Root Rot Disease Research Articles

Analyzing the defense response mechanism of Atractylodes macrocephala to Fusarium oxysporum through small RNA and degradome sequencing.

Fusarium oxysporum is a significant soil-borne fungal pathogen that affects over 100 plant species, including crucial crops like tomatoes, bananas, cotton, cucumbers, and watermelons, leading to wilting, yellowing, growth inhibition, and ultimately plant death. The root rot disease of A. macrocephala, caused by F. oxysporum, is one of the most serious diseases in continuous cropping, which seriously affects its sustainable development. In this study, we explored the interaction between A. macrocephala and F. oxysporum through integrated small RNA (sRNA) and degradome sequencing to uncover the microRNA (miRNA)-mediated defense mechanisms. We identified colonization of F. oxysporum in A. macrocephala roots on day 6. Nine sRNA samples were sequenced to examine the dynamic changes in miRNA expression in A. macrocephala infected by F. oxysporum at 0, 6, and 12 days after inoculation. Furthermore, we using degradome sequencing and quantitative real-time PCR (qRT-PCR), validated four miRNA/target regulatory units involved in A. macrocephala-F. oxysporum interactions. This study provides new insights into the molecular mechanisms underlying A. macrocephala's early defense against F. oxysporum infection, suggesting directions for enhancing resistance against this pathogen.

Study on the Identification, Biological Characteristics, and Fungicide Sensitivity of the Causal Agent of Strawberry Red Core Root Rot

Strawberry red core root rot disease affects the growth and yield of strawberry (Fragaria ananassa Duch), which leads to economic losses in China. The study employed a tissue separation method to isolate and identify the causal agent responsible for strawberry red core root rot. This was achieved by the observation of its morphological characteristics, sequencing analyses, and pathogenicity tests. The sensitivity of five chemical fungicides against the two species of Fusarium was determined using the mycelial growth rate method, and the biological characteristics of the two species were examined. The pathogens were identified as Fusarium solani and Fusarium oxysporum. The optimal conditions for the mycelial growth of F. solani and F. oxysporum were determined to be potato sucrose agar at 25 °C and pH 6, and potato dextrose agar at 30 °C and pH 8, respectively, with a 24:24 light cycle. The most suitable carbon and nitrogen sources for the mycelial growth of F. solani were sucrose and sodium nitrate (NaNO3), while for F. oxysporum, they were glucose and peptone. A fungicide sensitivity test indicated that Prochloraz had a good inhibitory effect on the growth of F. solani and F. oxysporum with EC50 values of 0.088 mg L−1 and 0.162 mg. The growth inhibition effect of Azoxystrobin to F. solani and Carbendazim to F. oxysporum was not obvious. This study provides a theoretical basis for further research on strawberry red core root disease and its prevention.

Promising antifungal behavior of biosynthesized bimetallic silver-copper oxide nanoparticles and Bacillus safensis against some strawberry rots

Promising nanomaterials combined with beneficial microbes contributed to bio-modulations that might increase yields. In order to combat several fungal infections that invade strawberries (Fragaria ananassa), this study assessed the interactions between the synthesized CuO NPs, bimetallic Ag–CuO NPs, and Bacillus safensis (BS-22) under various treatment circumstances. The effectiveness of BS-22, CuO NPs, and bimetallic Ag–CuO NPs against four different pathogens that cause gray mold disease and root rot on strawberry plants was determined. It was possible to successfully extract twenty-four endophytic bacterial isolates from hygienic strawberry plants that were indigenous. BS-22 isolate, which produced the most hydrogen cyanide (HCN), siderophores, gibberellic acid (GA3), and indole-3-acetic acid (IAA), was identified molecularly as Bacillus safensis. The most extensively studied treatments (foliar CuO NPs at 200 ppm + foliar Ag–CuO NPs at 200 ppm + BS-22) decreased the frequency and severity of black root rot disease in strawberry plants. Foliar CuO NPs (50 ppm) + foliar Ag–CuO NPs (50 ppm) showed significant increase of the total suspended solids (TSSs), total antioxidant capacity (TAC) content, and the total polyphenols content compared to the control and other treatments. The same treatment recorded the highest value in all characters of cell wall components except lignin character where BS-22 treatment had the best effect. All tested treatments significantly decreased disease incidence and severity when strawberry fruit stored at 22 °C ± 2 for 25 days on average. According to this study, foliar CuO NPs (200 ppm) + foliar Ag–CuO NPs (200 ppm) + BS-22 (as a soil drench) might be used as a substitute for gray mold and root rot diseases in strawberry development and biocontrol.

