Soilborne Phytopathogenic Fungi Research Articles

A Gene Cassette Vd276-280 in Verticillium dahliae Contains Two Genes that Affect Melanized Microsclerotium Formation and Virulence.

Verticillium dahliae is a soilborne phytopathogenic fungus causing Verticillium wilt on hundreds of plant species. Several sequenced genomes of V. dahliae are available, but functional characterization of most genes has just begun. Based on our previous comparison of the transcriptome from the wild-type and ΔVdCf2 strains, a significant upregulation of the gene cassette, Vd276-280, in the ΔVdCf2 strain was observed. In this study, the functional characterization of the Vd276-280 gene cassette was performed. Agrobacterium-mediated knockout of this gene cassette in V. dahliae significantly inhibited conidiation, melanized microsclerotium formation in the mutant strains, and their virulence toward cotton. Furthermore, deletion of individual genes in the Vd276-280 gene cassette identified that the disruption of VDAG_07276 and VDAG_07280 delayed microsclerotium formation, inhibited conidiation, and reduced virulence toward cotton. Our data suggest that VDAG_07276 and VDAG_07280 in the Vd276-280 gene cassette mainly act as positive regulators of development and virulence in V. dahliae.

In vitro and in vivo Effect of Weeds (Root) Extracts on Soil Borne Fungal Phytopathogens and Fungal Infected Legume Crop Bengal Gram (Cicer arietinum)

Background: Weed management during growing season has been a serious problem for many years. Worldwide, a 10% loss of agricultural products can be attributed to the competitive effect of weeds, despite their intensive control. Dactyloctenium aegyptium and Chenopodium album L. is an annual weed of cultivated fields. Methods: This investigation was done in 2020-2021. Root parts of both weeds Dactyloctenium aegyptium and Chenopodium album were collected from a nearby area, Sardar Vallabh Bhai Patel University of Agriculture and Technology, Meerut. To determine the antifungal potentials of both weeds Dactyloctenium aegyptium and Chenopodium album root extracts were determined by the food poisoning method against fungal phytopathogens. Methane, Ethyl acetate, Butyl alcohol, Benzene and Water-soluble root extracts of both weeds at different concentrations (5%, 10% and 15%) were used against fungal phytopathogens growth in laboratory conditions and also used on fungal infected related attributes of Bengal gram in a pot culture experiment in 1:10 ratio. Antioxidants of both weed extracts were done by DPPH, FRAP and ABTS methods. Result: Findings showed that application of 15% concentrated extracts has maximum antifungal effects against Fusarium oxysporum and Sclerotium rolfsi (70-80%). In the pot experiment, we find that at increased concentrations of methanolic extract (15%) infected Bengal gram crops show high effectiveness against fungal phytopathogens and improve different parameters such as germination, plant physiology and morphological characteristics. However, higher concentrations of methanol extract promoted these parameters and reduced fungal growth in both in vivo and vitro conditions Results of this study reported highly significant suppressive effects of higher concentrations (10% and 15%).

Evaluation of Bacillus isolates as a biological control agents against soilborne phytopathogenic fungi.

Pesticides, used in agriculture to control plant diseases, pose risks to the environment and human health. To address this, there's a growing focus on biocontrol, using microorganisms instead of chemicals. In this study, we aimed to identify Bacillus isolates as potential biological control agents. We tested 1574 Bacillus isolates for antifungal effects against pathogens like Botrytis cinerea, Fusarium solani, and Rhizoctonia solani. Out of these, 77 isolates formed inhibition zones against all three pathogens. We then investigated their lytic enzyme activities (protease, chitinase, and chitosanase) and the production of antifungal metabolites (siderophore and hydrogen cyanide). Coagulase activity was also examined to estimate potential pathogenicity in humans and animals. After evaluating all mechanisms, 19 non-pathogenic Bacillus isolates with significant antifungal effects were chosen. Molecular identification revealed they belonged to B. subtilis (n = 19) strains. The 19 native Bacillus strains, demonstrating strong antifungal effects in vitro, have the potential to form the basis for biocontrol product development. This could address challenges in agricultural production, marking a crucial stride toward sustainable agriculture.

