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Peanuts (Arachis hypogaea) are of significant agricultural importance due to their versatile uses, providing a valuable source of edible oil and protein-rich food products and serving in industrial applications. Peanuts are susceptible to various diseases, one of them being net syndrome, a poorly understood threat triggered by an undefined causal agent, with symptoms including black coloring and lesions of the peanut pod that affect product quality. In this study, amplicon sequencing was harnessed to explore the fungal and bacterial populations associated with the syndrome. Using this approach, we identified a specific Fusarium sp. amplicon sequence variant that demonstrated a significant correlation with the presence of net syndrome symptoms in both young and mature peanuts. This finding was further validated by Koch's postulates testing, including isolation, cultivation, and application of this strain to corroborate its involvement in net syndrome in peanuts. Our findings contribute to a better understanding of the interactions between peanuts and their microbial communities and to identification of the previously undetermined agent involved in net syndrome and the etiology of the disease.

Trichoderma spp. are widely used to enhance crop growth and suppress diverse diseases. However, inconsistent field efficacy remains a major barrier to their use as a reliable alternative to synthetic pesticides. Various strategies have been investigated to enhance the robustness of their application. Here, we evaluated how T. virens application methods (pre-, at-, and post-transplant) affect the growth of two tomato varieties and their rhizosphere fungal and bacterial communities. Although the greatest rhizosphere abundance of T. virens was observed in the post-transplant application, the at-transplant application promoted tomato growth the most, indicating that greater rhizosphere abundance does not necessarily result in better tomato growth. None of the application methods significantly altered the global rhizosphere fungal and bacterial communities of the tested varieties. Changes in specific microbial genera and guilds may underpin the enhanced tomato growth. We also investigated whether the resulting microbiome changes affect the mycelial growth and conidial germination of Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici, soilborne fungal pathogens of tomato, upon exposure to volatile compounds emitted by culturable rhizosphere microbes and metabolites extracted from the rhizosphere soils after Trichoderma treatments. Volatile compounds produced by cultured rhizosphere microbes after the at-transplant application suppressed the mycelial growth of both pathogens better than those after the other treatments. Similarly, water-soluble metabolites extracted from the rhizosphere soil samples after the at-transplant application most effectively suppressed the germination rate of F. oxysporum spores. Overall, our results suggest that the at-transplant application is most advantageous for promoting the growth of the tested tomato varieties and building soil suppressiveness against the tested fusaria. However, further studies are needed before applying this method to support tomato production. We discuss critical future questions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Trichoderma spp. are widely used to enhance crop growth and suppress diverse diseases. However, inconsistent field efficacy remains a major barrier to their use as a reliable alternative to synthetic pesticides. Various strategies have been investigated to enhance the robustness of their application. Here, we evaluated how T. virens application methods (pre-, at-, and post-transplant) affect the growth of two tomato varieties and their rhizosphere fungal and bacterial communities. Although the greatest rhizosphere abundance of T. virens was observed in the post-transplant application, the at-transplant application promoted tomato growth the most, indicating that greater rhizosphere abundance does not necessarily result in better tomato growth. None of the application methods significantly altered the global rhizosphere fungal and bacterial communities of the tested varieties. Changes in specific microbial genera and guilds may underpin the enhanced tomato growth. We also investigated whether the resulting microbiome changes affect the mycelial growth and conidial germination of Fusarium oxysporum f. sp. lycopersici and F. oxysporum f. sp. radicis-lycopersici, soilborne fungal pathogens of tomato, upon exposure to volatile compounds emitted by culturable rhizosphere microbes and metabolites extracted from the rhizosphere soils after Trichoderma treatments. Volatile compounds produced by cultured rhizosphere microbes after the at-transplant application suppressed the mycelial growth of both pathogens better than those after the other treatments. Similarly, water-soluble metabolites extracted from the rhizosphere soil samples after the at-transplant application most effectively suppressed the germination rate of F. oxysporum spores. Overall, our results suggest that the at-transplant application is most advantageous for promoting the growth of the tested tomato varieties and building soil suppressiveness against the tested fusaria. However, further studies are needed before applying this method to support tomato production. We discuss critical future questions.

