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Phosphorus (P) is one of the essential macronutrients for plant growth, being a highly required resource to improve the productive performance of several crops, especially in highly weathered soils. However, a large part of the nutrients applied in the form of fertilizers becomes “inert” in the medium term and cannot be assimilated by plants. Rationalizing the use of phosphorus is a matter of extreme importance for environmental sustainability and socioeconomic development. Therefore, alternatives to the management of this nutrient are needed, and the use of P-solubilizing microorganisms is an option to optimize its use by crops, allowing the exploration of less available fractions of the nutrient in soils and reducing the demand for phosphate fertilizers. The objective of this study is to discuss the importance of phosphorus and how microorganisms can intermediate its sustainable use in agriculture. In this review study, we present several studies about the role of microorganisms as phosphorus mobilizers in the soil. We describe the importance of the nutrient for the plants and the main problems related to the unsustainable exploitation of its natural reserves and the use of chemical fertilizers. Mainly we highlight how microorganisms constitute a fundamental resource for the release of the inert portion of the nutrient, where we describe several mechanisms of solubilization and mineralization. We also discussed the benefits that the inoculation of P-solubilizing microorganisms provides to crops as well as practices of using them as bioinoculants. The use of microorganisms as inoculants is a viable resource for the future of sustainable agriculture, mainly because its application can significantly reduce the application of P and, consequently, reduce the exploitation of phosphorus and its reserves. In addition, new research must be conducted for the development of new technologies, prospecting new biological products, and improvement of management practices that allow for higher efficiency in the use of phosphorus in agriculture.

Garlic is a health promoter that has important bioactive compounds. The bioactive extraction is an important step in the analysis of constituents present in plant preparations. The purpose of this study is to optimize the extraction with the best proportion of solvents to obtain total phenolic compounds (TPC) and thiosulfinates (TS) from dried garlic powder, and evaluate the antioxidant activities of the optimized extracts. A statistical mixture simplex axial design was used to evaluate the effect of solvents (water, ethanol, and acetone), as well as mixtures of these solvents, after two ultrasound extraction cycles of 15 min. Results showed that solvent mixtures with a high portion of water and pure water were efficient for TPC and TS recovery through this extraction procedure. According to the regression model computed, the most significant solvent mixtures to obtain high TPC and TS recovery from dried garlic powder are, respectively, the binary mixture with 75% water and 25% acetone and pure water. These optimized extracts presented oxygen radical absorbance capacity. Pure water was better for total antioxidant capacity, and the binary mixture of water–acetone (75:25) was better for DPPH scavenging activity. These optimized extracts can be used for industrial and research applications.

Bacterial inoculation stimulates growth and adaptation in micropropagated plants. This study evaluated the effects of biotization on in vitro seedling production and in vivo adaptation in two potato cultivars, Agatha and Duvira. Nine bacterial strains were tested for hormone production and ACC deaminase activity and then inoculated in vitro and re-inoculated in vivo. Growth, adaptation, and tuber production were assessed. Biotization significantly enhanced seedling growth, survival, and tuber yield. Biotized seedlings had a 1.3-fold higher survival rate than the controls. Azospirillum brasilense Ab-V5 and Rhizobium tropici CIAT 899 promoted at least one growth variable in both cultivars under in vitro and in vivo conditions. A. brasilense Ab-V5 consistently improved plant performance across production stages, with re-inoculated plants showing 1.2–1.3-fold increases in stem and root length and a 1.1-fold gain in total dry biomass. Additionally, inoculated plants produced 1.9 times more tubers than the controls. Biotization effects were strain-dependent, with A. brasilense Ab-V5 improving in vitro seedling quality and enhancing plant performance and survivability in vivo.

