Bipolaris sorokiniana-Induced Black Point, Common Root Rot, and Spot Blotch Diseases of Wheat: A Review

Do Organic Amendments Foster Only Beneficial Bacteria in Agroecosystems?: The Case of Bacillus paranthracis TSO55

Bacterial strain TSO55 was isolated from a commercial field of wheat (Triticum turgidum L. subsp. durum), under organic amendments, located in the Yaqui Valley, Mexico. Morphological and microscopical characterization showed off-white irregular colonies and Gram-positive bacillus, respectively. The draft genome sequence of this strain revealed a genomic size of 5,489,151 bp, with a G + C content of 35.21%, N50 value of 245,934 bp, L50 value of 8, and 85 contigs. Taxonomic affiliation showed that strain TSO55 belongs to Bacillus paranthracis, reported as an emergent human pathogen. Genome annotation identified 5743 and 5587 coding DNA sequences (CDSs), respectively, highlighting genes associated with indole production, phosphate and potassium solubilization, and iron acquisition. Further in silico analysis indicated the presence of three CDSs related to pathogenicity islands and a high pathogenic potential (77%), as well as the presence of multiple gene clusters related to antibiotic resistance. The in vitro evaluation of plant growth promotion traits was negative for indole production and phosphate and potassium solubilization, and it was positive but low (18%) for siderophore production. The biosynthetic gene cluster for bacillibactin (siderophore) biosynthesis was confirmed. Antifungal bioactivity of strain TSO55 evaluated against wheat pathogenic fungi (Alternaria alternata TF17, Bipolaris sorokiniana TPQ3, and Fusarium incarnatum TF14) showed minimal fungal inhibition. An antibiotic susceptibility assay indicated resistance to three of the six antibiotics evaluated, up to a concentration of 20 µg/mL. The beta hemolysis result on blood agar reinforced TSO55's pathogenic potential. Inoculation of B. paranthracis TSO55 on wheat seedlings resulted in a significant decrease in root length (-8.4%), total plant height (-4.2%), root dry weight (-18.6%), stem dry weight (-11.1%), and total plant dry weight (-15.2%) compared to the control (uninoculated) treatment. This work highlights the importance of analyzing the microbiological safety of organic amendments before application. Comprehensive genome-based taxonomic affiliation and bioprospecting of microbial species introduced to the soil by organic agricultural practices and any microbial inoculant will prevent the introduction of dangerous species with non-beneficial traits for crops, which affect sustainability and generate potential health risks for plants and humans.

Bacillus cabrialesii subsp. cabrialesii Strain TE5: A Promising Biological Control Bacterium Against the Causal Agent of Spot Blotch in Wheat

Strain TE5 was isolated from a wheat (Triticum turgidum L. subsp. durum) rhizosphere grown in a commercial field of wheat in the Yaqui Valley in Mexico. In this work, we present strain TE5 as a promising biological control agent against Bipolaris sorokiniana. First, after its genome sequencing through Illumina NovaSeq, this strain showed a genome size of 4,262,927 bp, with a 43.74% G + C content, an N50 value of 397,059 bp, an L50 value of 4 bp, and 41 contigs (>500 bp). Taxonomical affiliation was carried out by using overall genome relatedness indexes (OGRIs) and the construction of a phylogenomic tree based on the whole genome. The results indicated that strain TE5 identifies with Bacillus cabrialesii subsp. cabrialesii. Genomic annotation using Rapid Annotation Using Subsystems Technology (RAST) and Rapid Prokaryotic Genome Annotation (Prokka) indicated the presence of 4615 coding DNA sequences (CDSs) distributed across 330 subsystems, which included gene families associated with biocontrol, stress response, and iron competition. Furthermore, when the antiSMASH 7.1 platform was used for genome mining, the results indicated the presence of seven putative biosynthetic gene clusters related to the production of biocontrol metabolites, namely subtilosin A, bacillibactin, fengycin, bacillaene, bacilysin, surfactin, and rhizocticin A. Moreover, the antifungal activity of strain TE5 and its cell-free extract (CFE) was evaluated against Bipolaris sorokiniana, an emergent wheat pathogen. The results of in vitro dual confrontation showed fungal growth inhibition of 67% by strain TE5. Additionally, its CFE almost completely inhibited (93%) the growth of the studied phytopathogenic fungus on liquid media. Further observations of the impact of these bacterial metabolites on fungal spore germination exhibited inhibition of fungal spores through degrading the germinative hypha, avoiding mycelium development. Finally, the protective effect of strain TE5 against Bipolaris sorokiniana was evaluated for wheat seedlings. The results showed a significant decrease (83%) in disease severity in comparison with the plant infection without inoculation of the biological control agent. Thus, this work proposes Bacillus cabrialesii subsp. cabrialesii strain TE5 as a promising biological control agent against the wheat pathogen Bipolaris sorokiniana while suggesting lipopeptides as the potential mode of action, together with plant growth and defense stimulation.

Unlocking the role of silicon against biotic stress in plants

The requirement for agricultural crops continues to enhance with the continuous growth of the human population globally. Plant pathogenic diseases outbreaks are enhancing and threatening food security and safety for the vulnerable in different regions worldwide. Silicon (Si) is considered a non-essential element for plant growth. It regulates the biological functions, plant development and productivity, and balance the defense mechanism in response to fungal, bacterial and pest attacks. The optimum crop yield can be achieved by applying Si in agricultural systems through different methods to replace or minimize the use of synthetic fertilizers. This approach can be effective on crop production during limited resources, extreme climates, pests and diseases, and environmental pollution. Silicon can be applied as foliar spray, priming of seeds, soil water irrigation, soil amendment and soilless medium (hydroponic) to enhance plant performance and stress tolerance capacity during stress conditions. This article summarized the effective roles of Si and the ability to perform in agroecosystems for better crop production, food security and safety for sustainable agriculture in the future.

Impact of spot blotch pathogen Bipolaris sorokiniana on important seed quality parameters in wheat and its management with biocontrol agents and newer fungicide molecules

Spot blotch disease is prominent amongst several biotic stresses challenging wheat yield and quality. The impact of seed inoculation with Bipolaris sorokiniana, on important wheat seed quality of popular cultivar (cv.) DBW 187, was estimated in comparison to susceptible check WH 147. DBW 187 responded very effectively against pathogen keeping all parameters well ahead of susceptible check. The variety could resist declination in per cent germination with 8.07% in comparison to WH 147 which resulted in 14.72% reduction in germination after pathogen inoculation. Similarly, after pathogen's inoculation, speed of germination (80.06) and vigour index I (2677) and II (24379) were significantly higher in cv. DBW 187 as against cv. WH 147, which resulted in lower speed of germination and vigour index I and II, i.e. 74.37, 2249, and 16715, respectively. Amongst the biocontrol agents, Trichoderma harzianum was found to be the most effective in managing this pathogen, which caused 86.30% inhibition in mycelial growth of B. sorokiniana. Amongst the seven fungicides used to manage Bipolaris sorokiniana in vitro, tebuconazole 50% + trifloxystrobin 25% WG, propiconazole 25% EC both at 75 and 100 ppm, and kresoxim methyl 44.3% SC at 100 ppm were most effective against Bipolaris sorokiniana, causing complete inhibition in its radial growth. Conclusively, wheat cv. DBW 187 has capacity to resist seed health deterioration caused by the pathogen. Out of seven evaluated fungicides, the best three newer fungicide molecules, viz., tebuconazole 50% + trifloxystrobin 25% WG, propiconazole 25% EC, and kresoxim methyl 44.3% SC, can judiciously be utilized in combination with biocontrol agents, Trichoderma harzianum, T. asperellum, and Chaetomium globosum, keeping the fungicide load minimum for the effective management of B. sorokiniana.