A 2-year research was conducted to evaluate the effects of bean cultivar, herbicide and planting date on a plot scale in Zanjan Province, Iran. Weeds across plots were identified as 26 species. Weed density was often lower for the fourth planting date (25–30 June) than the first date (10–15 May) of Imazethapyr, Trifluralin, hand-weeding and control at seedling, flowering and maturity stages of bean growth. At seedling and flowering, there was a greater Rhizoctonia root rot incidence on the first planting date than the fourth date. Postponing cultivation to the fourth planting date decreased mean disease incidence up to 93% at flowering in 2014 and 75% at maturity in 2015. There were greater mean fly infestation ratings at the third (2014) and fourth (2015) planting dates of treatments. Fly infestation was lacking in beans planted at the second date of cultivar and herbicide treatments examined in 2015. Postponing planting from the first date to the fourth one increased mean plant dry matter up to 162% at flowering in 2015. The highest number of pods per plant and seeds per pod were recorded for the third (2014) and first-second (2015) planting dates. This study recommends a postponed planting to minimize disease, herbicide use and weed threats, and thus produce beans in sustainable agriculture.

Continuous cropping and soilborne diseases affect soil properties and soil microbial diversity and structure, which are the main factors posing obstacles to the continuous cropping of ginseng. This study explored the response of the physicochemical properties, enzyme activity, and microbial community of ginseng rhizosphere soil to continuous cropping and soilborne disease (root rot of ginseng). We used woodland soil without ginseng planting as a control to study these changes. The results showed that continuous cropping and soilborne disease significantly affected soil physicochemical properties, enzyme activities, and microbial communities. The levels of total nitrogen, hydrolyzable nitrogen, organic matter, and soil pH decreased significantly, while available phosphorus, available potassium, total phosphorus, and total potassium showed significant accumulation after continuous cropping. The activities of urease, catalase, sucrase, acid phosphatase, alkaline phosphatase, and polyphenol oxidase decreased significantly after continuous cropping. Using MiSeq high-throughput sequencing, we found that the alpha diversity and the number of bacterial and fungal communities significantly changed after continuous cropping and soilborne disease. A redundancy analysis suggests that soil physicochemical properties and enzyme activities also affect soil microbial communities. In summary, this study revealed the effects of continuous cropping and soilborne disease on soil and provides a theoretical basis for alleviating soilborne disease in ginseng. [ABSTRACT FROM AUTHOR]

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Cover crops represent a potential tool for suppression of soil borne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum 'October Glory') plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals. [ABSTRACT FROM AUTHOR]

• The effects of grafting on acid accumulation are negligible. • Sugar accumulation and profile are affected by grafting. • Grafing effects on sugars depend on specific scion-rootstock combinations. • Effects on volatile profile are limited and depend on scion-rootstock combinations. Melon landraces are highly appreciated by consumers who pay price premiums to compensate for lower yields, enabling on-farm conservation. However, they are highly susceptible to soilborne diseases. This study analyses the impact of Cucurbita and Cucumis rootstocks on the accumulation of flavor-related metabolites in Spanish landraces of the Ibericus melon group, as a strategy to promote their sustainable cultivation. Scion genotype was the main factor conditioning the accumulation of sugars and acids both under standard and saline organic farming conditions. The effects of grafting on organic acid accumulation were negligible, while the effects on sugar content were significant. The latter effects were dependent on specific scion-rootstock combinations, though wild Cucumis (e.g. Fian) rootstocks represent an alternative that should be further studied. The effect on the accumulation of volatiles was limited, and again depended on specific scion-rootstock combinations. The rootstock effect even differed between populations of the same landrace. [ABSTRACT FROM AUTHOR]