First Report of Phialocephala bamuru Causing Root Rot on Hard Fescue (Festuca brevipila) in the United States.

Turfgrasses are susceptible to a wide variety of ectotrophic root-infecting (ERI) fungi that cause root rot (Tredway et al., 2023). Among the root rot diseases, fairway patch, caused by Phialocephala bamuru P.T.W. Wong & C. Dong sp. nov., was recently identified and characterized in Australia infecting bermudagrass (Cynodon dactylon) and kikuyu (Pennisetum clandestinum) grass (Wong et al., 2015). Symptoms begin as small, 5-10 cm diameter patches of yellowed turf that may coalesce into larger areas of diseased grass. A characteristic sign of fairway patch is roots colonized by dark brown to black, ectotrophic mycelium. In June 2020, many tan colored, irregular-shaped patches ranging from 10-30 cm in diameter developed on a hard fescue (Festuca brevipila) cultivar 'Beacon' turfgrass field in North Brunswick, New Jersey, USA. The centers of these patches later died and became sunken or filled in partially by recovering hard fescue. The patches grew into tan irregular-shaped rings with diameters up to 3 m by Aug 2023. Symptoms were indicative of a root disease. Five 'Beacon' hard fescue soil cores at the interface of the symptomatic and non-symptomatic area were sampled in Aug 2023. Root and crown samples were observed under a dissecting microscope and dark ectotrophic hyphae were observed on both. Roots with visible ectotrophic mycelium were removed, rinsed in sterile water three times, cut into 5 mm pieces, and plated onto 10% potato dextrose agar amended with streptomycin and gentamicin at 100 mg/L (PDA+). The plates were incubated at 25°C in the dark for 5 days. The most abundant colonies being characteristic long, septate hyphae that were hyaline at the edge and dark brown to black in the center and resembled the fungus described in Wong et al., 2015. These colonies were subcultured onto PDA+ medium and selected for molecular identification. Other less abundant colonies could be identified using morphology after subcultured and had no record being pathogenic to turfgrass. To confirm the isolate's identity, its internal transcribed spacer (ITS) region was amplified in PCR using the ITS1F/ITS4 primers (Bellemain et al., 2010). The amplicon was then sequenced with both ITS1 and ITS4 primers by Sanger sequencing. Sequences were assembled (GenBank #PP000819). The consensus sequence was then BLASTn analyzed with default settings, and the result showed 99.64% sequence identity with P. bamuru (GenBank #MG195534.1). Koch's postulate was conducted in an environmentally controlled growth chamber. Six healthy 'Beacon' hard fescue plugs were sampled from the field. Three of the six plugs (treatment) were each inoculated with P. bamuru by placing 20 g of P. bamuru colonized millets beneath and around the plug before filling the pots with sand. The other three plugs (control) received the same treatment except the P. bamuru colonized millets were autoclaved. The pots were incubated in the growth chamber with a 16 h light period and 25/20°C day/night temperatures. Symptoms resembling those observed in the field appeared on the treatment pots after 21 days of incubation while the control pots remained healthy. The roots from the treatment pots were examined under the dissecting microscope to confirm the colonization of P. bamuru on the roots, and P. bamuru was reisolated and confirmed using the aforementioned morphological traits and molecular assays (GenBank #PP000820). This is the first report of a turfgrass root rot disease caused by P. bamuru in the United States. Further epidemiological, disease ecological, and pathogen biological studies are required to clarify the importance of this disease in the United States and establish proper disease containment or control measures.

