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This study aimed to explore transcriptomic distinctions between resistant (CS‐319) and susceptible (JAL‐42) groundnut (Arachis hypogaea) genotypes exposed to Sclerotium rolfsii infection across different developmental stages. Employing a de novo assembly‐based approach, we analysed the transcriptomic response in these groundnut plants under control and infected conditions at 24, 72 and 120 hours post‐inoculation (hpi). Our RNA‐Seq data yielded a total of 133,900,261 reads, revealing 7796 differentially expressed genes (DEGs). We constructed a gene regulatory network with 59 hub genes, identified 6783 transcription factors and uncovered 88,424 putative markers, including 17,236 simple‐sequence repeats (SSRs), 10,099 single‐nucleotide polymorphisms (SNPs) and 78,332 indels. Notably, the majority of DEGs were upregulated at 24 hpi in the resistant genotype, encompassing diverse functional categories such as pathogenesis‐related genes, defence‐related (R) genes, genes involved in plant–fungus interactions, oxidation–reduction‐related genes, transport, metabolism and proteolysis genes, along with transcription factors (FAR1, B3, GATA, NAC, WRKY, MYBC1 and bHLH), secondary metabolic pathway‐related genes and photosynthesis‐related genes. The up‐regulation of WRKY transcripts, associated with the activation of the jasmonic acid defence signalling pathway, potentially induced systemic acquired resistance (SAR). Conversely, these DEGs exhibited down‐regulation in the susceptible genotype. Furthermore, a total of 17,236 expressed sequence tag (EST)‐SSRs were identified from the unigenes, holding significant potential for advancing plant breeding through marker‐assisted methods, facilitating quantitative trait locus (QTL) mapping and evaluating genetic diversity among genotypes. This study's approach contributes to a more profound understanding of the molecular‐level defence mechanisms involved in the interaction between groundnuts and S. rolfsii. [ABSTRACT FROM AUTHOR]

The goal of the study was to assess the capability of the bacteria Pseudomonas aeruginosa AMBCD‐1 for paddy straw degradation as well as its biological control abilities against the plant wilt pathogen Fusarium. Fourier‐transform infrared spectroscopy (FTIR) data showed that AMBCD‐1 culture‐inoculated treatments dramatically reduced the levels of cellulose, lignin, and hemicelluloses in the deteriorated paddy straw. Additionally, a dual culture technique was utilized to investigate antagonistic activity in vitro using nutritional agar media and potato dextrose agar in equal proportions (1:1) for suppressing the growth of the fungus Fusarium oxysporum and Sclerotium rolfsii in order to assess the biocontrol properties of the chosen bacteria. Following incubation, it was shown that AMBCD‐1 exhibited a 66.67% antibacterial activity against the fungus Fusarium oxysporum. Furthermore, the pyocyanin pigment was also extracted from the P. aeruginosa AMBCD‐1 strain and confirmed at a mass value of 211.2 using liquid chromatography mass spectrometry (LC‐MS), with its standard peak observed at 1.48 min. The results revealed that bacterium P. aeruginosa AMBCD‐1 had the ability to biodegrade paddy straw and also inhibit the appearance of the wilt disease caused by Fusarium species in numerous crops. [ABSTRACT FROM AUTHOR]

Aconitum carmichaelii is a prominent medicinal plant widely used in Asian countries. Southern blight is one of the main soilborne diseases and has severely restricted the sustainable development of A. carmichaelii. Its causative pathogen was identified as Sclerotium rolfsii in 1981 in the main planting areas. Typical southern blight symptoms were observed on A. carmichaelii in Jiangyou, Sichuan, China, from 2020 to 2023, and five fungal strains were isolated from diseased A. carmichaelii plants. Fungal isolates formed white, fluffy, cotton‐like mycelium and dark brown, round or oval sclerotia. The lethal temperature for these isolates was 55°C, while they showed various resistant capacities against acid, alkaline and salt conditions and fungicides. Starch and ammonium chloride were the optimal carbon and nitrogen sources for the fungal isolates, respectively. Phylogenetic analysis based on concatenated sequences of rDNA internal transcribed spacer (ITS), large subunit (LSU) and β‐tubulin (TUB) revealed that these five isolates clustered independently into the Agroathelia clade but with <97% identity to reference strains and were characterized as Agroathelia sp. nov. Inoculation of fungal hyphal plugs on A. carmichaelii roots and plants caused severe southern blight symptoms. Cross‐pathogenicity tests demonstrated that the five isolates also displayed high pathogenicity on eggplant and tomato plants. These findings provide valuable insights into a novel southern blight pathogen of A. carmichaelii that may contribute to effective management of this disease. [ABSTRACT FROM AUTHOR]

Rhizome rot poses a significant threat to ginger cultivation, caused by a complex interaction of pathogens such as Pythium aphanidermatum, Fusarium oxysporum, Ralstonia solanacearum, Sclerotium rolfsii and Meloidogyne incognita. The pathogens were individually inoculated at 75, 105 and 135 days after planting (DAP), as well as in various combinations, to evaluate disease severity and symptom development. Results revealed that R. solanacearum exhibited the highest disease severity and fastest symptom development across all stages of inoculation, followed by P. aphanidermatum, F. oxysporum, S. rolfsii and M. incognita. The combined inoculation of pathogens significantly increased disease incidence and rhizome rot compared to individual inoculations, indicating synergistic interactions among the pathogens. Sequential inoculation experiments demonstrated that pre‐infection by M. incognita exacerbated disease severity, highlighting the role of nematodes in predisposing plants to secondary infections. [ABSTRACT FROM AUTHOR]

Chemical pesticides are synthetic substances created to manage plant pests. Frequent chemical usage causes extensive damage to crops and contributes to pest resistance, leading to environmental contamination, harm to non‐target organisms, the emergence of pesticide‐resistant species, and potential health hazards for humans. The aim of this study is to isolate, identify, and characterize biocontrol agents Trichoderma harzianum and evaluate their effects on various plant phytopathogens. T. harzianum biocontrol effects were tested against various fungal phytopathogens, including Sclerotium rolfsii, Alternaria sp., Pythium aphanidermatum, Macrophomina phaseolina, Fusarium oxysporum, Helminthosporium sativum, and Aspergillus niger. The results clearly showed that, compared to the other Trichoderma species, TVK1 demonstrated the highest ability to suppress phytopathogens, with a growth inhibition rate of 2.48 cm per day. TVK2 grows at a rate of 1.96 cm per day, whereas TVK5 grows at a rate of 1.98 cm per day. The level of antifungal volatile organic compounds produced by TVK1 spores was higher against plant pathogens compared to the other species examined. This compound inhibits the growth of plant pathogens. T. harzianum can eliminate 100% of S. rolfsii pathogens and 100% of Alternaria sp. Pathogens were reduced by 92.02% for A. niger, 94% for F. oxysporum, 100% for P. aphanidermatum, 94.07% for H. sativum, and 100% for M. phaseolina. In a detached leaf assay, TVK1 inhibited the growth of pathogens in various plant leaves, including tomato, mustard, and eggplant, when compared to both the commercially available fungicide and the control. The study confirms that the isolate TVK1 can combat various phytopathogens. Early application of T. harzianum can reduce the risk of phytopathogenic attacks on leaves and promote plant growth. [ABSTRACT FROM AUTHOR]