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

A 2-year research was conducted to evaluate the effects of bean cultivar, herbicide and planting date on a plot scale in Zanjan Province, Iran. Weeds across plots were identified as 26 species. Weed density was often lower for the fourth planting date (25-30 June) than the first date (10-15 May) of Imazethapyr, Trifluralin, hand-weeding and control at seedling, flowering and maturity stages of bean growth. At seedling and flowering, there was a greater Rhizoctonia root rot incidence on the first planting date than the fourth date. Postponing cultivation to the fourth planting date decreased mean disease incidence up to 93% at flowering in 2014 and 75% at maturity in 2015. There were greater mean fly infestation ratings at the third (2014) and fourth (2015) planting dates of treatments. Fly infestation was lacking in beans planted at the second date of cultivar and herbicide treatments examined in 2015. Postponing planting from the first date to the fourth one increased mean plant dry matter up to 162% at flowering in 2015. The highest number of pods per plant and seeds per pod were recorded for the third (2014) and first-second (2015) planting dates. This study recommends a postponed planting to minimize disease, herbicide use and weed threats, and thus produce beans in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Continuous cropping and soilborne diseases affect soil properties and soil microbial diversity and structure, which are the main factors posing obstacles to the continuous cropping of ginseng. This study explored the response of the physicochemical properties, enzyme activity, and microbial community of ginseng rhizosphere soil to continuous cropping and soilborne disease (root rot of ginseng). We used woodland soil without ginseng planting as a control to study these changes. The results showed that continuous cropping and soilborne disease significantly affected soil physicochemical properties, enzyme activities, and microbial communities. The levels of total nitrogen, hydrolyzable nitrogen, organic matter, and soil pH decreased significantly, while available phosphorus, available potassium, total phosphorus, and total potassium showed significant accumulation after continuous cropping. The activities of urease, catalase, sucrase, acid phosphatase, alkaline phosphatase, and polyphenol oxidase decreased significantly after continuous cropping. Using MiSeq high-throughput sequencing, we found that the alpha diversity and the number of bacterial and fungal communities significantly changed after continuous cropping and soilborne disease. A redundancy analysis suggests that soil physicochemical properties and enzyme activities also affect soil microbial communities. In summary, this study revealed the effects of continuous cropping and soilborne disease on soil and provides a theoretical basis for alleviating soilborne disease in ginseng.

Sudden death syndrome (SDS), caused by Fusarium virguliforme , is an important yield-limiting disease of soybean ( Glycine max ). From 1996 to 2022, cumulative yield losses attributed to SDS in North America totaled over 25 million metric tons, which was valued at over US $7.8 billion. Seed treatments are widely used to manage SDS by reducing early season soybean root infection by F. virguliforme . Fluopyram (succinate dehydrogenase inhibitor [SDHI] - FRAC 7), a fungicide seed treatment for SDS management, has been registered for use on soybean in the United States since 2014. A baseline sensitivity study conducted in 2014 evaluated 130 F. virguliforme isolates collected from five states to fluopyram in a mycelial growth inhibition assay and reported a mean EC 50 of 3.35 mg/liter. This baseline study provided the foundation for the objectives of this research: to detect any statistically significant change in fluopyram sensitivity over time and geographical regions within the United States and to investigate sensitivity to the fungicide pydiflumetofen. We repeated fluopyram sensitivity testing on a panel of 80 historical F. virguliforme isolates collected from 2006 to 2013 (76 of which were used in the baseline study) and conducted testing on 123 contemporary isolates collected from 2016 to 2022 from 11 states. This study estimated a mean absolute EC 50 of 3.95 mg/liter in isolates collected from 2006 to 2013 and a mean absolute EC 50 of 4.19 mg/liter in those collected in 2016 to 2022. There was no significant change in fluopyram sensitivity ( P = 0.1) identified between the historical and contemporary isolates. A subset of 23 isolates, tested against pydiflumetofen under the same conditions, estimated an absolute mean EC 50 of 0.11 mg/liter. Moderate correlation was detected between fluopyram and pydiflumetofen sensitivity estimates ( R = 0.53; P < 0.001). These findings enable future fluopyram and pydiflumetofen resistance monitoring and inform current soybean SDS management strategies in a regional and national context., Competing Interests: The author(s) declare no conflict of interest.

With the phase-out of methyl bromide due to its impact on ozone depletion, research has focused on developing alternative chemical and biologically based soil disinfestation methods. Anaerobic soil disinfestation (ASD) was developed to control plant-parasitic nematodes, weeds, and soilborne pathogens. However, whether farmers will adopt ASD methods on a large scale is unknown. This study evaluates the economic viability of using ASD in open-field, fresh-market tomato (Solanum lycopersicum) production, drawing on data from field experiments conducted in 2015 in Immokalee, FL, and Citra, FL. The experiment included three treatments: chemical soil fumigation (CSF), ASD1 [the standard ASD treatment with 1482 gal/acre molasses and 9 tons/acre composted poultry litter (CPL)], and ASD0.5 (the reduced rate ASD treatment with 741 gal/acre molasses and 4.5 tons/acre CPL). Results from the economic analysis show that ASD treatments require higher labor costs than CSF regarding land preparation and treatment application. However, yields from ASD treatments are higher than those resulting from CSF, and the improvement in yield was enough to offset the increased labor costs. Relative to CSF, ASD0.5, and ASD1 achieved additional net returns of $630.38/acre and $2770.13/acre, respectively, in Immokalee, FL. However, due to unexpected conditions unrelated to soil treatments, the net return of ASD1 was lower than that of CSF in Citra, FL. Breakeven analysis indicates that ASD treatments would remain favorable even with an increase in the molasses price. However, when the tomato price is low, ASD could potentially lose its advantage over CSF.