The Roadmap of Plant Antimicrobial Peptides Under Environmental Stress: From Farm to Bedside

Antimicrobial peptides (AMPs) are the most favorable alternatives in overcoming multidrug resistance, alone or synergistically with conventional antibiotics. Plant-derived AMPs, as cysteine-rich peptides, widely compensate the pharmacokinetic drawbacks of peptide therapeutics. Compared to the putative genes encrypted in the genome, AMPs that are produced under stress are active forms with the ability to combat resistant microbial species. Within this study, plant-derived AMPs, namely, defensins, nodule-specific cysteine-rich peptides, snakins, lipid transfer proteins, hevein-like proteins, α-hairpinins, and aracins, expressed under biotic and abiotic stresses, are classified. We could observe that while α-hairpinins and snakins display a helix-turn-helix structure, conserved motif patterns such as β1αβ2β3 and β1β2β3 exist in plant defensins and hevein-like proteins, respectively. According to the co-expression data, several plant AMPs are expressed together to trigger synergistic effects with membrane disruption mechanisms such as toroidal pore, barrel-stave, and carpet models. The application of AMPs as an eco-friendly strategy in maintaining agricultural productivity through the development of transgenes and bio-pesticides is discussed. These AMPs can be consumed in packaging material, wound-dressing products, coating catheters, implants, and allergology. AMPs with cell-penetrating properties are verified for the clearance of intracellular pathogens. Finally, the dominant pharmacological activities of bioactive peptides derived from the gastrointestinal digestion of plant AMPs, namely, inhibitors of renin and angiotensin-converting enzymes, dipeptidyl peptidase IV and α-glucosidase inhibitors, antioxidants, anti-inflammatory, immunomodulating, and hypolipidemic peptides, are analyzed. Conclusively, as phytopathogens and human pathogens can be affected by plant-derived AMPs, they provide a bright perspective in agriculture, breeding, food, cosmetics, and pharmaceutical industries, translated as farm to bedside.

Resistance Mechanisms of Plant Pathogenic Fungi to Fungicide, Environmental Impacts of Fungicides, and Sustainable Solutions

The significant reduction in agricultural output and the decline in product quality are two of the most glaring negative impacts caused by plant pathogenic fungi (PPF). Furthermore, contaminated food or transit might introduce mycotoxins produced by PPF directly into the food chain. Eating food tainted with mycotoxin is extremely dangerous for both human and animal health. Using fungicides is the first choice to control PPF or their toxins in food. Fungicide resistance and its effects on the environment and public health are becoming more and more of a concern, despite the fact that chemical fungicides are used to limit PPF toxicity and control growth in crops. Fungicides induce target site alteration and efflux pump activation, and mutations in PPF result in resistance. As a result, global trends are shifting away from chemically manufactured pesticides and toward managing fungal plant diseases using various biocontrol techniques, tactics, and approaches. However, surveillance programs to monitor fungicide resistance and their environmental impact are much fewer compared to bacterial antibiotic resistance surveillance programs. In this review, we discuss the PPF that contributes to disease development in plants, the fungicides used against them, factors causing the spread of PPF and the emergence of new strains, the antifungal resistance mechanisms of PPF, health, the environmental impacts of fungicides, and the use of biocontrol agents (BCAs), antimicrobial peptides (AMPs), and nanotechnologies to control PPF as a safe and eco-friendly alternative to fungicides.

Nanowarriors from Mentha: Unleashing Nature's Antimicrobial Arsenal with Cerium Oxide Nanoparticles

Medicinal plant-based cerium oxide nanoparticles (CeO2NPs) possessed excellent antimicrobial properties against multiple strains of Gram-positive and Gram-negative bacteria. The CeO2NPs are popular because their electropositive charged surface causes oxidation of plasma membrane and facilitates the penetration of CeO2NPs inside the pathogen body. In the present research work, CeO2NPs stabilized with Mentha leaf extract; as a result, nanoparticles surface-bonded with various functional groups of phytochemicals which enhanced the therapeutic potential of CeO2NPs. The inhibition percentage of CeO2NPs was evaluated against eight pathogenic Gram-positive bacteria Staphylococcus aureus and Streptococcus epidermidis; Gram-negative bacteria Escherichia coli, Stenotrophomonas maltophilia, Comamonas sp., Halobacterium sp., and Klebsiella pneumoniae; and plant bacteria Xanthomonas sp. The antifungal properties of CeO2NPs were evaluated against three pathogenic fungal species Bipolaris sorokiniana, Aspergillus flavus, and Fusarium oxysporum via the streak plate method. The antimicrobial inhibitory activity of CeO2NPs was good to excellent. The current research work clearly shows that three different medicinal plants Mentha royleana, Mentha longifolia, and Mentha arvensis based CeO2NPs, variation in nanoparticle sizes, and surface-to-volume ratio of green CeO2NPs are three factors responsible to generate and provoke antimicrobial activities of CeO2NPs against human pathogenic bacteria and plant infecting fungi. The results show that CeO2NPs possessed good antimicrobial properties and are effective to use for pharmaceutical applications and as a food preservative because of low toxicity, organic coating, and acceptable antimicrobial properties. This study showed a rapid and well-organized method to prepare stable phytochemical-coated CeO2NPs with three different plants M. royleana, M. longifolia, and M. arvensis with remarkable antibacterial and antifungal characteristics.

Mutagenesis-Derived Resistance to Black Point in Wheat

Black point, a severe global wheat disease, necessitates deploying resistant cultivars for effective control. However, susceptibility remains prevalent among most wheat cultivars. Identifying new sources of resistance and understanding their mechanisms are crucial for breeding resistant cultivars. This study pinpointed black point resistance in an ethyl methane sulfonate (EMS)-mutagenized wheat population of Wanyuanbai 1 (WYB) and analyzed resistant mutants using RNA-Seq. The findings revealed the following: (i) wyb-18, among 10,008 EMS-mutagenized lines, exhibited robust resistance with significantly lower black point incidence under artificial Bipolaris sorokiniana inoculation in 2020 and 2021 (average incidence of 5.2% over 2 years), markedly reduced compared with WYB (50.9%). (ii) wyb-18 kernels displayed black point symptoms at 12 days after inoculation (dai), 3 days later than WYB. At 15 dai, wyb-18 kernels had isolated black spots, unlike WYB kernels, where the entire embryo turned black. (iii) wyb-18 showed heightened antioxidant enzyme activity, including peroxidase, catalase, and superoxide dismutase. (iv) Analysis of 543 differentially expressed genes between wyb-18 and WYB at 9 dai identified enrichment in the MAPK signaling pathway through KEGG analysis. Ten genes in this pathway exhibited upregulated expression, while one was downregulated in wyb-18. Among these genes, PR1, WRKY11, SAPK5, and TraesCS1A02G326800 (chitin recognition protein) consistently showed upregulation in wyb-18, making them potential candidates for black point resistance. These results offer valuable germplasm resources for breeding and novel insights into the mechanisms of black point resistance.

Transcriptome-Wide Identification and Expression Analysis of Genes Encoding Defense-Related Peptides of Filipendula ulmaria in Response to Bipolaris sorokiniana Infection

Peptides play an essential role in plant development and immunity. Filipendula ulmaria, belonging to the Rosaceae family, is a medicinal plant which exhibits valuable pharmacological properties. F. ulmaria extracts in vitro inhibit the growth of a variety of plant and human pathogens. The role of peptides in defense against pathogens in F. ulmaria remains unknown. The objective of this study was to explore the repertoire of antimicrobial (AMPs) and defense-related signaling peptide genes expressed by F. ulmaria in response to infection with Bipolaris sorokiniana using RNA-seq. Transcriptomes of healthy and infected plants at two time points were sequenced on the Illumina HiSeq500 platform and de novo assembled. A total of 84 peptide genes encoding novel putative AMPs and signaling peptides were predicted in F. ulmaria transcriptomes. They belong to known, as well as new, peptide families. Transcriptional profiling in response to infection disclosed complex expression patterns of peptide genes and identified both up- and down-regulated genes in each family. Among the differentially expressed genes, the vast majority were down-regulated, suggesting suppression of the immune response by the fungus. The expression of 13 peptide genes was up-regulated, indicating their possible involvement in triggering defense response. After functional studies, the encoded peptides can be used in the development of novel biofungicides and resistance inducers.