BACKGROUND: Sclerotium rolfsii is a destructive soil‐borne fungal pathogen which is distributed worldwide. In previous study, the succinate dehydrogenase inhibitor (SDHI) fungicide benzovindiflupyr has been identified for its great antifungal activity against Sclerotium rolfsii. This study is aimed to investigate the resistance risk and mechanism of benzovindiflupyr in Sclerotium rolfsii. RESULTS: Eight stable benzovindiflupyr‐resistant isolates were generated by fungicide adaptation. Although the obtained eight resistant isolates have a stronger pathogenicity than the parental sensitive isolate, they have a fitness penalty in the mycelial growth and sclerotia formation compared to the parental isolate. A positive cross‐resistance existed in the resistant isolates between benzovindiflupyr and thifluzamide, carboxin, boscalid and isopyrazam. Three‐point mutations, including SdhBN180D, SdhCQ68E and SdhDH103Y, were identified in the benzovindiflupyr‐resistant isolates. However, molecular docking analysis indicated that only SdhDH103Y could influence the sensitivity of Sclerotium rolfsii to benzovindiflupyr. After mycelial co‐incubation of resistant isolates and the sensitive isolate, resistance genes may be transmitted to the sensitive isolate. The in vivo efficacy of benzovindiflupyr and thifluzamide against benzovindiflupyr‐resistant isolates was a little lower than that against the sensitive isolate but with no significant difference. CONCLUSION: The results suggested a low to medium resistance risk of Sclerotium rolfsii to benzovindiflupyr. However, once resistance occurs, it is possible to spread in the population of Sclerotium rolfsii. This study is helpful to understanding the risk and mechanism of resistance to benzovindiflupyr in multinucleate pathogens such as Sclerotium rolfsii. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Peanut southern blight disease, caused by Sclerotium rolfsii, is a destructive soil‐borne fungal disease. The current control measures, which mainly employ succinate dehydrogenase inhibitors, are prone to resistance and toxicity to non‐target organisms. As a result, it is necessary to explore the potential of eco‐friendly fungicides for this disease. RESULTS: Fourteen novel phthalide compounds incorporating amino acid moieties were designed and synthesized. The in vitro activity of analog A1 [half maximal effective concentration (EC50) = 332.21 mg L−1] was slightly lower than that of polyoxin (EC50 = 284.32 mg L−1). It was observed that on the seventh day, the curative activity of A1 at a concentration of 600.00 mg L−1 was 57.75%, while the curative activity of polyoxin at a concentration of 300.00 mg L−1 was 42.55%. These results suggested that our compound exhibited in vivo activity. Peanut plants treated with A1 showed significant agronomic improvements compared to the untreated control. Several compounds in this series exhibited superior root absorption and conduction in comparison to the endothermic fungicide thifluzamide. The growth promotion and absorption‐conduction experiments demonstrated the reason for the superior in vivo activity of the target compound. Cytotoxic assays have demonstrated that this series of targeted compounds exhibit low toxicity levels toward human lo2 liver cells. CONCLUSION: Our results provide a new strategy for the design and synthesis of novel green compounds. Furthermore, the target compound A1 can serve as a lead for further development of green fungicides. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The advancement of environmentally friendly chemical synthesis in both academic and corporate research has recently taken on enormous relevance. Pesticides are substances, either chemical or biological, that are used to get rid of or lessen the impact of pests. To control the fungi in crops a new set of isoxazolylpyrimidine derivatives were planned, synthesized, and characterized. The compounds indicated were synthesized in high yields, and their structures were determined using elemental analysis, 1H NMR, 13C NMR, and LCMS. HPLC was used to assess the purity of the synthesized molecules, and the purity of some compounds were found to be >98 % a/a while a couple were found to be >95 % a/a. The synthesized compounds were assessed for their antifungal activity. Among these, compounds 5d, 5h, and 5l exhibit substantial antifungal action and considerably suppress the growth of Rhizoctonia solani, Sclerotium rolfsii, and Macrophominaphaseolina. Macrophominaphaseolina inhibition percentages were 77.60, 70.49, 69.03, Sclerotium rolfsii inhibition percentages were 78.73, 74.03, 68.44, and Rhizoctonia solani inhibition percentages were 81.77, 76.29, and 71.01 for compounds 5 d, 5 h and 5 l respectively. The plausible mechanism of fungal inhibitory activities of rationally designed isoxazolyl pyrimidine derivatives is attributed to the blocking of the oxygen activation of HEME iron in membrane‐bound 14α‐demethylase. The presence of pyrimidine unit in designed materials is a vital factor for inducing antifungal activities, which was further corroborated through the density functional theory (DFT),molecular docking studies and molecular dynamics simulation studies. [ABSTRACT FROM AUTHOR]

Ginger rhizome rot is one of the most important diseases brought about by the interaction of various pathogens. The present study revealed the association of Pythium aphanidermatum, Fusarium oxysporum, Fusarium solani, Sclerotium rolfsii, Ralstonia solanacearum and Meloidogyne hapla causing the rhizome rot of ginger. The use of specific primers revealed the species‐level identification of the pathogen and Koch postulates proved the pathogenicity of individual pathogen. Till date, there are no resistant varieties available and the available management strategies are cumbersome because of the complex nature of pathogens involved. In the present study, we evaluated the effect of different elicitors to induce resistance against complex pathogens. External application of elicitors resulted in higher expression of defence response genes such as the ethylene responsive transcription factor, HMGR, HMGS, HSP, ABC, MLO, WRKY, callose synthase, glucanase and PR‐5. All the genes were expressed in higher folds as compared to zero hours during the real‐time PCR analysis. External application of methyl jasmonate as prophylactic manner resulted in reduced per cent disease incidence and rhizome rot as compared to curative treatments. [ABSTRACT FROM AUTHOR]

BACKGROUND: Peanut stem rot caused by Sclerotium rolfsii is an epidemic disastrous soil‐borne disease. Recently, natural products tend to be safe alternative antifungal agents to combat pathogens. RESULTS: This work determined the preliminary antifungal activity of 29 essential oils against S. rolfsii and found that Ligusticum chuanxiong essential oil (LCEO) showed the best antifungal activity, with an EC50 value of 81.79 mg L−1. Sixteen components (98.78%) were identified in LCEO by gas chromatography‐mass spectrometry analysis, the majority by volume comprising five phthalides (93.14%). Among these five phthalides, butylidenephthalide was the most effective compound against S. rolfsii. Butylidenephthalide not only exhibited favorable in vitro antifungal activity against the mycelial growth, sclerotia production and germination of S. rolfsi, but also presented efficient in vivo efficacy in the control of peanut stem rot. Seven days after application in the glasshouse, the protective and curative efficacy of butylidenephthalide at 300 mg L−1 (52.02%, 44.88%) and LCEO at 1000 mg L−1 (49.60%, 44.29%) against S. rolfsii were similar to that of the reference fungicide polyoxin at 300 mg L−1 (54.61%, 48.28%). Butylidenephthalide also significantly decreased the oxalic acid and polygalacturonase content of S. rolfsii, suggesting a decreased infection ability on plants. Results of biochemical actions indicated that butylidenephthalide did not have any effect on the cell membrane integrity and permeability but significantly decreased nutrient contents, disrupted the mitochondrial membrane, inhibited energy metabolism and induced reactive oxygen species (ROS) accumulation of S. rolfsii. CONCLUSION: Our results could provide an important reference for understanding the application potential and mechanisms of butylidenephthalide in the control of S. rolfsii. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The present study employed microRNA (miRNA) sequencing and metabolome profiling of Trichoderma parental strains and fusants during normal growth and interaction with the phytopathogen Sclerotium rolfsii Sacc. In‐vitro antagonism indicated that abiotic stress‐tolerant Tricho‐fusant FU21 was examined as a potent biocontroller with mycoparasitic action after 10 days. During interaction with the test pathogen, the most abundant uprising intracellular metabolite was recognized as l‐proline, which corresponds to held‐down l‐alanine, associated with arginine and proline metabolism, biosynthesis of secondary metabolites, and nitrogen metabolism linked to predicted genes controlled by miRNAs viz., cel‐miR‐8210‐3p, hsa‐miR‐3613‐5p, and mml‐miR‐7174‐3p. The miRNAs‐ mml‐miR‐320c and mmu‐miR‐6980‐5p were found to be associated with phenylpropanoid biosynthesis, transcription factors, and signal transduction pathways, respectively, and were ascertained downregulated in potent FU21_IB compared with FU21_CB. The amino benzoate degradation and T cell receptor signaling pathways were regulated by miRNAs cel‐miR‐8210 and tca‐miR‐3824 as stress tolerance mechanisms of FU21. The intracellular metabolites l‐proline, maleic acid, d‐fructose, Myo‐inositol, arabinitol, d‐xylose, mannitol, and butane were significantly elevated as potential biocontrol and stress‐tolerant constituents associated with miRNA regulatory pathways in potent FU21_IB. A network analysis between regulatory miRNA‐predicted genes and intracellular metabolomics acknowledged possible biocontrol pathways/mechanisms in potent FU21_IB to restrain phytopathogen. [ABSTRACT FROM AUTHOR]