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

BACKGROUND: Dimethyl disulfide (DMDS) is used as a preplant soil fumigant for weed and soilborne pathogen control in plasticulture vegetable crops. The objective of this research was to determine the control efficacy of emulsifiable concentrate (EC) formulation of DMDS or DMDS + chloropicrin (Pic) on weed and Fusarium wilt in tomato (Solanum lycopersicum L.) plasticulture. RESULTS: The effective DMDS rates required to provide 50% (ER50) control of purple nutsedge (Cyperus rotundus L.) were 210 and 340 kg ha−1 at 4 weeks after fumigation (WAF) in fall 2017 and fall 2018, respectively, while these values increased to 348 and >467 kg ha−1, respectively, at 12 WAF. The ER50 values of DMDS + Pic were 150 and 240 kg ha−1 at 4 WAF in fall 2017 and fall 2018, respectively, while these values increased to 255 and 450 kg ha−1, respectively, at 12 WAF. DMDS + Pic was generally more effective than DMDS for C. rotundus control. The high rates of DMDS or DMDS + Pic provided adequate C. rotundus control in early season but failed to provide effective control by season end. In addition, DMDS + Pic injections through drip tape effectively reduced Fusarium oxysporum f. sp. lycopersici (FOL) inoculum while DMDS alone was generally ineffective. CONCLUSION: Injection of the EC formulation of DMDS or DMDS + Pic through drip tape should have been provided a viable option for C. rotundus and Fusarium wilt control in plastic‐mulched tomato. However, supplemental weed management actions, such as herbicide applications, may be required to achieve season‐long control. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Biochar and activated carbon adsorb and deactivate pathogen-produced cell wall degrading enzymes (CWDEs). • The deactivation rates of biochar-immobilized pectinase and cellulases were higher than that of activated carbon. • Immobilization and deactivation of CWDEs and toxic metabolites (TMs) decrease symptom severity in tomato seedlings. Greenhouse vegetable production aggravates soilborne diseases. Biochar has been recently considered as soil amendment to effectively prevent soilborne diseases. This study evaluates the immobilization and deactivation of pathogen-produced cell wall degrading enzymes (CWDEs) and toxic metabolites (TMs) by biochar to understand the mechanism involved in tomato Fusarium wilt , with activated carbon as the control. The results reveal that cellulase takes shorter time to reach the adsorption equilibrium than pectinase does. The adsorption isotherm of pectinase follows the Langmuir model, and the adsorption isotherm of cellulase follows the Freundlich model. The adsorption capacity of pectinase is greater than that of cellulase on biochar (on activated carbon). The adsorbed enzymes are completely immobilized and observably deactivated. The activity of immobilized pectinase decreases as 43.01 % of the original activity on biochar and 44.91 % on activated carbon. But the activity of immobilized cellulase decreases only as 1.88 % on biochar and 3.89 % on activated carbon. The tomato seedling bioassay analysis demonstrates that the adsorption of CWDEs and TMs is conducive to the reduction of disease severity. However, these established models (or laboratory simulation) cannot explain the enzyme adsorption process of biochar in the real soil, which requires the further exploration in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