Some Chemical and Biological Methods to Control Pepper Root Rot Disease in Iraq

Background: Pepper growing fields in the Babil and Wasit governorates in Iraq, are suffering from a decline in production due to the spread of root rot diseases. The use of biological control techniques, such as the use of beneficial bacteria in the rhizosphere and natural plant extracts, along with chemical fungicides, has recently contributed to reducing the damage of plant pathogens globally. Methods: In this research, the main cause of root rot disease in pepper plants was isolated and diagnosed using polymerase chain reaction technology using (TEF-1α) gene, antagonistic activities of 75 rhizobacterial isolates, natural extracts of garlic and nerium and the fungicides of Promess and Tecto 500 SC were tested in vitro against the pathogen, then the superior bacterial isolates were identified. The ability of biological and chemical agents to control the disease was tested under greenhouse conditions according to the completely randomized design (CRD). Result: The results of isolation showed that the fungus Fusarium solani was dominance and the isolate Fsw45 was the most virulent. 3 of 75 rhizobacterial isolates outperformed the pathogen in an antagonistic tests and identified as Pseudomonas mendocina, P. fluorescens and Staphylococcus kloosii also the fungicides and botanical extracts showed significant antagonistic activities as well in vitro. Under greenhouse conditions, the fungicide treatments excelled in disease control by 100%. As for the 3 bacterial isolates, they achieved a significant reduction in the percentage of disease incidence and disease severity index, their abilities were higher than the nerium and garlic extracts.

One stone two birds: Endophytes alleviating trace elements accumulation and suppressing soilborne pathogen by stimulating plant growth, photosynthetic potential and defense related gene expression

In the present investigation, we utilized zinc nanoparticles (Zn-NPs) and bacterial endophytes to address the dual challenge of heavy metal (HM) toxicity in soil and Rhizoctonia solani causing root rot disease of tomato. The biocontrol potential of Bacillus subtilis and Bacillus amyloliquefaciens was harnessed, resulting in profound inhibition of R. solani mycelial growth and efficient detoxification of HM through strong production of various hydrolytic enzymes and metabolites. Surprisingly, Zn-NPs exhibited notable efficacy in suppressing mycelial growth and enhancing the seed germination (%) while Gas chromatography-mass spectrometry (GC-MS) analysis unveiled key volatile compounds (VOCs) crucial for the inhibition of pathogen. Greenhouse trials underscored significant reduction in the disease severity (%) and augmented biomass in biocontrol-mediated plants by improving photosynthesis-related attributes. Interestingly, Zn-NPs and biocontrol treatments enhanced the antioxidant enzymes and mitigate oxidative stress indicator by increasing H2O2 concentration. Field experiments corroborated these findings, with biocontrol-treated plants, particularly those receiving consortia-mediated treatments, displayed significant reduction in disease severity (%) and enhanced the fruit yield under field conditions. Root analysis confirmed the effective detoxification of HM, highlighting the eco-friendly potential of these endophytes and Zn-NPs as fungicide alternative for sustainable production that foster soil structure, biodiversity and promote plant health.

Characterization, phylogenetic analysis and toxigenic potential of Fusarium incarnatum‐equiseti species complex isolates associated with root rot disease in vegetables

AbstractFusarium incarnatum‐equiseti species complex infects a wide variety of food crops. Six fungal isolates were isolated from rotted roots of Dolichos lablab (hyacinth bean), Trichosanthes dioica (pointed gourd), Momordica dioica (spiny gourd), Capsicum frutescens (chilli) and Pisum sativum (garden pea), and identified as Fusarium spp., belonging to Fusarium incarnatum‐equiseti species complex (FIESC), through conidial morphology, sporodochia on carnation leaf agar medium and sequencing of nuclear ITS‐rRNA and transcription elongation factor 1α gene. Multilocus phylogenetic analysis demonstrated their inclusion within the Incarnatum clade of FIESC. All of them were self‐incompatible and failed to pair with other isolates. Vegetative incompatibility affected their pathogenicity and host specificity. The isolates secreted extracellular cell wall degrading enzymes cellulase (0.033 ± 0.002–0.403 ± 0.020 U.mL−1), polygalacturonase (0.005 ± 0.0001–0.392 ± 0.010 U.mL−1) and pectin‐lyase (0.015 ± 0.001–0.407 ± 0.012 U.mL−1) for direct penetration to root tissue. They also secreted toxic metabolites that inhibited germination of Cicer arietium (chickpea) and Pisum sativum (garden pea) seeds. The isolates exhibited complete pathogenicity on their original hosts (death due to root rotting, Disease Severity Index‐ 100%) but less pathogenicity in other non‐host plants (yellowing of lower leaves without sign of root rot, Disease Severity Index‐ <20%). This study reported the production of plant cell wall degrading enzymes and toxic metabolites by some pathogens belonging to FIESC and three new hosts of the pathogen such as hyacinth bean, spiny gourd and garden pea, from the Indian subcontinent.

