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Plants shape their surrounding soil, influencing subsequent plant growth in a phenomenon known as plant–soil feedback (PSF). This feedback is driven by chemical and microbial legacies. Here, we cultivated six crops from two functional groups, i.e., three grasses (Lolium , Triticum , and Zea) and three legumes (Glycine , Lens , and Medicago), to condition a living soil. Subsequently, the same species were sown as response plants on conspecific and heterospecific soils. We employed high-throughput sequencing in tandem with soil chemistry, including total organic matter, pH, total nitrogen, electrical conductivity, phosphorus, and macro and micro-nutrients. Our results showed that Glycine exhibited the strongest negative PSF, followed by Triticum and Zea , while Lolium displayed low feedback. Conversely, Lens demonstrated robust positive PSF, with Medicago exhibiting slight positive feedback. Soil chemistry significance indicated only higher Cl content in Triticum soil, while Lens displayed higher Zn and Mn contents. Microbial diversity exhibited no significant variations among the six soils. Although conditioning influenced the abundance of functionally important microbial phyla associated with each plant, no specificity was observed between the two functional groups. Moreover, each crop conditioned its soil with a substantial proportion of fungal pathogens. However, co-occurrence analysis revealed a strong negative correlation between all crop's biomass and fungal pathogens, except Glycine , which exhibited a strong negative correlation with mutualists such as Arthrobacter and Bacillus. This underscores the complexity of predicting PSFs, emphasizing the need for a comprehensive understanding of plant interactions with both pathogens and mutualists, rather than focusing solely on host-specific pathogens. [ABSTRACT FROM AUTHOR]

Forecasting the effects of global change drivers on ecosystems is one of the most pressing challenges for scientists worldwide. Particularly, climate change and exotic pathogens might have a large impact on plant community dynamics and ecosystem functioning through changes in carbon uptake and sinks. Nevertheless, we still have a poor understanding of the combined effects of these two drivers on plant communities. Here, we explored the impact of rainfall reduction and exotic pathogens on the carbon balance of Mediterranean tree species. For this, we performed a 3‐year field experiment taking advantage of rainfall exclusion infrastructures (30% exclusion) installed in the southernmost European oak forests invaded by the aggressive exotic pathogen Phytophthora cinnamomi. We measured a set of 10 variables representative of tree carbon sources (photosynthetic rates) and sinks (primary production, reproduction, defence, and reserves) in adult trees of three species in two forest types: closed forests of Quercus suber and Q. canariensis, and open woodlands of Q. suber and Olea europaea. We found a large variability in the sensitivity of the different carbon sources and sinks to the effects of drought and pathogens, from variables highly sensitive to both factors (carbon fixation and reproduction, root chemistry) to variables only responsive to drought (litter production) or totally unresponsive (tree trunk, leaf chemistry). Although negative effects predominated, positive effects of rainfall exclusion were also detected in wet years, likely due to a reduction of pathogen abundance in drier soil. Trade‐offs between carbon sinks appeared in all tree species, but rainfall exclusion only modified trade‐offs in Q. suber, the species most susceptible to P. cinnamomi. Synthesis. We provide evidence on the complexity of the combined effects of abiotic (drought) and biotic (pathogens) global change drivers on carbon source and sinks of adult trees, including both negative direct effects and positive indirect effects. Our results showed that these effects varied among co‐existing species, particularly for carbon sinks directly related to tree demography (reproduction). Therefore, long‐term changes in the structure of Mediterranean mixed forests might be expected towards the dominance of species highly resistant to both drought and pathogens. [ABSTRACT FROM AUTHOR]

Background: Verticilium dahliae is the most important wilt pathogen of olive trees with a broad host range causing devastating diseases currently without any effective chemical control. Traditional detection methodologies are based on symptoms-observation or lab-detection using time consuming culturing or molecular techniques. Therefore, there is an increasing need for portable tools that can detect rapidly V. dahliae in the field. Results: In this work, we report the development of a novel method for the rapid, reliable and on-site detection of V. dahliae using a newly designed isothermal LAMP assay and crude extracts of olive wood. For the detection of the fungus, LAMP primers were designed targeting the internal transcribed spacer (ITS) region of the rRNA gene. The above assay was combined with a purpose-built prototype portable device which allowed real time quantitative colorimetric detection of V. dahliae in 35 min. The limit of detection of our assay was found to be 0.8 fg/μl reaction and the specificity 100% as indicated by zero cross-reactivity to common pathogens found in olive trees. Moreover, detection of V. dahliae in purified DNA gave a sensitivity of 100% (Ct < 30) and 80% (Ct > 30) while the detection of the fungus in unpurified crude wood extracts showed a sensitivity of 80% when multisampling was implemented. The superiority of the LAMP methodology regarding robustness and sensitivity was demonstrated when only LAMP was able to detect V. dahliae in crude samples from naturally infected trees with very low infection levels, while nested PCR and SYBR qPCR failed to detect the pathogen in an unpurified form. Conclusions: This study describes the development of a new real time LAMP assay, targeting the ITS region of the rRNA gene of V. dahliae in olive trees combined with a 3D-printed portable device for field testing using a tablet. The assay is characterized by high sensitivity and specificity as well as ability to operate using directly crude samples such as woody tissue or petioles. The reported methodology is setting the basis for the development of an on-site detection methodology for V. dahliae in olive trees, but also for other plant pathogens. [ABSTRACT FROM AUTHOR]

Anaerobic soil disinfestation (ASD) is a novel, eco-friendly method to improve soil health. This method creates oxygen-free conditions by adding organic amendments as a carbon source, saturating the soil to field capacity, and then covering it with plastic. These anaerobic conditions reduce soilborne pathogens, enhance microbial diversity, and increase crop productivity. This review provides an overview of the different organic amendments used in ASD, their impact on managing soilborne pathogens, the role of beneficial microbiomes, and the challenges associated with adopting ASD. It also emphasizes the potential benefits of ASD and the innovative approach to advancing it for sustainable agriculture. [ABSTRACT FROM AUTHOR]

Carrot (Daucus carota L. subsp. sativus) cultivation is important in Argentina, with the Garay department in Santa Fe province being a key production area. In recent years, dry rot symptoms have afflicted various carrot cultivars, resulting in substantial field losses and postharvest discards. Several soilborne pathogens, including Fusarium species, have been implicated in similar carrot diseases globally. This study aimed to identify the specific causal agent responsible for dry rot in carrots in central Argentina to enable targeted disease management strategies. Samples of symptomatic carrots were collected from fields in the Garay department. Fungal isolates were obtained from the infected tissue and subjected to morphological and molecular analyses. Pathogenicity tests were conducted to confirm the ability of the isolates to cause disease symptoms in carrots. Based on morphological and molecular identification, isolates were identified as Fusarium nirenbergiae, Fusarium triseptatum and Fusarium solani. Pathogenicity tests demonstrated that the three Fusarium species were capable of causing dry rot symptoms in carrots. This study represents the first report of Fusarium nirenbergiae, Fusarium triseptatum and Fusarium solani causing dry rot in carrots in Argentina. [ABSTRACT FROM AUTHOR]