Background: Sclerotium rolfsii, the causal agent of peanut southern blight, has become increasingly prevalent and harmful in China, causing serious economic losses to the peanut industry. To effectively manage peanut southern blight, this study evaluated the bioactivity of the new‐generation sterol demethylation inhibitor (DMI) fungicide mefentrifluconazole against peanut S. rolfsii. Results: In this study, the DMI fungicide mefentrifluconazole exhibited excellent inhibitory activity against the mycelial growth of S. rolfsii, with a mean EC50 value of 0.21 ± 0.11 mg L−1 and a range of 0.02 to 0.55 mg L−1 for 261 isolates collected from Hebei, Henan and Shandong provinces. Mefentrifluconazole significantly reduced the biomass of mycelia and affected the morphology of hyphae. Although sclerotia were more tolerant to mefentrifluconazole than mycelial growth, mefentrifluconazole greatly inhibited the formation and germination of sclerotia. In addition, sclerotia produced by mefentrifluconazole‐treated mycelia were deficient in nutrients (e.g., protein, carbohydrate and lipid). These results indicated that mefentrifluconazole may reduce the population of S. rolfsii in the following year. In greenhouse experiments, mefentrifluconazole showed control efficacy and good persistence against peanut S. rolfsii. The preventative and curative activities of mefentrifluconazole at 200 mg L−1 against southern blight still reached 95.36% and 60.94%, respectively, after 9 days of application. No correlation was observed for the sensitivity of S. rolfsii to mefentrifluconazole and the tested DMI, quinone outside inhibitor and succinate dehydrogenase inhibitor fungicides. Conclusion: All data indicated that mefentrifluconazole could provide favorable control efficacy against S. rolfsii from peanuts and reduce the infection and population of S. rolfsii in the following year. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Surveys were conducted in the five southern rice‐producing states of Arkansas, Louisiana, Mississippi, Missouri and Texas in the United States during the 2018 and 2019 cropping seasons to determine the distribution and pathogenicity of fungal pathogens associated with seedling blight in rice. A total of 349 pathogenic fungal isolates were collected and identified as belonging to four genera: Rhizoctonia solani, Fusarium spp., Sclerotium rolfsii and Marasmius graminum based on morphological characteristics, molecular analysis and Koch's postulates. R. solani (252 out of 349 pathogenic isolates) was the most prevalent fungus isolated from diseased samples. Of the 252 pathogenic R. solani isolates, 245 were further classified as anastomosis group 11 (AG‐11) and 7 as AG‐4. Isolates of R. solani AG‐4 and M. graminum were the most aggressive, with the highest stand loss (63% to 100%) and median disease rating (DR; 5.0), followed by isolates of R. solani AG‐11 (stand loss = 4% to 100% and DR = 0.6 to 5.0), Fusarium spp. (stand loss = 26% to 48% and DR = 2.0 to 5.0) and S. rolfsii (stand loss = 33% to 48% and DR = 2.0 to 3.0) in causing seedling blight in rice. R. solani (62% to 83% of total pathogenic isolates) and Fusarium spp. (10% to 24% of total pathogenic isolates) were predominant in all the five states surveyed. S. rolfsii and M. graminum were present only in Louisiana and Texas. The results of this first systematic survey of rice seedling diseases in the southern United States will help develop effective fungicide seed treatment strategies for control of stand loss caused by seedling blight, one of the major factors limiting rice production. [ABSTRACT FROM AUTHOR]

Stem rot, caused by the Sclerotium rolfsii, imposes severe yield losses in peanuts (Arachis hypogaea L.) worldwide. Breeding for resistance is challenging because not enough is known about mechanisms for resistance. The goals of this study were to (a) evaluate the field resistance of recombinant inbred lines derived from a resistant × susceptible cross, (b) associate quantitative loci (QTLs), and (c) reveal potential mechanisms for resistance. Lines were inspected during 3 yr in field conditions. Plants were manually inoculated and rated for three parameters: disease level, number of damaged plants/center, and disease power. Significant effects were found for the lines and the environment in all three parameters. Heritability and year‐to‐year correlations were highly significant, suggesting a consistent response of the lines to the stem rot pressure. Quantitative trait loci mapping was performed based on a previously constructed genetic map. Overall, 20 significant QTLs were found for the resistance parameters, concentrating in four locations on chromosomes A07, A03, B03, and B05. Out of the four loci, three were reported in previous studies with different genetic backgrounds suggesting a wide effect. The B05 QTL was the strongest, with the phenotypic variation explained of 11.6–21.7%. Interestingly, this QTL is colocalized with a previously identified major locus for branching habit trait. An additional field trial performed on 14 lines found a significant branching habit effect, wherein bunch‐types lines were more resistant than spreading‐types, suggesting that plant architecture can be a possible factor influencing the infection rate of S. rolfsii on the field level. Core Ideas: Stem rot, caused by the Sclerotium rolfsii, imposes severe yield losses in peanuts worldwide.We evaluate the field resistance in RIL population, reveal potential mechanisms for resistance.A significant found QTL was colocalized with a previously identified major locus for branching habit.Plant architecture may be an important factor influencing the infection rate of S. rolfsii on the field level. [ABSTRACT FROM AUTHOR]

A severe outbreak of foot rot and head rot disease of cabbage was observed during September 2017 to November 2019 in major cabbage growing regions of southern Karnataka state of India. The disease incidence ranged between 3% and 28%. The initial symptoms were observed as tan, water‐soaked lesions at the point of infection and development of mycelia, followed by quick wilting of the whole plant. Subsequently, numerous sclerotia were produced. The pathogen isolated on PDA medium produced white fluffy aerial mycelia and numerous reddish‐brown sclerotia after 7−10 days. A total of 18 fungal isolates were used for mycelial compatibility analysis. Isolate SrBoC28 was used to test for pathogenicity on cabbage, marigold, chilli and brinjal plants. Typical disease symptoms on leaves, stem and roots were evident 5, 8 and 10 days' post‐inoculation respectively. The isolate was pathogenic on all tested hosts, and the identity was confirmed by re‐isolation and morpho‐cultural and molecular studies. The latter were based on amplification of ITS‐rDNA and phylogenetic analysis which showed 100% sequence similarity with reference sequences. The identity was confirmed as S. rolfsii. This is a well‐known pathogen and causes disease on various economically important crop plants. To date, there are no reports on the association between S. rolfsii and foot and head rot disease of cabbage in India and elsewhere. Thus, to the best of our knowledge, this is the first report of foot rot and head rot of cabbage caused by S. rolfsii in India. [ABSTRACT FROM AUTHOR]