Evaluation of the Efficiency of Ordinary and Nano-Chitosan in Stimulating Acquired Systemic Resistance of Cucumber Plants Against the Fungus Fusarium solani Which Causes Root Rot Disease

Evaluation of the Efficiency of Ordinary and Nano-Chitosan in Stimulating Acquired Systemic Resistance of Cucumber Plants Against the Fungus Fusarium solani Which Causes Root Rot Disease

Studying on Antifungal Activities of Streptomyces Isolated from Soil and Its Biocontrol Potential Against Fusarium of Chili’s Root Rot Disease

Seven Streptomyces strains from chili farm soil, including Strep-1, Strep-2, Strep-4, Strep-5, Strep-6, Strep-8, and Strep-10, were screened for their antifungal activities against Fusarium sp. of chili's root rot disease. The results showed that Streptomyces sp. Strep-4 and Streptomyces sp. Strep-8 performed potential abilities to control the pathogenic Fusarium of which means of antifungal efficacies were 43,88 ± 3,21% and 51,8 ± 2,54%, in turn. Extensive researches on the effects of inoculum factors on antifungal activity of Streptomyces sp. Strep-8 resulted that this strain spontaneously synthesized the antifungal compounds to control Fusarium in the culture condition with pH 7, 40oC of culture temperature, and 7 days of culture time. The results proved that Streptomyces sp. Strep-8 with its thermophilic ability not only provided significant inhibitory activity against pathogenic Fusarium sp. in vitro also promised to be a potential biological control agent to eliminate this fungus on fields. Moreover, using Streptomyces sp. Strep-8 as a biological control agent helps reduce the use of fungicides which contributes to boosting the sustainability of agricultural ecosystems worldwide.

Induction of Resistance and Defense Mechanisms of Geranium Plants Against Root Rot Disease Using Gallic Acid and 3,5-dinitrobenzoic Acid.

Induction of Resistance and Defense Mechanisms of Geranium Plants Against Root Rot Disease Using Gallic Acid and 3,5-dinitrobenzoic Acid.

Characterization of biologically synthesized copper nanoparticles by Aspergillus carbonarius and evaluation of their activity in reducing the pathogenic stress of tomatoes infected with Fusarium oxysporum

This study was conducted to evaluate the efficiency of the fungus Aspergillus carbonarius in the synthesis of copper nanoparticles (CuNPs) from copper chloride solution, with the characterization of these nanoparticles and the demonstration of their effectiveness in inhibiting the pathogenic fungus Fusarium oxysporum causing tomato root rot disease. The results indicated that the treatment of copper chloride solution at 150 mM with A. carbonarius filtrate led to the production of CuNPs which characterized by a color change from blue to green, with the highest absorbance observed at 300 nm. X-ray diffraction (XRD) results revealed the crystalline structure with peaks at angles 28.47286, 47.43258, and 56.20644 ◦ corresponding to (111), (220), and (311) planes, respectively, matching the JCPDS card number 01-081-1841. Scanning electron microscopy images showed cubic, pyramidal, and prismatic shapes with dimensions ranging from 15 - 84.291 nm. In laboratory experiment, CuNPs inhibited the growth of the pathogenic fungus, with an inhibition zone of 1.6 cm, compared to copper chloride which recorded 0.9 cm. In the field, , the treatment of CuNPs led to an increase in the stress resistance indicators, reaching the highest values for CuNPs when combined with the fungicide Medazim in the American tomato cultivar. The concentrations of total phenols and glutathione in this treatment were 2.56 mg/g and 0.322 µg/g, respectively. The lowest concentration of proline was recorded as 4.31 µg/g in the treatment involving CuNPs against the fungal infection. CuNPs with the fungicide medazim, significantly outperformed other treatments, registering lowest disease severity at 12.22% in the American cultivar, compared to the highest disease severity was recorded in the treatment with the pathogenic fungus alone, reaching 91.16% in the Dutch cultivar. CuNPs significantly increased tomato fruit weight, both in healthy and infected plants. The American, Turkish, and Dutch tomato cultivars infected with the pathogenic fungus and treated with under + medazim showed higher productivity, reaching 6432.55, 6334.34, and 6305.73 g.plant-1, compared to the lowest productivity in the treatment of these cultivars with the pathogenic fungus, reaching 1008.34, 977.45, and 833.78 g.plant-1, respectively