Endophytic Streptomyces sp. NEAU-DD186 from Moss with Broad-Spectrum Antimicrobial Activity: Biocontrol Potential Against Soilborne Diseases and Bioactive Components.

Soilborne diseases cause significant economic losses in agricultural production around the world. They are difficult to control because a host plant is invaded by multiple pathogens, and chemical control often does not work well. In this study, we isolated and identified an endophytic Streptomyces sp. NEAU-DD186 from moss, which showed broad-spectrum antifungal activity against 17 soilborne phytopathogenic fungi, with Bipolaris sorokiniana being the most prominent. The strain also exhibited strong antibacterial activity against soilborne phytopathogenic bacteria Ralstonia solanacearum. To evaluate its biocontrol potential, the strain was prepared into biofertilizer by solid-state fermentation. Response surface methodology was employed to optimize the fermentation conditions for maximizing spore production and revealed that the 1:1 ratio of vermicompost to wheat bran, a temperature of 28°C, and 50% water content with an inoculation amount of 15% represented the optimal parameters. Pot experiments showed that the application of biofertilizer with a spore concentration of 108 CFU/g soil could effectively suppress the occurrence of tomato bacterial wilt caused by R. solanacearum and wheat root rot caused by B. sorokiniana, and the biocontrol efficacy was 81.2 and 72.2%, respectively. Chemical analysis of strain NEAU-DD186 extracts using nuclear magnetic resonance spectrometry and mass analysis indicated that 25-O-malonylguanidylfungin A and 23-O-malonylguanidylfungin A were the main active constituents, which showed high activity against R. solanacearum (EC50 of 2.46 and 2.58 µg ml-1) and B. sorokiniana (EC50 of 3.92 and 3.95 µg ml-1). In conclusion, this study demonstrates that Streptomyces sp. NEAU-DD186 can be developed as biofertilizer to control soilborne diseases.

Temperature sensitivity of soil-borne fungal phytopathogens depends on niche breadth and land use types

Soil-borne fungal plant pathogens pose great threats to agricultural productivity and native ecosystems. However, the roles of niche breadth and land-use types in regulating the response of soil-borne fungal plant pathogens to temperature changes largely remain unclear. Here, we surveyed soil pathogens from different valleys where croplands, grasslands, and woodlands scattered in mosaic patterns. We found that pathogen richness increased with increasing temperature in grasslands but not in croplands and woodlands. After classifying the pathogens based on temperature niche, we found that the richness of specialists was sensitive to temperature changes and increased with increasing temperature in grasslands and croplands. By contrast, the richness of neutrals (those taxa not defined as generalists or specialists) did not change with temperature gradients regardless of land-use types. Additionally, pathogens were more abundant and diverse in croplands than those in grasslands and woodlands, and this pattern persisted across the temperature gradient. Our results provide evidence that temperature change and land use types could additively affect the diversity of plant pathogens in soils. This work advances our understanding of how niche breadth affects the response of pathogens to temperature, highlighting the importance of climate change and land use in regulating the abundance and diversity of pathogens.

Prevalent Plant Growth Hormone Indole-3-acetic Acid Produced by Streptomyces sp. VSMKU1027 and its Potential Antifungal Activity against Phytofungal Pathogens

Microorganisms and plants can produce indole-3-acetic acid (IAA) by mechanisms that either involve tryptophan or do not involve tryptophan. The control of Zone of inhibition (ZOI) ranged from 1.2 cm to 1.0 cm. A promising antagonistic isolate, Streptomyces sp. VSMKU1027, exhibited robust antagonistic activity against two significant soil-borne phytopathogenic fungi, namely Rhizoctonia solani and Fusarium oxysporum, outperforming the control. The morphology of both R. solani and F. oxysporum, including their sclerotium and spores, became condensed and indistinct, and mycelial disintegration was observed due to the action of VSMKU1027, in contrast to the control. The isolate significantly produced antimicrobial traits and hydrolytic enzymes except hydrogen cyanide and cellulase. Furthermore, the promising isolate VSMKU1027 was identified as Streptomyces sp. based on its morphological, physiological, and biochemical characteristics. In comparison to the control, the isolate VSMKU1027 demonstrated increased synthesis of IAA and the hydrolytic enzyme protease with the corresponding substrates. The production of IAA was optimized on the sixth day, at 35°C and pH 6.5. The highest generation of IAA was recorded, with an ISP2 and 0.4% concentration of L-tryptophan.