The plants of Meliaceae are native to tropical and subtropical regions as the Americas, west India, Southeast Asia, and Southern China. Many species of the genera Khaya, Swietenia, Aphanamixis, and Melia in this family are known as medicinal plants and have biological activities such as antiviral, antimicrobial, antifeeding, insecticidal, and cytotoxic properties. The objectives of this research are to characterize and evaluate the bioactive limonoids from several plants of Meliaceae against phytopathogenic fungi. During the search of antifungal compounds from the plants of Meliaceae, the three methanol extracts of Melia dubia, Aphanamixis polystachya, and Swietenia macrophylla were found to suppress the mycelial growth of several phytopathogenic fungi. Nine limonoids isolated from M. dubia (1–2), A. polystachya (3–5), and S. macrophylla (6–9) were evaluated, for the first time, their antifungal effectiveness against nine phytopathogenic fungi Fusarium oxysporum, Magnaporthe oryzae, Sclerotium rolfsii, Rhizoctonia solani, Alternaria spp., and Botrytis cinerea, and three oomycetes Phytophthora species. Limonoids 2, 3, 6, and 8 displayed a remarkable broad-spectrum antifungal activity against all the test fungi. Sclerotium rolfsii was highly sensitive to the four limonoids with IC50 values ranging from 79.4 to 128.0 µg/mL. Notably, chisocheton compound G (3) isolated from A. polystachya and khayanolide B (8) isolated from S. macrophylla were the most potent antifungal limonoids and exhibited a dose-dependent activity against Phytophthora species. Compounds 2 and 9 displayed moderate activity against M. oryzae. Our study results demonstrated the discovery of antifungal and lead compounds from the group of limonoids for application in the control of fungal plant diseases. [ABSTRACT FROM AUTHOR]

Developing markers linked to key traits has been a focus of peanut (Arachis hypogaea L.) genomics in the postgenome era. Multiple disease resistance traits have been found to be qualitative and controlled by major quantitative trait loci (QTL) or even single genes while others are more complex. Southern stem rot (stem rot in short) is a devastating disease of peanut caused by the fungus Sclerotium rolfsii. It has been one of the most damaging diseases of peanut with regard to both cost of control and yield loss in the southeastern United States for the last decade. The disease is initiated annually from sclerotia in the soil. The nonuniform distribution of these propagules leads to the nonuniform development of disease, which makes phenotyping and genetic mapping of resistance difficult. Here we report the mapping of two QTL regions controlling stem rot resistance in peanut. Using careful field evaluation, resistant and susceptible bulks were identified from a recombinant inbred line (RIL) population and subjected to QTL sequencing (QTL‐seq). Developed SNP markers linked to the QTL were validated in a blind selection test by selecting only with markers in a part of the population not used for initial analysis. The lines selected for bulk sequencing also were shown to have strong separation for resistance in an independent field experiment. This work not only delivers markers for marker‐assisted selection (MAS) for an important disease in peanut but shows that QTL‐seq can work effectively even when considering highly complex, and quantitative traits. [ABSTRACT FROM AUTHOR]

BACKGROUND Sclerotium rolfsii is a soil‐borne phytopathogenic fungus that causes diseases in economically important crops. Eradication of the fungus is hampered by its wide range of hosts, as well as its capacity to form sclerotia. Recently, we have shown that the endophytic fungus Daldinia cf. concentrica emits biologically active volatile organic compounds (VOCs); we also demonstrated that one VOC, trans‐2‐octenal, was the most effective against various phytopathogenic fungi. Thus, the aim of this study was to examine the potential of this compound to control hyphae and sclerotia of S. rolfsii, both in vitro and in soil. RESULTS: We found that in vitro exposure of S. rolfsii mycelium to trans‐2‐octenal in air fully inhibits and kills the fungus. Elimination of sclerotia viability occurred at the same concentration, but direct contact between the sclerotia and the compound was needed. trans‐2‐Octenal also affected the viability of both hyphae and sclerotia of S. rolfsii in small pots containing loam soil. CONCLUSION: We suggest the use of trans‐2‐octenal as a novel compound to control S. rolfsii. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The current study aimed at developing diverse Trichoderma fusants for fungicides, drought, and salt tolerance with enhanced antagonistic activity against Sclerotium rolfsii Sacc. Trichoderma virens NBAII Tvs12 (mycoparasitic) and Trichoderma koningii MTCC796 (multistress tolerant) were used as parental strains for development of interspecific protoplast fusants. A total of 36 stable fusants were used for mycoparasitism, fungicides, and abiotic stresses (drought and salt) tolerance. The results revealed 20 homozygous progenies showing characteristics of either one parental strain and 14 heterozygous mutants depicting traits of both parental strains. A novel concept of inhibition coefficient was established using growth‐related key parameters that represent the pathogen biology and the biocontrol‐related biophysics of Trichoderma fusants. The results indicated a differential inhibition coefficient of the test pathogen and the highest (92.88%) inhibition coefficient of S. rolfsii was observed by interstable fusant Fu21. It also grew better under fungicides and abiotic stress (drought and salt) conditions. The molecular characterization and heterozygosity analysis evidenced the highest observed heterozygosity (0.5441) and gene flow (0.3872) in stable heterozygous Fu21. Principal coordinates analysis exhibited 62.7% of total variability. The ecofriendly heterozygous Trichoderma fusant (Fu21) might be useful for biocontrol of stem rot disease under adverse conditions or as a part of integrated disease management. The study addressed development of diverse Trichoderma fusants for fungicides, drought and salt tolerance, gene specific confirmation for heterozygous and homozygous mutants, and identified potent fusants for biocontrol activity against the pathogen Sclerotium rolfsii. The potent fusant (Fu21) derived from the current study could be utilized for in vivo inhibition of S. rolfsii causing stem rot in groundnut by formulating an effective bioformulation with a low dose of fungicides as part of integrated disease management under adverse conditions (abiotic stresses‐drought and salt). [ABSTRACT FROM AUTHOR]

Expression of altered glycans such as TF, Tn, and sTn antigens has been observed in a number of carcinomas which are targeted in cancer therapy. Sclerotium rolfsii lectin (SRL) is known to recognize TF and its substituted forms. Clinical potential of SRL has been demonstrated by studying its interaction with different types of cancer cells. Here we report, in vitro studies of SRL on breast cancer MDA‐MB‐468 cells and in vivo studies with MCF‐7 xenografts. In vitro growth inhibitory studies of SRL on metastatic triple negative breast cancer MDA‐MB‐468 cells were performed by MTT assay, flow cytometry, adhesion, and CAM assay. In vivo efficacy studies of SRL were performed using NOD SCID mice bearing MCF‐7 xenografts. SRL has strong binding to MDA‐MB‐468 cells with MFI of 85.5 and has growth inhibitory effect with IC50 of 32 μg/ml at 48 hr. SRL has antiangiogenesis effect and also anti adhesive effect with fibronectin and collagen at 20 μg/ml by 36% and 42%, respectively. In vivo efficacy studies of SRL on NOD SCID mice bearing MCF‐7 xenogratfs revealed 61.77% and 75.71% tumor regressing effect, respectively, at 20 and 30 mg/kg body weight without any toxicity. All these results substantiate clinical potential of SRL on breast cancer. [ABSTRACT FROM AUTHOR]