Effect of Bio Control Agents on Controlling Root Rot and Damping-off Disease of Cucumber Seedlings Caused by Rhizoctonia solani

Root rot and seedlings damping-off disease caused by Rhizoctonia solani is the most damaging disease of cucumber. This disease causes reducing yield in cucumber. This study conducted laboratory and greenhouse conditions to find out the efficacy of biological control agents, Trichoderma harzianum, Bacillus subtilis, the chemical compound Bion, and fungicide revanol. The results of pathogenicity test of R. solani on cucumber seeds showed that R. solanihas led to a significant reduction in the percentage of germination and seed rot compared to the control treatment, which amounted to 100%. The results showed the ability of all control agents used in this study to reduce the incidence of the disease. The Bion (benzothiadiazole) treatment showed significant effect and outperformed the other treatments in increasing the activity of the peroxidase enzyme, which was recorded at 14,440 (unit. minute-1.g wet weight-1). It also achieved the highest significant increase in total phenolics 1.52 (mg -1 . gram wet weight -1). Biological control agent T. harzianum has outperformed on other treatments in causing an increase in the activity of the polyphenol oxidase enzyme, it has recorded 1811.7 (unit. minute - 1 .gram of wet weight - 1 leaf).

Role of Hydrogen Peroxide (H2O2) and Trichoderma koningii in Reducing Root Rot Disease of Tomato Causing by Fusarium solani

Two isolates of the pathogenic fungus Fusarium solani the causative of tomato root rot disease named Fs1 and Fs2 were isolated from tomato plants infected with root rot disease. Results showed that both examined isolates had significant effects on the percentage of seed germination of tomato and damping-off disease. Thus, isolate Fs1 was more effective than isolate Fs2, as it recorded a percentage of germination and damping-off 56.6 and 71.6% respectively, compared to the control treatment, which recorded 100 and 0% respectively. It was found that the use of hydrogen peroxide (H2O2) at concentrations of 50, 100 and 200 ppm had a significant effect on the fungal radial growth, dry weight (DW) and sporulation of F. solani. Antifungal activity of H2O2 appeared even at the lowest concentration (50 ppm), which inhibited radial growth to 49.33%, and decreased the dry weight to 498 mg, and the sporulation to 3.75×106 spores. Additionally, the results indicated significant inhibitory effects of hydrogen peroxide (H2O2) and the bioagent Trichoderma koningii on F. solani growth. It was noticed that H2O2 has compatible effects with T. koningii, where the antagonistic ability of T. koningii against F. solani increased when the concentration of H2O2 had increased. The results revealed that the treatment F. solani + H2O2 (200 ppm) + T. koningii significantly reduced the percentage of damping-off and plant survival to 9.40 and 5.39% respectively, in comparison with the control treatment and F. solani alone treatment, which reached 20.22, 14.48, 34.32 and 67.41% respectively.

First report of root rot of strawberry caused by Fusarium cugenangense, a member of the F. oxysporum species complex, in Tennessee, USA.

