed significant antifungal activity against Botrytis cinerea and Colletotrichum acutatum, with compound 4 proving to be the most potent. Despite moderate cytotoxicity against the human cancer cell line HepG2, compounds 3 and 4 emerge as promising fungicides for combating Septoria tritici blotch, anthracnose, and gray mold.

Sowing Date and Seed Rate Influence on Septoria Leaf Blotch Occurrence in Winter Wheat

Septoria leaf blotch (SLB), caused by Zymoseptoria tritici, is one of the most important foliar diseases of wheat. The management of this disease is assisted by selecting a sowing time and seeding density that is less favorable to the pathogen. The aim of this research was to evaluate the severity of SLB on winter wheat cv. ‘Etana’ sown at three different sowing times and three seed rates. The severity assessments were performed on the upper two leaves three times during the growth stages using the phenological growth stage key developed by the Biologische Bundesanstalt, Bundessortenamt, and Chemical industry (BBCH), namely stages 37–41, 59–65, and 75. The area under the disease progress curve (AUDPC) was evaluated in each plot. In 2022, seed rates showed significant differences (p = 0.0047), while sowing times did not show significant differences. In contrast, both seed rate and sowing time showed significant effects in 2021 (p = 0.0004 for sowing time and p < 0.0001 for seed rate). During the 2021 growth stage BBCH 75, late sowing times exhibited a significant reduction in SLB on the first leaf. The reduction ranged from 47.0% to 52.6% compared to the optimal sowing time, and from 59.2% to 66.2% compared to the early sowing time. At optimal sowing times (between 11 September and 25 September), seed rates of 400 and 450 seeds/m2 resulted in a low SLB. At late sowing times in 2022, a lower SLB (43.2% compared to the early sowing time) was obtained from seed rates of 400 seeds/m2. No significant interaction was observed between sowing time and seed rate across both study years. In the absence of interaction, the effects of sowing time and seed rate on SLB severity were independent and not additive. In 2022, the highest values of AUDPC were recorded for the early sowing time and the highest seed rate. Increasing the seed rate (450 seeds m−2) gave higher AUDPC at early sowing time with significant differences compared to other seed rates at optimal or late sowing times. In conclusion, our findings highlight the significant influence of sowing time and seed rate on SLB severity in winter wheat. Understanding these factors can inform agricultural practices to better manage SLB. Future research should explore additional agronomic practices and environmental factors to develop comprehensive strategies for SLB management.

Association mapping of septoria tritici blotch resistance in bread wheat in Bale and Arsi highlands, Ethiopia

Septoria tritici blotch (STB) caused by the fungal pathogen Zymoseptoria tritici, anamorph Septoria tritici Rob. ex Desm., is an important wheat pathogen worldwide, reported to be major wheat production threating factor, posing considerable yield loss every year. Developing resistant cultivars is an efficient, economical, environmentally friendly and simple approach for managing STB. This study was carried out to evaluate spring bread wheat lines for their reaction to STB disease under field conditions; to associate phenotypic and genotypic data for identification of STB disease resistance; and to identify genomic region(s) associated with resistance to STB in spring bread wheat lines. Two hundred forty (240) spring bread wheat lines were evaluated under field conditions in non-replicated trials, using an augmented design. The trials were conducted at three locations (Kulumsa Agricultural Research Center, Madda Walabu University Research Site and Sinana Agricultural Research Center) in 2017 main cropping season (July to December). Out of these 240 wheat lines, 123 of them were genotyped with 10263 single nucleotide polymorphism (SNPs) markers and population structure and association mapping analysis was done. The wheat lines showed significant variations in percentage disease severity and area under the disease progress curve at all the three locations they were evaluated. The wheat lines were classified as resistant, moderately resistant, moderately susceptible and susceptible based on the percentage disease severity scored. Five wheat lines were found to be resistant to STB in all the three locations and are recommended for direct release by the national program and parentage purposes in wheat breeding programs. The 123 wheat lines were clustered into 3 subpopulations in which the first cluster contained 99 wheat lines; the second 17 and the last one 7. Among the polymorphic 8127 SNPs markers, 26 markers on chromosomes 7B, 1D, 3A, 2B, 6B and 3D were found to be significantly (P < 0.001) associated with STB resistance so that they can be utilized for marker assisted selection and gene pyramiding in resistance breeding programs.