Atractylenolides compounds (atractylenolide-I, atractylenolide- II and atractylenolide- III) extracted from Atractylenolides macrocephala were analysed for their differential presence in the rhizome of both the infected and healthy plants and its fungitoxicity on prophylactic treatment with polysaccharides of Chrysanthemum indicum against Sclerotium rolfsii. It was evident that the plant under stress by pathogen has instigated the significant synthesis and accumulation of atractylenolide- II and atractylenolide- III in the rhizome of plants as a result of elicitation with polysaccharides of C. indicum. Our results also showed that the absence of atractylenolide- II in the rhizome made the plant susceptible to S. rolfsii. Furthermore, on in vitro antifungal studies, exogenous application of atractylenolide- II with the concentration of 200 μg/ml showed a significant inhibitory effect on mycelial growth by achieving a 77.23% antifungal activity rate, and a minimal inhibitory effect at a concentration of 12.5 μg/ml with atractylenolide- II. To our knowledge, this novel study on phytoalexins in A. macrocephala suggested that A. macrocephala plants produce elevated levels of atractylenolide- II and atractylenolide- III in a pattern typical of phytoalexins, in response to an eliciting treatment after infection. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the potentiality of three compatible rhizosphere microbes, viz. fluorescent Pseudomonas aeruginosa ( PHU094), Trichoderma harzianum ( THU0816) and Mesorhizobium sp. ( RL091), in community to mobilise antioxidant mechanisms in chickpea under the challenge of Sclerotium rolfsii. The microbes were applied as seed treatment in different combinations in two sets and the pathogen was inoculated in one of the sets after 3 weeks of sowing. A comparative study was conducted on the effect of the microbial combinations on host antioxidant mechanisms between the two sets. In pathogen challenged plants host defence responses included higher accumulation of hydrogen peroxide ( H2O2) at petiolar and interveinal regions of leaf and high activities of catalase ( CAT), glutathione reductase ( GR) and guaiacol peroxidase ( GPx) compared to unchallenged plants. The antioxidant enzyme activities increased 1.8-3.3 and 1.9-3.1 folds at 48 and 72 h, respectively, in the triple microbe treated challenged plants compared to unchallenged ones. Although, ascorbate peroxidase ( APX) activity was significantly low, ascorbic acid ( AA) and chitinase accumulation was high in the pathogen challenged plants. Antioxidant flavonols associated with host defence namely myricetin, quercetin and kaempferol also accumulated in high amounts in pathogen challenged plants. Among the microbial treatments, the triple microbe combination induced the highest response in all parameters as compared to dual or single application of the same microbes. The triple microbe consortium modulated the chickpea antioxidant mechanisms more efficiently and modulation of oxidative stress was directly correlated with lower plant mortality, thus demonstrating the synergistic behaviour of the microbes in protecting chickpea from the pathogen. [ABSTRACT FROM AUTHOR]

Objectives Sclerotium rolfsii lectin ( SRL), isolated from soil born phytopathogenic fungus Sclerotium rolfsii, exhibits exquisite binding specificity to the oncofoetal Thomsen-Friedenreich (Galβ1,3Gal NAcα- O-Ser/Thr, T or TF) antigen and associated glycans. In the present study, we report anti-proliferative activity of SRL and investigate underlying mechanisms of SRL-induced apoptosis, in the human ovarian cancer cell line PA-1. Materials and methods SRL-induced anti-proliferative effects were determined using MTT assay and induction of apoptosis was determined by flow cytometry, confocal microscopy and western blot analysis. Results SRL inhibited population growth of PA-1 cells in a dose- and time-dependent manner with maximum inhibition (71.3 ± 1.9%) occurring at concentration of 50 μg/ml after 72 h incubation. Observed effects of SRL could be blocked by competing glycoproteins, asialomucin, mucin and fetuin. Treatment with SRL resulted in increase in hypodiploid cell population as determine by cell cycle analysis. Increase in numbers of annexin V- PI positive cells, and cleavage of PARP confirmed apoptosis-inducing activity of SRL. Involvement of caspases in SRL-mediated apoptosis was determined by cleavage of caspases-3, -8 and -9 in a time-dependent manner, thereby suggesting possible involvement of both intrinsic and extrinsic caspase-dependent pathways. Conclusion The present study demonstrates anti-proliferative and apoptosis-inducing activity of SRL that can be exploited for potential application in ovarian cancer research. [ABSTRACT FROM AUTHOR]

A wheat endophytic bacterium ( Pseudomonas aeruginosa PW09) was evaluated for its ability to trigger an induced systemic resistance response in cucumber against biotic and abiotic stresses. PW09 was applied to cucumber seeds, and the seedlings were subjected to Sclerotium rolfsii infection and NaCl (150 m m). The role of PW09 was evaluated in alleviating the stresses by assessing plant mortality due to S. rolfsii infection and biomass accumulation under NaCl stress as well as at the physiological level through phenylpropanoid metabolism, antioxidant activities and proline accumulation. The endophyte reduced seedling mortality by 60% and increased biomass accumulation significantly under S. rolfsii (7%) and NaCl (18%) stresses, respectively, compared with endophyte-untreated seedlings. Application of PW09 also induced higher accumulation of proline (1.3- and 1.4-fold) and total phenolics (1.2- and 1.1-fold) and activities of polyphenol oxidase (4.3- and 1.5-fold), phenylalanine ammonia lyase (1.29- and 1.27-fold) and superoxide dismutase (2.5- and 1.39-fold) under S. rolfsii and NaCl stresses, indicating the ability of the wheat endophyte PW09 in alleviating both biotic and abiotic stresses in cucumber. [ABSTRACT FROM AUTHOR]

The population structure of Sclerotium rolfsii from autumn-sown sugar beet crops in Mediterranean-type climate regions of Chile, Italy, Portugal and Spain was determined by analyses of mycelial compatibility groups (MCGs) and pathogenicity to 11 economically important plant species. Twelve MCGs (i-xii) were identified among 459 S. rolfsii isolates. MCG iii was the most prevalent group in all countries except Italy. MCG i, the most abundant group (64·7% of isolates) was identified in Portugal and Spain. The remaining MCGs were restricted to various regions within one country (ii, vi, ix) or different countries (v), or to specific localities (iv, vii, viii, x, xi, xii). MCGs iv, vii and x each comprised one isolate. Fields extensively sampled in southern Spain were infected with one to three MCGs. Plant species differed in susceptibility to MCG tester isolates with a MCG by species interaction. Cluster analyses allowed selection into five MCG groupings and grouped plant species into species-groups 1 (broccoli, chickpea, sunflower, tomato) and 2 (cotton, pepper, sugar beet, watermelon). MCG groupings 1 (i, ix), 2 (ii, iii, vi, viii) and 5 (x, xii) were moderately virulent to species-group 1 and mildly virulent to species-group 2. MCG groupings 3 (iv, v, xi) and 4 (vii) were mildly virulent to both species-groups. Across MCG groups, species were rated highly susceptible (chickpea, sunflower), susceptible (cotton, pepper, tomato, watermelon), moderately resistant (broccoli, melon, sugar beet) and resistant (corn, wheat). Establishing the MCG population structure and virulence variability among S. rolfsii isolates should help in the management of sclerotium root rot diseases. [ABSTRACT FROM AUTHOR]

Mycelial compatibility is assayed mainly by pairing mycelial plugs of field isolates on Petri dishes with agar media. Although methodologically simple, mycelial compatibility testing requires an artificial growth medium that permits the identification of compatible and incompatible interactions. In this work, several growth media were studied to assess consistently mycelial interactions between Sclerotium rolfsii isolates. A modification of Patterson's medium with an increment of 25% glucose from the original concentration at a rate of 23.4 g/l and amended with 180 μl/l of red food colouring was the most effective combination for enhancing the size, density and distinctiveness of the aversion zone between incompatible isolates. This medium allowed the unequivocal identification of compatible and incompatible reactions of a set of five S. rolfsii isolates, which could be determined quickly after 5 days of incubation in the dark at 25°C. This new formulation improved significantly and consistently the assessment of the aversion zone reaction that was visible as a red line on the colony reverse as compared to that assessed using previous media formulations, for which the visualization of aversion zones was scarcely discernible. The utility of the improved growth medium was validated by microscopic observations of the contact area of hyphal pairings between isolates of S. rolfsii in microscope slide cultures. [ABSTRACT FROM AUTHOR]

Field studies were conducted to characterize the genetic nature of resistance to southern blight (caused by Sclerotium rolfsii Sacc.) exhibited by the cowpea [Vigna unguiculata (L.)Walp.] cultivars Carolina Cream and Brown Crowder and to determine if a genetic relationship exists for this resistance between the two cultivars. Examination of the comparative frequency distributions of the parental and progeny populations of the "Carolina Cream" x "Magnolia Blackeye" and "Brown Crowder" x "Magnolia Blackeye" crosses and the corresponding segregation data indicates that the southern blight resistances exhibited by "Carolina Cream" and "Brown Crowder" are conditioned by single dominant genes. Examination of the segregation data from the parental and progeny populations of the "Carolina Cream" x "Brown Crowder" cross suggests that the two resistance genes are not allelic. The availability of each of the resistance genes in cultivar-type genetic backgrounds should allow for rapid incorporation of southern blight resistance genes into other cowpea cultivars by the application of conventional plant breeding methodologies. [ABSTRACT FROM AUTHOR]

