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There is an enormous body of the literature, proving that soil amendments enhance plant growth/yield and prevent the impact of pathogens/toxins. To the best of our knowledge, there is no comprehensive assessment focused on the synergistic effects of microorganisms and soil amendments with biochar or compost for upgrading the current fertilizers towards a more sustainable agriculture. The main objective of the present work is to discuss the most current information needed for developing advanced soil amendments using microorganisms along with safe, sustainable and low‐cost waste sourced materials. The first step in designing the biofertilizer is the selection of a microorganism from among a variety of bacterial/fungi strains that have been identified as plant growth promoting (PGP) in the literature. This study classifies the effective types of soil microorganisms with respect to their functionality to facilitate the choice of the best compatible microbial strain(s) in order to satisfy the host environment requirements. The second part is dedicated to various inorganic and organic carriers, such as perlite, peat, fly ash and compost, for delivering of microorganism into the soils. The role of carriers in the survival and the functional contribution of the microbes to soil–plant systems are investigated. Lastly, biochar is evaluated as a promising microbial carrier together with its influence on the soil biota including microorganisms and plants. The superior features of biochar, for example high surface area, porosity, customizable structure, high stability, carbon sequestration and synergy, with other fertilizers are also discussed. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant-associated bacteria play an important role in the enhancement of plant growth and productivity. Gluconacetobacter azotocaptans is an exceptional bacterium considering that till today it has been isolated and reported only from Mexico and Canada. It is a plant growth-promoting bacterium and can be used as biofertilizer for different crops and vegetables. The objective of the current study was to evaluate the inoculation effect of Gluconacetobacter azotocaptans DS1, Pseudomonas putida CQ179, Azosprillium zeae N7, Azosprillium brasilense N8, and Azosprillium canadense DS2, on the growth of vegetables including cucumber, sweet pepper, radish, and tomato. All strains increased the vegetables' growth; however, G. azotocaptans DS1 showed better results as compared to other inoculated and control plants and significantly increased the plant biomass of all vegetables. Therefore, the whole genome sequence of G. azotocaptans DS1 was analyzed to predict genes involved in plant growth promotion, secondary metabolism, antibiotics resistance, and bioremediation of heavy metals. Results of genome analysis revealed that G. azotocaptans DS1 has a circular chromosome with a size of 4.3 Mbp and total 3898 protein-coding sequences. Based on functional analysis, genes for nitrogen fixation, phosphate solubilization, indole acetic acid, phenazine, siderophore production, antibiotic resistance, and bioremediation of heavy metals including copper, zinc, cobalt, and cadmium were identified. Collectively, our findings indicated that G. azotocaptans DS1 can be used as a biofertilizer and biocontrol agent for growth enhancement of different crops and vegetables. [ABSTRACT FROM AUTHOR]

The use of chemical fertilizers strongly promotes productivity in agricultural crops; therefore, large amounts of chemical fertilizers have been used. The use of plant growth-promoting bacteria may be a strategy to reduce the use of chemical fertilizers; however, little is known about the effect of chemical fertilization on the performance of these bacteria through plant–microbe interactions. The present study aimed to verify the performance of Bacillus subtilis, Azospirillum brasilense, B. pumilus, B. amyloliquefaciens, Herbaspirillum seropedicae, Gluconacetobacter diazotrophicus, and the mixtures A. brasilense + B. subtilis, B. pumilus + B. amyloliquefaciens, and H. seropedicae + G. diazotrophicus on parameters such as nitrogen and phosphorus extraction from soil, the concentrations of these nutrients in maize plants, and plant growth in both fertilized and unfertilized soil. The results showed that H. seropedica increased the nitrogen content by 6.6 g kg−1 in leaves and 2.2 g kg−1 in the root when comparing the unfertilized with the fertilized condition. G. diazotrophicus increased the nitrogen content by 3.7 g kg−1 in leaves and 2.4 g kg−1 in the root. B. pumilus increased the phosphorous content by 1.7 g kg−1 in leaves, and B. amyloliquefaciens increased the phosphorous content by 0.61 g kg−1. The present study showed that even though the bacteria presented good performance related to plant growth under fertilized conditions, H. seropedicae, G. diazotrophicus, B. pumilus, and B. amyloliquefaciens could be used in the maize crop with a reduced chemical fertilization dose. [ABSTRACT FROM AUTHOR]