Bacterial biocontrol agents that antagonize soilborne pathogens are increasingly considered alternatives to chemical pesticides, but their in vivo efficacy is often inconsistent, restricting commercial use. The efficacy of a biocontrol agent can depend on rhizosphere competence and its interaction with native microbiomes, which can affect ecosystem functioning. This study investigated the capacity of a Bacillus cereus sensu lato biocontrol strain (S-25) to persist on roots and in the rhizosphere of cucumber and evaluated its impact on bacterial and fungal community composition in the rhizosphere in the absence and presence of Rhizoctonia solani, the causative agent of damping-off disease in young seedlings. Following amendment, S-25 abundance in the cucumber rhizosphere decreased by two orders of magnitude but remained relatively high for the duration of the experiment, in contrast to the root surface, where it was not detected. Amendment with S-25 significantly reduced the incidence of disease caused by R. solani without reducing the relative abundance of the fungal pathogen. Interestingly, R. solani did not substantially alter the rhizosphere microbial community, whereas S-25 reduced bacterial diversity and facilitated a shift in community composition, with increased relative abundance of Acidobacteriota and Actinomycetota, and reduced abundance of Pseudomonadota, Bacteroidota, and Verrucomicrobiota. Collectively, this study provides important insights into the mode of persistence of biocontrol agents and their effect on native microbiomes in the rhizosphere of pathogen-inoculated plants. It demonstrates that amendment can significantly alter local microbiomes and suggests that optimizing amendment regimes or selecting strains with higher rhizosphere competence can enhance future biocontrol agents.

Abstract Background Verticilium dahliae is the most important wilt pathogen of olive trees with a broad host range causing devastating diseases currently without any effective chemical control. Traditional detection methodologies are based on symptoms-observation or lab-detection using time consuming culturing or molecular techniques. Therefore, there is an increasing need for portable tools that can detect rapidly V. dahliae in the field. Results In this work, we report the development of a novel method for the rapid, reliable and on-site detection of V. dahliae using a newly designed isothermal LAMP assay and crude extracts of olive wood. For the detection of the fungus, LAMP primers were designed targeting the internal transcribed spacer (ITS) region of the rRNA gene. The above assay was combined with a purpose-built prototype portable device which allowed real time quantitative colorimetric detection of V. dahliae in 35 min. The limit of detection of our assay was found to be 0.8 fg/μl reaction and the specificity 100% as indicated by zero cross-reactivity to common pathogens found in olive trees. Moreover, detection of V. dahliae in purified DNA gave a sensitivity of 100% (Ct 30) while the detection of the fungus in unpurified crude wood extracts showed a sensitivity of 80% when multisampling was implemented. The superiority of the LAMP methodology regarding robustness and sensitivity was demonstrated when only LAMP was able to detect V. dahliae in crude samples from naturally infected trees with very low infection levels, while nested PCR and SYBR qPCR failed to detect the pathogen in an unpurified form. Conclusions This study describes the development of a new real time LAMP assay, targeting the ITS region of the rRNA gene of V. dahliae in olive trees combined with a 3D-printed portable device for field testing using a tablet. The assay is characterized by high sensitivity and specificity as well as ability to operate using directly crude samples such as woody tissue or petioles. The reported methodology is setting the basis for the development of an on-site detection methodology for V. dahliae in olive trees, but also for other plant pathogens.

Using microorganisms as biocontrol agents against soilborne plant pathogens is a promising alternative to chemical pesticides. However, only some biocontrol agents have proven effective under field conditions. This study explores the potential of highly resilient microalgae isolated from harsh environments, such as Biological Soil Crusts and agricultural fields in semi-arid regions, as a novel and sustainable approach to biocontrol. Fifty-nine microalgal strains, including thirteen cyanobacteria and forty-six green algae, were isolated and identified. Dual-culture plate assays and toxicity tests of microalgal growth media were conducted to evaluate the antifungal activity of the isolates against eight representative soilborne pathogens. The results showed that many microalgae strains exhibited significant inhibitory effects on the growth of specific fungal pathogens, although the activity varied among different microalgal strains and pathogen species. Some strains even promoted the growth of certain fungi. The lack of a clear pattern in the antifungal activity highlights the complexity and specificity of the interactions between microalgae and soilborne pathogens. An "Inhibition Effectiveness" metric was developed to quantify biocontrol potential based on fungal growth inhibition. The green algal genus Desmodesmus, particularly Desmodesmus subspicatus isolates, showed higher antifungal efficacy than other genera. While the inhibitory mechanisms remain unclear, the results demonstrate the promising biocontrol capabilities of microalgae from extreme environments like BSCs. Further research could unlock novel opportunities for sustainable disease management by harnessing specific microalgal strains or synergistic strain combinations targeting soilborne pathogens. [ABSTRACT FROM AUTHOR]

Plants shape their surrounding soil, influencing subsequent plant growth in a phenomenon known as plant–soil feedback (PSF). This feedback is driven by chemical and microbial legacies. Here, we cultivated six crops from two functional groups, i.e., three grasses (Lolium, Triticum, and Zea) and three legumes (Glycine, Lens, and Medicago), to condition a living soil. Subsequently, the same species were sown as response plants on conspecific and heterospecific soils. We employed high-throughput sequencing in tandem with soil chemistry, including total organic matter, pH, total nitrogen, electrical conductivity, phosphorus, and macro and micro-nutrients. Our results showed that Glycine exhibited the strongest negative PSF, followed by Triticum and Zea, while Lolium displayed low feedback. Conversely, Lens demonstrated robust positive PSF, with Medicago exhibiting slight positive feedback. Soil chemistry significance indicated only higher Cl content in Triticum soil, while Lens displayed higher Zn and Mn contents. Microbial diversity exhibited no significant variations among the six soils. Although conditioning influenced the abundance of functionally important microbial phyla associated with each plant, no specificity was observed between the two functional groups. Moreover, each crop conditioned its soil with a substantial proportion of fungal pathogens. However, co-occurrence analysis revealed a strong negative correlation between all crop’s biomass and fungal pathogens, except Glycine, which exhibited a strong negative correlation with mutualists such as Arthrobacter and Bacillus. This underscores the complexity of predicting PSFs, emphasizing the need for a comprehensive understanding of plant interactions with both pathogens and mutualists, rather than focusing solely on host-specific pathogens.

Anaerobic soil disinfestation (ASD) is a novel, eco-friendly method to improve soil health. This method creates oxygen-free conditions by adding organic amendments as a carbon source, saturating the soil to field capacity, and then covering it with plastic. These anaerobic conditions reduce soilborne pathogens, enhance microbial diversity, and increase crop productivity. This review provides an overview of the different organic amendments used in ASD, their impact on managing soilborne pathogens, the role of beneficial microbiomes, and the challenges associated with adopting ASD. It also emphasizes the potential benefits of ASD and the innovative approach to advancing it for sustainable agriculture.