Verticillium dahliae is one of the most devastating soilborne pathogens for horticulture production. The pathogen has a broad host range and currently there is no effective chemical disease management, therefore, novel sustainable integrated disease management strategies should be considered. In this respect, we questioned whether the soil application of common microbiological growth media can influence the plant—microbe interactions and, subsequently, offer protection against V. dahliae. Indeed, the addition of Nutrient Broth (NB) and Potato Dextrose (PD) in non-sterilized soil reduced Verticillium wilt symptoms in eggplants. The addition of NB in sterilized soil did not reduce the disease symptoms compared to controls, however the addition of PD enhanced plant protection against V. dahliae. Following the results of a split root bioassay in eggplants, the possibility that NB and PD triggered the plant defense mechanisms against V. dahliae was excluded, since NB and PD did not reduce wilt symptom. Therefore, PD may be used as an easy food source for V. dahliae, detouring the pathogen from the root system of plants, while NB may affect the soil microbiome by enhancing antagonism in rhizosphere, or antagonistic interaction between V. dahliae and rhizospheric microbiome. Subsequently, several bacterial strains were isolated from the NB-treated rhizosphere and examined for their biocontrol activity against V. dahliae. Among the examined strains, a Pseudomonas putida strain, Z13, significantly reduced Veticillium severity and incidence under greenhouse conditions.

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for root rot disease severity using a scale of 0–100% roots affected. Among the tested cover crops, the grass cover crops triticale (×Triticosecale Wittm. ex A. Camus.), annual ryegrass (Lolium multiflorum L.), Japanese millet (Echinochloa esculenta (A. Braun) H. Scholz), and the legumes Austrian winter pea (Pisum sativum var. arvense (L.) Poir) and cowpea ‘Iron and Clay’ (Vigna unguiculata (L.) Walp.), showed lower root rot disease severity and post-emergence damping-off in the soil inoculated with P. nicotianae, R. solani, or P. vexans compared to the other crops. Since these cover crops can act as non-host crops and benefit the main crop in one way or another, they can be used in the production system. Further research is recommended to evaluate their performance in a natural field setting.

Hyperspectral sensors combined with machine learning are increasingly utilized in agricultural crop systems for diverse applications, including plant disease detection. This study was designed to identify the most important wavelengths to discriminate between healthy and diseased peanut (Arachis hypogaea L.) plants infected with Athelia rolfsii, the causal agent of peanut stem rot, using in-situ spectroscopy and machine learning. In greenhouse experiments, daily measurements were conducted to inspect disease symptoms visually and to collect spectral reflectance of peanut leaves on lateral stems of plants mock-inoculated and inoculated with A. rolfsii. Spectrum files were categorized into five classes based on foliar wilting symptoms. Five feature selection methods were compared to select the top 10 ranked wavelengths with and without a custom minimum distance of 20 nm. Recursive feature elimination methods outperformed the chi-square and SelectFromModel methods. Adding the minimum distance of 20 nm into the top selected wavelengths improved classification performance. Wavelengths of 501–505, 690–694, 763 and 884 nm were repeatedly selected by two or more feature selection methods. These selected wavelengths can be applied in designing optical sensors for automated stem rot detection in peanut fields. The machine-learning-based methodology can be adapted to identify spectral signatures of disease in other plant-pathogen systems.

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 10 8 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 (EC 50 of 2.46 and 2.58 µg ml -1 ) and B. sorokiniana (EC 50 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., Competing Interests: The author(s) declare no conflict of interest.

Fusarium culmorum (Fc) and F. graminearum (Fg) belong to the predominant causal agents of fusarium crown and root rot (FCR) in wheat. While many studies have been done to investigate crown rot, including stem base infection, root colonization and mycotoxin production associated with root rot is not well understood. In this study the impact of mycotoxins on the colonization of wheat roots and stem bases was analysed by using Fc and Fg isolates that varied in both quantity and types of trichothecenes they produce. Seedling inoculations in growth chambers with a high deoxynivalenol (DON)‐ and 3‐acetyldeoxynivalenol (3ADON)‐producing isolate led to more severe symptoms and 20‐times greater colonization of the stem base, as measured by Fc DNA accumulation, than isolates that produced less DON/3ADON. In contrast to stem base colonization, in vitro inoculations of roots with a Tri5 deletion mutant deficient in Fg trichothecene production led to three‐times higher colonization than the wildtype. Furthermore, an Fc isolate that produced low levels of zearalenone resulted in twice the level of colonization of a high DON/3ADON‐producing isolate included in the study. When root inoculation with a low DON/3ADON‐producing Fc isolate was supplemented with exogenous DON, DON production decreased by more than half per unit weight of Fc DNA, and root colonization doubled compared to the untreated control. Therefore, in contrast to its potential role as an aggressiveness factor in stem base infection, trichothecene production by Fc and Fg is detrimental to the early stages of wheat root colonization in FCR. [ABSTRACT FROM AUTHOR]