Unraveling the dynamics of wheat leaf blight complex: isolation, characterization, and insights into pathogen population under Indian conditions

Wheat, a staple food crop for 35% of the global population, faces a threat from Helminthosporium leaf blight (HLB), a complex of spot blotch (Bipolaris sorokiniana) and tan spot (Pyrenophora-tritici-repentis) diseases under warm and humid conditions. However, in Indian conditions, the knowledge of existing pathogen populations associated with the HLB complex is limited and largely dominated by only B. sorokiniana (spot blotch). To address this, diseased samples were collected from all six wheat growing zones during 2020-2022. The pathogenic species were identified through in-depth morphological characterization, supplemented with ITS-rDNA and GAPDH sequence analysis, a diagnostic SCAR marker, and pathogenicity studies on two wheat varieties: Sonalika and HD2733. The 32 isolates collected from 10 different states consist of B. spicifera (12.5% of all isolates), Exserohilum rostratum (9.3%), Bipolaris oryzae (3.1%), and B. sorokiniana (75%). B. sorokiniana exhibited the highest disease severity on both varieties. Other lesser-known pathogenic species also produced comparable disease severity as B. sorokiniana isolates and, therefore are economically important. Unraveling pathogen composition and biology aids in disease control and resistance breeding. Our study highlights economically impactful and lesser-known pathogenic species causing wheat leaf blight/spot blotch in India, guiding both current management and future resistance breeding strategies in plant pathology.

Fabrication of three-dimension hierarchical structure CuO nanoflowers and their antifungal mechanism against Bipolaris sorokiniana

Nanomaterials are widely investigated in sustainable agriculture owing to their unique physicochemical properties, especially Cu-based nanomaterial with eco-friendliness and essential for plant. However, the effect of CuO nanomaterial on Bipolaris sorokiniana (B. sorokiniana) is yet to be systematically understood. In this study, a three-dimension hierarchical structure CuO nanoflower (CuO NF) with ultrathin petals and excellent dispersibility in water was constructed and proved to have outstanding antifungal activity against B. sorokiniana with the inhibition rate of 86 % in mycelial growth, 74 % in mycelial dry weight and 75 % in conidial germination. Furthermore, the antifungal mechanism was assigned to the production of reactive oxygen species in intracellular caused by antioxidant mimicking activity of CuO NF to damage of cell membrane integrity and result cellular leakage. Additionally, the good control effect of CuO NF on wheat diseases caused by B. sorokiniana was demonstrated through pot experiment. This article firstly reveals the antifungal activity and mechanism of CuO NF on B. sorokiniana, and establishes the relationship between enzyme-like activity of CuO NF and its antifungal activity, which provides a promising application of Cu-based nanomaterial as nanofungicide in plant protection and a theoretical foundation for structure design of nanomaterials to improve their antifungal activities.

Beneficial Microorganisms as Bioprotectants against Foliar Diseases of Cereals: A Review

Cereal production plays a major role in both animal and human diets throughout the world. However, cereal crops are vulnerable to attacks by fungal pathogens on the foliage, disrupting their biological cycle and photosynthesis, which can reduce yields by 15-20% or even 60%. Consumers are concerned about the excessive use of synthetic pesticides given their harmful effects on human health and the environment. As a result, the search for alternative solutions to protect crops has attracted the interest of scientists around the world. Among these solutions, biological control using beneficial microorganisms has taken on considerable importance, and several biological control agents (BCAs) have been studied, including species belonging to the genera Bacillus, Pseudomonas, Streptomyces, Trichoderma, Cladosporium, and Epicoccum, most of which include plants of growth-promoting rhizobacteria (PGPRs). Bacillus has proved to be a broad-spectrum agent against these leaf cereal diseases. Interaction between plant and beneficial agents occurs as direct mycoparasitism or hyperparasitism by a mixed pathway via the secretion of lytic enzymes, growth enzymes, and antibiotics, or by an indirect interaction involving competition for nutrients or space and the induction of host resistance (systemic acquired resistance (SAR) or induced systemic resistance (ISR) pathway). We mainly demonstrate the role of BCAs in the defense against fungal diseases of cereal leaves. To enhance a solution-based crop protection approach, it is also important to understand the mechanism of action of BCAs/molecules/plants. Research in the field of preventing cereal diseases is still ongoing.

Bacillus velezensis BV01 Has Broad-Spectrum Biocontrol Potential and the Ability to Promote Plant Growth

To evaluate the potential of a bacterial strain as a fungal disease control agent and plant growth promoter, its inhibitory effects on phytopathogens such as Bipolaris sorokiniana, Botrytis cinerea, Colletotrichum capsici, Fusarium graminearum, F. oxysporum, Neocosmospora rubicola, Rhizoctonia solani, and Verticillium dahliae were investigated. The results showed that the inhibitory rates in dual-culture and sterile filtrate assays against these eight phytopathogens ranged from 57% to 83% and from 36% to 92%. The strain was identified as Bacillus velezensis based on morphological and physiological characterization as well as phylogenetic analyses of 16S rRNA and the gyrase subunit A protein (gyrA) regions. The results demonstrated that B. velezensis was able to produce fungal cell-wall-degrading enzymes, namely, protease, cellulase, and β-1,3-glucanase, and the growth-promotion substances indole-3-acetic acid (IAA) and siderophore. Furthermore, B. velezensis BV01 had significant control effects on wheat root rot and pepper Fusarium wilt in a greenhouse. Potted growth-promotion experiments displayed that BV01 significantly increased the height, stem diameter, and aboveground fresh and dry weights of wheat and pepper. The results imply that B. velezensis BV01, a broad-spectrum biocontrol bacterium, is worth further investigation regarding its practical applications in agriculture.

Prevalence and Importance of the Necrotrophic Effector Gene ToxA in Bipolaris sorokiniana Populations Collected from Spring Wheat and Barley

Bipolaris sorokiniana is a necrotrophic fungal pathogen that causes foliar and root diseases on wheat and barley. These diseases are common in all wheat- and barley-growing regions, with more severe outbreaks occurring under warm and humid conditions. B. sorokiniana can also infect a wide range of grass species in the family Poaceae and secrete ToxA, an important necrotrophic effector also identified other wheat leaf spotting pathogens. In this study, the prevalence and virulence role of ToxA were investigated in a collection of 278 B. sorokiniana isolates collected from spring wheat and barley in the Upper Midwest of the United States or other places, including 169 from wheat leaves, 75 from wheat roots, 30 from barley leaves, and 4 from wild quack grass leaves. ToxA was present in the isolates from wheat leaves, wheat roots, and wild grass leaves but was absent from isolates collected from barley leaves. Prevalence of ToxA in wheat leaf isolates (34.3%) was much higher than that in wheat root isolates (16%). Sequencing analysis revealed the presence of two haplotypes, with the majority being BsH2. All ToxA+ isolates produced the functional effector in liquid cultures. Pathogenicity assays revealed that ToxA+ isolates caused significantly more disease on spring wheat lines harboring Tsn1 than their tsn1 mutants, suggesting that the ToxA-Tsn1 interaction plays an important role in spot blotch development. This work confirms the importance of ToxA in B. sorokiniana populations infecting wheat and, thus, the need to eliminate Tsn1 from spring wheat cultivars to reduce susceptibility to spot blotch.

Additive screening and formula optimization of microbial inhibitor having disease prevention and growth promotion effects on Avena sativa

In order to develop environment friendly microbial inhibitor that can also control disease and promote oat (Avena sativa) growth, the growth rate method and response surface methodology were used to screen wetting agents, preservatives and protective agents at optimal concentrations in this study. Antagonistic activity of the tested bacterium and cell-free fermentation liquid against pathogenic fungi was evaluated on potato dextrose agar (PDA) substratum plates by dual culture technique. Oxford cup method was used to measure antagonistic reaction between screened bacteria. According to each screened bacteria with 50 mL were mixed and cultured in Luria-bertani (LB) substratum. Additives of Wetting agents, UV-protectors, and preservatives were screened by single factor test on the growth concentration of screened mixed bacteria. Afterwards, the optimal additives and concentrations were screened by Box-Behnken method. The microbial inhibitor was detected according to national standards GB20287-2006 and tested on oat in a pot experiment. The results showed that: (1) Functional bacteria which including Bacillus velezensis and Brevundimonas faecalis had control effects of 50.00% to 83.29% on three pathogenic fungi, and their cell free-fermentation liquid could inhibit the growth of pathogenic fungi from 23.51% to 39.90%; (2) Tween-80 was most suitable as wetting agents for Mix biocontrol bacteria (MBB) with 1.00% mass fraction; Sorbitol was selected as UV protective agents for MBB with 0.50% mass fraction. And methyl paraben was used as a preservative for MBB, with 0.50% mass fraction; (3) The most effective adjuvant contained 14.96 mL/L Tween-80, 5.12 g/L methylparaben and 5.6 g/L sorbitol; and (4) The microbial inhibitor controlled 45.57% of oat root rot and increased plant height, root length and seedling biomass. This study provides a suitable environment for the protection of mixed biocontrol bacteria, and lays a foundation for the prevention and control of oat diseases, the promotion of growth and the improvement of quality.