The objective of this work was to test the effect of water limitation on Copaifera langsdorffii Desf. cultivated in mining tailings from the dam rupture in Mariana City, Brazil. Plants were grown in the mining tailing and under two conditions: field capacity (FC) and 50% FC for 60 days. The effects of water restriction on growth, gas exchange, water potential, and leaf anatomy of C. langsdorffii were evaluated. The experimental design was completely randomized with two treatments and 15 replicates, and data was submitted to one-way ANOVA to p < 0.05. Mining tailings showed adequate nutrient levels and the presence of Al, Cd, Pb, and Cr as well as very small particles of 1.19 μm in diameter. The reduction in water availability promoted no changes in the shoot fresh weight, however, increased this parameter for the roots. In addition, water limitation increased plant investment in the root system while reduced biomass allocation to shoots. Lower water levels also increased the root length, number of leaves, and leaf area. However, both water potential and content were not changed by reduced water availability. Lower water levels also increased gas exchange parameters and chlorophyll content. In addition, 50% FC increased the stomatal length/width ratio and their size though no effect in stomatal density was found. Thus, Copaifera langsdorffii grows and thrives in mining tailings even under reduced water availability up to 50% FC showing potential for reforestation systems.

PurposeDam failures release tons of mining tailings into the environment, and these kinds of disasters have increased in recent years. For instance, a major failure occurred in Brazil in 2015 at the Fundão dam located in the Mariana city. This event released iron mining tailings for hundreds of kilometers. Because the tailings completely covered the soil in these regions, this study aimed to investigate the effects of reduced water supply in this substrate on the growth, ecophysiological, and anatomical traits of Cenostigma pluviosum, a native species with potential for use in reforestation systems.MethodsMining tailings were collected from areas 4 km away from the dam failure location, and the contents of nutrients and potentially toxic elements as well as diameter of the tailing particles were measured. Cenostigma pluviosum seeds were germinated directly in the tailings and the seedlings were irrigated at conditions of maximum water holding capacity (HC) and 50% of this capacity (50% HC) for 40 days. Growth, gas exchange, water status, and leaf anatomical parameters were evaluated.ResultsMining tailings contained macro and micronutrients for plants, but Pb, Cd, Cr, and Al were also detected. Particle size of the tailings was small at 1.12 µm diameter. Water limitation caused no significant changes in growth parameters. Moreover, 50% HC elicited no effect on photosynthesis, but reduced transpiration and stomatal conductance. The 50% HC treatment increased stomatal density but had no effect on stomatal size. Leaf tissues became thinner in plants under 50% HC.ConclusionMining tailings from Fundão dam failure induced no toxicity in C. pluviosum plants and a reduction in water availability did not cause water stress, thereby favoring reforestation systems. Similar species may perform equally well with tailings from iron mining industry showing equivalent traits.