We report the results of a 3-year study in which we collected and analyzed soil and yield data from experimental plots in six commercial processing tomato fields in Yolo and Solano counties in California. Our objective was to assess the effect of soil chemistry and soil-delivered nutrients and fungicides on tomato plant health and fruit yield at harvest. Marketable yield, leaf necrosis, and fruit loss due to sunburn differed significantly between individual fields, with averages ranging from 81.2-138.5 Mg ha−1, 32-72% leaf necrosis and 1.9 to 8.8% sunburnt fruit, respectively. Higher-yielding fields showed significantly lower levels of leaf necrosis and sunburn damage and a positive correlation with pre-plant soil parameters such as potassium concentration and cation exchange capacity (CEC). Interestingly, soil amendments of composted poultry manure or other nutrient supplements in low-CEC fields, but not high-CEC fields, resulted in higher fruit yield and less leaf necrosis. While all fields showed symptoms typical of Verticillium wilt and some fields showed symptoms of Fusarium wilt, Fusarium crown and root rot, corky root, and root knot nematode, none of our soil amendments, including chemical and biological fungicides, significantly or consistently reduced incidence or severity of these diseases. We discuss our findings in the context of premature vine decline of tomato, an emerging phenomenon in production fields in the Sacramento Valley, which is characterized by the loss of plant vigor and canopy cover at the onset of fruit ripening and for which causative agent(s) and management options in California remain elusive. (247 words). [ABSTRACT FROM AUTHOR]

Adding biochar to soil and soilless media can help protect plants against diseases caused by soilborne pathogens. There are a number of direct and indirect mechanisms that are potentially responsible for this effect. This study tested the hypothesis that biochar adsorption and consequent deactivation of cell wall degrading enzymes (CWDEs) and toxic metabolites produced by soilborne pathogens can help defend plant roots against pathogen attack. The specific objectives were to: (i) quantify adsorption and inactivation of model extracellular pathogenic enzymes (polygalacturonase and cellulase) by 4 model biochars; and (ii) determine the effect of biochar adsorption of CWDEs and toxic metabolites produced by Fusarium oxysporum f. sp. radicis lycopersici (FORL) on the severity of disease symptoms in tomato seedlings. All the enzyme adsorption isotherms were strongly non-linear and well-described by the Langmuir model. Maximum adsorption capacity ( Q m ) was generally greater for polygalacturonase than cellulase on a given biochar, and reached as high as 448 g polygalacturonase per kg biochar. There was no straightforward relationship between biochar adsorption capacity and its surface area or any other biochar characteristics. The adsorbed enzymes were 100% immobilized by the biochars, and the immobilized enzymes were revealed to be substantially deactivated. Activity of immobilized polygalacturonase ranged from 16 to 30% on the four biochars, and activity of immobilized cellulase ranged from 5 to 9%. There were no significant relationships between deactivation extent and any determined biochar physical and chemical characteristic or substrate/product adsorption characteristics. In the tomato seedling bioassay, the adsorption of FORL-produced enzymes and toxic metabolites led to substantially lessened disease-like symptom severity. Thus, the hypothesis was successfully confirmed. We anticipate that adsorption/deactivation of virulence factors by biochar is part of the puzzle responsible for biochar's varied impacts on severity of soilborne disease, but not the only part. This is because most biochar dose-disease resistance curves are non-monotonic, and reveal best results at some interim biochar dose. This would not be the case if only adsorption/deactivation was important, since in that event, increasing biochar dose would increasingly remove virulence factors from near the plant roots. [ABSTRACT FROM AUTHOR]