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Background: The erratic alterations in climate being experienced in agriculture, such as extended periods of drought or heavy rainfalls, are bringing increasing concerns about nitrogen (N) management. Even in high-input farming systems, unpredictable weather patterns can cause N deficiencies and result in nutrient losses that contribute to major pollution issues in groundwater, lakes, and even the oceans. Our present understanding of the beneficial interactions between N-deficient-challenged plants and plant-associated bacteria (PAB), mainly of the phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria, is largely based on studies performed at the level of whole-plant fitness and impacts of crop yields via the abilities of bacteria to synthesize indole acetic acid and/or produce the enzyme 1-aminocyclopropane-1-carboxylate deaminase which reduces endogenous ethylene levels. Much less is known about the complex interaction that occur from the PAB’s abilities to produce N ureide (allantoin and allantoate) and how these purine intermediaries function as an N source and prime stress signals for the growth of both partners.Methods: This review examines the noteworthy progress made on understanding the bacterial ureide pathway with the aim to elaborate possible scenarios to unravel the complex nature of PAB-plant interactions at the purine level. Tables with updated information on PAB growth-promoting activities, N metabolism, and abilities to hydrolyze purine intermediates as well as allantoin for colony growth are included.Results: As in plants, the metabolism of ureides in PAB covers the pathways from the deamination of the nucleobase guanine up to its conversion into glyoxylate, NH4+, and/or NH3 to recycle C and N. More important, in PAB, the full set of riboswitch-modulated genes encoding the enzymes involved in the synthesis and catabolism of ureides, as well as purine transporters, is expressed primarily under stressful conditions leading to N deficiency. Thus, PAB might act as a stress-induced source of purines for the plant N metabolism, or could become scavengers of the plant-synthesized purines for colony replication. Consumption of purine intermediaries or ureides by PAB may hinder the symbiotic efficiency of rhizobia-nodulated N2-fixing legumes. The impact of soil xanthine, hypoxanthine, and allantoin pools on the plants or PAB ureide synthesis is also discussed.Conclusions: Given widespread concerns for crop losses due to the drastically changing climate and prevailing agricultural practices, the understanding of the interactive signaling for the purine metabolisms between PAB and plants takes on a major importance, as it may support management decisions necessary to maintain PAB biodiversity and the agricultural services provided by PAB to crops. [ABSTRACT FROM AUTHOR]

Copyright of Cientifica is the property of Fundacao de Apoio a Pesquisa e Extensao and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Pathology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background and aims To assess the impacts of soil microbes and plant genotype on the composition of maize associated bacterial communities. Methods Two genotypes of Brazilian maize were planted indoors on sterile sand, a deep underground subsoil, and a nutrient-rich topsoil from the Amazon jungle (terra preta). DNA was extracted from rhizospheres, phyllospheres, and surface sterilized roots for 16S rDNA fingerprinting and next generation sequencing. Results Neither plant genotype nor soil type appeared to influence bacterial diversity in phyllospheres or endospheres. Rhizospheres showed strikingly similar 16S rDNA ordination of both fingerprinting and sequencing data, with soil type driving grouping patterns and genotype having a significant impact only on sterile sand. Rhizospheres grown in non-sterile soils contained greater bacterial diversity than sterile-sand grown ones, however the dominant OTUs (species of Proteobacteria and Bacteroidetes) were found in all rhizospheres suggesting seeds as a common source of inoculum. Rhizospheres of the commercial hybrid appeared to contain less bacterial diversity than the landrace. Conclusions Maize rhizospheres receive diverse bacteria from soil, are influenced by the genotype or treatment of the seed, and are dominated by species of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. As many dominant 16S rDNA sequences were observed in rhizospheres grown in both sterile and non-sterile substrate, we conclude that the most common bacterial cells in juvenile maize rhizospheres are seed transmitted. [ABSTRACT FROM AUTHOR]

