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Microorganisms in the soil and rhizosphere can release part of the total phosphorus in the soil through solubilization, mineralization, and an increase of the root absorption surface. The ability of phosphate solubilizing bacteria and mycorrhizal fungi to promote higher yield and profitability in co-inoculated soybean was investigated. For this purpose, field and greenhouse experiments were conducted in the years 2020 and 2021 in Brazil. In the field, the first factor was composed of microorganism application on soybean (simple inoculation with Bradyrhizobium; co-inoculation with Bacillus strains; co-inoculation with arbuscular mycorrhiza), and the second factor consisted of the application or not of phosphate fertilizer (0 and 100 kg ha-1 of P2O5). In the greenhouse, treatments of the first factor were maintained with 50 % of the phosphate fertilization and one treatment added (standard inoculation with 100 % of the fertilization). Plant growth, roots, nodules, leaf nutrition, yield, and profitability were evaluated. In 2020, co-inoculation increased plant height, the number of pods, grains, and profitability index. The co-inoculation with Bacillus strains and arbuscular mycorrhiza promoted yield increase only associated with phosphate fertilization, by 813 and 761 kg ha-1 compared to standard inoculation, respectively. In 2021, there were increases for pods, grains, yield, gross profit, net income, and profitability index. Co-inoculation with Bacillus strains and arbuscular mycorrhiza promoted increased soybean yield and profitability, confirming itself as a sustainable technology for Brazilian soybean fields. Made available in DSpace on 2022-07-04T12:19:39Z (GMT). No. of bitstreams: 1 Increase-in-yield-leaf-nutrient-and-probability-of-soybean.pdf: 1165720 bytes, checksum: 06e1bd942272ae9bab84f5e36fa431de (MD5) Previous issue date: 2022

The objective of this study was to improve rice and maize yields using native Azospirillum-based biofertilizer. To reach this objective, samples of rhizosphere soil, non-rhizosphere soil and roots of maize plants were collected from the particular locations of Samanko and Bamako of the south Mali. Thirty-three different colonies of bacteria were isolated from the different samples. Based on their better growth in nitrogen free semi-solid medium, their morphological, biochemical and plant growth promotion characteristic, ten bacterial isolates were identified as Azospirillum isolates following the Bergey?s Manual of Determinative Bacteriology. Ten isolates were selected: Az1, Az2, Az3, Az4, Az5, Az6, Az7, Az8, Az9 and Az10. Strain Az6 showed great potential on both rice and maize production. Therefore, this strain is suggested for large scale rice and maize fields? application. While the Azospirillum sp. Az5, Az6 and Az10 strains are suggested for large scale application in maize field, which may reduce production cost. Top dressing with 25% of the recommended nitrogen-fertilizer was found to decrease maize grain yield. Made available in DSpace on 2020-07-03T11:11:37Z (GMT). No. of bitstreams: 1 Malian-native.pdf: 796657 bytes, checksum: 54a72c006d3f2334350ccc293b08cdc0 (MD5) Previous issue date: 2020

The mycotoxigenic fungus Fusarium verticillioides is the primary maize pathogen and causes the maize stalk and ear rot diseases with significant economic losses. Furthermore, the excessive use of fungicides to control F. verticillioides constitutes threats to the environment and human health. Thus, sustainable alternatives such as biological control are needed to minimize the hazards associated with the current method. Although much is known about the vulnerability of the maize silks as a gateway for several fungal pathogens invading the developing grains, studies on the chemical properties of silk extracts and their resident microbiota are scarce. This study isolated and characterized bacteria and fungi that colonize the maize stigma to assess new potential biocontrol agents. The samples were collected from maize fields in the Brazilian localities of Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR, and Goiânia-GO. One hundred sixty-seven microorganisms were isolated, 46% endophytic and 54% epiphytic. First, the antagonist activity was evaluated by the agar disc diffusion method performed in triplicate, and 83% of the isolates showed antagonist activity against F. verticillioides. Then, the 42 most efficient isolates were identified based on the partial sequencing of the bacterial 16S rRNA gene and fungi ITS region. The bacteria belong to the genera Bacillus (57.1%), Burkholderia (23.8%), Achromobacter (7.1%), Pseudomonas (2.4%), and Serratia (2.4%), while the fungi are Penicillium (2.4%), Candida (2.4), and Aspergillus (2.4%). The results showed that microorganisms from maize stigma might represent new promising agents for F. verticillioides control. RESUMO - O fungo micotoxigênico Fusarium verticillioides é o principal patógeno do milho e causa doenças do colmo e da podridão da espiga com perdas econômicas significativas. Além disso, o uso excessivo de fungicidas no controle de F. verticillioides constitui uma ameaça ao meio ambiente e à saúde humana. Assim, alternativas sustentáveis, como o controle biológico, são necessárias para minimizar os riscos associados ao método atual. Este estudo isolou e caracterizou bactérias e fungos que colonizam o estigma do milho para avaliar novos agentes de biocontrole em potencial. As amostras foram coletadas em campos de milho nas localidades brasileiras de Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR e Goiânia-GO. Cento e sessenta e sete microrganismos foram isolados, 46% endofíticos e 54% epifíticos. O teste de antagonismo empregando a técnica de disco de difusão em meio sólido, mostrou que 83% dos isolados apresentaram atividade antagonista contra F. verticillioides. Em seguida, 42 isolados mais eficientes foram identificados a partir do sequenciamento parcial do gene 16S rRNA bacteriano e da região ITS de fungos. Os isolados bacterianos pertencem ao gênero Bacillus (57,1%), Burkholderia (23,8%), Achromobacter (7,1%), Pseudomonas (2,4%) e Serratia (2,4%), enquanto os fungos são Penicillium (2,4%), Candida (2.4), e Aspergillus (2,4%). Os resultados mostraram que microrganismos do estigma do milho podem representar novos agentes promissores para o controle de F. verticillioides. Made available in DSpace on 2022-09-16T12:07:36Z (GMT). No. of bitstreams: 1 Microorganisms-from-corn-stigma-with-biocontrol-potential-of-Fusarium-verticillioides.pdf: 973895 bytes, checksum: 32254c4d45d2d89c81ccb982e20bc287 (MD5) Previous issue date: 2022