High-Quality Nuclear Genome and Mitogenome of Bipolaris sorokiniana LK93, a Devastating Pathogen Causing Wheat Root Rot

Bipolaris sorokiniana, one of the most devastating hemibiotrophic fungal pathogens, causes root rot, crown rot, leaf blotching, and black embryos of gramineous crops worldwide, posing a serious threat to global food security. However, the host-pathogen interaction mechanism between B. sorokiniana and wheat remains poorly understood. To facilitate related studies, we sequenced and assembled the genome of B. sorokiniana LK93. Nanopore long reads and next generation sequencing short reads were applied in the genome assembly, and the final 36.4-Mb genome assembly contains 16 contigs with the contig N50 of 2.3 Mb. Subsequently, we annotated 11,811 protein-coding genes. Of these, 10,620 were functional genes, 258 of which were identified as secretory proteins, including 211 predicted effectors. Additionally, the 111,581-bp mitogenome of LK93 was assembled and annotated. The LK93 genomes presented in this study will facilitate research in the B. sorokiniana-wheat pathosystem for better control of crop diseases. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Genetics and breeding for resistance against four leaf spot diseases in wheat (Triticum aestivum L.)

In wheat, major yield losses are caused by a variety of diseases including rusts, spike diseases, leaf spot and root diseases. The genetics of resistance against all these diseases have been studied in great detail and utilized for breeding resistant cultivars. The resistance against leaf spot diseases caused by each individual necrotroph/hemi-biotroph involves a complex system involving resistance (R) genes, sensitivity (S) genes, small secreted protein (SSP) genes and quantitative resistance loci (QRLs). This review deals with resistance for the following four-leaf spot diseases: (i) Septoria nodorum blotch (SNB) caused by Parastagonospora nodorum; (ii) Tan spot (TS) caused by Pyrenophora tritici-repentis; (iii) Spot blotch (SB) caused by Bipolaris sorokiniana and (iv) Septoria tritici blotch (STB) caused by Zymoseptoria tritici.

Managing spot blotch disease in wheat: Conventional to molecular aspects

Spot blotch (SB) caused by Bipolaris sorokiniana (teleomorph Cochliobolus sativus) is one of the devastating diseases of wheat in the warm and humid growing areas around the world. B. sorokiniana can infect leaves, stem, roots, rachis and seeds, and is able to produce toxins like helminthosporol and sorokinianin. No wheat variety is immune to SB; hence, an integrated disease management strategy is indispensable in disease prone areas. A range of fungicides, especially the triazole group, have shown good effects in reducing the disease, and crop-rotation, tillage and early sowing are among the favorable cultural management methods. Resistance is mostly quantitative, being governed by QTLs with minor effects, mapped on all the wheat chromosomes. Only four QTLs with major effects have been designated as Sb1 through Sb4. Despite, marker assisted breeding for SB resistance in wheat is scarce. Better understanding of wheat genome assemblies, functional genomics and cloning of resistance genes will further accelerate breeding for SB resistance in wheat.

Antagonistic Strain Bacillus halotolerans Jk-25 Mediates the Biocontrol of Wheat Common Root Rot Caused by Bipolaris sorokiniana

Common root rot caused by Bipolaris sorokiniana infestation in wheat is one of the main reasons for yield reduction in wheat crops worldwide. The bacterium strain JK-25 used in the current investigation was isolated from wheat rhizosphere soil and was later identified as Bacillus halotolerans based on its morphological, physiological, biochemical, and molecular properties. The strain showed significant antagonism to B. sorokiniana, Fusarium oxysporum, Fusarium graminearum, and Rhizoctonia zeae. Inhibition of B. sorokiniana mycelial dry weight and spore germination rate by JK-25 fermentation supernatant reached 60% and 88%, respectively. The crude extract of JK-25 was found, by Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), to contain the surfactin that exerted an inhibitory effect on B. sorokiniana. The disruption of mycelial cell membranes was observed under laser scanning confocal microscope (LSCM) after treatment of B. sorokiniana mycelium with the crude extract. The antioxidant enzyme activity of B. sorokiniana was significantly reduced and the oxidation product malondialdehyde (MDA) content increased after treatment with the crude extract. The incidence of root rot was significantly reduced in pot experiments with the addition of JK-25 culture fermentation supernatant, which had a significant biological control effect of 72.06%. Its ability to produce siderophores may help to promote wheat growth and the production of proteases and pectinases may also be part of the strain's role in suppressing pathogens. These results demonstrate the excellent antagonistic effect of JK-25 against B. sorokiniana and suggest that this strain has great potential as a resource for biological control of wheat root rot strains.

Evaluation of Selenium Nanoparticles in Inducing Disease Resistance against Spot Blotch Disease and Promoting Growth in Wheat under Biotic Stress

In the present study, SeNPs were synthesized using Melia azedarach leaf extracts and investigated for growth promotion in wheat under the biotic stress of spot blotch disease. The phytosynthesized SeNPs were characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The in vitro efficacy of different concentrations of phytosynthesized SeNPs (i.e., 100 μg/mL, 150 μg/mL, 200 μg/mL, 250 μg/mL, and 300 μg/mL) was evaluated using the well diffusion method, which reported that 300 μg/mL showed maximum fungus growth inhibition. For in vivo study, different concentrations (10, 20, 30, and 40 mg/L) of SeNPs were applied exogenously to evaluate the morphological, physiological, and biochemical parameters under control conditions and determine when infection was induced. Among all treatments, 30 mg/L of SeNPs performed well and increased the plant height by 2.34% compared to the control and 30.7% more than fungus-inoculated wheat. Similarly, fresh plant weight and dry weight increased by 17.35% and 13.43% over the control and 20.34% and 52.48% over the fungus-treated wheat, respectively. In leaf surface area and root length, our findings were 50.11% and 10.37% higher than the control and 40% and 71% higher than diseased wheat, respectively. Plant physiological parameters i.e., chlorophyll a, chlorophyll b, and total chlorophyll content, were increased 14, 133, and 16.1 times over the control and 157, 253, and 42 times over the pathogen-inoculated wheat, respectively. Our findings regarding carotenoid content, relative water content, and the membrane stability index were 29-, 49-, and 81-fold higher than the control and 187-, 63-, and 48-fold higher than the negative control, respectively. In the case of plant biochemical parameters, proline, sugar, flavonoids, and phenolic contents were recorded at 6, 287, 11, and 34 times higher than the control and 32, 107, 33, and 4 times more than fungus-inoculated wheat, respectively. This study is considered the first biocompatible approach to evaluate the potential of green-synthesized SeNPs as growth-promoting substances in wheat under the spot blotch stress and effective management strategy to inhibit fungal growth.

Combination of Aspergillus niger MJ1 with Pseudomonas stutzeri DSM4166 or mutant Pseudomonas fluorescens CHA0-nif improved crop quality, soil properties, and microbial communities in barrier soil

Soil salinization and acidification seriously damage soil health and restricts the sustainable development of planting. Excessive application of chemical fertilizer and other reasons will lead to soil acidification and salinization. This study focus on acid and salinized soil, investigated the effect of phosphate-solubilizing bacteria, Aspergillus niger MJ1 combined with nitrogen-fixing bacteria Pseudomonas stutzeri DSM4166 or mutant Pseudomonas fluorescens CHA0-nif on crop quality, soil physicochemical properties, and microbial communities. A total of 5 treatments were set: regular fertilization (T1), regular fertilization with MJ1 and DSM4166 (T2), regular fertilization with MJ1 and CHA0-nif (T3), 30%-reducing fertilization with MJ1 and DSM4166 (T4), and 30%-reducing fertilization with MJ1 and CHA0-nif (T5). It was found that the soil properties (OM, HN, TN, AP, AK, and SS) and crop quality of cucumber (yield production, protein, and vitamin C) and lettuce (yield production, vitamin C, nitrate, soluble protein, and crude fiber) showed a significant response to the inoculated strains. The combination of MJ1 with DSM4166 or CHA0-nif influenced the diversity and richness of bacterial community in the lettuce-grown soil. The organismal system-, cellular process-, and metabolism-correlated bacteria and saprophytic fungi were enriched, which were speculated to mediate the response to inoculated strains. pH, OM, HN, and TN were identified to be the major factors correlated with the soil microbial community. The inoculation of MJ1 with DSM4166 and CHA0-nif could meet the requirement of lettuce and cucumber growth after reducing fertilization in acid and salinized soil, which provides a novel candidate for the eco-friendly technique to meet the carbon-neutral topic.