Using microorganisms as biocontrol agents against soilborne plant pathogens is a promising alternative to chemical pesticides. However, only some biocontrol agents have proven effective under field conditions. This study explores the potential of highly resilient microalgae isolated from harsh environments, such as Biological Soil Crusts and agricultural fields in semi-arid regions, as a novel and sustainable approach to biocontrol. Fifty-nine microalgal strains, including thirteen cyanobacteria and forty-six green algae, were isolated and identified. Dual-culture plate assays and toxicity tests of microalgal growth media were conducted to evaluate the antifungal activity of the isolates against eight representative soilborne pathogens. The results showed that many microalgae strains exhibited significant inhibitory effects on the growth of specific fungal pathogens, although the activity varied among different microalgal strains and pathogen species. Some strains even promoted the growth of certain fungi. The lack of a clear pattern in the antifungal activity highlights the complexity and specificity of the interactions between microalgae and soilborne pathogens. An “Inhibition Effectiveness” metric was developed to quantify biocontrol potential based on fungal growth inhibition. The green algal genus Desmodesmus, particularly Desmodesmus subspicatus isolates, showed higher antifungal efficacy than other genera. While the inhibitory mechanisms remain unclear, the results demonstrate the promising biocontrol capabilities of microalgae from extreme environments like BSCs. Further research could unlock novel opportunities for sustainable disease management by harnessing specific microalgal strains or synergistic strain combinations targeting soilborne pathogens.

Abstract Background Disease suppressiveness of soils to fungal root pathogens is typically induced in the field by repeated infections of the host plant and concomitant changes in the taxonomic composition and functional traits of the rhizosphere microbiome. Here, we studied this remarkable phenomenon for Bipolaris sorokiniana in two wheat cultivars differing in resistance to this fungal root pathogen. Results The results showed that repeated exposure of the susceptible wheat cultivar to the pathogen led to a significant reduction in disease severity after five successive growth cycles. Surprisingly, the resistant wheat cultivar, initially included as a control, showed the opposite pattern with an increase in disease severity after repeated pathogen exposure. Amplicon analyses revealed that the bacterial families Chitinophagaceae, Anaerolineaceae and Nitrosomonadaceae were associated with disease suppressiveness in the susceptible wheat cultivar; disease suppressiveness in the resistant wheat cultivar was also associated with Chitinophagaceae and a higher abundance of Comamonadaceae. Metagenome analysis led to the selection of 604 Biosynthetic Gene Clusters (BGCs), out of a total of 2,571 identified by AntiSMASH analysis, that were overrepresented when the soil entered the disease suppressive state. These BGCs are involved in the biosynthesis of terpenes, non-ribosomal peptides, polyketides, aryl polyenes and post-translationally modified peptides. Conclusion Combining taxonomic and functional profiling we identified key changes in the rhizosphere microbiome during disease suppression. This illustrates how the host plant relies on the rhizosphere microbiome as the first line of defense to fight soil-borne pathogens. Microbial taxa and functions identified here can be used in novel strategies to control soil-borne fungal pathogens.

Background: Disease suppressiveness of soils to fungal root pathogens is typically induced in the field by repeated infections of the host plant and concomitant changes in the taxonomic composition and functional traits of the rhizosphere microbiome. Here, we studied this remarkable phenomenon for Bipolaris sorokiniana in two wheat cultivars differing in resistance to this fungal root pathogen. Results: The results showed that repeated exposure of the susceptible wheat cultivar to the pathogen led to a significant reduction in disease severity after five successive growth cycles. Surprisingly, the resistant wheat cultivar, initially included as a control, showed the opposite pattern with an increase in disease severity after repeated pathogen exposure. Amplicon analyses revealed that the bacterial families Chitinophagaceae, Anaerolineaceae and Nitrosomonadaceae were associated with disease suppressiveness in the susceptible wheat cultivar; disease suppressiveness in the resistant wheat cultivar was also associated with Chitinophagaceae and a higher abundance of Comamonadaceae. Metagenome analysis led to the selection of 604 Biosynthetic Gene Clusters (BGCs), out of a total of 2,571 identified by AntiSMASH analysis, that were overrepresented when the soil entered the disease suppressive state. These BGCs are involved in the biosynthesis of terpenes, non-ribosomal peptides, polyketides, aryl polyenes and post-translationally modified peptides. Conclusion: Combining taxonomic and functional profiling we identified key changes in the rhizosphere microbiome during disease suppression. This illustrates how the host plant relies on the rhizosphere microbiome as the first line of defense to fight soil-borne pathogens. Microbial taxa and functions identified here can be used in novel strategies to control soil-borne fungal pathogens. [ABSTRACT FROM AUTHOR]

A new disease of commercially cultivated Mursalitza mountain tea (Sideritis scardica Griseb.) was discovered and diagnosed for the first time in Bulgaria. Disease symptoms included yellowing and stunting, stem and root rot, sudden wilt and premature death on predominantly young newly replanted seedlings and less frequently on mature one- and two-year-old plants. Disease incidence increased throughout the season and in 2021 the disease totally caused 35% and 45% crop losses in the two surveyed fields. All isolates obtained from symptomatic plants were identified by microscopic observation of their morphological characteristics as Fusarium culmorum (Wm.G.Sm.) Sacc. and Fusarium oxysporum Schlecht. emend. Snyder and Hansen. Pathogenicity of all isolates was confirmed on 30-day-old Mursalitza mountain tea seedlings grown in pots with artificially inoculated soils. All inoculated plants showed symptoms identical to those observed on "naturally" infected plants grown in the surveyed field sites. The inoculated pathogens were consistently reisolated from symptomatic tissues. Further efforts are needed to evaluate the full range of biotic and abiotic components involved in the etiology of the stem and root rot which results in early decline of the crop; an effective disease control program should be designed and implemented. Commercial and semi-commercial cultivation is an important means of protection for indigenous populations of Mursalitza mountain tea in the country. Hence, apart from the economic losses; the disease is likely to compromise the conservation of this endangered botanical species and to impede the restoration of its natural habitats in the wild. [ABSTRACT FROM AUTHOR]

Crops are often simultaneously threatened by abiotic and biotic stress factors but the stress response of the plant holobiont is not well understood, despite the high importance of this response to ensure future plant production. Therefore, the aim of this study was to assess the impact of individual and combined abiotic (ionic and osmotic) and biotic (Verticillium dahliae and Fusarium oxysporum) stress factors on plant performance and on the bacterial composition of the root endosphere in tomato. Structure and function of the microbiota was analyzed by 16S ribosomal RNA gene amplicon sequencing and a complementary cultivation approach, including in vitro and in vivo assays. Under all stress conditions, tomato growth and photosynthetic activity was reduced. Combined abiotic stressors with F. oxysporum but not with V. dahliae infection led to an additive negative effect on plant performance. All stress conditions induced a microbiome shift, and changed the relative abundance of phyla such as Firmicutes and classes of Proteobacteria. Endophytes identified as Bacillus, Paenibacillus, and Microbacterium spp. showed tolerance to abiotic stress conditions and plant beneficial effects. Stressor-specific enrichments of beneficial bacteria in the root were discovered (e.g., Paenibacillus in roots infected with F. oxysporum and Microbacterium in roots infected with V. dahliae). Interestingly, endophytes that were able to promote plant growth were obtained only from roots exposed to individual biotic and combined abiotic and biotic stress conditions but not individual abiotic stressors. Our study revealed stressor-specific enrichment of beneficial bacteria in tomato roots, which has implications for novel plant protection strategies.