Development of agronomic practices that maximize the use of natural resources to improve soil health and crop productivity is critical for long-term sustainability of agricultural technologies. In Ontario, Canada, the most conventional maize production practice follows a 3-year rotation with soybeans and ploughing of the land before planting and after harvesting. This technology yields 8-10 t ha of maize. We became aware of a long-term no-till strip row farming system developed by an Ontario grower where maize yields are double that of the average for the province. This study set out to identify what factors contribute to such a massive yield increase and the basis for this superior method of maize production. In a 2-year field study, we compared a variety of biotic and abiotic factors associated with yields at this highly productive site with those of two average yielding sites. The no-till strip row farming system grew maize and soybeans in alternate strips rotated yearly and had higher plant populations, better root architecture, higher plant biomass, and 75 % greater (18.35 t ha) grain yield compared to a nearby farm that used conventional production practices. About 21 % of the yield increase resulted from early planting, greater number of seeds planted, and healthier ears/seeds. The remaining 54 % increase was linked to larger ears, which we tentatively attribute to beneficial effects conferred by the microorganisms that develop in this unique agro-ecosystem. The average net return at the no-till site was estimated to be CDN (Canadian) $2000 ha, which was 400 % higher than the net returns of the conventional sites. The study concludes that no-till management where soil remains undisturbed when combined with yearly rotations of an appropriate legume crop, growing crops exactly on the same cropping rows every year, and optimization of plant density creates a sustainable technology for maximizing maize yields. [ABSTRACT FROM AUTHOR]

Background Plant growth promoting rhizobacteria (PGPR) are functionally diverse group of bacteria having immense potential as biofertilizers and biopesticides. Depending upon their function, they may serve as partial replacements for chemical fertilizer or pesticides as an eco-friendly and cost-effective alternatives as compared to their synthetic counterparts. Therefore, isolation, characterization and practical evaluation of PGPRs having the aforementioned multifaceted beneficial characteristics, are essentially required. This study describes the detailed polyphasic characterization of Bacillus sp. strain RMB7 having profound broad spectrum antifungal activity and plant growth promoting potential. Results Based on 16S rRNA gene sequencing, strain RMB7 was identified as Bacillus specie. This strain exhibited the production of 8 mg. L-1 of indole-3-acetic acid (IAA) in tryptophansupplemented medium. It was able to solubilize 50.6 mg. L-1 tri-calcium phosphate, reduced 601ɳmol acetylene h-1/vial and inhibited >70% growth of nine fungal phytopathogens tested in vitro. Under natural pathogen pressure, inoculation with strain RMB7 and RMB7- supernatant conferred resistance by arugula plant against Pythium irregulare with a concurrent growth improvement over non-inoculated plants. The T-RFLP analysis based on 16S rRNA gene showed that inoculation with RMB7 or its supernatant have a major impact on the indigenous rhizosphere bacterial population. Mass spectrometric analysis revealed the production of lipopeptide surfactins as well as iturin A presence in crude extract of RMB7. PCR-amplification further confirmed the presence of genes involved in the biosynthesis of these two bioactive lipopeptide compounds. Conclusions The data show that Bacillus sp. strain RMB7 has multifaceted beneficial characteristics. It may be an ideal plant growth promoting as well as biocontrol agent, for its integrated use in disease and nutrient management strategies. [ABSTRACT FROM AUTHOR]