Quantitative trait loci for resistance to black point caused by Bipolaris sorokiniana in bread wheat

Black point disease is a serious concern in wheat production worldwide. In this study, we aimed to identify the major quantitative trait loci (QTL) for resistance to black point caused by Bipolaris sorokiniana and develop molecular markers for marker-assisted selection (MAS). A recombinant inbred line (RIL) population derived from a cross between PZSCL6 (highly susceptible) and Yuyou1 (moderately resistant) was evaluated for black point resistance at four locations under artificial inoculation with B. sorokiniana. Thirty resistant and 30 susceptible RILs were selected to form resistant and susceptible bulks, respectively, which were genotyped by the wheat 660 K SNP array. Two hundred and four single-nucleotide polymorphisms (SNPs) were identified, among which 41(20.7%), 34 (17.2%), 22 (11.1%), and 22 (11.1%) were located on chromosomes 5A, 5B, 4B, and 5D, respectively. The genetic linkage map for the RIL population was constructed using 150 polymorphic SSR and dCAPS markers. Finally, five QTL were detected on chromosomes 5A, 5B, and 5D, designated QBB.hau-5A, QBB.hau-5B.1, QBB.hau-5B.2, QBB.hau-5D.1, and QBB.hau-5D.2, respectively. All resistance alleles were contributed by the resistant parent Yuyou1. QBB.hau-5D.1 is likely to be a new locus for black point resistance. The markers Xwmc654 and Xgwm174 linked to QBB.hau-5A and QBB.hau-5D.1, respectively, have potential utility in MAS-based breeding.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01356-6.

Development of Diagnostic Markers and Applied for Genetic Diversity Study and Population Structure of Bipolaris sorokiniana Associated with Leaf Blight Complex of Wheat

Bipolaris sorokiniana, a key pathogenic fungus in the wheat leaf blight complex, was the subject of research that resulted in the development of fifty-five polymorphic microsatellite markers. These markers were then used to examine genetic diversity and population structure in Indian geographical regions. The simple sequence repeat (SSR) like trinucleotides, dinucleotides, and tetranucleotides accounted for 43.37% (1256), 23.86% (691), and 16.54% (479) of the 2896 microsatellite repeats, respectively. There were 109 alleles produced by these loci overall, averaging 2.36 alleles per microsatellite marker. The average polymorphism information content value was 0.3451, with values ranging from 0.1319 to 0.5932. The loci's Shannon diversity varied from 0.2712 to 1.2415. These 36 isolates were divided into two main groups using population structure analysis and unweighted neighbour joining. The groupings were not based on where the isolates came from geographically. Only 7% of the overall variation was found to be between populations, according to an analysis of molecular variance. The high amount of gene flow estimate (N_M = 3.261 per generation) among populations demonstrated low genetic differentiation in the entire populations (F_ST = 0.071). The findings indicate that genetic diversity is often minimal. In order to examine the genetic diversity and population structure of the B. sorokiniana populations, the recently produced microsatellite markers will be helpful. This study's findings may serve as a foundation for developing improved management plans for the leaf blight complex and spot blotch of wheat diseases in India.

Fungal Pathogens Associated with Crown and Root Rot in Wheat-Growing Areas of Northern Kyrgyzstan

Fungal species associated with crown and root rot diseases in wheat have been extensively studied in many parts of the world. However, no reports on the relative importance and distribution of pathogens associated with wheat crown and root rot in Kyrgyzstan have been published. Hence, fungal species associated with wheat crown/root rot were surveyed in three main wheat production regions in northern Kyrgyzstan. Fungal species were isolated on 1/5 strength potato-dextrose agar amended with streptomycin (0.1 g/L) and chloramphenicol (0.05 g/L). A total of 598 fungal isolates from symptomatic tissues were identified using morphological features of the cultures and conidia, as well as sequence analysis of the nuclear ribosomal internal transcribed spacer (ITS) region, the translation elongation factor 1α (TEF1), and the RNA polymerase II beta subunit (RPB2) genes. The percentage of fields from which each fungus was isolated and their relative percentage isolation levels were determined. Bipolaris sorokiniana, the causal agent of common root rot, was the most prevalent pathogenic species isolated, being isolated from 86.67% of the fields surveyed at a frequency of isolation of 40.64%. Fusarium spp. accounted for 53.01% of all isolates and consisted of 12 different species. The most common Fusarium species identified was Fusarium acuminatum, which was isolated from 70% of the sites surveyed with an isolation frequency of 21.57%, followed by Fusarium culmorum, Fusarium nygamai, Fusarium oxysporum, and Fusarium equiseti, all of which had a field incidence of more than 23%. Inoculation tests with 44 isolates representing 17 species on the susceptible Triticum aestivum cv. Seri 82 revealed that Fusarium pseudograminearum and F. culmorum isolates were equally the most virulent pathogens. The widespread distribution of moderately virulent B. sorokiniana appears to be a serious threat to wheat culture, limiting yield and quality. With the exception of F. culmorum, the remaining Fusarium species did not pose a significant threat to wheat production in the surveyed areas because common species, such as F. acuminatum, F. nygamai, F. oxysporum, and F. equiseti, were non-pathogenic but infrequent species, such as Fusarium redolens, Fusarium algeriense, and F. pseudograminearum, were highly or moderately virulent. Curvularia inaequalis, which was found in three different fields, was mildly virulent. The remaining Fusarium species, Fusarium solani, Fusarium proliferatum, Fusarium burgessii, and Fusarium tricinctum, as well as Microdochium bolleyi, Microdochium nivale, and Macrophomina phaseolina, were non-pathogenic and considered to be secondary colonizers. The implications of these findings are discussed.

Epiphytic and Endophytic Fungi Colonizing Seeds of Two Poaceae Weed Species and Fusarium spp. Seed Degradation Potential In Vitro

Fungi colonizing the surface and endosphere of two widespread Poaceae weed species, Avena fatua and Echinochloa crus-galli, were isolated to compare the taxonomic composition between the plant species, location, and year of the seed collection. The seed-degrading potential of Fusarium isolated from the seeds was tested by inoculating seeds of E. crus-galli with spore suspension. Molecular identification of epiphytic and endophytic fungal genera was performed by sequencing the ITS region of rDNA. Endophytes comprised of significantly lower fungal richness compared to epiphytes. A significant taxonomic overlap was observed between the endosphere and seed surface. The most abundant genera were Alternaria, Fusarium, Cladosporium, and Sarocladium. Analysis of similarities and hierarchical clustering showed that microbial communities were more dissimilar between the two plant species than between the years. Fusarium isolates with a high potential to infect and degrade E. crus-galli seeds in laboratory conditions belong to F. sporotrichioides and F. culmorum.

Biocontrol potential and action mechanism of Bacillus amyloliquefaciens DB2 on Bipolaris sorokiniana

Introduction

Bipolaris sorokiniana is the popular pathogenic fungi fungus which lead to common root rot and leaf spot on wheat. Generally, chemical fungicides are used to control diseases. However, the environmental pollution resulting from fungicides should not be ignored. It is important to study the mode of antagonistic action between biocontrol microbes and plant pathogens to design efficient biocontrol strategies.

Results

An antagonistic bacterium DB2 was isolated and identified as Bacillus amyloliquefaciens. The inhibition rate of cell-free culture filtrate (CF, 20%, v/v) of DB2 against B. sorokiniana reached 92.67%. Light microscopy and scanning electron microscopy (SEM) showed that the CF significantly altered the mycelial morphology of B. sorokiniana and disrupted cellular integrity. Fluorescence microscopy showed that culture filtrate destroyed mycelial cell membrane integrity, decreased the mitochondrial transmembrane potential, induced reactive oxygen species (ROS) accumulation, and nuclear damage which caused cell death in B. sorokiniana. Moreover, the strain exhibited considerable production of protease and amylase, and showed a significant siderophore and indole-3-acetic acid (IAA) production. In the detached leaves and potted plants control assay, B. amyloliquefacien DB2 had remarkable inhibition activity against B. sorokiniana and the pot control efficacy was 75.22%. Furthermore, DB2 suspension had a significant promotion for wheat seedlings growth.