The importance of crop-associated microbiomes for the health and field performance of plants has been demonstrated in the last decades. Sugar beet is the most important source of sucrose in temperate climates, and-- as a root crop--yield heavily depends on genetics as well as on the soil and rhizosphere microbiomes. Bacteria, fungi, and archaea are found in all organs and life stages of the plant, and research on sugar beet microbiomes contributed to our understanding of the plant microbiome in general, especially of microbiome-based control strategies against phytopathogens. Attempts to make sugar beet cultivation more sustainable are increasing, raising the interest in biocontrol of plant pathogens and pests, biofertilization and --stimulation as well as microbiome-assisted breeding. This review first summarizes already achieved results on sugar beet-associated microbiomes and their unique traits, correlating to their physical, chemical, and biological peculiarities. Temporal and spatial microbiome dynamics during sugar beet ontogenesis are discussed, emphasizing the rhizosphere formation and highlighting knowledge gaps. Secondly, potential or already tested biocontrol agents and application strategies are discussed, providing an overview of how microbiome-based sugar beet farming could be performed in the future. Thus, this review is intended as a reference and baseline for further sugar beet-microbiome research, aiming to promote investigations in rhizosphere modulation-based biocontrol options. [ABSTRACT FROM AUTHOR]

Post flowering stalk rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of phenomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. To investigate the pathogenicity of Fusarium spp. causing PFSR sixty isolates were toothpick inoculated between the first and second node at 55 days after sowing during the tassel formation stage of the crop in Kharif (Rainy season), and Rabi (Winter season) season field trials. Ten most virulent Fusarium isolates, based on the highest observed disease index, were identified by homology and phylogenetic analyses of partial sequences of the translation elongation factor 1 α (Tef-1α). Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into nine clusters. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vivo situations and high disease severity in field experiments. Pathogenicity test during the Kharif season showed 12 isolates with virulent disease symptoms with a mean severity ranging between 50 to 67 percent disease index (PDI) whereas in Rabi season, only five isolates were considered virulent, and the mean severity ranged between 52 to 67 PDI. Based on pathological characterization and molecular identification, 10 strains of Fusarium species namely, Fusarium acutatum (2/10), Fusarium verticillioides (Syn. Gibberella fujikuroi var. moniliformis) (7/10), Fusarium andiyazi (2/10) recorded the highest diseases index. All these species are part of the Fusarium fujikuroi species complex (FFSC). The distribution of virulent isolates is specific to a geographical location with a hot humid climate. Increased knowledge regarding the variability of Fusarium spp. responsible for PFSR of maize occurring across wide geographical locations of India will enable more informed decisions to be made to support the management of the disease, including screening for resistance in maize-inbred lines. [ABSTRACT FROM AUTHOR]

Post flowering stalk rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of phenomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. To investigate the pathogenicity of Fusarium spp. causing PFSR sixty isolates were toothpick inoculated between the first and second node at 55 days after sowing during the tassel formation stage of the crop in Kharif (Rainy season), and Rabi (Winter season) season field trials. Ten most virulent Fusarium isolates, based on the highest observed disease index, were identified by homology and phylogenetic analyses of partial sequences of the translation elongation factor 1 α (Tef-1α). Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into nine clusters. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vivo situations and high disease severity in field experiments. Pathogenicity test during the Kharif season showed 12 isolates with virulent disease symptoms with a mean severity ranging between 50 to 67 percent disease index (PDI) whereas in Rabi season, only five isolates were considered virulent, and the mean severity ranged between 52 to 67 PDI. Based on pathological characterization and molecular identification, 10 strains of Fusarium species namely, Fusarium acutatum (2/10), Fusarium verticillioides (Syn. Gibberella fujikuroi var. moniliformis) (7/10), Fusarium andiyazi (2/10) recorded the highest diseases index. All these species are part of the Fusarium fujikuroi species complex (FFSC). The distribution of virulent isolates is specific to a geographical location with a hot humid climate. Increased knowledge regarding the variability of Fusarium spp. responsible for PFSR of maize occurring across wide geographical locations of India will enable more informed decisions to be made to support the management of the disease, including screening for resistance in maize-inbred lines.

Soil degradation remains an ongoing process that is exacerbated by the effects of climate change. Consequently, these processes decrease soil organic matter and nutrient contents, soil biological functions, and plant productivity. The addition of organic amendments (OAs) to the soil is a widespread practice to enhance soil quality and the health of agricultural soils. One of the most significant microbial hotspots controlling the processes, dynamics, and cycling of nutrients, carbon and water in terrestrial ecosystems is the rhizosphere. Understanding the continuing transformations of OAs and the distribution of different factors (C, nutrients, and microbial activities) across and along roots is crucial in the rhizosphere. The application of OAs to soil increases soil organic matter and nutrients, water holding capacity, improves soil structure and stimulates soil microbial activity and biomass. This review evaluates the role of the rhizosphere microbial community in organically amended soils for promoting plant growth and health. The diversity of the rhizosphere microbiome and the mechanisms used in plant protection are discussed. [ABSTRACT FROM AUTHOR]

The early detection of pathogen infections in plants has become an important aspect of integrated disease management. Although previous research demonstrated the idea of applying digital technologies to monitor and predict plant health status, there is no effective system for detecting pathogen infection before symptomatology appears. This paper presents the use of a low-cost and portable electronic nose coupled with machine learning (ML) models for early disease detection. Several artificial neural network models were developed to predict plant physiological data and classify processing tomato plants and soil samples according to different levels of pathogen inoculum by using e-nose outputs as inputs, plant physiological data, and the level of infection as targets. Results showed that the pattern recognition models based on different infection levels had an overall accuracy of 94.4–96.8% for tomato plants and between 94.81% and 96.22% for soil samples. For the prediction of plant physiological parameters (photosynthesis, stomatal conductance, and transpiration) using regression models or tomato plants, the overall correlation coefficient was 0.97–0.99, with very significant slope values in the range 0.97–1. The performance of all models shows no signs of under or overfitting. It is hence proven accurate and valid to use the electronic nose coupled with ML modeling for effective early disease detection of processing tomatoes and could also be further implemented to monitor other abiotic and biotic stressors. [ABSTRACT FROM AUTHOR]

Verticillium is a genus of ascomycete fungi that encompasses several plant pathogenic species, and cause severe annual yield losses on many economically important crops worldwide. One of the most important species in this genus, is V. longisporum , which causes disease mainly on plants in the Brassicaceae family. Genome analysis of V. longisporum strain VL1 revealed a number of candidate effector genes that may be associated with fungal virulence. One of these candidate effector-genes encodes a putative endolysin-like protein. Endolysins are hydrolytic enzymes that are secreted by bacteriophages and recently, they have been identified in fungal genomes as well. In this study, the potential role of this gene has been investigated in V. longisporum. Our data showed that this gene was highly induced in the fungus during Brassica napus infection and its overexpression significantly increased V. longisporum virulence, indicating an involvement in the fungal infection process. • Verticillium longisporum is a soilborne pathogen attacks mainly Brassicaceae plants. • Endolysins are lytic enzymes produced mainly by bacteriophages. • Recently, putative endolysin-like proteins have been identified in fungal genomes. • The putative Vl3720 endolysin-like protein is involved in V. longisporum virulence. [ABSTRACT FROM AUTHOR]