VdPT1 Encoding a Neutral Trehalase of Verticillium dahliae Is Required for Growth and Virulence of the Pathogen.

Verticillum dahliae is a soil-borne phytopathogenic fungus causing destructive Verticillium wilt disease. We previously found a trehalase-encoding gene (VdPT1) in V. dahliae being significantly up-regulated after sensing root exudates from a susceptible cotton variety. In this study, we characterized the function of VdPT1 in the growth and virulence of V. dahliae using its deletion-mutant strains. The VdPT1 deletion mutants (ΔVdPT1) displayed slow colony expansion and mycelial growth, reduced conidial production and germination rate, and decreased mycelial penetration ability and virulence on cotton, but exhibited enhanced stress resistance, suggesting that VdPT1 is involved in the growth, pathogenesis, and stress resistance of V. dahliae. Host-induced silencing of VdPT1 in cotton reduced fungal biomass and enhanced cotton resistance against V. dahliae. Comparative transcriptome analysis between wild-type and mutant identified 1480 up-regulated and 1650 down-regulated genes in the ΔVdPT1 strain. Several down-regulated genes encode plant cell wall-degrading enzymes required for full virulence of V. dahliae to cotton, and down-regulated genes related to carbon metabolism, DNA replication, and amino acid biosynthesis seemed to be responsible for the decreased growth of the ΔVdPT1 strain. In contrast, up-regulation of several genes related to glycerophospholipid metabolism in the ΔVdPT1 strain enhanced the stress resistance of the mutated strain.

Endophytic Streptomyces sp. NEAU-ZSY13 from the leaf of Perilla frutescens, as a promising broad-spectrum biocontrol agent against soil-borne diseases.

Soil-borne diseases cause significant economic losses in global agricultural production. These diseases are challenging to control due to the invasion of multiple pathogens into host plants, and traditional chemical control methods often yield unsatisfactory results. In this study, we isolated and identified an endophytic Streptomyces, designated as NEAU-ZSY13, from the leaf of Perilla frutescens. This isolate exhibited broad-spectrum antifungal activity against 17 soil-borne phytopathogenic fungi, with Bipolaris sorokiniana being the most prominent. Additionally, it displayed strong antibacterial activity against the soil-borne phytopathogenic bacterium Ralstonia solanacearum. To assess its biocontrol potential, the isolate was utilized to produce a biofertilizer through solid-state fermentation. The fermentation conditions were optimized using response surface methodology to maximize the spore production. The results revealed that more abundant spores were produced with a 1:2 ratio of vermicompost to wheat bran, 60% water content, 20% inoculation amount and 28°C. Subsequent pot experiments demonstrated that the application of the biofertilizer with a spore concentration of 108 CFU/g soil effectively suppressed the occurrence of tomato bacterial wilt caused by R. solanacearum and wheat root rot caused by B. sorokiniana, with biocontrol efficacies of 72.2 and 78.3%, respectively. Chemical analysis of NEAU-ZSY13 extracts, using nuclear magnetic resonance spectrometry and mass analysis, identified niphimycin C and niphimycin A as the primary active constituents. These compounds exhibited high activity against R. solanacearum (EC50 of 3.6 and 2.4 μg mL-1) and B. sorokiniana (EC50 of 3.9 and 3.4 μg mL-1). In conclusion, this study demonstrates the potential of Streptomyces sp. NEAU-ZSY13 as a biofertilizer for the control of soil-borne diseases.

The Extracellular Lipopeptides and Volatile Organic Compounds of Bacillus subtilis DHA41 Display Broad-Spectrum Antifungal Activity against Soil-Borne Phytopathogenic Fungi.