Background: Endophytes are microbes that live within plants such as maize (corn, Zea mays L.) without causing disease. It is generally assumed that most endophytes originate from soil. If this is true, then as humans collected, domesticated, bred and migrated maize globally from its native Mexico, they moved the species away from its native population of endophyte donors. The migration of maize persists today, as breeders collect wild and exotic seed (as sources of diverse alleles) from sites of high genetic diversity in Mexico for breeding programs on distant soils. When transported to new lands, it is unclear whether maize permits only selective colonization of microbes from the Mexican soils on which it co-evolved, tolerates shifts in soil-derived endophytes, or prevents colonization of soil-based microbes in favour of seed-transmitted microbes. To test these hypotheses, non-sterilized seeds of three types of maize (pre-domesticated-Mexican, ancient-Mexican, modern-temperate) were planted side-by-side on indigenous Mexican soil, Canadian temperate soil or sterilized sand. The impact of these soil swaps on founder bacterial endophyte communities was tested using 16S-rDNA profiling, culturing and microbial trait phenotyping. Results: Multivariate analysis showed that bacterial 16S-rDNA TRFLP profiles from young, surface-sterilized maize plants were more similar when the same host genotype was grown on the different soils than when different maize genotypes were grown on the same soil. There appeared to be two reasons for this result. First, the largest fraction of bacterial 16S-signals from soil-grown plants was shared with parental seeds and/or plants grown on sterilized sand, suggesting significant inheritance of candidate endophytes. The in vitro activities of soil-derived candidate endophytes could be provided by bacteria that were isolated from sterile sand grown plants. Second, many non-inherited 16S-signals from sibling plants grown on geographically-distant soils were shared with one another, suggesting maize can select microbes with similar TRFLP peak sizes from diverse soils. Wild, pre-domesticated maize did not possess more unique 16S-signals when grown on its native Mexican soil than on Canadian soil, pointing against long-term co-evolutionary selection. The modern hybrid did not reject more soil-derived 16S-signals than did ancestral maize, pointing against such rejection as a mechanism that contributes to yield stability across environments. A minor fraction of 16S-signals was uniquely associated with any one soil. Conclusion: Within the limits of TRFLP profiling, the candidate bacterial endophyte populations of pre-domesticated, ancient and modern maize are partially buffered against the effects of geographic migration --- from a Mexican soil associated with ancestral maize, to a Canadian soil associated with modern hybrid agriculture. These results have implications for understanding the effects of domestication, migration, ex situ seed conservation and modern breeding, on the microbiome of one of the world’s most important food crops. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of American Journal of Potato Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Pathology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of American Journal of Potato Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents a study which examines the toxicity of condensed distiller's solubles (CDS) to pathogen-infested soils and disease suppression. It states that the study found that CDS contains moderate levels of organic acids, minor concentrations of isobutyric and propionic acids. Moreover, the study suggests that the organic acids component of CDS enables to suppress the disease in muck and sandy-loam soils.

The efficacy of condensed distiller's solubles (CDS), a co-product of ethanol production from corn, rich in organic matter, and high in carbon to nitrogen ratio, was tested as a pre-plant amendment against Verticillium wilt of eggplant and potato scab in potato soils from commercial fields and against damping-off diseases of radish and cucumber seedlings in a peat-based mix and muck soil. Eggplants grown in a potato soil amended with CDS (1% mass/mass) showed less Verticillium wilt and increased fresh (37-54%) and dry (31-45%) plant biomass compared to the control in the greenhouse. In a potato soil with medium levels of disease, CDS (1 or 2%) increased the percentage of marketable tubers by 116% under greenhouse, 119% under micro-plot and 75% under field conditions. In the growth room, CDS (1, 2, and 4%) amendment to a peat-based mix infested with Rhizoctonia solani 1 week before planting seeds improved the percentage of healthy radish seedlings (22-72% healthy seedlings compared to 2% in the control). Levels of disease suppression increased with the incubation time prior to planting. Disease control effect of CDS was not consistent between different batches of peat-based mix. In a non-suppressive batch of peat-based mix, disease suppression by CDS was enhanced by a bio-control agent, Trichoderma hamatum 382. In muck soil from a commercial field naturally-infested with Pythium spp., CDS (0.25, 0.5, and 1%) provided protection of cucumber seedlings from damping-off immediately after incorporation, but the maximum protection was seen after 1 week with all three rates. The number of total bacteria was enhanced in the CDS-amended muck soil. In the micro-plots, CDS (0.5 and 1%) as an amendment to muck soil 2 weeks before planting improved the percentage of healthy cucumber seedlings and fresh plant weight compared to the control. CDS is not toxic to the pathogens and disease suppression is believed to be due to biological activity stimulated by CDS in the substrate. [ABSTRACT FROM AUTHOR]