Wheat Fusarium crown rot (FCR) is caused predominantly by Fusarium pseudograminearum across most wheat-producing countries; this fungal disease needs a specific combination of fungicides to control it. In this research, the efficacy of four fungicides against F. pseudograminearum is tested using in vitro assays. Our results showed that fludioxonil had an EC50 of 0.0447 mg/L, followed by difenoconazole (0.3845 mg/L) and tebuconazole (0.4919 mg/L). Azoxystrobin (2.6019 mg/L) was also effective. Commercially available fungicides with the first three ingredients as active ingredients were further tested for the control of FCR. Cruiser Plus and Celest presented higher efficacies in an environmentally controlled pot assay. Further testing in the field achieved a higher level of control by Cruiser Plus than Celest at the seedling (72.34% vs. 62.55%) and adult (56.76% vs. 47.78%) stages in a field plot experiment. When tested in naturally infected wheat fields in Linzhang, Hebei Province, applications of the two fungicides resulted in relative control efficacies of 45.17% and 38.57%, respectively, and grain yields were increased by dressing with Cruiser Plus (8.7%) and with Celest (5.3%). Furthermore, seed dressing combined with additional spraying in early spring resulted in significantly better control of FCR and higher grain yield than seed dressing treatment alone (10.4% and 7.4%, respectively). Similar results were obtained when tested in Xian County, Hebei Province, with a disease control efficacy of 40.36–59.91% and a yield increase of 4.2–7.5%. Integrated measures of dressing (Cruiser Plus and Celest) combined with spraying (Horizon) showed higher control efficacy to FCR. [ABSTRACT FROM AUTHOR]

In May of 2019, Scabiosa atropurpurea samples with brown discoloration, soft rot of the crown and lower stem, with presence of white mycelium and black sclerotia (Supp. Fig. 1A, B) were collected from a 0.10 ha open field diversified cut flower production in San Luis Obispo County, CA. Approximately 30 to 40% of the scabiosa crop planted in a quarter of the field, exhibited symptoms. Symptomatic crowns and lower stems from five plants were surface disinfested by rinsing in 0.1% Tween 20, soaking in 70% ethanol for 30 s, 1% sodium hypochlorite for 2 min and sterile water. Disinfested tissue was placed in 1/10 potato dextrose agar (PDA) and incubated at 20°C (12 h photoperiod). Resulting colonies (n = 5) formed abundant white mycelia, with black sclerotia formed on the outer edge of the plates after two weeks (Suppl. Fig. 1C). Sclerotia (n = 50) had an average size of 1.6 (± 0.19) mm in diameter. Morphological identification resulted in Sclerotinia sp. (Hao et al., 2003). The pathogen was further identified by DNA extraction of two hyphal tipped isolates, followed by amplification and sequencing of the rDNA internal transcribed spacer (ITS) region, ITS1/ITS4 (White et al. 1990), calmodulin (CaM), CAL-228F/CAL-737R (Carbone and Kohn, 1999), and DNA replication licensing factor Mcm7 Mcm7-709for/Mcm7-1348rev (Schmitt et al., 2009). NCBI BLAST searches with consensus sequences for each maker revealed 99 to 100% identity with S. minor ex-types for all loci (Supp. Table 1). A maximum parsimony multilocus phylogenetic analysis clustered Californian isolates with reference strains of S. minor (Supp. Fig. 1F). Sequences were deposited in GenBank (Supp. Table 1). Pathogenicity tests were conducted with isolate CS435, which was transferred onto PDA plates and incubated at 20°C for one week. Inoculum consisted of CS435 infested PDA plugs (1 cm3). In the greenhouse, the experiment was set as a complete randomized design and observed for six weeks. Fourteen-week-old scabiosa 'Merlot Red' grown in 3.78 L pots (n = 6), were inoculated by wounding plants at 0.5 cm above the crowns with a 1 mm probe. Inoculum was placed directly on top of the wound and was secured with parafilm. Negative control plants (n = 6) were wounded as above and inoculated with PDA plugs. In experiment 1(19.4 (± 3) °C, RH 46.9), 83% of plants exhibited yellowing of the lower leaves and wilting at one week post inoculation (wpi). Symptoms progressed over time until wilting, major leaf and stem necrosis, was observed in all inoculated plants (Supp. Fig 1E, D). Plant mortality incidence at five wpi was 83%. Pathogen signs including white mycelia and black sclerotia were also observed. In experiment 2 (20.0 (± 10) °C, RH 39.6), 66% of the total plants were symptomatic at five wpi: 33% exhibited yellowing of the lower leaves and wilting, and 33% of plants died. Disease did not develop in non-inoculated plants in either experiment. S. minor was successfully reisolated from surface disinfested tissue of at least 50% (Exp. 1) and 100% (Exp. 2) of inoculated plants, yielding identical sequences to those of the inoculated isolate. S. minor is a soil-borne pathogen that infects tomato, lettuce, brassica, and sunflower crops in California. This study stablishes S. minor as a new soil-borne pathogen of Scabiosa in California. Soil-borne pathogens are a recurrent issue in the cut flower industry, characterizing new pathogens in these crops can inform crop advisors and disease diagnostician to improve disease management in the ornamental industry.

BACKGROUND: The effectiveness of metam potassium, 1,3‐dichloropropene, chloropicrin, and different ratios of 1,3‐dichloropropene and chloropicrin on the reduction of natural and artificial inoculum of Macrophomina phaseolina were investigated in laboratory and field experiments. Additionally, a multivariate meta‐analysis with data from six field trials conducted in Florida from 2012 to 2018 was performed. RESULTS: In small‐plot field experiments using drip stakes, the highest rate (468 L ha−1) of metam potassium was most effective in controlling M. phaseolina in infected crowns buried at 15.2 cm from the point of fumigant injection, whereas none of the rates was able to reduce inoculum buried at 30.5 cm. In closed‐container experiments, use of the highest rate of 1,3‐dichloropropene (168 kg ha−1) resulted in the highest level of pathogen control. Different rates of chloropicrin also reduced inoculum when compared to the non‐treated control. 1,3‐dichloropropene + chloropicrin at different ratios were also highly effective in controlling M. phaseolina. Results from the meta‐analysis of open‐field experiments indicated that metam potassium and 1,3‐dichloropropene + chloropicrin (63:35, v:v) treatments were significantly more effective in reducing M. phaseolina than the 1,3‐dichloropropene + chloropicrin (39:60, v:v) treatment; however, metam potassium was not as effective at the side of the beds. CONCLUSION: 1,3‐dichloropropene alone and in mixture with chloropicrin were more effective in reducing inoculum of M. phaseolina than chloropicrin alone, indicating the fungicidal efficacy of 1,3‐dichloropropene. Formulation with higher 1,3‐dichloropropene concentration performed better than the formulation with higher chloropicrin concentration in field trials. Metam potassium was effective when applied at the highest rate, but with limited lateral movement perpendicular to the drip irrigation line. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The cereal cyst nematode (CCN) Heterodera and crown rot caused by Fusarium species limit cereal production and yield potential. Losses increase when CCN and crown rot occur together, especially under water stress conditions. The objective of this study was to investigate the interactions among Heterodera filipjevi, Fusarium culmorum, and drought on a set of wheat germplasm with differing levels of resistance/tolerance to CCN, crown rot and drought. Plant emergence was significantly reduced (56% seedling death) when seeds were planted in a water stress environment where F. culmorum and H. filipjevi were present. Crown rot was more severe under water stress compared with Fusarium inoculation alone. The number of cysts fell significantly when H. filipjevi was co-inoculated with F. culmorum, revealing an antagonistic interaction between the nematode and fungus. The highest number of cysts was found on the susceptible accession 'Seri' under water stress conditions. Water stress caused a significant reduction in plant height, while F. culmorum inoculation did not, unless combined with water stress. Yield components were significantly reduced by each of the single stresses and losses were greater when plants were exposed to double or triple stresses. Water stress and F. culmorum inoculation caused a significant reduction in spike weight and seeds per spike. The chlorophyll content of wheat leaves was negatively affected by water stress and inoculation by both nematode and fungus. In conclusion, water stress exacerbates the damage caused by CCN and crown rot, and planting drought-resistant varieties would be an ideal solution to reduce losses. [ABSTRACT FROM AUTHOR]