Effective protocols for in vitro rooting for woody fruit trees are still a challenge for in vitro seedling production, especially when there is a need to insert new cultivars or rootstocks. These protocols are essential to accelerate studies in plant breeding programs and for seedling distribution. This study evaluated the use of 6-Benzylaminopurine (IBA) in in vitro rooting of Pyruscomunnis rootstocks, clones ‘OHxF87’ and Pyrodwarf. Explant exposure times (0, 24, 48, 72, and 96 hours) to 20 mg L-1 IBA were tested for in vitro rooting. The exposure to IBA resulted in rooting rates above 80%, surpassing some results reported in the literature. The 24-hour treatment provided 81,81% survival, leading to an average growth of five roots with 19 mm length, for ‘OHxF87’ rootstock. The same exposure time resulted in the highest survival rate (75%) and the highest mean root number, seven roots per plant with 10 mm length, for ‘PDW’ rootstock. Root formation did not occur in the absence of synthetic auxin. Therefore, it can be concluded that a 24-hour exposure at 20 mg L-1 IBA was sufficient to promote in vitro rooting in ‘OHxF87’ and Pyrodwarf rootstocks’. RESUMO: Protocolos eficazes de enraizamento in vitro de frutíferas lenhosas ainda são um desafio para produção de mudas in vitro, especialmente quando há necessidade de inserção de novas cultivares ou porta-enxerto. Esses protocolos são essenciais para acelerar estudos nos programas de melhoramento genético e também para distribuição posterior das mudas. Nesse sentido, o objetivo deste estudo foi avaliar a utilização da 6-Benzilaminopurina no enraizamento in vitro de porta-enxerto Pirus comunnis, clones ‘OHxF87’ e Pyrodwarf. Para o enraizamento, foi testado o tempo de exposição dos explantes ao AIB. Para tanto, foram utilizados 20 mg L-1 do fitohormônio nas horas 0, 24, 48, 72 e 96 horas. A exposição ao AIB resultou em taxas de enraizamento acima de 80%, superando alguns resultados encontrados na literatura. Para o porta-enxerto ‘OHxF87’, o tratamento de 24 horas proporcionou 81,81% de sobrevivência, promovendo em média cinco raízes com comprimento de 19 mm. O mesmo tratamento para o porta-enxerto ‘PDW’ resultou na maior taxa de sobrevivência (75%), bem como no maior número médio de raízes, sete raízes por planta, com comprimento de 10 mm. Na ausência de auxina sintética, a formação de raízes não ocorreu. Assim sendo, podemos concluir que o tempo de exposição de 24 horas a 20 mg L-1 de IBA foi suficiente para promover o enraizamento de porta-enxertos Pyrus communis de ‘OHxF87’ e ‘PDW’.

Based on the concepts of circular economy and bioeconomy, the reuse of agrifood residues through vermicomposting can help solve serious environmental problems such as soil contamination and degradation, erosion and climate change. In this sense, the objective was to identify, quantify and analyze the physical, chemical, hormonal, amino acid content and microbial biodiversity of three formulations of vermicompost, with and without inoculation of microorganisms from native forest and commercial formulation, aiming at the production of an organic fertilizer rich in microorganisms for use in sustainable production systems. As a result, the vermicompost formulations presented values higher than the minimum requirements stipulated by Brazilian legislation for the registration of class A composite organic fertilizer. There is a significant difference between the vermicomposts, in the parameters related to the content of phosphorus, auxin, tryptophan and organic matter, as well as the relation between humic and fulvic acids. Bacillus sp. and Trichoderma sp. were also influenced by the type of vermicompost formulation. In addition, inoculation with microorganisms from native forest promoted an increase in biodiversity, in which the presence of Actinomyces sp. and Azotobacter chrooccocum contribute to the reduction in the levels of heavy metals in the compost. It is concluded that vermicomposting is a potential tool in the reuse of agri-food residues, with expressive microbial diversity that can influence plant growth, suppression of pathogens, minimize or reduce the effects of biotic and abiotic stresses on plant production, in addition to contributing to maintenance of soil biodiversity, integral fertility and resilience to climate change.

Copper (Cu) plays crucial biochemical and physiological functions in plants. However, at high concentrations, Cu can become extremely toxic, inducing several physiological changes and symptoms of toxicity. The aim was to analyze the anatomical and physiological changes of the bromeliad, Billbergia zebrina, in response to Cu excess under in vitro conditions. B. zebrina plants, previously established in vitro, were transferred to culture media containing 0, 2, 20, or 200 µM Cu. Growth traits and enzyme activity of superoxide dismutase and ascorbate peroxidase were measured over a period of 80 days. To verify the biological activity of roots grown under different Cu concentrations, a biospeckle laser was used at 20 and 80 days. Biomass accumulation, Cu content and anatomical analyses were performed at 80 days. Plants did not show any visible signs of disturbance and all plants survived the experimental treatments. Plants grown with 200 µM Cu showed anatomical changes, such as increased stomatal index and thicker exodermal cell walls of the roots, which may aid in heavy metal tolerance. High biological activity was observed only at 20 days. This biological activity was linked to increased thickness of the cell wall at the exodermis. The Cu content evidenced that the anatomical changes were effective against the transport of excess Cu into the plants. Although Cu exposure affected leaf and root anatomy as well as growth, exposure only induced minimal changes in the antioxidant system. B. zebrina tolerates high amounts of Cu and could potentially be used as a bioindicator species.