• Green fluorescent protein (GFP) labeling of bacteria has been used to study their infection of and localization in plants, but strong autofluorescence from leaves and the relatively weak green fluorescence of GFP-labeled bacteria restrict its broader application to investigations of plant–bacterial interactions. • A stable and broad-host-range plasmid vector (pDSK-GFPuv) that strongly expresses GFPuv protein was constructed not only for in vivo monitoring of bacterial infection, localization, activity, and movement at the cellular level under fluorescence microscopy, but also for monitoring bacterial disease development at the whole-plant level under long-wavelength ultraviolet (UV) light. • The presence of pDSK-GFPuv did not have significant impact on the in vitro or in planta growth and virulence of phytobacteria. A good correlation between bacterial cell number and fluorescence intensity was observed, which allowed us to rapidly estimate the bacterial population in plant leaf tissue. We demonstrated that GFPuv-expressing bacteria can be used to screen plants that are compromised for nonhost disease resistance and Agrobacterium attachment. • The use of GFPuv-labeled bacteria has a wide range of applications in host–bacterial interaction studies and bacterial ecology-related research. [ABSTRACT FROM AUTHOR]

Alcohol production from corn is gaining importance in Ontario, Canada, and elsewhere. A major cost of corn production is the cost of chemical fertilizers and these continue to increase in price. The competitiveness of alcohol with fossil fuels depends on access to low-cost corn that allows growers to earn a sustainable income. In this study we set out to determine if we can identify root-associated microorganisms from Ontario-grown corn that can enhance the nutrient flow to corn roots, directly or indirectly, and help minimize the use of extraneous fertilizer. Bacteria were isolated from corn rhizosphere and screened for their capacity to enhance corn growth. The bacteria were examined for their ability to fix nitrogen, solubilize phosphate, and produce indole acetic acid (IAA) and antifungal substances on potato dextrose agar. Bacterial suspensions were applied to pregerminated seed of four corn varieties (39D82, 39H84, 39M27, and 39T68) planted in sterilized sand and unsterilized cornfield soil. The plants were grown under greenhouse conditions for 30 days. Three isolates were identified as having growth-promoting effect. These bacteria were identified as to species by biochemical tests, fatty acid profiles, and 16S rDNA sequence analysis. Corn rhizosphere isolates, Gluconacetobacter azotocaptans DS1, Pseudomonas putida CQ179, and Azospirillum lipoferum N7, provided significant plant growth promotion expressed as increased root/shoot weight when compared to uninoculated plants, in sand and/or soil. All strains except P. putida CQ179 were capable of nitrogen fixation and IAA production. Azospirillum brasilense, however, produced significantly more IAA than the other isolates. Although several of the strains were also able to solubilize phosphate and produce metabolites inhibitory to various fungal pathogens, these properties are not considered as contributing to growth promotion under the conditions used in this study. These bacteria will undergo field tests for their effect on corn growth. [ABSTRACT FROM AUTHOR]

Copyright of American Journal of Potato Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Reports on results of a mail survey of growers to estimate potato common scab prevalence and economic loss in Canada. Survey feasibility; Overall response rate; Mean prevalence of scab.

Determines the potential for spreading Streptomyces on seed tubers into field soil. Enumeration of populations of pathogens on diseased and healthy tuber surfaces; Use of colony polymerase chain reaction to detect gene of the thaxtomin biosynthetic pathway;Decline in the density of pathogenic populations.

Investigates the suppression of Rhizoctonia and Pythium damping-off of radish and cucumber seedlings by adding fish emulsion to peak mix or soil. Focus on the efficacy of fish emulsion in enhancing plant growth and suppressing seedling damping-off diseases; Results suggesting that fish emulsion may not be toxic to the pathogens but may create a biological climate in peat substrate or soil that is suppressive to the disease.