Fusarium oxysporum f. sp. niveum (Fon) is a devastating soil-borne fungus causing Fusarium wilt in watermelon. The present study investigated the biochemical mechanism underlying the antifungal activity exhibited by the antagonistic bacterial strain DHA41, particularly against Fon. Molecular characterization based on the 16S rRNA gene confirmed that DHA41 is a strain of Bacillus subtilis, capable of synthesizing antifungal lipopeptides, such as iturins and fengycins, which was further confirmed by detecting corresponding lipopeptide biosynthesis genes, namely ItuB, ItuD, and FenD. The cell-free culture filtrate and extracellular lipopeptide extract of B. subtilis DHA41 demonstrated significant inhibitory effects on the mycelial growth of Fon, Didymella bryoniae, Sclerotinia sclerotiorum, Fusarium graminearum, and Rhizoctonia solani. The lipopeptide extract showed emulsification activity and inhibited Fon mycelial growth by 86.4% at 100 µg/mL. Transmission electron microscope observations confirmed that the lipopeptide extract disrupted Fon cellular integrity. Furthermore, B. subtilis DHA41 emitted volatile organic compounds (VOCs) that exhibited antifungal activity against Fon, D. bryoniae, S. sclerotiorum, and F. graminearum. These findings provide evidence that B. subtilis DHA41 possesses broad-spectrum antifungal activity against different fungi pathogens, including Fon, through the production of extracellular lipopeptides and VOCs.

Hyphopodium-Specific Signaling Is Required for Plant Infection by Verticillium dahliae.

For successful colonization, fungal pathogens have evolved specialized infection structures to overcome the barriers present in host plants. The morphology of infection structures and pathogenic mechanisms are diverse according to host specificity. Verticillium dahliae, a soil-borne phytopathogenic fungus, generates hyphopodium with a penetration peg on cotton roots while developing appressoria, that are typically associated with leaf infection on lettuce and fiber flax roots. In this study, we isolated the pathogenic fungus, V. dahliae (VdaSm), from Verticillium wilt eggplants and generated a GFP-labeled isolate to explore the colonization process of VdaSm on eggplants. We found that the formation of hyphopodium with penetration peg is crucial for the initial colonization of VdaSm on eggplant roots, indicating that the colonization processes on eggplant and cotton share a similar feature. Furthermore, we demonstrated that the VdNoxB/VdPls1-dependent Ca2+ elevation activating VdCrz1 signaling is a common genetic pathway to regulate infection-related development in V. dahliae. Our results indicated that VdNoxB/VdPls1-dependent pathway may be a desirable target to develop effective fungicides, to protect crops from V. dahliae infection by interrupting the formation of specialized infection structures.

Fusarium oxysporum f. sp. niveum Pumilio 1 Regulates Virulence on Watermelon through Interacting with the ARP2/3 Complex and Binding to an A-Rich Motif in the 3' UTR of Diverse Transcripts.