Conclusion

B. amyloliquefaciens DB2 can be taken as a potential biocontrol agent to inhibit B. sorokiniana on wheat and promote wheat growth.

Transcriptome-based analysis of resistance mechanisms to Bipolaris sorokiniana, a common wheat root-rot disease

In common root and crown rot (CRR), Bipolaris sorokiniana (Sace.) is one of the important in wheat, causing considerable yield losses globally. Sources of resistance can provide a feasible and effective method of control for plant disease management. However, knowledge on mechanisms of resistance is scarce. We screened 33 wheat genotypes against B. sorokiniana under greenhouse and field conditions. In addition, real-time quantitative PCR (qPCR) analysis using ten novel candidate gene markers, Cre3, EDS1, LTP5, PGIP, PR-1, PIEP1, TLP, UGT, Stb6 and PFT, was conducted on leaves and roots, along with changes in activity of antioxidant enzymes, peroxidase, catalase, β-1,3-glucanase, and phenolic content for their involvement in disease impact mechanisms. Lowest disease severity was in 'Alvand', followed by 'Baharan' and 'Bam' as resistant genotypes. Quantitative gene expression showed that, although the candidate defence genes were upregulated 1.24- to 3.5-fold in wheat roots and leaves inoculated with B. sorokiniana, they were highly regulated in resistant varieties 'Alvand', 'Mehregan' and 'Bam'. Cre3, a resistance gene to cereal cyst nematode Heterodera filipjevi, was regulated in cultivars resistant to B. sorokiniana. Similar results were obtained for Stb6, a gene resistant to Septoria tritici blotch, EDS1 resistant to powdery mildew, Blumeria graminis, and the genes PR-1 and UGT resistant to leaf rust, Puccinia triticina. Antioxidant enzyme activity also showed the highest increases in resistant genotypes. In conclusion, the T. aestivum-B. sorokiniana interaction in resistant wheat cultivars uses defence-related genes and enzymes that protect wheat towards sustainable development. Further such studies will shed light on simultaneous resistance to other diseases in wheat cultivars.

Validation of Novel spot blotch disease resistance alleles identified in unexplored wheat (Triticum aestivum L.) germplasm lines through KASP markers

BACKGROUND

During the last few decades, the diverse sources of resistance, several genes and QTLs for spot blotch resistance have been identified. However, a large set of germplasm lines are still unexplored that have the potential to develop highly resistant wheat cultivars for the target environments. Therefore, the identification of new sources of resistance to spot blotch is essential for breeding programmes to develop spot blotch resistant cultivars and sustain wheat production. The association mapping panel of 294 diverse bread wheat accessions was used to explore new sources of spot blotch disease resistance and to identify genomic regions using genome wide association analysis (GWAS). The genotypes were tested in replicated trials for spot blotch disease at three major hot spots in India (Varanasi in UP, Pusa in Bihar, and Cooch Behar in West Bengal). The area under the disease progress curve (AUDPC) was calculated to assess the level of resistance in each genotype.

RESULTS

A total of 19 highly and 76 moderately resistant lines were identified. Three accessions (EC664204, IC534306 and IC535188) were nearly immune to spot blotch disease. The genotyping of all accessions resulted in a total of 16,787 high-quality polymorphic SNPs. The GWAS was performed using a Compressed Mixed Linear Model (CMLM) and a Mixed Linear Model (MLM). A total of seven significant MTAs, common in both the models and consistent across the environment, were further validated to develop KASP markers. Four MTAs (AX-94710084, AX-94865722, AX-95135556, and AX-94529408) on three chromosomes (2AL, 2BL, and 3BL) have been successfully validated through the KASP marker.

CONCLUSIONS

The new source of resistance was identified from unexplored germplasm lines. The genomic regions identified through GWAS were validated through KASP markers. The marker information and the highly resistant sources are valuable resources to rapidly develop immune or near immune wheat varieties.

Heritable priming by Trichoderma: A sustainable approach for wheat protection against Bipolaris sorokiniana

Crop plants encounter a variety of biotic challenges in the field and faces significant reduction in crop yield. In the current scenario of an ever increasing global population, there is an urgent need to protect plant health by using sustainable approach to maximize the crop productivity and to mitigate the food demands. Nowadays, we mostly rely on chemical crop protection techniques, which are causing a number of environmental and health difficulties. Defence priming is a chemical-free, eco-friendly, and sustainable strategy of crop protection, which is also called "green vaccination. In the present study, for the first time, we used Trichoderma as a priming agent to protect wheat crop from spot blotch disease. We have established Trichoderma-mediated defence priming in wheat against Bipolaris sorokiniana for sustainable crop improvement. We have characterised the morphological, disease phenotype, biochemical and yield parameters of Trichoderma-primed and non-primed wheat under disease pressure. Trichoderma-primed plants were found to be more protected against B. sorokiniana as compared to non-primed plants. Biochemical studies indicated that there is no direct defence response after priming stimulus but the defence response was activated only after triggering stimulus in terms of enhanced defence metabolites in primed plants as compared to non-primed plants. In the present study, since defence was activated only when required, that is under disease pressure, there was no unnecessary allocation of resources towards defence. Hence, no yield penalty was shown in primed plants as compared to control. We further evaluated the inheritance of primed state to the next generation and found that progeny of primed parents also performed better than progeny of non-primed parents under disease pressure in terms of protection from B. sorokiniana as well as yield performance. This strategy has the potential to protect crop without any yield penalty and causing environmental degradation. Our research findings indicate that Trichoderma-mediated defence priming could be an alternative approach for improving wheat productivity under biotic stress. To be our best knowledge, this is the first documented report for the Trichoderma-mediated defence priming and induced inheritance in wheat plant. This study will open new arenas in sustainable crop protection strategies for the exploitation of defence priming in crop plants.

Draft Genome Sequence of Priestia sp. Strain TSO9, a Plant Growth-Promoting Bacterium Associated with Wheat (Triticum turgidum subsp. durum) in the Yaqui Valley, Mexico

Strain TSO9 was isolated from a commercial field of wheat (Triticum turgidum L. subsp. durum) located in the Yaqui, Valley, Mexico. Here, the genome of this strain was sequenced, obtaining a total of 5,248,515 bp; 38.0% G + C content; 1,186,514 bp N50; and 2 L50. Based on the 16S rRNA gene sequencing, strain TSO9 was affiliated with the genus Priestia. The genome annotation of Priestia sp. TSO9 contains a total of 147 RNAs, 128 tRNAs, 1 tmRNA, and 5512 coding DNA sequences (CDS) distributed into 332 subsystems, where CDS associated with agricultural purposes were identified, such as (i) virulence, disease, and defense (57 CDS) (i.e., resistance to antibiotics and toxic compounds (34 CDS), invasion and intracellular resistance (12 CDS), and bacteriocins and ribosomally synthesized antibacterial peptides (10 CDS)), (ii) iron acquisition and metabolism (36 CDS), and (iii) secondary metabolism (4 CDS), i.e., auxin biosynthesis. In addition, subsystems related to the viability of an active ingredient for agricultural bioproducts were identified, such as (i) stress response (65 CDS). These genomic traits are correlated with the metabolic background of this strain, and its positive effects on wheat growth regulation reported in this work. Thus, further investigations of Priestia sp. TSO9 are necessary to complement findings regarding its application in agroecosystems to increase wheat yield sustainably.

Root rot a silent alfalfa killer in China: Distribution, fungal, and oomycete pathogens, impact of climatic factors and its management

Alfalfa plays a significant role in the pasture ecosystems of China's north, northeast, and northwest regions. It is an excellent forage for livestock, improves soil structure, prevents soil erosion, and has ecological benefits. Presently root rot is a significant threat to the alfalfa productivity because of the survival of the pathogens as soil-borne and because of lack of microbial competition in the impoverished nutrient-deficient soils and resistant cultivars. Furthermore, these regions' extreme ecological and environmental conditions predispose alfalfa to root rot. Moisture and temperature, in particular, have a considerable impact on the severity of root rot. Pathogens such as Fusarium spp. and Rhizoctonia solani are predominant, frequently isolated, and of major concern. These pathogens work together as disease complexes, so finding a host genotype resistant to disease complexes is challenging. Approaches to root rot control in these regions include mostly fungicides treatments and cultural practices and very few reports on the usage of biological control agents. As seed treatment, fungicides such as carbendazim are frequently used to combat root rot; however, resistance to fungicides has arisen. However, breeding and transgenic approaches could be more efficient and sustainable long-term control strategies, especially if resistance to disease complexes may be identified. Yet, research in China is mainly limited to field investigation of root rot and disease resistance evaluation. In this review, we describe climatic conditions of pastoral regions and the role of alfalfa therein and challenges of root rot, the distribution of root rot in the world and China, and the impact of root rot pathogens on alfalfa in particular R. solani and Fusarium spp., effects of environmental factors on root rot and summarize to date disease management approach.