Strawberry (Fragaria × ananassa Duch) in Tennessee is cultivated on plastic mulched beds annually, and production is limited primarily by multiple oomycete and fungal root rot pathogens that result in reduced vigor and black root rot disease symptoms. In early June 2018, plants (cv. Chandler) with reduced shoot vigor and size, and black, necrotic stunted roots were collected from Rhea County, TN. Roots and crowns of 10 plants were cut into 1-3 cm pieces and surface sterilized with 0.6% NaOCl, followed by 70% ethanol for 1 min each, and plated on water agar. White mycelia produced after 3 days were transferred to potato dextrose agar amended with 10 mg/liter rifampicin. After 10 days, fungal colonies were light purple on the surface and dark purple on the colony underside, later developing blue-black pigmentation on the underside. Microconidia on carnation leaf agar were ovoid to ellipsoid, aseptate or septate and 8.0 to 24.2 (13.7) × 3.0 to 4.5 (3.8) μm in size, macroconidia were 3 to 5 septate and falcate to almost straight and 33.7 to 52.8 (44.4) × 4.0 to 5.5 (4.9) μm in size (n=80); both conidia were produced on monophialides. Chlamydospores were globose and subglobose, formed terminally and intercalary on aerial, submerged, and surface mycelium, singly or in pairs and were abundantly produced in sucrose broth and on synthetic nutrient-poor agar (SNA) (diam. 7.6 μm). Morphology was consistent with Fusarium oxysporum (Leslie and Summerell, 2006) and F. cugenangense, a member of the F. oxysporum species complex, as described by Maryani et al. (2019). Fungal mycelia were used for PCR (Phire Plant Direct PCR Master Mix, Thermo Scientific, CA) and the translational elongation factor 1-α (EF1α) region was amplified with primers EF-1/EF-2 (O'Donnell et al., 1998), internal transcribed spacer (ITS) regions amplified with primers ITS1/ITS2 (White et al. 1990), and the RNA polymerase second largest subunit region (RPB2) with primer pairs 5f2/7cr and 7cf/11ar (O'Donnell et al., 2022). PCR products of isolate SC5 were sequenced, and sequences compared to all sequences in the FUSARIOID-ID database using polyphasic identification (Crous et al., 2021) with EF1α (GenBank Accession No. ON703236) and RPB2 (OR472390) sequences. The highest similarity (100%) was with isolates of F. cugenangense, including ex-type isolate InaCC F984 (99.94% similarity) (Maryani et al., 2019). F. cugenangense is closely related to F. callistephi and F. elaeidis, but both species lack chlamydospores, and F. elaeidis has polyphialides (Lombard et al, 2019). To satisfy Koch's postulates, healthy rooted strawberry plants produced in soilless media were transplanted into 4 plastic pots (1.2-liter) containing 5% (w/v) fungal inoculum (grown on barley grain) and mixed into the top 5-cm of peat-based soilless medium. Pots were incubated at 25°C and 50% RH in a growth chamber. Four pots without inoculum served as controls. The trial was repeated. Within 8 weeks, all inoculated plants had low vigor, with necrotic and stunted roots. Root sections of control and inoculated plants were plated, and the pathogen was re-isolated from diseased roots of all inoculated plants only and confirmed as F. cugenangense based on morphology and sequence analysis. To our knowledge, this is the first report of F. cugenangense, or any member of the F. oxysporum species complex, causing root rot of strawberry in Tennessee and could be an important component of the production-limiting black root rot disease complex of strawberry.

Effects of Exogenous Application of Methyl Jasmonate and Salicylic Acid on the Physiological and Molecular Response of 'Dusa' Avocado to Rosellinia necatrix.