Organo-mineral fertilizers supplemented with biological additives are an alternative to chemical fertilizers. In this study, thermoresistant microorganisms from composting mass were isolated by two-step procedures. First, samples taken at different time points and temperatures (33 days at 52 ºC, 60 days at 63 ºC, and over 365 days at 26 ºC) were pre-incubated at 80 oC for 30 minutes. Second, the microbial selection by in vitro culture-based methods and heat shock at 60 oC and 100 oC for 2h and 4h. Forty-one isolates were able to grow at 60 °C for 4h; twenty-seven at 100 °C for 2h, and two at 100 °C for 4h. The molecular identification by partial sequencing of the 16S ribosomal gene using universal primers revealed that thirty-five isolates were from eight Bacillus species, one Brevibacillus borstelensis, three Streptomyces thermogriseus, and two fungi (Thermomyces lanuginosus and T. dupontii). Data from amylase, phytase, and cellulase activity assays and the enzymatic index (EI) showed that 38 of 41 thermo-resistant isolates produce at least one enzyme. For amylase activity, the highest EI value was observed in Bacillus licheniformis (isolate 21C2, EI= 4.11), followed by Brevibacillus borstelensis (isolate 6C2, EI= 3.66), Bacillus cereus (isolate 18C2, EI= 3.52), and Bacillus paralicheniformis (isolate 20C2, EI= 3.34). For phytase, the highest EI values were observed for Bacillus cereus (isolate 18C2, EI= 2.30) and Bacillus licheniformis (isolate 3C1, EI= 2.15). Concerning cellulose production, B. altitudinis (isolate 6C1) was the most efficient (EI= 6.40), followed by three Bacillus subtilis (isolates 9C1, 16C2, and 19C2) with EI values of 5.66, 5.84, and 5.88, respectively, and one B. pumilus (isolate 27C2, EI= 5.78). The selected microorganisms are potentially useful as a biological additive in organo-mineral fertilizers and other biotechnological processes. Resumo Os fertilizantes organo-minerais suplementados com aditivos biológicos são uma alternativa aos adubos químicos. Neste estudo, microrganismos termoresistentes foram isolados de compostagem por procedimentos de duas etapas. Inicialmente, as amostras tomadas em diferentes períodos e temperaturas (33 dias a 52 ºC, 60 dias a 63 ºC e mais de 365 dias a 26 ºC) foram pré-incubadas a 80 oC por 30 minutos. Posteriormente, a seleção microbiana foi conduzida por métodos baseados em cultura in vitro e choque térmico a 60 oC e 100 oC por 2h e 4h. Quarenta e um isolados foram capazes de crescer a 60 °C por 4h; vinte e sete a 100 °C por 2h e dois a 100 °C por 4h. A identificação molecular por sequenciamento parcial do gene ribossomal 16S usando primers universais revelou que trinta e cinco isolados eram de oito espécies de Bacillus, um Brevibacillus borstelensis, três Streptomyces thermogriseus e dois fungos (Thermomyces lanuginosus e T. dupontii). Os dados dos ensaios de atividade de amilase, fitase e celulase e o índice enzimático (IE) mostraram que 38 dos 41 isolados termorresistentes produziram pelo menos uma enzima. Para a atividade da amilase, o maior valor de IE foi observado em Bacillus licheniformis (isolado 21C2, IE = 4,11), seguido por Brevibacillus borstelensis (isolado 6C2, IE = 3,66), Bacillus cereus (isolado 18C2, IE = 3,52) e Bacillus paralicheniformis (isolado 20C2, IE = 3,34). Para a fitase, os maiores valores de IE foram observados para B. cereus (isolado 18C2, IE = 2,30) e B. licheniformis (isolado 3C1, IE = 2,15). Em relação à produção de celulose, B. altitudinis (isolado 6C1) foi o mais eficiente (IE = 6,40), seguido por três Bacillus subtilis (isolados 9C1, 16C2 e 19C2) com valores de IE de 5,66, 5,84 e 5,88, respectivamente, e um B. pumilus (isolado 27C2, IE = 5,78). Pode-se inferir que os microrganismos selecionados são potencialmente úteis como aditivos biológicos em fertilizantes organo-minerais e outros processos biotecnológicos.