Early sowing has potential to reduce negative impacts of summer drought on soybean productivity in southern Europe. However, performing early sowing into cool and moist soil conditions may increase risks of soilborne pathogens that cause damping-off disease. We investigated whether and to what extent soybean germination, emergence, nodulation, and early biomass growth was affected when inoculated with Rhizoctonia solani, an important causal agent of damping-off disease. We conducted this study through four complementary approaches: (i) in vitro laboratory tests, (ii) field experiments including two sowing dates (early and conventional), (iii) growth-chamber experiments, and (iv) modeling. The pathogen caused disease symptoms and significantly reduced (P ≤ 0.001) radicle growth in vitro but failed to cause disease under field or growth-chamber conditions. No biological suppressiveness of the field soil to R. solani was found when tested in the growth chamber. Final field emergence rates ranged from 72 to 92% for early and conventional sowing, respectively, while those in the growth chamber ranged from 80 to 100%. Under field conditions, abiotic stresses were the major causes of nonemergence while biotic stresses had only minor impact on seedling emergence. A significant effect of sowing date (P < 0.001) was observed on the average shoot and root length and on the number of average nodules per plantlet. The overall prediction quality of the SIMPLE model was very good for both sowing dates. The contrasts between laboratory and field experiments in terms of disease development, time to emergence, and early growth parameters are discussed.[Figure: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

During the monitoring period of alder decline phenomenon in Slovakia, indicative symptoms of Phytophthora diseases were observed in riverside stands in Slovakia. The study aimed to test the presence and diversity of Phytophthora species in declining alder stands. The samples were collected from six stands situated by rivers/streams in the central and eastern parts of Slovakia. Phytophthora plurivora and P. cactorum were detected in soil, root and water samples. The most isolated species was P. plurivora. Both Phytophthora species have been recognized in the literature as the perpetrators of black alder dieback together with other species, such as P. alni or P. polonica. To our knowledge, this is the first report of P. plurivora and P. cactorum in riverside stands with the main share of black alder in Slovakia. [ABSTRACT FROM AUTHOR]

Aims: To isolate and characterize fungi associated with diseased soybean seedlings in Midwestern soybean production fields and to determine the influence of environmental and edaphic factors on their incidence. Methods and Results: Seedlings were collected from fields with seedling disease history in 2012 and 2013 for fungal isolation. Environmental and edaphic data associated with each field was collected. 3036 fungal isolates were obtained and assigned to 76 species. The most abundant genera recovered were Fusarium (73%) and Trichoderma (11.2%). Other genera included Mortierella, Clonostachys, Rhizoctonia, Alternaria, Mucor, Phoma, Macrophomina and Phomopsis. Most recovered species are known soybean pathogens. However, non‐pathogenic organisms were also isolated. Crop history, soil density, water source, precipitation and temperature were the main factors influencing the abundance of fungal species. Conclusion: Key fungal species associated with soybean seedling diseases occurring in several US production regions were characterized. This work also identified major environment and edaphic factors affecting the abundance and occurrence of these species. Significance and Impact of the Study: The identification and characterization of the main pathogens associated with seedling diseases across major soybean‐producing areas could help manage those pathogens, and devise more effective and sustainable practices to reduce the damage they cause. [ABSTRACT FROM AUTHOR]

Sclerotinia have 250 especies in tropical and subtropical crops. S. sclerotiorum, S. minor y S. trifoliorum are the main species althoug other have been reported. Rots in stem, crown, rhizome, flower, fruit greening, pods, fruits; blights in buds and flower, foliar spots and wilt) are the major symptoms and presence of white mould with presence of black sclerotia are the main signs caused in tropical crops like: pea, alfalfa, cotton, almonds, onion, chinesse cabbage, black berry, strawberry, bean, sunflower, ginger, lentil, peanut, peach, water melon, pear, soybean, tomato, grape and carrot. The knowledge and the possibilities of precise diagnosis of the different species of Sclerotinia constitutes a main element to establish efficient management measures in tropical crops of economic interest.

Managing plant health is a great challenge for modern food production and is further complicated by the lack of common ground between the many disciplines involved in disease control. Here we present the concept of rhizosphere immunity, in which plant health is considered as an ecosystem level property emerging from networks of interactions between plants, microbiota and the surrounding soil matrix. These interactions can potentially extend the innate plant immune system to a point where the rhizosphere immunity can fulfil all four core functions of a full immune system: pathogen prevention, recognition, response and homeostasis. We suggest that considering plant health from a meta-organism perspective will help in developing multidisciplinary pathogen management strategies that focus on steering the whole plant-microbe-soil networks instead of individual components. This might be achieved by bringing together the latest discoveries in phytopathology, microbiome research, soil science and agronomy to pave the way toward more sustainable and productive agriculture.

Soil degradation remains an ongoing process that is exacerbated by the effects of climate change. Consequently, these processes decrease soil organic matter and nutrient contents, soil biological functions, and plant productivity. The addition of organic amendments (OAs) to the soil is a widespread practice to enhance soil quality and the health of agricultural soils. One of the most significant microbial hotspots controlling the processes, dynamics, and cycling of nutrients, carbon and water in terrestrial ecosystems is the rhizosphere. Understanding the continuing transformations of OAs and the distribution of different factors (C, nutrients, and microbial activities) across and along roots is crucial in the rhizosphere. The application of OAs to soil increases soil organic matter and nutrients, water holding capacity, improves soil structure and stimulates soil microbial activity and biomass. This review evaluates the role of the rhizosphere microbial community in organically amended soils for promoting plant growth and health. The diversity of the rhizosphere microbiome and the mechanisms used in plant protection are discussed.