Fusarium oxysporum f. sp. niveum (Fon), a soilborne phytopathogenic fungus, causes watermelon Fusarium wilt, resulting in serious yield losses worldwide. However, the underlying molecular mechanism of Fon virulence is largely unknown. The present study investigated the biological functions of six FonPUFs, encoding RNA binding Pumilio proteins, and especially explored the molecular mechanism of FonPUF1 in Fon virulence. A series of phenotypic analyses indicated that FonPUFs have distinct but diverse functions in vegetative growth, asexual reproduction, macroconidia morphology, spore germination, cell wall, or abiotic stress response of Fon. Notably, the deletion of FonPUF1 attenuates Fon virulence by impairing the invasive growth and colonization ability inside the watermelon plants. FonPUF1 possesses RNA binding activity, and its biochemical activity and virulence function depend on the RNA recognition motif or Pumilio domains. FonPUF1 associates with the actin-related protein 2/3 (ARP2/3) complex by interacting with FonARC18, which is also required for Fon virulence and plays an important role in regulating mitochondrial functions, such as ATP generation and reactive oxygen species production. Transcriptomic profiling of ΔFonPUF1 identified a set of putative FonPUF1-dependent virulence-related genes in Fon, possessing a novel A-rich binding motif in the 3' untranslated region (UTR), indicating that FonPUF1 participates in additional mechanisms critical for Fon virulence. These findings highlight the functions and molecular mechanism of FonPUFs in Fon virulence. IMPORTANCE Fusarium oxysporum is a devastating plant-pathogenic fungus that causes vascular wilt disease in many economically important crops, including watermelon, worldwide. F. oxysporum f. sp. nievum (Fon) causes serious yield loss in watermelon production. However, the molecular mechanism of Fusarium wilt development by Fon remains largely unknown. Here, we demonstrate that six putative Pumilio proteins-encoding genes (FonPUFs) differentially operate diverse basic biological processes, including stress response, and that FonPUF1 is required for Fon virulence. Notably, FonPUF1 possesses RNA binding activity and associates with the actin-related protein 2/3 complex to control mitochondrial functions. Furthermore, FonPUF1 coordinates the expression of a set of putative virulence-related genes in Fon by binding to a novel A-rich motif present in the 3' UTR of a diverse set of target mRNAs. Our study disentangles the previously unexplored molecular mechanism involved in regulating Fon virulence, providing a possibility for the development of novel strategies for disease management.

Revealing the Mechanisms for Linalool Antifungal Activity against Fusarium oxysporum and Its Efficient Control of Fusarium Wilt in Tomato Plants

Fusarium oxysporum f. sp. radicis-lycopersici (Forl) is a destructive soil-borne phytopathogenic fungus that causes Fusarium crown and root rot (FCRR) of tomato, leading to considerable field yield losses. In this study, we explored the antifungal capability of linalool, a natural plant volatile organic component, against Forl and its role in controlling FCRR symptoms in tomatoes. Our results showed that Forl mycelial growth was inhibited by the linalool treatment and that the linalool treatment damaged cell membrane integrity, enhanced reactive oxygen species levels, depleted glutathione, and reduced the activities of many antioxidant enzymes in Forl. Transcriptomic and proteomic analyses demonstrated that linalool also downregulated metabolic biosynthetic pathways at the transcript and protein levels, including redox, transporter activity, and carbohydrate metabolism in Forl. Moreover, linalool significantly decreased the expression of many Forl pathogenic genes, such as cell wall degrading enzymes (CWDEs) and G proteins, which is likely how a Forl infection was prevented. Importantly, exogenously applied linalool activated the salicylic acid (SA) and jasmonic acid (JA) defensive pathways to improve disease resistance and relieved the negative effects of Forl on plant growth. Taken together, we report that linalool is an effective fungicide against Forl and will be a promising green chemical agent for controlling FCRR.

ESTUDO DO CRESCIMENTO MICELIAL DE MACROPHOMINA SPP. NO BRASIL, SUA PATOGENICIDADE E SENSIBILIDADE A FUNGICIDA

ABSTRACT Macrophomina (Botryosphaeriaceae) is one of the main genera of soilborne phytopathogenic fungi, which causes root and seed rot in more than 800 host plants worldwide. Recent phylogenetic studies identified the species M. phaseolina and M. pseudophaseolina in Trianthema portulacastrum and Boerhavia diffusa in melon and watermelon production areas in northeastern Brazil. Therefore, the objective of this study was: i) to verify the effect of temperature and salinity on the mycelial growth of M. phaseolina, M. pseudophaseolina and M. euphorbiicola, ii) to assess their pathogenicity on melon and watermelon seedlings, and iii) to determine their sensitivity to the fungicide carbendazim. The optimal temperature for mycelial growth rate (MGR) for Macrophomina spp. ranged from 27.18 ºC (CMM4771 – M. pseudophaseolina) to 31.80 ºC (CMM4763 – M. phaseolina). For the effect of salinity on mycelial growth of Macrophomina isolates, the EC50 ranged from 103.76 (CMM4868 – M. euphorbiicola) to 315.25 mM (CMM4801 – M. pseudophaseolina). The pathogenicity test demonstrated that M. phaseolina, M. pseudophaseolina and M. euphorbiicola are pathogenic on melon with M. phaseolina exhibiting a higher level of virulence. Macrophomina euphorbiicola isolates did not cause disease in watermelon. The most sensitive isolates to the fungicide carbendazim were CMM4868, CMM4867 (M. euphorbiicola) and CMM1531 (M. phaseolina) with EC50 of 0.003, 0.012 and 0.012 mg.L-1 a.i., respectively. All Macrophomina spp. used in these experiments were pathogenic to the tested melon and watermelon cultivars with the exception of the M. euphorbiicola isolate that did not cause damage to watermelon.