Rock phosphate (RP) is a natural source of phosphorus for agriculture, with the advantage of lower cost and less impact on the environment when compared to synthetic fertilizers. However, the release of phosphorus (P) from RP occurs slowly, which may limit its short-term availability to crops. Hence, the use of P-solubilizing microorganisms to improve the availability of P from this P source is an interesting approach, as microorganisms often perform other functions that assist plant growth, besides solubilizing P. Here, we describe the characterization of 101 bacterial isolates obtained from the rhizosphere and endosphere of maize plants for their P solubilizing activity in vitro, their growth-promoting activity on millet plants cultivated in soil amended with RP, and their gene content especially associated with phosphate solubilization. For the in vitro solubilization assays, two mineral P sources were used: rock phosphate from Araxá (Brazil) mine (AP) and iron phosphate (Fe-P). The amounts of P released from Fe?P in the solubilization assays were lower than those released from AP, and the endophytic bacteria outperformed the rhizospheric ones in the solubilization of both P sources. Six selected strains were evaluated for their ability to promote the growth of millet in soil fertilized with a commercial rock phosphate (cRP). Two of them, namely Bacillus megaterium UFMG50 and Ochrobactrum pseudogrignonense CNPMS2088, performed better than the others in the cRP assays, improving at least six physiological traits of millet or P content in the soil. Genomic analysis of these bacteria revealed the presence of genes related to P uptake and metabolism, and to organic acid synthesis. Using this approach, we identified six potential candidates as bioinoculants, which are promising for use under field conditions, as they have both the genetic potential and the experimentally demonstrated in vivo ability to improve rock phosphate solubilization and promote plant growth. Made available in DSpace on 2021-01-28T09:04:32Z (GMT). No. of bitstreams: 1 Genomic-phenotypic.pdf: 1672978 bytes, checksum: bc132d3d2c1f99aa667e9190c3823856 (MD5) Previous issue date: 2021

Sorghum bicolor adapts to phosphorus (P) deficient soils through mechanisms that contribute to its absorption and solubilization, including the association with microorganisms. The direct application of rock phosphate (RP) and the inoculation with phosphate solubilizing bacteria (PSB) is a sustainable alternative for P supply to the crops. The aim of this study was to evaluate the effect of PSB inoculation of two sorghum genotypes with different P responses (BR007 - efficient and responsive and SC283 - efficient and non-responsive), cultivated in soil fertilized with RP and triple superphosphate (TSP), in greenhouse and field experiments. The sorghum genotypes were inoculated separately with the Bacillus strains that are efficient in P solubilization, B116 and B70, and cultivated under different P fertilization sources (TSP, RP, ½TSP + ½RP). The results suggest that the inoculation response was dependent on sorghum genotype, P source and microbial strain. Inoculation of the genotype BR007 significantly increased root biomass and grain P content under greenhouse conditions, as well as yield and grain P content in field experiments, but no effect was observed on genotype SC283. The use of PSB as bioinoculants, in combination with RP, is a promising alternative to reduce the use of synthetic fertilizers, contributing to the sustainable sorghum production. Made available in DSpace on 2021-01-28T09:04:44Z (GMT). No. of bitstreams: 1 Sorghum-genotypes-response-to-inoculation-with-phosphate-solubilizing-bacteria-2020.pdf: 629206 bytes, checksum: 3b0cfee46107f874253d109f052878ff (MD5) Previous issue date: 2020 Título em português: Resposta de genótipos de sorgo à inoculação com bactérias solubilizadoras de fosfato.