Enzyme activity and population genetic structure analysis in wheat associated with resistance to Bipolaris sorokiniana-common root rot diseases

Common root rot disease (CRR) caused by Bipolaris sorokiniana (Sacc.) (Pleosporaceae), is an important fungal disease of wheat, Triticum aestivum (Poaceae), causing considerable yield losses globally. Incorporating genetic resistance in cultivated crops is considered the most efficient and sustainable solution to counter root rot diseases. Moreover, resistance to CCR is quantitative in nature, and thus the mechanism is poorly understood. To this aim, we analyzed the activities of defense-related enzymes; peroxidase (POX), superoxide dismutase (SOD), polyphenol oxidase (PPO), catalase (CAT), phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU) and chitinase (CHI), as well as total phenol content (TPC) to CRR on the three known resistant wheat 'Alvand' and 'Bam', 'Mehregan' at different time points (wpi) following CRR pathogen, B. sorokiniana inoculation. Of which, were selected out of 33 wheat cultivars previously screened for resistance to CRR. We also analyzed the genetic variability of the entire germplasm, 33 wheat cultivars using seven simple sequence repeat (SSR) primer pairs. The activity of antioxidant enzymes was increased in the related resistant genotypes. Of which, 'Bam' had the highest increase in PPO, and GLU activities, followed by 'Alvand' in SOD, PAL, and CHI significantly. Whereas, 'Mehregan' showed the highest level of TPC, POX, and CAT activities. In addition, five out of seven used SSR primers produced a total of 20 polymorphic bands, of which the number of alleles in each gene locus varied within 3-7 bands. The polymorphism information content (PIC) value also ranged from 0.44 to 0.81, with the mean of 0.65, Shannon Information Index (I) between 0.29 and 0.63 with an average of 0.47 per locus, and Nei's gene diversity (h) value varied from 0.16 to 0.44 with an average of 0.32. The average number of effective alleles was 1.52, ranging between 1.21 and 1.8. The gene locus Xgwm 140 showed the highest diversity in the population genetic structure, which explains the ability of the primers to resolve the assayed germplasm. Thus, resistance to CRR in wheat was mainly related to the enhancement of antioxidant enzymes, although the specific metabolic pathways require further study. This study presents new insights for understanding resistance mechanisms of the selected wheat cultivars to CRR, thus improving wheat yield in the future.

Using tank-mix adjuvant improves the physicochemical properties and dosage delivery to reduce the use of pesticides in unmanned aerial vehicles for plant protection in wheat

BACKGROUND

Unmanned aerial vehicles (UAVs) are widely used to improve the efficiency of pesticide applications. Low-volume spraying operations require more efficient deposition of droplets on the target surface. Therefore, pesticide deposition and retention on plant surfaces is a serious challenge for modern precision agriculture. Tank-mix adjuvants have been used to improve spray dilutions performance; however, their effects on the physicochemical properties of spray dilutions, dosage delivery, and pesticide dosage are unclear.

RESULTS

Tank-mix adjuvant 8860 significantly improved the physicochemical properties of spray dilutions, inhibited spray droplets rebound, improved the wetting and spreading performance of spray dilutions on wheat leaves, and increased the effective deposition of tebuconazole on wheat leaves. Even when its dosage was reduced by one-third, the spray solution still showed excellent disease control and effective deposition of the active ingredient on wheat leaves.

CONCLUSION

The use of appropriate tank-mix adjuvants in UAV-based plant protection for wheat can significantly improve the performance of spray dilutions, increase the efficiency of pesticide dosage delivery, and improve disease control. These adjuvants can also help reduce the pesticide use while ensuring their effectiveness. © 2022 Society of Chemical Industry.

Mechanisms of Resistance to Spot Blotch in Yunnan Iron Shell Wheat Based on Metabolome and Transcriptomics

Spot blotch (SB) is a fungal disease that threatens wheat yield and quality. Presently, the molecular mechanism against SB is unclear. In this study, the resistant variety Zhenkang iron shell wheat (Yunmai 0030) and susceptible variety Lincang iron shell wheat (Yunmai 0608) were selected by identifying SB of Yunnan iron shell wheat. The metabolome and transcriptome of leaves of two varieties at different positions were detected using the systemic acquired resistance theory to investigate the molecular and physiological changes in Yunnan iron shell wheat under SB stress. We found that the genes and metabolites related to benzoxazinoid biosynthesis and arginine and proline metabolism were highly enriched after infection with leaf blight. The enriched differential metabolites mainly included phenolic acids, alkaloids, and flavonoids. We further observed that DIBOA- and DIMBOA-glucoside positively affected iron shell wheat resistance to leaf blight and proline and its derivatives were important for plant self-defense. Furthermore, we confirmed that the related metabolites in benzoxazinoid biosynthesis and arginine and proline metabolism positively affected Triticum aestivum ssp. resistance to SB. This study provides new insights into the dynamic physiological changes of wheat in response to SB, helps us better understand the mechanism of resistance to SB, and contributes to the breeding and utilization of resistant varieties.

Antifungal Macrolides Kongjuemycins from Coral-Associated Rare Actinomycete Pseudonocardia kongjuensis SCSIO 11457

Four new macrolides, kongjuemycins A and B1-B3 (1-4), were isolated from a coral-associated actinomycete Pseudonocardia kongjuensis SCSIO 11457. Their structures were characterized by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. The absolute configurations of 1 and 2 were established by electronic circular dichroism calculation and the modified Mosher's method. Kongjuemycins displayed antifungal activity against three phytopathogenic fungi.

Fungal Pathogens Associated with Crown and Root Rot of Wheat in Central, Eastern, and Southeastern Kazakhstan

Kazakhstan is the fourteenth largest wheat producer in the world. Despite this fact, there has not been a comprehensive survey of wheat root and crown rot. A quantitative survey was conducted for the purpose of establishing the distribution of fungi associated with root and crown rot on wheat (Triticum spp.). During the 2019 growing season, samples were taken from the affected plants’ roots and stem bases. A total of 1221 fungal isolates were acquired from 65 sites across the central (Karagandy region), eastern (East Kazakhstan region), and southeastern (Almaty region) parts of the country and identified using morphological and molecular tools. The internal transcribed spacer (ITS), translation elongation factor 1-alpha (EF1-α), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) sequences were successfully used to identify the species of fungal isolates. It was found that Bipolaris sorokiniana (44.80%) and Fusarium acuminatum (20.39%) were the most predominant fungal species isolated, which were present in 86.15 and 66.15% of the fields surveyed, respectively, followed by F. equiseti (10.16%), Curvularia spicifera (7.62%), F. culmorum (4.75%), F. oxysporum (4.10%), F. redolens (2.38%), Rhizoctonia solani AG2-1 (1.06%), Nigrospora oryzae (0.98%), C. inaequalis (0.90%), F. pseudograminearum (0.74%), F. flocciferum (0.74%), Macrophomina phaseolina (0.66%), F. cf. incarnatum (0.33%), Fusarium sp. (0.25%), and F. torulosum (0.16%). A total of 74 isolates representing 16 species were tested via inoculation tests on the susceptible Triticum aestivum cv. Seri 82 and the results revealed that F. culmorum and F. pseudograminearum, B. sorokiniana, Fusarium sp., R. solani, F. redolens, C. spicifera, C. inaequalis, and N. oryzae were virulent, whereas others were non-pathogenic. The findings of this investigation demonstrate the presence of a diverse spectrum of pathogenic fungal species relevant to wheat crown and root rot in Kazakhstan. To the best of our knowledge, this is the first report of F. pseudograminearum, Fusarium sp., C. spicifera, and C. inaequalis as pathogens on wheat in Kazakhstan.