Antagonism Of Trichoderma Species Against Major Soil Borne Plant Pathogens

In the current study, ten isolates of Trichoderma harzianum and T. hamatum collected from different agro climatic zones of Maharashtra were tested for antagonism against important soil borne phytopathogenic fungi (Fusarium ciceri, Rhizoctonia bataticola and Sclerotium rolfsii) using dual culture assay. In comparison to the controls, all T. harzianum isolates had a significant antagonistic effect on pathogen mycelial growth in dual cultures. T. harzianum (AkTr2) inhibited radial mycelial growth by 77.78%, 78.52% and 75.93% in Fusarium ciceri, Rhizoctonia bataticola and Sclerotium rolfsii respectively. Whereas T. hamatum (AkTm1) inhibited 75.93%, 75.56% and 73.70% growth of Fusarium ciceri, Rhizoctonia bataticola and Sclerotium rolfsii respectively. The isolate AkTr2 was the most promising and resulted in the greatest growth inhibition in R. bataticola, while AkTm1 resulted in the least growth inhibition in Sclerotium rolfsii (73.70 %).

Soil-borne plant pathogenic fungi biodiversity of sunflower

Diseases caused by soil-borne phytopathogenic fungi are a serious problem for agricultural crops, including sunflower crops. The limited possibilities of measures to control them further increases the interest and focus on them. This article reveals data on the species composition, occurrence rate of soil-borne plant pathogenic fungi isolated from the soil of sunflower. Here, 11 species of true fungi and 1 species of oomycetes have been isolated. The highest incidence rate was recorded in the Fusarium oxysporum fungi species. During the study, pathogenic fungi specific to sunflower have also been isolated.

Growth-Promoting and Protective Effect of Trichoderma atrobrunneum and T. simmonsii on Tomato against Soil-Borne Fungal Pathogens

Trichoderma fungi are promising candidates for biocontrol agents and plant growth promoters. Trichoderma atrobrunneum and T. simmonsii were evaluated for the control of soil-borne phytopathogenic fungi, in the present study. Dual culture tests with Rhizoctonia solani and Fusarium oxysporum f. sp. lycopersici were used to conduct in vitro evaluation. In the presence of Trichoderma, phytopathogen’s growth rate was inhibited up to 59.70% for R. solani and 42.57% for F. oxysporum. Greenhouse trials with potted tomato plants demonstrated that Trichoderma caused a significant increase of stem height and fresh stem weight in pathogen-inoculated plants, compared with the negative control (plants artificially inoculated with the phytopathogen only). Except for T. simmonsii, plant growth was not significantly enhanced by a Trichoderma presence in the positive control (healthy plants). The overall performance of the two Trichoderma species studied was equivalent to that of the T. harzianum T22 commercial strain. All the tested species were found to be effective in suppressing colony growth and disease development of the soil borne pathogens in dual cultures and potted plants, indicating that they could be used as biocontrol agents. Our findings are discussed in the context of enhancing endophytic microorganisms’ application in crop production systems.

The Proportion of Soil-Borne Fungal Pathogens Increases with Elevated Organic Carbon in Agricultural Soils.