Plants evolve a strategy to survive the attacks of potential pathogens by inducing the microbial signal molecules. In this study, plant defence responses were induced in four different varieties of Arachis hypogaea (J-11, GG-20, TG-26 and TPG41) using the fungal components of Sclerotium rolfsii in the form of fungal culture filtrate (FCF) and mycelial cell wall (MCW), and the levels of defence-related signal molecule salicylic acid (SA), marker enzymes such as peroxidase (POX), phenylalanine ammonia lyase (PAL), β-1,3-glucanase and lignin were determined. There was a substantial fold increase in POX, PAL, SA, β-1,3-glucanase and lignin content in FCF- and MCW-treated plants of all varieties of groundnut when compared to that of control plants. The enzyme activities were much higher in FCF-treated plants than in MCW-treated plants. The increase in fold activity of enzymes and signal molecule varied between different varieties. These results indicate that the use of fungal components (FCF and MCW) had successfully induced systemic resistance in the four different varieties of groundnut plants against Sclerotium rolfsii. [ABSTRACT FROM AUTHOR]

Peanut is vulnerable to a range of foliar diseases such as spotted wilt caused by Tomato spotted wilt virus (TSWV), early (Cercospora arachidicola) and late (Cercosporidium personatum) leaf spots, southern stem rot (Sclerotium rolfsii), and sclerotinia blight (Sclerotinia minor). In this study, we report the generation of 17,376 peanut expressed sequence tags (ESTs) from leaf tissues of a peanut cultivar (Tifrunner, resistant to TSWV and leaf spots) and a breeding line (GT-C20, susceptible to TSWV and leaf spots). After trimming vector and discarding low quality sequences, a total of 14,432 high-quality ESTs were selected for further analysis and deposition to GenBank. Sequence clustering resulted in 6,888 unique ESTs composed of 1,703 tentative consensus (TCs) sequences and 5185 singletons. A large number of ESTs (5717) representing genes of unknown functions were also identified. Among the unique sequences, there were 856 EST-SSRs identified. A total of 290 new EST-based SSR markers were developed and examined for amplification and polymorphism in cultivated peanut and wild species. Resequencing information of selected amplified alleles revealed that allelic diversity could be attributedmainly to differences in repeat type and length in the SSR regions. In addition, a few additional INDEL mutations and substitutions were observed in the regions flanking the microsatellite regions. In addition, some defense-related transcripts were also identified, such as putative oxalate oxidase (EU024476) and NBS-LRR domains. EST data in this study have provided a new source of information for gene discovery and development of SSR markers in cultivated peanut. A total of 16931 ESTs have been deposited to the NCBI GenBank database with accession numbers ES751523 to ES768453. [ABSTRACT FROM AUTHOR]

Exudates from sclerotia of two Sclerotium rolfsii isolates (one causing collar rot in Cicer arietinum, isolate VC971, and the other leaf spots in Rauvolfia serpentina, isolate VL016) were assayed for their antifungal activity against 26 fungi consisting of plant parasites as well as saprophytes. Spore germination of all the test fungi was affected by the exudates reaching 100% in some cases. Foliar spray with exudates of isolate VL016 significantly reduced disease incidence of balsam ( Impatiens balsamina) powdery mildew caused by Erysiphe cichoracearum and pea ( Pisum sativum) powdery mildew caused by Erysiphe pisi, under field conditions. Characterization of exudates from 25 isolates of S. rolfsii revealed pH ranging from 3.8 to 5.3 and colour from light yellow to deep yellow. Among the phenolic acids found in the exudates were tannic, gallic, caffeic, vanillic, ferulic, chlorogenic and cinnamic acids. Oxalic acid was also found in varied amounts. Among the phenolic acids, ferulic acid was found to be present at high concentration in exudates of most isolates (3.9–153.4 μg/ml). The antioxidant properties of phenolics, which generally inhibit fungal morphogenesis including spore germination along with the antifungal nature of some phenolics are chiefly attributed to the inhibitory effect of sclerotial exudates of S. rolfsii. Additionally, both the isolates VC971 and VL016 showed almost similar antifungal activities despite they are of different origin and thereby demonstrate the antifungal nature of sclerotial exudates. [ABSTRACT FROM AUTHOR]

The endogenous localisation of peroxidase and hydrogen peroxide (H2O2) was detected when gametophytes of the fern, Ceratopteris richardii, were exposed to the plant pathogenic fungi Sclerotium rolfsii and Sclerotinia sclerotiorum and Phytophthora infestans, an oomycete, in a gnotobiotic system. This was accomplished by light microscopy using 3,3′-diaminobenzidine, guaiacol and H2O2 and starch potassium iodide (KI) staining procedures, which facilitated the observation of the reaction in vivo and in situ, without physically damaging the tissues. All three staining methods promoted staining at the rhizoid regions. Although most of the cells were destroyed when gametophytes were exposed to S. rolfsii and S. sclerotiorum, there was staining where mycelial growth was confluent with cell walls. A qualitative test confirmed that the colour change in starch KI agar medium, as well as in the histochemical test with starch KI, was because of H2O2 secreted by S. rolfsii or S. sclerotiorum and not because of oxalic acid. When gametophytes were exposed to P. infestans, no infection occurred, but localisation of H2O2 and peroxidase was detected irrespective of staining methods tested. Based on the observation on gametophytes grown in presence of P. infestans, it is possible that the peroxidase in plants coupled with H2O2 may prevent the invasion of nonpathogens by functioning as a barrier. This fern–pathogen model system has potential for application as a tool to study the host–parasite interaction in a gnotobiotic system. [ABSTRACT FROM AUTHOR]

Abstract Sclerotium rolfsii Sacc. causes disease of numerous crop plants worldwide, including groundnuts. Control of this pathogen is difficult as it produces sclerotia which overwinter in the soil to emerge as inoculum and cause disease the following season. Various chemical, biological and cultural control strategies have been suggested and implemented, some of which have reduced disease incidence in the field. No studies have yet been undertaken in South Africa to control this disease on groundnut, either chemically, biologically or by cultural practices. In this study, several strategies were investigated for the control of S. rolfsii on groundnuts. Difenoconazole was identified as a fungicide that could possibly be applied in combination with Trichoderma harzianum , a biological antagonist of S. rolfsii , above carbendazim and flusilazole, and chlorothalonil. Difenoconazole significantly reduced the growth rate of S. rolfsii but not of T. harzianum . The cultivation of infected fields with an inversion plough significantly reduced infection of groundnuts by S. rolfsii and also improved the quality of the produce, while yield was not increased. Lower plant density increased the incidence of disease in an infected field, and is therefore not considered to be a viable form of cultural control. [ABSTRACT FROM AUTHOR]

Efficacy of seven strains of Pseudomonas fluorescens (Pfs1-7), plant growth-promoting rhizobacteria (PGPR), were tested under field conditions for their ability to protect Cicer arietinum against Sclerotium rolfsii infection. Best protection was observed in strain Pfs3 where 23% seedling mortality was recorded in comparison to 44% in non-treated control. To correlate the induction of phenolic compounds by the PGPRs with disease resistance, qualitative and quantitative alterations of phenolic compounds in different parts of C. arietinum were estimated following PGPR application as seed treatment. High performance liquid chromatographic (HPLC) analysis of the leaves, collars and roots of the PGPR-treated and non-treated (control) plants showed the presence of gallic, ferulic, chlorogenic and cinnamic acids with varied amounts in the PGPRtreated as well as non-treated (control) plants. Maximum accumulation of cinnamic acid was observed in plants treated with Pfs3 strain (1660 ng g[sup -1] fresh wt.) which was almost 19.5 times higher than untreated control plants and also significantly high when compared to other PGPR treatments. Pfs3 also caused maximum accumulation of total phenolics and gallic acid in all chickpea plant parts as compared to other treatments and untreated control. A direct relationship between the level of total phenolics and seedling survivability was observed. PGPR-mediated induction of phenolic compounds as a biochemical barrier in C. arietinum against S. rolfsii infection is envisaged. [ABSTRACT FROM AUTHOR]