Methyl jasmonate (MeJA) and salicylic acid (SA) are important in mediating plant responses to abiotic and biotic stresses. MeJA and SA can act as elicitors by triggering plant defense responses similar to those induced by pathogens and may even provide long-term protection against them. Thus, exogenous application of MeJA and SA could protect susceptible avocado plants against white root rot (WRR) disease caused by the necrotrophic fungus Rosellinia necatrix, one of the main diseases affecting avocado orchards. This work evaluates the effects of MeJA or SA on the physiological and molecular response of susceptible 'Dusa' avocado rootstock and their ability to provide some protection against WRR. The application of MeJA and SA in avocado increased photoprotective mechanisms (nonphotochemical chlorophyll fluorescence quenching) and upregulated the glutathione S-transferase, suggesting the triggering of mechanisms closely related to oxidative stress relief and reactive oxygen species scavenging. In contrast to SA, MeJA's effects were more pronounced at the morphoanatomical level, including functional traits such as high leaf mass area, high stomatal density, and high root/shoot ratio, closely related to strategies to cope with water scarcity and WRR disease. Moreover, MeJA upregulated a greater number of defense-related genes than SA, including a glu protease inhibitor, a key gene in avocado defense against R. necatrix. The overall effects of MeJA increased 'Dusa' avocado tolerance to R. necatrix by inducing a primed state that delayed WRR disease symptoms. These findings point toward the use of MeJA application as an environmentally friendly strategy to mitigate the impact of this disease on susceptible avocado orchards.

Control of coptis root rot by combination of Bacillus cereus isolate Y9 and other antagonistic microorganisms

Root rot is a destructive soil-borne disease of Coptis chinensis, which depends on chemical control at present, and more attention should be paid to biocontrol of disease. In the present research, isolate Y9 isolated from healthy root samples of Coptis, was identified as Bacillus cereus. Further screening and pot experiments showed that B. cereus isolate Y9 inhibited the growth of the main causal agents of coptis root rot disease (Fusarium solani and F. avenaceum) and seven other phytopathogenic fungi. The application of B. cereus isolate Y9 and compatible Trichoderma harzianum, T. atroviride and B. amyloliquefaciens, singly and in combination were found to be effective against Fusarium root rot in vitro and in field experiments. In field experiments, combinations of T. harzianum + B. amyloliquefaciens + Y9 (HYJ, in ratio of 1:1:1) showed the highest control efficacy of 63.85%, which was higher than the expected value (53.18%), indicating synergistic effect on the control of coptis root rot. Therefore, B. cereus isolate Y9 may be a potential biological control agent, and combined use with T. harzianum and B. amyloquefaciens offered even greater potential. The long-term effects of isolate B. cereus Y9 and its combinations on C. chinensis should be assessed in different locations and seasons in the future.

Screening of the Biocontrol Efficacy of Potent Trichoderma Strains against Fusarium oxysporum f.sp. ciceri and Scelrotium rolfsii Causing Wilt and Collar Rot in Chickpea.

Chickpeas contribute to half of the pulses produced in India and are an excellent source of protein, fibers, carbohydrates, minerals, and vitamins. However, the combination of the wilt and root rot diseases drastically lowers its yield. The use of antagonist microbes that restrict the growth of other phytopathogens is an ecofriendly approach to combat the serious threats raised by the plant pathogens. Trichoderma spp. are well known as biocontrol agents, especially against soil- and seed-borne phytopathogens. In this study, 21 Trichoderma isolates that were collected from different rhizospheric soils were evaluated against two notorious soil-borne pathogens, such as Fusarium oxysproum f.sp. ciceri and Sclerotium rolfsii. The maximum percentage of inhibition against the tested pathogens was observed in Trichoderma isolate PBT13 (72.97%, 61.1%) followed by PBT3 (72.23%, 59.3%). The mycelial extension rate method, dual culture (antagonism), production of cell-wall degrading enzymes (CWDs), and antifungal metabolites (by GC-MS) were used as selection criteria for potent Trichoderma isolates. Among the 21 isolates, PBT3, PBT4, PBT9, and PBT13 exhibited high antagonistic activity, production of antifungal metabolites, and chitinase and β-1,3-glucanase activity. These four species were subjected to molecular characterization using an internal transcribed spacer (ITS 1 and ITS4). The results of molecular characterization identified the four species as T. virnes, T. asperellum, T. lixii, and T. harzianum. Moreover, significant chitinase and β-1,3-glucanase activities of all Trichoderma isolates were recorded in the growth medium. Trichoderma harzianum (isolate PBT13) was found to exhibit the highest chitinase activity in terms of zone formation (4.40 ± 0.17 cm), whereas Trichoderma virens (isolate PBT3) exhibited the highest β-1,3-glucanase activity1.511 μmole/min. A GC-MS analysis of ethyl extracts from two isolates of Trichoderma (PBT9, PBT13) revealed the presence of 28 VOCs. Overall, this study suggests that these four Trichoderma strains are promising biological control agents (BCAs) and could be developed as bio-pesticides after stringent field trials for the management of soil-borne diseases of chickpeas.