ABSTRACTSoil-borne fungal phytopathogens are important threats to soil and crop health. However, their community composition and environmental determinants remain unclear. Here, we explored the effects of agricultural fertilization regime (i.e., organic material application) on soil fungal phytopathogens, using data sets from a combination of field survey and long-term experiment. We found that soil organic carbon was the key factor that affected the diversity and relative abundance of fungal phytopathogens in agricultural soils. The dominant genera of phytopathogens including Monographella was also strongly associated with soil organic carbon. In addition, the elevated soil organic carbon enhanced the node proportion of phytopathogens and the positive interactions within the fungal community in the network. Results of the long-term experiment revealed that applications of crop straw and fresh livestock manure significantly increased the proportion of phytopathogens, which were associated with the elevated soil organic carbon. This work offers new insights into the occurrence and environmental factors of fungal phytopathogens in agricultural soils, which are fundamental to control their impacts on the soil and crop systems.IMPORTANCE Fungal phytopathogens are important threats to soil and crop health, but their community composition and environmental determinants remain unclear. We found that soil organic carbon is the key factor of the prevalence of fungal phytopathogens through a field survey, which is also supported by our long-term (6-year) experiment showing the applications of crop straw and fresh livestock manure significantly increased the proportion of fungal phytopathogens. These findings advance our understanding of the occurrence and environmental drivers of soil-borne fungal phytopathogens under agricultural fertilization regime and have important implications for the control of soil-borne pathogens.

A fungal effector suppresses the nuclear export of AGO1–miRNA complex to promote infection in plants

Communication between interacting organisms via bioactive molecules is widespread in nature and plays key roles in diverse biological processes. Small RNAs (sRNAs) can travel between host plants and filamentous pathogens to trigger transkingdom RNA interference (RNAi) in recipient cells and modulate plant defense and pathogen virulence. However, how fungal pathogens counteract transkingdom antifungal RNAi has rarely been reported. Here we show that a secretory protein VdSSR1 (secretory silencing repressor 1) from Verticillium dahliae, a soil-borne phytopathogenic fungus that causes wilt diseases in a wide range of plant hosts, is required for fungal virulence in plants. VdSSR1 can translocate to plant nucleus and serve as a general suppressor of sRNA nucleocytoplasmic shuttling. We further reveal that VdSSR1 sequesters ALY family proteins, adaptors of the TREX complex, to interfere with nuclear export of the AGO1–microRNA (AGO1–miRNA) complex, leading to a great attenuation in cytoplasmic AGO1 protein and sRNA levels. With this mechanism, V. dahliae can suppress the accumulation of mobile plant miRNAs in fungal cells and succedent transkingdom silencing of virulence genes, thereby increasing its virulence in plants. Our findings reveal a mechanism by which phytopathogenic fungi antagonize antifungal RNAi-dependent plant immunity and expand the understanding on the complex interaction between host and filamentous pathogens.

INFLUENCE OF NUTRIENTS SOURCE ON RADIAL GROWTH OF MACROPHOMINA PHASEOLINA (TASSI.) GOID

Sesame (Sesamum indicum L.) is oil seed crop of India and asian countries mostly preferred due to rich in its edible oil content (50%) and protein (23%) and having sufficient carbohydrate (15%). Macrophomina phaseolina is a soil borne phytopathogenic fungus having a wide host range of about 500 cultivated and wild plant species worldwide. In the present investigation nineteen nutrients were tested against Macrophomina phaseolina at 100, 150, 200 and 250 ppm concentrations that enhanced mycelial growth but lowest mycelial growth was recorded on Monoammonium phosphate and Ferrous sulphate over control. All the nutrients significantly influenced growth of test fungi when compared with control under In vitro conditions.

Trans-Kingdom RNA Silencing in Plant-Fungal Disease Control.

Trans-kingdom RNA interference (RNAi) has been reported in several plant-fungal pathosystems. Our recent works have demonstrated natural RNAi transmission from cotton plants into Verticillium dahliae, a soil-borne phytopathogenic fungus that infects host roots and proliferates in vascular tissues, and successful application of trans-kingdom RNAi in cotton plants to confer Verticillium wilt disease resistance. Here, we provide a detailed protocol of cotton infection with V. dahliae, fungal hyphae recovery from infected cotton stems, and transmitted small RNA detection developed from our previous studies for trans-kingdom RNAi assays.