Plant-based screening experiments were conducted with the aim of identifying biocontrol bacteria and fungi for seed treatment of maize. Candidate microorganisms were evaluated for their protective effects against soilborne infections by species of Fusarium, Globisporangium (syn. Pythium) and Rhizoctonia. The microorganisms tested were bacteria and fungi from maize roots or other sources, including some active microbial components of commercial biocontrol products. Due to the method of isolation chosen, the majority of bacteria from maize roots were spore formers, most of them species of the genera Bacillus,Brevibacillus and Paenibacillus. In pot tests with the potting substrate inoculated with F. culmorum, the level of control provided by seed treatment with the most efficacious bacterial and fungal isolates was comparable or close to the chemical reference seed treatment thiram. The most effective bacteria were species of Pseudomonas, Burkholderia and Streptomyces. Among a subset of approx. 100 bacteria studied, the in vivo and in vitro activities against F.culmorum were only weakly correlated, although some strains deviated from this pattern. The most effective fungi were two strains of Clonostachys rosea and isolates of Trichoderma. The latter and a strain of Gliocladium virens provided also protection against R.solani. Activity against Globisporangium ultimum was recorded for one isolate of Trichoderma and the two strains of C. rosea. A reduction in the impact of seedborne F. culmorum was also observed after seed treatment with two strains of F. oxysporum f. sp. strigae. The results are discussed in relation to previous reports on rhizosphere bacteria of maize and their use in biocontrol of plant pathogens or for plant growth promotion. [ABSTRACT FROM AUTHOR]

Apple replant disease (ARD), incited by a pathogen complex including Pythium ultimum , causes stunted growth or death of newly planted trees at replant sites. Development and deployment of resistant or tolerant rootstocks offers a cost-effective, ecologically friendly, and durable approach for ARD management. Maximized exploitation of natural resistance requires integrated efforts to identify key regulatory mechanisms underlying resistance traits in apple. In this study, miRNA profiling and degradome sequencing identified major miRNA pathways and candidate genes using six apple rootstock genotypes with contrasting phenotypes to P. ultimum infection. The comprehensive RNA-seq dataset offered an expansive view of post-transcriptional regulation of apple root defense activation in response to infection from P. ultimum. Several pairs of miRNA families and their corresponding targets were identified for their roles in defense response in apple roots, including miR397-laccase, miR398-superoxide dismutase, miR10986-polyphenol oxidase, miR482-resistance genes, and miR160-auxin response factor. Of these families, the genotype-specific expression patterns of miR397 indicated its fundamental role in developing defense response patterns to P. ultimum infection. Combined with other identified copper proteins, the importance of cellular fortification, such as lignification of root tissues by the action of laccase, may critically contribute to genotype-specific resistance traits. Our findings suggest that quick and enhanced lignification of apple roots may significantly impede pathogen penetration and minimize the disruption of effective defense activation in roots of resistant genotypes. The identified target miRNA species and target genes consist of a valuable resource for subsequent functional analysis of their roles during interaction between apple roots and P. ultimum. [ABSTRACT FROM AUTHOR]

Apple replant disease (ARD), incited by a pathogen complex including Pythium ultimum, causes stunted growth or death of newly planted trees at replant sites. Development and deployment of resistant or tolerant rootstocks offers a cost-effective, ecologically friendly, and durable approach for ARD management. Maximized exploitation of natural resistance requires integrated efforts to identify key regulatory mechanisms underlying resistance traits in apple. In this study, miRNA profiling and degradome sequencing identified major miRNA pathways and candidate genes using six apple rootstock genotypes with contrasting phenotypes to P. ultimum infection. The comprehensive RNA-seq dataset offered an expansive view of post-transcriptional regulation of apple root defense activation in response to infection from P. ultimum. Several pairs of miRNA families and their corresponding targets were identified for their roles in defense response in apple roots, including miR397-laccase, miR398-superoxide dismutase, miR10986-polyphenol oxidase, miR482-resistance genes, and miR160-auxin response factor. Of these families, the genotype-specific expression patterns of miR397 indicated its fundamental role in developing defense response patterns to P. ultimum infection. Combined with other identified copper proteins, the importance of cellular fortification, such as lignification of root tissues by the action of laccase, may critically contribute to genotype-specific resistance traits. Our findings suggest that quick and enhanced lignification of apple roots may significantly impede pathogen penetration and minimize the disruption of effective defense activation in roots of resistant genotypes. The identified target miRNA species and target genes consist of a valuable resource for subsequent functional analysis of their roles during interaction between apple roots and P. ultimum.

Lettuce is the most commonly cultivated leafy vegetable in Greece, available in the market throughout the year. In this study, an emerging foliar disease observed in commercial farms has been associated to the pathogen Fusarium equiseti, a member of the Fusarium incarnatum-equiseti species complex (FIESC). Thirty F. equiseti isolates obtained from symptomatic lettuce plants were identified on the basis of morphology and evaluated for their pathogenicity. The isolates were further characterized using amplification and sequence analysis of the internal transcribed region (ITS-rDNA), and of the translation elongation factor 1-alpha (TEF1-a), calmodulin (CAM), beta-tubulin (Bt), and small subunit (SSU) genes. Moreover, a novel RT-qPCR assay was developed, designing a primer pair and a probe based on the TEF1-a sequences. This assay showed high specificity, amplifying F. equiseti DNA samples, while no amplification product was observed from samples of other common soilborne fungi. The generated RT-qPCR assay could be a useful tool for the detection and quantification of F. equiseti in soil samples deriving from fields cultivated with lettuce and other leafy vegetables, hosts of this specific pathogen.

The early detection of pathogen infections in plants has become an important aspect of integrated disease management. Although previous research demonstrated the idea of applying digital technologies to monitor and predict plant health status, there is no effective system for detecting pathogen infection before symptomatology appears. This paper presents the use of a low-cost and portable electronic nose coupled with machine learning (ML) models for early disease detection. Several artificial neural network models were developed to predict plant physiological data and classify processing tomato plants and soil samples according to different levels of pathogen inoculum by using e-nose outputs as inputs, plant physiological data, and the level of infection as targets. Results showed that the pattern recognition models based on different infection levels had an overall accuracy of 94.4–96.8% for tomato plants and between 94.81% and 96.22% for soil samples. For the prediction of plant physiological parameters (photosynthesis, stomatal conductance, and transpiration) using regression models or tomato plants, the overall correlation coefficient was 0.97–0.99, with very significant slope values in the range 0.97–1. The performance of all models shows no signs of under or overfitting. It is hence proven accurate and valid to use the electronic nose coupled with ML modeling for effective early disease detection of processing tomatoes and could also be further implemented to monitor other abiotic and biotic stressors.

Wheat Fusarium crown rot (FCR) is caused predominantly by Fusarium pseudograminearum across most wheat-producing countries; this fungal disease needs a specific combination of fungicides to control it. In this research, the efficacy of four fungicides against F. pseudograminearum is tested using in vitro assays. Our results showed that fludioxonil had an EC50 of 0.0447 mg/L, followed by difenoconazole (0.3845 mg/L) and tebuconazole (0.4919 mg/L). Azoxystrobin (2.6019 mg/L) was also effective. Commercially available fungicides with the first three ingredients as active ingredients were further tested for the control of FCR. Cruiser Plus and Celest presented higher efficacies in an environmentally controlled pot assay. Further testing in the field achieved a higher level of control by Cruiser Plus than Celest at the seedling (72.34% vs. 62.55%) and adult (56.76% vs. 47.78%) stages in a field plot experiment. When tested in naturally infected wheat fields in Linzhang, Hebei Province, applications of the two fungicides resulted in relative control efficacies of 45.17% and 38.57%, respectively, and grain yields were increased by dressing with Cruiser Plus (8.7%) and with Celest (5.3%). Furthermore, seed dressing combined with additional spraying in early spring resulted in significantly better control of FCR and higher grain yield than seed dressing treatment alone (10.4% and 7.4%, respectively). Similar results were obtained when tested in Xian County, Hebei Province, with a disease control efficacy of 40.36–59.91% and a yield increase of 4.2–7.5%. Integrated measures of dressing (Cruiser Plus and Celest) combined with spraying (Horizon) showed higher control efficacy to FCR.