The soilborne fungi Sclerotinia sclerotiorum, Rhizoctonia solani and the oomycete Pythium ultimum are among the most destructive pathogens for lettuce production. The application of the biocontrol agent Paenibacillus alvei K165 to the transplant soil plug of lettuce resulted in reduced S. sclerotiorum, R. solani and P. ultimum foliar symptoms and incidence compared to untreated controls, despite the suppressive effect of the pathogens on the rhizosphere population of K165. In vitro, K165 inhibited the growth of S. sclerotiorum and R. solani but not P. ultimum. Furthermore, the expression of the pathogenesis‐related (PR) gene PR1, a marker gene of salicylic acid (SA)‐dependent plant defence, and of the Lipoxygenase (LOX) and Ethylene response factor 1 (ERF1) genes, markers of ethylene/jasmonate (ET/JA)‐dependent plant defence was recorded. K165‐treated plants challenged with P. ultimum showed up‐regulation of PR1, whereas challenge with R. solani resulted in up‐regulation of LOX and ERF1, and challenge with S. sclerotiorum resulted in up‐regulation of PR1, LOX and ERF1. This suggests that K165 triggers the SA‐ and the ET/JA‐mediated induced systemic resistance against P. ultimum and R. solani, respectively, while the simultaneous activation of the SA and ET/JA signalling pathways is proposed for S. sclerotiorum. [ABSTRACT FROM AUTHOR]

Straw returning is a sustainable way that does not destroy soil ecology in agronomic management. Some studies have found that straw returning may aggravate or reduce soilborne diseases in the past few decades. Despite the increasing number of independent studies investigated the effect of straw returning on root rot of crops, the quantitative analysis regarding the relationship between straw returning and crop root rot is still undefined. In this study, keywords co-occurrence matrix was extracted from 2489 published studies (published from 2000 to 2022, the same below) on controlling soilborne diseases of crops. The methods used for soilborne diseases prevention have shifted from chemical to biological and agricultural control since 2010. As root rot is the soilborne disease with the largest weight in keyword co-occurrence according to statistics, we further collected 531 articles focusing on crop root rot. Notably, the 531 studies are mainly distributed in the United States, Canada, China and other countries in Europe and the south and southeast of Asia, and focus on the root rot of soybean, tomato, wheat and other important grain crops or economic crops. Based on the meta-analysis of 534 measurements in 47 previous studies, we explored how 10 management factors (soil pH/texture, type/size of straw, depth/rate/cumulative amount of application, days after application, beneficial/pathogenic microorganism inoculated before application and annual N-fertilizer input) during straw returning affect root rot onset worldwide. The results showed that straw size and microorganisms inoculated before straw returning are the key factors affecting the incidence of root rot. In combination with actual agricultural production, detailed advice applicable to traditional farming system on the optimization management of straw returning was given. This study emphasized the significance of straw pretreatment and farmland management to reduce soilborne diseases during straw returning. • Research overview of soilborne disease is shown in keywords co-occurrence matrix. • Root rot is the most studied soilborne disease in recent 20 years. • Root-rot onset is predicated using 9 factors during straw incorporation. • Straw size and microbes inoculated in soil are the key factors of root-rot onset. • Straw pretreatment is essential to control soilborne diseases. [ABSTRACT FROM AUTHOR]

Silicon (Si) plays a pivotal role in the nutritional status of a wide variety of monocot and dicot plant species and helps them, whether directly or indirectly, counteract abiotic and/or biotic stresses. In general, plants with a high root or shoot Si concentration are less prone to pest attack and exhibit enhanced tolerance to abiotic stresses such as drought, low temperature, or metal toxicity. However, the most remarkable effect of Si is the reduction in the intensities of a number of seedborne, soilborne, and foliar diseases in many economically important crops that are caused by biotrophic, hemibiotrophic, and necrotrophic plant pathogens. The reduction in disease symptom expression is due to the effect of Si on some components of host resistance, including incubation period, lesion size, and lesion number. The mechanical barrier formed by the polymerization of Si beneath the cuticle and in the cell walls was the first proposed hypothesis to explain how this element reduced the severity of plant diseases. However, new insights have revealed that many plant species supplied with Si have the phenylpropanoid and terpenoid pathways potentiated and have a faster and stronger transcription of defense genes and higher activities of defense enzymes. Photosynthesis and the antioxidant system are also improved for Si-supplied plants. Although the current understanding of how this overlooked element improves plant reaction against pathogen infections, pest attacks, and abiotic stresses has advanced, the exact mechanism(s) by which it modulates plant physiology through the potentiation of host defense mechanisms still needs further investigation at the genomic, metabolomic, and proteomic levels. [ABSTRACT FROM AUTHOR]