Copyright of Canadian Journal of Microbiology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study investigated strain-dependent variability in Escherichia coli survival in soil, and strain-dependent responses to variations in some soil conditions. Collections of E. coli were isolated from swine manure slurry, and from manured soil following 6 days of incubation in the laboratory. The bacteria were fingerprinted by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). During the course of the incubation the composition of the E. coli community changed dramatically suggesting that E. coli phylotypes, distinguishable by ERIC-PCR fingerprinting, varied significantly in their ability to survive in soil under these conditions. A representative isolate from one ERIC group which increased in abundance in soil (designated strain C279) and one which decreased (designated strain C278) were chosen for comparison. These strains persisted comparatively when inoculated into loam soil. However, when added into a loam soil or a sandy soil supplemented with 10% (v/v) swine manure slurry, strain C279 increased in abundance 10-fold, whereas strain C278 did not. At 4°C, or in a clay loam soil, manure slurry did not support the growth of strain C279. These results indicate that the community composition of E. coli populations in manured soils can be very dynamic, and that strains able to proliferate in manured soils can have a selective advantage. [Copyright &y& Elsevier]

Forty-three Fusarium oxysporum strains and one Fusarium solani strain were analyzed for genetic diversity. These strains represent a wide range of geographic locations and were collected primarily from tomato (Lycopersicon esculentum) roots. Among all 43 F. oxysporum strains, 21 were not pathogenic to tomato, 20 were pathogenic, including 13 strains of Fusarium oxysporum lycopersici and seven strains of Fusarium oxysporum radicis-lycopersici, and two were other formae speciales of the fungus. Genetic diversity of all 43 strains was assessed by vegetative compatibility group (VCG), sequence analysis of the rDNA internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene, and amplified fragment length polymorphism (AFLP). Most of the F. o. lycopersici strains were assigned to VCG 0030, while most nonpathogenic ones were incompatible with each other. ITS region analysis grouped the strains into four clusters. The nonpathogenic F. oxysporum strains were in two groups, while the pathogenic strains were placed in two different groups. Pathogenic and nonpathogenic strains were also separated into different clusters based on AFLP data, although some nonpathogenic strains grouped with pathogenic strains. The population of pathogenic strains was less diverse than that of the nonpathogenic strains, suggesting that the pathogenic strains were possibly of monophyletic origin. For both pathogenic and nonpathogenic F. oxysporum strains, no relationship was observed between the genetic profiles and geographic origin; this may indicate that pathogens did not originate independently at each locality.Key words: Fusarium oxysporum, VCG, rDNA (ITS) sequence, AFLP.Les auteurs ont analysé la diversité génétique chez 43 souches du Fusarium oxysporum et une souche du Fusarium solani. Ces souches proviennent d'un grand nombre de localités géographiques et ont été récoltées surtout sur des racines de tomate (Lycopersicon esculentum). Sur l'ensemble des 43 souches du F. oxysporum, 21 ne sont pas pathogènes pour la tomate, 20 sont pathogènes, incluant 13 souches du Fusarium oxysporum lycopersici et sept souches de Fusarium oxysporum radicis-lycopersici, alors que deux autres constituent des formae speciales du champignon. La diversité génétique de l'ensemble des 43 souches a été évaluée selon les groupes de compatibilité végétative (VCG), par l'analyse séquentielle de l'ADNr des espaceurs internes transcrits (ITS1 et ITS2) et de l'ARNr du gène 5,8S, ainsi que par l'amplification du polymorphisme de la longueur des fragments (AFLP). La plupart des souches du F. o. lycopersici appartiennent au VCG 0030, alors que la majorité des souches non-pathogènes sont incompatibles les unes avec les autres. L'analyse des régions ITS regroupe les souches en quatre ensembles. Les souches non-pathogènes du F. oxysporum constituent deux groupes, alors que les souches pathogènes se retrouvent dans deux groupes différents. Les souches pathogènes et non-pathogènes se retrouvent également dans des ensembles différents sur la base des données de l' AFLP, bien que certaines souches non-pathogènes se regroupent avec des souches pathogènes. La population des souches pathogènes est moins diversifiée que celle des souches non-pathogènes, ce qui suggère que les souches pathogènes sont possiblement d'origine monophylétique. Pour les souches pathogènes aussi bien que non-pathogènes du F. oxysporum, on ne perçoit pas de relation entre les profiles génétiques et l'origine géographique, ce qui peut indiquer que ces champignons pathogènes n'ont pas d'origine indépendante dans chaque localitéMots clés : Fusarium oxysporum, VCG, séquence de l'ADNr (ITS), AFLP.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Manures and by-products derived from the processing of plants and animals have been used for centuries as sources of fertiliser, but beneficial or detrimental effects on plant diseases were never thoroughly investigated. We found that certain organic amendments controlled a variety of soilborne diseases of potato (including common scab and verticillium wilt), various pests (including plant parasitic nematodes) and weeds at nine field locations in Ontario and Prince Edward Island, Canada. The mechanism of disease control for highnitrogen-containing amendments is the generation of ammonia and / or nitrous acid following degradation of the amendments by microorganisms. The formation of these products to concentrations lethal to pathogens is regulated by the soil pH, organic matter content, nitrification rate, sand content and buffering capacity. Liquid swine manure reduced scab and wilt, but at only three of six locations tested. In acidic soils, swine manure killed Verticillium dahliae within a day after application, but had no effect in neutral or alkaline soils. The toxic components in the manure were identified as volatile fatty acids. Ammonium lignosulfonate reduced scab at all six sites tested. The mechanism of disease control is not yet known. Although many of these amendments reduced pathogen populations, total soil microorganism numbers increased by 10- to 1000-fold after application, indicating that not all organisms were killed. Understanding the mode of action of amendments is essential for the improvement of their effectiveness and assimilation into crop production systems. If costs can be decreased and benefits ensured, organic amendments will have a major role in reducing plant diseases. The discussion on use of these amendments is based on cost/ benefit analysis as well as societal and regulatory considerations. [ABSTRACT FROM AUTHOR]