Thirty isolates of Sclerotium rolfsii Sacc. from different hosts and regions of Brazil were studied in relation to morphology, mycelial compatibility, analysis of genomic DNA through random amplified polymorphic DNA (RAPD), variation within the nuclear rDNA [internal transcribed spacers (ITS)] and sequencing of ITS fragments. There was considerable variability among isolates in relation to the number, size and location of sclerotia on the medium surface. Thirteen mycelial compatibility groups (MCG) were identified among 23 isolates. Seven isolates were only self-compatible. With the exception of group 3, where all the isolates came from soybean, there was no apparent correlation between group and isolate origin. On the basis of RAPD profiles, 11 haplotypes (A to K) were identified. There was an association between the RAPD groups and MCG. Haplotypes A, B, D, G, I and K belonged to MCG groups 1, 2, 3, 4, 5 and 6, respectively. All other RAPD haplotypes contained incompatible isolates. Polymerase chain reaction (PCR) amplification with primers 4R and 5F amplified two fragments containing ITS1, ITS2 and 5.8 S rDNA sequences, that were present in all isolates, with molecular sizes of 739 and 715 bp. Restriction analysis of PCR products showed that the two fragments had sequence divergency which is referred to as ‘ITS types’. Four arbitrarily chosen soybean isolates (2, 6, 7 and 23) and two non-soybean isolates (11 and 22) were used to investigate the variation within the ITS sequence and its role in the phylogeny. The strict consensus of nine most-parsimonious trees inferred from the data set which included six isolates of S. rolfsii, four of which have two different ‘ITS types’, showed three well-supported groupings. The neighbour-joining tree inferred from the data set also showed three major clades as did the parsimony tree. The major difference was that in the neighbour-joining tree the ‘ITS type’ 11 was resolved and... [ABSTRACT FROM AUTHOR]

Acquired resistance to the antibiotic polyoxin-D was studied in two phytopathogenic fungi, Alternaria solani Sorauer, and Sclerotium rolfsii Sacc. The ED50 value of the antibiotic for A. solani was 100 ftg/ml and S. rolfsii 200 fig/ml. A. solani and S. rolfsii could be trained to tolerate concentrations up to 1.000 (Ag/ml and 2.200 Hg/ml respectively. The acquired resistance in both cases was not lost on continued subculturing in fungicide-free media. On transfer to fungicide-free media, Polyoxin-resistant strains of both the fungi showed faster growth rate and appreciable reduction in sporulation compared to the original strains. The adapted strain of A. solani showed cross-resistance to Cycloheximide and Difolatan but not to Hinosan and Bayleton. [ABSTRACT FROM AUTHOR]

Sclerotium rolfsii Sacc. is an aggressive soil-borne pathogen of many crop plants in the tropics and subtropics (Aycock 1966). It is commonly found in Egypt on several economic crops including soybeans (El-Helaly et al. 1966). of invaded tissues. Such pathological effects have been attributed to diffusible enzymes, toxins, or their combination (Tribe 1955). The nature of plant pathogenesis incited by the pathogen has been reviewed by Watkins (1966) and Aycock (1966). A number of plant pathogens including S. rolfsii produce phosphatidases (Tseng and Bateman 1968) which hydrolyze the various ester linkages in lecithin and related phospholipids (Butt and Beevers 1966). Since phospho- lipids are among the primary constituents of higher plant cell membranes, the production of phosphatidases by phytopathogens during pathogenesis may be related to the changes in host cell premeability that have often been associated with certain plant diseases (Lai et al. 1968). This possible role of phosphatidases in pathogenesis by S. rolfsii has not been established. Therefore, this study was undertaken to investigate the role of this enzyme in the virulence of S. rolfsii. [ABSTRACT FROM AUTHOR]

Intact mature sclerotia of Sclerotium rolfsii Sacc. and Sclerotium cepivorum Berk. produced in culture are impermeable to the apoplastic tracer sulphorhodamine G. Both of these species produce sclerotia with rinds. Some movement of sulphorhodamine into sclerotia of Rhizoctonia solani Kühn, which have no rind, occurred but the fluorochrome was arrested after permeation of at most the outer five layers of cells. In all cases, low permeability depended on an intact outer layer, and when sclerotia of each species were bisected to provide direct access of sulphorhodamine to all tissue layers, the fluorochrome permeated the cell walls and extracellular matrix (where present) of man cells within the sclerotium. A marked reduction in permeability of intact sclerotia occurs at maturity in a number of species and might be important in long-term survival. [ABSTRACT FROM AUTHOR]

An isolate of Trichoderma harzianum which is less effective than G. virens in suppressing S. rolfsii and R. solani was compared with G. virens for various mechanisms of antagonism in vitro, viz., antagonism in dual culture/hyphal parasitism, parasitism of sclerotia, and antibiosis. G. virens and T. harzianum were equally effective in parasitizing the hyphae of R. solani. Only T. harzianum parasitized the hyphae of S. rolfsii, and the two antagonists were comparable with respect to antibiosis on the test pathogens. However, G. virens readily parasitized the sclerotia of the test pathogens and was found to be more effective than T. harzianum in destroying the sclerotia. Under SEM. G. virens was found to colonize, penetrate, and sporulate inside the sclerotia of the test pathogens. Parasitism of sclerotia is suggested as the principal mechanism of biological control of S. rolfsii and R. solani by G. virens. [ABSTRACT FROM AUTHOR]

The antimycotic activity of medicagenic acid and of some synthetic derivatives thereof was tested against plant pathogenic fungi. In general they all possess antimycotic activity. Furthermore, in the case of Sclerotium rolfsii, compounds where the hydroxyl functions of the aglycon remained unchanged (medicagenic acid and its dimethyl ester) or could be enzymically released (3-0-β-D-glucoside of medicagenic acid dimethyl ester) were significantly more active than compounds where these functions were modified by acetylation or methylation. Selective 2-0-methylation of medicagenic acid and comparison of the antimycotic activity of the resulting derivative against S. rolfsii to that of other derivatives suggests that a potential free hydroxyl at position 3 is essential to antimycotic activity. [ABSTRACT FROM AUTHOR]

Among the three nitrofurans tested Furazolidone completely inhibited the in vitro growth of Sclerotium rolfsii, even at 100 µg/ml. Nitrofurantoin affected complete inhibition of mycelial growth only at 1000 µg/ml while nitrofurazone was not toxic even at 1000 µg/ml. Sclerotial germination was inhibited by the three nitrofurans. Mild chlorosis developed in the margin of soybean leaves following 24 h of root dip treatment with nitrofurazone. Foliar application of the nitrofurans drastically reduced the fungal and bacterial population in the soybean rhizosphere, whereas actinomycete population was found to be increased significantly. All the three nitrofurans reduced disease severity: but only furazolidone increased the yield. Von den drei getesteten Nitrofuranen wurde das in vitro Wachstum von Sclerotium rolfsii schon bei 100 µg/ml Furazolidon völlig unterdrückt. Dagegen wurde das Myzelwachstum erst bei 1000 µg/ml Nitrofurantoin ganz gehemmt und Nitrofurazon zeigte noch keine Toxität bei 1000 µg/ml. Die Sklerotienkeimung wurde bei allen drei Nitrofuranen gehemmt. Nach einer 24stündigen Wurzeltauchbehandlung mit Nitrofurazon entwickelten sich mittlere Chlorose an den Rändern von Sojabohnenblättern. Eine Blattapplikation der Nitrofurane verursachte eine drastische Reduzierung der pilzlichen und bakteriellen Population der Sojabohnenrhizosphäre, dagegen wurde eine signifikante Erhöhung der Actinomycetenpopulation beobachtet. Alle drei Nitrofurane reduzierten die Befallsstärke, eine Ertragserhöhung wurde jedoch nur nach einer Furazolidonbehandlung ermittelt. [ABSTRACT FROM AUTHOR]