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Fusarium wilt of Luffa , caused by Fusarium oxysporum f. sp. luffae , causes great losses in Luffa plants worldwide. In this study, 45 accessions of Luffa germplasm were used to determine their resistance to F. oxysporum f. sp. luffae isolates (FOLUST, FOLUSC, Fomh16, and Fol114) in two independent trials. In the first trial, only FOLUST was used to preliminarily identify resistant accessions. Nine accessions of Luffa acutangula and five of L. aegyptiaca were resistant to the FOLUST isolate. In the second trial, the other three isolates were then used to reevaluate the 14 resistant accessions. The results indicated that the 14 accessions were resistant to FOLUSC but exhibited variable resistance to the Fomh16 and Fol114 isolates. Eight accessions of L. acutangula and one accession of L. aegyptiaca were resistant to Fol114. Seven accessions of L. acutangula and one accession of L. aegyptiaca were resistant to Fomh16. Despite the lack of any symptoms, the F. oxysporum f. sp. luffae isolates were recovered from the hypocotyls of all resistant accessions at 28 days postinoculation, except for isolates FOLUSC and FOLUST on one accession (LA140). A high percentage (87.5%) of accessions collected from Bangladesh were identified as resistant, highlighting the effect of local adaptation on resistance. These results provide potentially valuable genetic resources for breeding programs to develop new varieties or rootstocks that could be beneficial for controlling soilborne diseases in different cucurbit crops and further investigating the mechanisms of resistance to F. oxysporum f. sp. luffae in Luffa plants., Competing Interests: The author(s) declare no conflict of interest.

Fusarium oxysporum f. sp. fragariae and Macrophomina phaseolina are soilborne fungi leading impactful economical losses to strawberry growers worldwide. Symptoms caused by both pathogens are very similar and include vascular discoloration, wilting, stunting, and dieback of plants, but no fruit damage. An extraction of phenolic and volatile compounds was performed on strawberry fruits from three different cultivars while being grown in a plant growth medium infested by each pathogen. Inoculated plants showed higher content of certain phenolic compounds which have antifungal and antioxidant activity and may have a positive impact on strawberry shelf life. On the other hand, root and vascular infections caused by F. oxysporum and M. phaseolina were able to significantly alter strawberry aroma by reducing or increasing the content of specific volatile compounds which also have an important impact on fruit quality. The changes induced in the aroma profiles of the three strawberry cultivars do not only have organoleptic and economic implications for strawberry growers but play an important role in the plant defense system against pathogens. The results indicate a potential of this line of research to develop new tools for the detection and control of soil pathogens. • Cultivar 'Rociera' showed a low susceptibility to Fusarium oxysporum f. sp. fragariae. • Infection by a soilborne pathogen fosters the accumulation of phenolic compounds. • Strawberry fruit aroma is altered due to plant infection by soilborne fungi. [ABSTRACT FROM AUTHOR]

Rice cultivation in South America is undergoing several intensification processes for economic reasons that cause more rice to be planted continuously on the same soils. This intensification makes the long-term biological and economic sustainability of systems questionable. Among the most common problems that threaten sustainability in intensified systems is pest and disease pressure. In this context, the primary rice diseases were studied during a 6-year period in a long-term experiment of rice rotations established in 2012 in Uruguay. The experiment consisted of six rice rotations with other crops with different duration and intensification levels. The main disease found was stem rot and, to a lesser extent, aggregate sheath spot and sheath spot of rice. These diseases are of importance in intensified rice systems because they produce sclerotia that accumulate in soils. Disease occurrence was variable among years and rotations. Stem rot incidence increased rapidly in the experiment, reaching values close to 85% in the third year, while the severity varied each year. Sheath spot incidence and severity were low and varied with the year. Continuous rice (CR) reached the highest occurrence values for stem rot, but other systems with short pastures in rotation did not differ. Aggregate sheath spot and sheath spot were of importance only in CR and in some years. When levels of intensification were compared, systems with less time (25 to 60%) occupied with rice showed lower disease severity and higher yields. Comparing CR with rice rotation with pastures of different lengths (1 to 3 years), disease occurrence was higher in 2 of the 4 years analyzed. However, yields were consistently lower, denoting that other factors are influencing productivity. Stem and sheath diseases appear not to be a limiting factor in the medium term in intensified rice systems. Also, there are several alternatives of rice intensification incorporating crops and pastures in the rotation., Competing Interests: The author(s) declare no conflict of interest.