Bacterial endophytes constitute an essential part of the plant microbiome and are described to promote plant health by different mechanisms. The close interaction with the host leads to important changes in the physiology of the plant. Although beneficial bacteria use the same entrance strategies as bacterial pathogens to colonize and enter the inner plant tissues, the host develops strategies to select and allow the entrance to specific genera of bacteria. In addition, endophytes may modify their own genome to adapt or avoid the defense machinery of the host. The present review gives an overview about bacterial endophytes inhabiting the phytosphere, their diversity, and the interaction with the host. Direct and indirect defenses promoted by the plant–endophyte symbiont exert an important role in controlling plant defenses against different stresses, and here, more specifically, is discussed the role against biotic stress. Defenses that should be considered are the emission of volatiles or antibiotic compounds, but also the induction of basal defenses and boosting plant immunity by priming defenses. The primed defenses may encompass pathogenesis-related protein genes (PR family), antioxidant enzymes, or changes in the secondary metabolism. [ABSTRACT FROM AUTHOR]

Soils with highly uniform textural, physical, and chemical characteristics still give rise to crop stand variability. Seed quality is one of the factors adding to yield variability and has become a concern for corn growers. Hybrid seed producers claim that their seeds provide a uniformity in crop emergence and productivity, but they do not always provide detailed studies to support this claim. Based on growers' concerns, we examined fields planted with three different hybrid varieties and found that 25% to 50% of the stand had relatively weak vigor, where seed variety A showed 15% of seedlings with lower vigor, and varieties B and C had 30% of seedlings with low vigor. These apparent differences in plant vigor prompted us to initiate a cursory investigation to identify how seed size influenced seedling vigor and if the seedling's microbial profile played a role in the early growth stages of three commonly grown corn hybrids in Ontario. Seeds were separated based on size, prior to conducting a growth room study. Different sizes of seeds from the same seed lot showed significant differences in vigor capacity and related biometric components. Significant differences were also found in their nutritional composition and microbial profiles within the different seed sizes and the roots and shoots of seedlings derived from such seeds. The results clearly indicate that seed size greatly impacts the plant growth and its microbiome, resulting in seedlings with different plant vigor, microbiomes, and performance. [ABSTRACT FROM AUTHOR]