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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]

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]

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]

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 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.)

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.)

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]