Identification and Pathogenicity of Fungi Associated with Leaf Spot of Muskmelon in Eastern Shandong Province, China

Leaf spot is a serious disease in the growth and development of muskmelon, which can affect its quality and yield. Over the past years, Malianzhuang Muskmelon Base, the main muskmelon producing area in Shandong Province, China, has been seriously affected by leaf spot. Since 2018, symptomatic leaves were collected from 11 production areas of this base to determine the pathogens of muskmelon foliar diseases. Two-hundred fungal strains were isolated and 10 genera and 17 species were identified based on morphological characteristics and multilocus phylogenetic analysis (ITS, GADPH, RPB2, HIS3, EF-1α, and LSU). The most frequently isolated species from each sampling area was Alternaria tenuissima with 77 strains, followed by A. alternata. Pathogenicity experiments showed that A. alternata, A. tenuissima, Fusarium neocosmosporiellum (formerly Neocosmospora vasinfecta), F. acuminatum, Exserohilum rostratum, Bipolaris sorokiniana, and Stagonosporopsis cucurbitacearum (formerly Didymella bryoniae) could cause symptoms highly similar to those of infected leaves observed under natural conditions in the field. Therefore, these fungal isolates are considered to be the primary pathogens causing muskmelon leaf spot, and A. tenuissima and A. alternata were the most common and virulent pathogens in this study. In addition, this is the first study of F. neocosmosporiellum, F. acuminatum, E. rostratum, and B. sorokiniana as pathogens associated to muskmelon leaf spot in China as well as the world.

Monitoring of Host Suitability and Defense-Related Genes in Wheat to Bipolaris sorokiniana

Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat worldwide. This study investigated the aggressiveness of B. sorokiniana isolates from different wheat-growing areas of Bolu province in Turkey on the cultivar Seri-82. Host susceptibility of 55 wheat cultivars was evaluated against the most aggressive isolate. Our results indicated that the cultivars Anafarta and Koç-2015 were the most resistant. A specific and sensitive qPCR assay was developed for detecting the pathogen in plant tissues and evaluating wheat plants with different resistance levels. Three primer sets, BsGAPDHF/BsGAPDHR, BsITSF/BsITSR, and BsSSUF/BsSSUR, were designed based on glyceraldehyde-3-phosphate dehydrogenase, internal transcribed spacers, and 18S rRNA loci of B. sorokiniana with detection limits of 1, 0.1, and 0.1 pg of pathogen DNA, respectively. The qPCR assay was highly sensitive and did not amplify DNA from the other closely related fungal species and host plants. The protocol differentiated wheat plants with varying degrees of resistance. The assay developed a useful tool for the quantification of the pathogen in the early stages of infection and may provide a significant contribution to a more efficient selection of wheat genotypes in breeding studies. In the present study, expression levels of PR proteins, phenylalanine ammonia-lyase, catalase, ascorbate peroxidase, and superoxide dismutase enzymes were upregulated in Anafarta (resistant) and Nenehatun (susceptible) cultivars at different post-infection time points, but more induced in the susceptible cultivar. The results showed considerable variation in the expression levels and timing of defense genes in both cultivars.

Antagonistic Strain Bacillus amyloliquefaciens XZ34-1 for Controlling Bipolaris sorokiniana and Promoting Growth in Wheat

Common root rot, caused by Bipolaris sorokiniana, is one of the most prevalent diseases of wheat and has led to major declines in wheat yield and quality worldwide. Here, strain XZ34-1 was isolated from soil and identified as Bacillus amyloliquefaciens based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence. Culture filtrate (CF) of strain XZ34-1 showed a high inhibition rate against B.sorokiniana and had a broad antifungal spectrum. It also remarkably inhibited the mycelial growth and spore germination of B. sorokiniana. In pot control experiments, the incidence and disease index of common root rot in wheat seedlings were decreased after treatment with CF, and the biological control efficacy was significant, up to 78.24%. Further studies showed XZ34-1 could produce antifungal bioactive substances and had the potential of promoting plant growth. Lipopeptide genes detection with PCR indicated that strain XZ34-1 may produce lipopeptides. Furthermore, activities of defense-related enzymes were enhanced in wheat seedlings after inoculation with B.sorokiniana and treatment with CF, which showed induced resistance could be produced in wheat to resist pathogens. These results reveal that strain XZ34-1 is a promising candidate for application as a biological control agent against B.sorokiniana.

Fungi Inhabiting the Wheat Endosphere

Wheat production is influenced by changing environmental conditions, including climatic conditions, which results in the changing composition of microorganisms interacting with this cereal. The group of these microorganisms includes not only endophytic fungi associated with the wheat endosphere, both pathogenic and symbiotic, but also those with yet unrecognized functions and consequences for wheat. This paper reviews the literature in the context of the general characteristics of endophytic fungi inhabiting the internal tissues of wheat. In addition, the importance of epigenetic regulation in wheat-fungus interactions is recognized and the current state of knowledge is demonstrated. The possibilities of using symbiotic endophytic fungi in modern agronomy and wheat cultivation are also proposed. The fact that the current understanding of fungal endophytes in wheat is based on a rather small set of experimental conditions, including wheat genotypes, plant organs, plant tissues, plant development stage, or environmental conditions, is recognized. In addition, most of the research to date has been based on culture-dependent methods that exclude biotrophic and slow-growing species and favor the detection of fast-growing fungi. Additionally, only a few reports of studies on the entire wheat microbiome using high-throughput sequencing techniques exist. Conducting comprehensive research on the mycobiome of the endosphere of wheat, mainly in the context of the possibility of using this knowledge to improve the methods of wheat management, mainly the productivity and health of this cereal, is needed.

Synthetic Oligopeptides Mimicking γ-Core Regions of Cysteine-Rich Peptides of Solanum lycopersicum Possess Antimicrobial Activity against Human and Plant Pathogens

Plant cysteine-rich peptides (CRPs) represent a diverse group of molecules involved in different aspects of plant physiology. Antimicrobial peptides, which directly suppress the growth of pathogens, are regarded as promising templates for the development of next-generation pharmaceuticals and ecologically friendly plant disease control agents. Their oligopeptide fragments are even more promising because of their low production costs. The goal of this work was to explore the antimicrobial activity of nine short peptides derived from the γ-core-containing regions of tomato CRPs against important plant and human pathogens. We discovered antimicrobial activity in peptides derived from the defensin-like peptides, snakins, and MEG, which demonstrates the direct involvement of these CRPs in defense reactions in tomato. The CRP-derived short peptides appeared particularly active against the gram-positive bacterium Clavibacter michiganensis, which causes bacterial wilt—opening up new possibilities for their use in agriculture to control this dangerous disease. Furthermore, high inhibitory potency of short oligopeptides was demonstrated against the yeast Cryptococcus neoformans, which causes serious diseases in humans, making these peptide molecules promising candidates for the development of next-generation pharmaceuticals. Studies of the mode of action of the two most active peptides indicate fungal membrane permeabilization as a mechanism of antimicrobial action.

Identification of QTLs for Spot Blotch Resistance in Two Bi-Parental Mapping Populations of Wheat

Spot blotch (SB) disease caused by the hemibiotrophic pathogen Bipolaris sorokiniana inflicting major losses to the wheat grown in warm and highly humid areas of the Indian subcontinent, including Bangladesh, necessitates identification of QTLs stably expressing in Indian subcontinent conditions. Thus, two RIL mapping populations, i.e., WC (WUYA × CIANO T79) and KC (KATH × CIANO T79), were phenotyped at Dinajpur, Bangladesh for three consecutive years (2013-2015) and genotyped on a DArTseq genotyping by sequencing (GBS) platform at CIMMYT, Mexico. In both populations, quantitative inheritance along with transgressive segregation for SB resistance was identified. The identified QTLs were mostly minor and were detected on 10 chromosomes, i.e., 1A, 1B, 2A, 2B, 2D, 4B, 4D, 5A, 5D, and 7B. The phenotypic variation explained by the identified QTLs ranged from 2.3–15.0%, whereby QTLs on 4B (13.7%) and 5D (15.0%) were the largest in effect. The identified QTLs upon stacking showed an additive effect in lowering the SB score in both populations. The probable presence of newly identified Sb4 and durable resistance gene Lr46 in the identified QTL regions indicates the importance of these genes in breeding for SB resistance in Bangladesh and the whole of South Asia.