Salt stress is one of several major abiotic stresses that affect plant growth and development, and there are many evidences that silicon can ameliorate the injuries caused by high salinity. This study presents the results of an assay concerning: (1) the effect of in vitro NaCl-induced salt stress in cape gooseberry plants and (2) the possible mitigating effect of silicon in saline conditions. For that, nodal segments were inoculated in Murashige and Skoog (MS) medium under salinity (0.5 and 1.0% NaCl) with different silicic acid concentrations (0, 0.5 and 1.0g L-1). Phytotechnical characteristics, photosynthetic pigments content, and leaf anatomy were evaluated after 30 days. Shoot length, root length, number of leaves and buds, fresh and dry weight, pigment content, stomatal density and leaf blade thickness were drastically reduced by increased salt level. The supply of silicon (1.0g L-1) has successfully mitigated the effect of salinity at 0.5% NaCl for chlorophyll, carotenoids, stomatal density and leaf blade thickness. When salt stress was about 1.0%, Si was not effective anymore. In conclusion, we affirmed that, in in vitro conditions, salt stress is harmful for cape gooseberry plants and the addition of silicon showed effective in mitigating the saline effects of some features. RESUMO: O estresse salino é um dos tipos de estresses abióticos mais severos que afetam o crescimento e desenvolvimento vegetal e existem muitas evidências de que o silício possa amenizar os danos causados pela elevada salinidade. Este estudo apresenta os resultados de uma pesquisa que investigou: (1) o efeito do estresse salino in vitro induzido por NaCl em plantas de fisális e (2) o possível efeito mitigador do silício nas condições salinas. Para isso, segmentos nodais foram inoculados em meio de cultura Murashige e Skoog com dois níveis de salinidade (0,5 e 1,0% de NaCl) adicionado de ácido silícico (0; 0,5 e 1,0g L-1). Características fitotécnicas, conteúdo de pigmentos fotossintéticos e anatomia foliar foram avaliados aos 30 dias. O comprimento da parte aérea e da raiz, número de folhas e gemas, massa fresca e seca, conteúdo de pigmentos, densidade estomática e espessura do limbo foliar diminuíram drasticamente devido ao aumento do nível de salinidade. A aplicação de 1,0g L-1 silício atenuou com sucesso os efeitos salinos para as variáveis conteúdo de pigmentos e anatomia foliar quando a salinidade era de 0,5% NaCl. Já quando o nível de NaCl dobrou, o silício não se mostrou efetivo. Concluindo, pode-se afirmar que, em condições in vitro, o estresse salino é prejudicial à fisális e a adição de silício mostra-se efetiva na mitigação dos efeitos salinos em determinadas características.

Growth-promoting bacteria are already used in sustainable agricultural systems in Brazil. The market is dominated by inoculants and biological pesticides, which do not reach the full potential of this tool in the agricultural sector. This study aimed to evaluate four bacterial strains for the presence of growth promotion mechanisms, as well as the reduction of Asian rust severity in soybean plants and its effects on three antioxidant enzymes during pathogenesis. The plants were treated using the bacterial cells and/or their biosurfactants before inoculation of the pathogen (IOP). Severity was measured based on a diagrammatic scale at 14, 18 and 21 days after IOP, and the activities of the enzymes SOD, CAT, and APX were evaluated 21 days after IOP. Treatments containing only bacterial cells were not efficient in reducing the severity, with losses of leaf area reaching 15%, while the addition of biosurfactants led to a result that is similar to the biofungicide, based on Bacillus subtilis (Serenade®). The presence of direct growth promotion mechanisms can be observed in all isolates, as well as the role of bacterial metabolites, especially lipopeptides, in the biological control of diseases and the modulation of the plant’s immune response.