The sclerotia of Sclerotium rolfsii Sacc. survived in natural soil for 225 days under controlled moisture at 50% water holding capacity (WHC) after which there was a progressive reduction in the population of viable sclerotia. At 390 days only 48% were recovered. Sclerotia survived well at moisture contents up to 75% WHC but at 100% the population declined rapidly and none were recovered after 60 days. The contents of the sclerotia were found to lyse without germination leaving hollow rinds. Such lysis was found to be favoured between 25 and 40 °C. At and below 20 °C no such lysis was recovered and more than 80% sclerotia were recovered even after 60 days. [ABSTRACT FROM AUTHOR]

Sclerotium production by Sclerotinia sclerotiorum (Lib.) de Bary, Sclerotium rolfsii Sacc. and S. delphinii Welch was enhanced by white light, the most effective wavelengths being in the blue and near-ultraviolet regions of the spectrum. Sensitivity of dark-grown cultures to light decreased with age. The effect of light appeared to be through the direct induction of sclerotium initials on undifferentiated hyphae. The relevance of these observations to the general study of sclerotium morphogenesis is discussed. [ABSTRACT FROM AUTHOR]

Thirteen fungal species were isolated from diseased plants of Striga hermonthica (Del.) Benth in northern Ghana. The pathogenicity of 12 isolates of the fungal species including Curvularia fallax Boed, Fusarium equiseti (Corda) Sacc., Fusarium equiseti var. bullatum (Sherb.) Wollenw., F. oxysporum Schlecht, F. solani (Mart) Sacc., Macrophomina phaseolina (Tassi) Goidan, and Sclerotium rolfsii (Sacc.) were evaluated against S. hermonthica under controlled environmental conditions. All isolates were pathogenic to S. hermonthica when propagated on wheat (Triticum aestivum. L.) grains and incorporated pre-plan ting into the soil. However, their virulence differed. Two isolates of F. oxysporum and one isolate of F. solani reduced the emergence of S. hermonthica by 88%. 98%, and 76%, respectively. Sorghum (Sorghum bicolor (L.) Moench) yield was increased by 26% when S. hermonthica was controlled. In contrast, in the control treatment with S. hermonthica no yield could be obtained. The P. oxysporum isolates were not pathogenic on sorghum. Germination tests indicated that the F. oxysporum isolates were highly pathogenic to S. hermonthica seeds. Although the F. solani isolate reduced the emergence of S. hermonthica in the pot experiments, it did not influence germination. This indicates that pathogens may attack different stages in the life cycle of S. hermonthica. [ABSTRACT FROM AUTHOR]

Two simple formulations of an antagonistic strain of Trichoderma koningii were employed against southern blight disease caused by Sclerotium rolfsii seedling, potted outdoor and field-grown tomatoes (cvs. lfe No. 1 and Ibadan Local). Corn cob germling inoculum and mycelium powder of T. koningii significantly controlled (P≤0.05) symptoms of damping off, blight and wilting in both tomato cultivars. The populations of the antagonist increased from an initial 1× 104 to about 1 × 106 colony-forming units per g of soil in the protected plants. Moreover, sclerotial counts decreased significantly (P≤0.05) in these soils and those sclerotia found had been parasitized by T. koningii. Trichoderma-protected plants were more vigorous than those in the other treatment categories. The significance of these results is discussed in relation to the use of Trichoderma in appropriately simplified formulations. [ABSTRACT FROM AUTHOR]

Aqueous suspensions of conidia of 285 wild-type strains and mutants of Glioctadium virens. Trichoderma hamatum, T. harzianum and T. viride were tested against Sclerotium rolfsii in the greenhouse. Ten strains of G. ufrens and four strains of T. harzianum suppressed damping-off of snapbean by 30–50% and blight by 36–74%. All strains of T. hamatum and T. viride tested as conidia were ineffective. In general, strains of G. virens were more effective in suppressing disease in the greenhouse than strains of T. harzianum. Several strains of G. virens and T. harzianum used alone were equal to or more effective than double and triple mixtures of such strains in disease suppression. Of four formulations of G. virens tested, germlings, alginate-bran-fermenter biomass pellets, and Pyrax-fermenter biomass mixtures reduced disease considerably and all three formulations were more effective than conidia in aqueous suspension. Strain Gl-3 of G. virens added to soil as Pyrax-fermenter biomass mixtures in amounts to provide colony- forming units ranging from 1·5 × 103 to 1·2 x 104 per g soil provided statistically significant protection of the host m all concentrations. The extent of biological control with strains GI-3 and GI-21 of G. virens also depended on the strain of the pathogen used. Both strains effectively suppressed disease caused by strain Sr-1 (small sclerotia) of S. rolfsii. They were partially effective against strain Sr-116 (medium size sclerotia) and ineffective against strain Sr-3 (large sclerotia). Although strains GI-3 and Cd-21 colonized the sclerotia of all three strains of S. rolfsii soil effectively, they only reduced germinability of sclerotia of strain Sr-l. [ABSTRACT FROM AUTHOR]

Taraxacum officinale (dandelion) is a medicinal plant that occurs in various countries and is also reported as an invasive plant in some parts of the world. Recently, a severe case of southern blight was observed in dandelion in the Medicinal Plant House at the State University of Maringa, Umuarama, State of Parana, Brazil. A dense, cottony mycelial growth and the formation of sclerotia were observed on the plants. The fungus was isolated, inoculated into healthy plants and re-isolated. Samples were sequenced for rDNA regions ITS4 and ITS5. The inoculated plants presented symptoms of southern blight, beginning at the base of the plant and eventually killing the plant. DNA analysis revealed a 99% species identity index for Athelia rolfsii (anamorph: Sclerotium rolfsii). [ABSTRACT FROM AUTHOR]

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The potent biocontrol agent Trichoderma interfusant (Fu21) derived by protoplast fusion of mycoparasitic T.virens NBAII Tvs12 and multistress (fungicides and abiotic stress) tolerant T. koningii MTCC796. The chitin‐induced exometabolites harvested by culturing the diverse and stress tolerant Trichoderma fusant (Fu21) and utilized for synthesis of green silver nanoparticles (Ag‐NPs). Green Ag‐NPs characterized for size (62.6 nm in PSA), shape (spherical with 59.66 ± 4.18 nm under SEM), stability (51.2 mv as ZETA) and purity (3.40 ke V peak corresponded to the binding energy of silver under EDAX). A Fourier transform infrared spectroscopy exhibited electromagnetic spectra of various functional groups of exometabolites conforming the synthesis of green Ag‐NPs. We investigated novel route and mechanism of mycelial degradation at minimum inhibitory concentration (MIC) of green nanoformulation (20 μg Ag.ml−1) to restrain phytopathogen Sclerotium rolfsii. The antifungal action of green Ag‐NPs on MIC at 3 DAI elevated the mycelial cell membrane leakages (sugars and proteins), lipid peroxidation, depressed the respiratory chain dehydrogenase activity and destroyed the structure of S. rolfsii mycelia (SEM morphology) which cause phytopathogen to die. The use of green Ag‐NPs as antifungal agent is considered to be eco‐friendly resource, alternate to fungicides and cost‐effective means to diminish phytopathogen S. rolfsii causing stem rot in groundnut. Further, bioefficacy of green Ag‐NPs against S. rolfsii may be tested under field condition in groundnut rhizosphere which proved sustainability and it's advancement towards greener chemistry. [ABSTRACT FROM AUTHOR]