This study investigates whether Phytophthora species may have been repeatedly introduced in natural habitats through restoration projects. Six plant species across five research locations in three counties within the San Francisco Bay Area were tested for pathogen infection of stems, roots and for rhizosphere infestation at failing restoration sites. Where possible, the same hosts were evaluated in one neighboring un-restored site disturbed by the presence of culverts, drainages or trails that also intersected the restoration site, and in a naturally regenerated and undisturbed control site. Although native or endemic pathogens were isolated from all three types of sites, Phytophthora species were never isolated from control undisturbed sites. Statistical analyses confirmed that percentage of positive Phytophthora isolations was significantly higher in restoration sites and adjoining disturbed sites than in control sites. Presence of Phytophthora species was correlated with disease symptoms, plant death and lack of regeneration. Furthermore, six of eight Phytophthora species isolated in the field had previously been reported from plant production facilities providing stock for habitat restoration. To our knowledge, this is the first controlled survey linking the presence of entire Phytophthora species assemblages to failing restoration projects and to the plant production facilities that provide plant stock for restoration, while showing that Phytophthora species are absent in neighboring undisturbed sites. This study further proves that these pathogens are spreading from restoration sites through disturbance pathways. [ABSTRACT FROM AUTHOR]

The performance of snake melon [Cucumis melo var. flexuosus (L.)] in organic farming was studied under high biotic and salt stress conditions. Soilborne diseases (mainly caused by Macrophomina phaseolina and Neocosmospora falciformis), combined with virus incidence [Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), and Tomato leaf curl New Delhi virus (ToLCNDV)] and Podosphaera xanthii attacks, reduced yield by more than 50%. Snake melon susceptibility to M. phaseolina and Monosporascus cannonballus was proved in pathogenicity tests, while it showed some degree of resistance to Neocosmospora keratoplastica and N. falciformis. On the contrary, salt stress had a minor impact, although a synergic effect was detected: yield losses caused by biotic stress increased dramatically when combined with salt stress. Under biotic stress, grafting onto the melon F1Pat81 and wild Cucumis rootstocks consistently reduced plant mortality in different agroecological conditions, with a better performance compared to classic Cucurbita commercial hybrids. Yield was even improved under saline conditions in grafted plants. A negative effect was detected, though, on consumer acceptability, especially with the use of Cucurbita rootstocks. Cucumis F1Pat81 rootstock minimized this side effect, which was probably related to changes in the profile of sugars, acids, and volatiles. Grafting affected sugars and organic acid contents, with this effect being more accentuated with the use of Cucurbita rootstocks than with Cucumis. In fact, the latter had a higher impact on the volatile organic compound profile than on sugar and acid profile, which may have resulted in a lower effect on consumer perception. The use of Cucumis rootstocks seems to be a strategy to enable organic farming production of snake melon targeted to high-quality markets in order to promote the cultivation of this neglected crop.

The performance of snake melon [ Cucumis melo var. flexuosus (L.)] in organic farming was studied under high biotic and salt stress conditions. Soilborne diseases (mainly caused by Macrophomina phaseolina and Neocosmospora falciformis), combined with virus incidence [ Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), and Tomato leaf curl New Delhi virus (ToLCNDV)] and Podosphaera xanthii attacks, reduced yield by more than 50%. Snake melon susceptibility to M. phaseolina and Monosporascus cannonballus was proved in pathogenicity tests, while it showed some degree of resistance to Neocosmospora keratoplastica and N. falciformis. On the contrary, salt stress had a minor impact, although a synergic effect was detected: yield losses caused by biotic stress increased dramatically when combined with salt stress. Under biotic stress, grafting onto the melon F1Pat81 and wild Cucumis rootstocks consistently reduced plant mortality in different agroecological conditions, with a better performance compared to classic Cucurbita commercial hybrids. Yield was even improved under saline conditions in grafted plants. A negative effect was detected, though, on consumer acceptability, especially with the use of Cucurbita rootstocks. Cucumis F1Pat81 rootstock minimized this side effect, which was probably related to changes in the profile of sugars, acids, and volatiles. Grafting affected sugars and organic acid contents, with this effect being more accentuated with the use of Cucurbita rootstocks than with Cucumis. In fact, the latter had a higher impact on the volatile organic compound profile than on sugar and acid profile, which may have resulted in a lower effect on consumer perception. The use of Cucumis rootstocks seems to be a strategy to enable organic farming production of snake melon targeted to high-quality markets in order to promote the cultivation of this neglected crop. [ABSTRACT FROM AUTHOR]

Anaerobic soil disinfestation (ASD) is a nonchemical soil treatment where an easily decomposable carbon source is incorporated into soil, which is then irrigated to saturation and tarped to create anaerobic conditions, which prompts shifts in the soil microbiota from aerobes to anaerobes. ASD has been tested successfully for soilborne disease management in a variety of cropping systems but has not been sufficiently investigated in ornamentals. In this study, ASD was evaluated in soil-based and soilless substrates commonly used in specialty cut flower production using two model pathosystems: Rhizoctonia solani - Zinnia elegans and Phytophthora drechsleri - Gerbera jamesonii . Each substrate was mixed with pathogen-infested vermiculite and amended with either wheat bran, tomato pomace, or soybean meal as the carbon source. Amended substrates were incubated at 25°C for 4 weeks and used as growing substrates for the two crops mentioned above, which were monitored weekly for disease development for up to 5 weeks posttransplant. Additional experiments tested the effect of plant age and inoculum concentration in the substrate on ASD efficacy. Results showed that ASD has the potential to be deployed successfully for the control of Rhizoctonia stem rot in both substrates. Conversely, ASD was not effective at controlling Phytophthora crown rot on gerbera daisy in any of the experiments conducted in this study. More research is needed to understand the influence of carbon amendments, inoculum thresholds, and environmental conditions on ASD efficacy., Competing Interests: The author(s) declare no conflict of interest.

Phytophthora nicotianae and P. citrophthora isolates were subjected to mefenoxam and chlorine sensitivity evaluations at different concentrations, and for chlorine, different exposure times. Based on mefenoxam sensitivity, the isolates of the two species were divided in six sensitivity groups with EC50 values ranging from sensitive (0.04 ppm mefenoxam) to highly insensitive (greater than 123.69 ppm mefenoxam), with 86% of isolates being sensitive to mefenoxam. Chlorine sensitivity testing indicated strong interactions between chlorine concentration and exposure time for both species. Increased mortality was observed with increased concentration and exposure time to chlorine. For some isolates, close to 100% mortality was only reached at 6 ppm active chlorine and at an exposure time of 60 min. Because highly mefenoxam-insensitive isolates were detected from South African citrus nurseries, this fungicide should be used with care as a curative method for management of diseases caused by Phytophthora spp. It is recommended that chlorination of irrigation water, at 6 ppm active chlorine and exposure of more than 60 min, is used to eliminate P. nicotianae and P. citrophthora propagules from irrigation water as a preventative measure for these diseases.