Biocontrol potential of an artificial synthetic bacterial consortium against peony root rot disease

Tree peony (Paeonia suffruticosa), a traditional Chinese cultivated flowering shrub and a prominent landscaping plant, is subject to root rot. The key symptoms of root rot include black roots and the yellowing of leaves. Biological control is an effective and eco-friendly strategy for managing this disease. This study focused on the isolation, identification, and biological control of the pathogens causing peony root rot. Utilizing tissue isolation, pathogenicity determination, and rDNA-ITS sequence analysis, Fusarium solani and Fusarium oxysporum were determined to be the primary causal agents of peony root rot. Illumina MiSeq high-throughput sequencing of 16 s-rDNA was used to investigate and characterize bacterial community structure and diversity in healthy and diseased peony roots, rhizosphere, and bulk soil. Results indicated that the presence of pathogenic fungi influences the structure of the rhizosphere bacterial community and that peony roots exhibit a strong selective effect on root bacterial colonization. Variations in the composition of the endophytic microbial community in healthy and diseased roots exceeded the variation in the rhizosphere. Proteobacteria and Actinobacteria are the dominant taxa in the rhizosphere and among root endophytes, comprising 90–96 % of the bacterial microbiota. The rhizosphere of healthy plants exhibits a significant enrichment in Proteobacteria (79.6 %) and Actinobacteria (14.9 %), while root endophytes in healthy plats exhibit enrichment in Proteobacteria (83.5 %). In contrast, the rhizosphere and root endophytes in diseased plants are abundant in Proteobacteria (69 % and 66.1 %, respectively). Notably, nine strains of biocontrol bacteria were isolated. Three synthetic bacterial consortia were then constructed based on inhibitory assays and the dissolving rates of phosphorus and potassium exhibited by the candidate bacteria. The synthetic bacterial consortia were evaluated for biocontrol and growth promotion properties. The constructed synthetic consortium with the best performance reduced the average morbidity and mortality of treated plants by 27.59 % and 55.56 %, respectively, compared to the untreated control. In summary, synthetic bacterial consortium I (SCI) exhibited the best disease control and growth-promoting effects on tree peony. Using a synthetic bacterial consortium represents a new and novel approach to the biological control of peony root rot.

Biocontrol potential and mechanism of action of Bacillus tequilensis JK-11 against wheat root rot disease

Biocontrol potential and mechanism of action of Bacillus tequilensis JK-11 against wheat root rot disease

Diversity and Pathogenicity of Fusarium Root Rot Fungi from Canola (Brassica napus) in Alberta, Canada.

Root rot disease poses a significant threat to canola (Brassica napus), underscoring the need for a comprehensive understanding of its causal agents for more effective disease mitigation. The composition and diversity of fungal pathogens associated with root rot of canola in Alberta, Canada, were evaluated from plant tissue samples collected in 2021 and 2022. The study revealed Fusarium spp. as the predominant pathogens found in almost all surveyed fields. Fusarium avenaceum, F. redolens, and F. solani were among the most frequently recovered species. Greenhouse trials confirmed their pathogenicity, with F. avenaceum and F. sporotrichioides found to be particularly aggressive. Additionally, F. sporotrichioides and F. commune were identified for the first time as canola root rot pathogens. Inoculation with isolates of most species resulted in significant reductions in seedling emergence, plant height, and shoot and root dry weights. Analysis of translation elongation factor 1-α (TEF-1α) and internal transcribed spacer (ITS) sequences confirmed the identity of the Fusarium spp., while concatenating the ITS and TEF-1α sequences enabled improved species differentiation. Geographic and year effects did not influence fungal diversity or aggressiveness, as determined by principal component analysis. This study emphasized the high diversity and impact of Fusarium spp. in causing canola root rot.