The use of bioinoculants with plant growth-promoting bacteria (PGPB) is a sustainable agricultural practice that has been expanding worldwide. Thus, it is fundamental to characterize these bacteria molecularly to provide better security and traceability for bioinoculants production. This work aimed to identify, characterize and develop specific molecular markers for Bacillus strains related to plant-growing promotion. Five strains were identified as B. pumillus (B32), B. thuringiensis (B116), B. megaterium (B119) and B. subtilis (B2082 and B2084), using 16S rRNA gene sequencing, MALDI-TOF mass spectrometry and/or protein crystal detection. Repetitive element palindromic (Rep-PCR) and amplified ribosomal DNA restriction analysis (ARDRA) techniques allowed the discrimination of the strains, except B2082 and B2084 that presented identical genetic profiles, indicating that they are the same or genetically close isolates. Moreover, specific molecular markers were developed for B116 and B119 strains and may be used for microbial inoculants quality control, strains traceability and to detail PGPB colonization. Made available in DSpace on 2020-11-27T09:01:12Z (GMT). No. of bitstreams: 1 Polyphasic.pdf: 1274871 bytes, checksum: ae5ae13c67072f75d900c27735c04fb9 (MD5) Previous issue date: 2020

Cratylia argentea is a leguminous shrub native to the cerrado, which has great potential for forage production and recovery of degraded areas. This study aimed to isolate, characterize, and select efficient rhizobial strains in symbiosis with Cratylia argentea . Rhizobacteria were isolated from the nodules of 12-month-old plants and cultivated in pots containing cerrado soil. Twenty-five bacterial strains were obtained, which displayed extensive variability with respect to morphological and symbiotic characteristics. Cratylia argentea seeds were planted in pots containing 5kg of cerrado soil and maintained in the greenhouse. The treatments consisted of 25 rhizobial isolates, two controls (without nitrogen and without inoculation), with or without nitrogen fertilization (5mgN·plant-1·week-1), and four replications. Plants were cultivated for 150 days after planting seeds to evaluate nodule number, nodule dry weight, shoot and root dry weight, shoot and root N content, and relative and symbiotic efficiency. Thirteen isolates improved shoot dry weight (up to 65.8%) and shoot nitrogen concentration (up to 76%) compared with those of control treatments. Two isolates, 4 (CR42) and 22 (CR52), conferred higher symbiotic efficiency values of approximately 20%. Therefore, these two rhizobial isolates displayed the highest potential as beneficial inoculants to optimize the symbiotic efficiency for Cratylia and to increase the incorporation of nutrients and biomass into the productive system in the cerrado. RESUMO: Cratylia argentea é uma leguminosa arbustiva nativa do cerrado, com alto potencial para produção de forragem e recuperação de áreas degradadas. Este trabalho teve como objetivo isolar, caracterizar e selecionar estirpes de rizóbios eficientes na simbiose com C. argentea. As bactérias foram isoladas de nódulos de plantas com 12 meses de idade, cultivadas em solo de cerrado, em vasos. Foram obtidas 25 estirpes, que apresentaram alta variabilidade em relação às características morfológicas e simbióticas. Sementes de C. argentea foram plantadas em potes contendo 5kg de solo de cerrado, e mantidos em casa de vegetação. Os tratamentos consistiram em 25 isolados, controle (sem N e sem inoculação) e adubação nitrogenada (5mgN·planta-1·semana-1), em quatro repetições. As plantas foram colhidas 150 dias após o plantio para avaliar o número e a massa seca de nódulos, a massa seca e concentração de nitrogênio da parte área e das raízes. Foram calculadas as eficiências relativas e simbióticas. Treze estirpes se destacaram quanto ao acúmulo de massa seca (até 65,8%) e acúmulo de nitrogênio (até 76%), da parte aérea, em relação ao tratamento controle. Dentre estas, as estirpes 4 e 22 apresentaram maiores eficiências simbióticas (em torno de 20%). Portanto, estas estirpes apresentaram potencial para formulação de inoculantes, visando otimizar o processo simbiótico rizóbio-Cratylia e a incorporação de biomassa e nutrientes em sistema produtivos no cerrado.

This work presents indicators to assess the conservation status of forest patches in fragmented landscapes. However, how can we evaluate the conservation status of forest patches in order to compare it to a hypothetical situation of well-preserved vegetation without human disturbance? It is possible to measure some ecological processes, like nutrient cycling, canopy, edaphic, topographic and hydrological parameters, as well as landscape attributes, and associate them to conservation status. When the attributes of original well-preserved forest are unknown because they are seldom found, it is possible to compare patches by assessing the variability of their attributes. To this end, parameters related to canopy, soil, topography and landscape were analyzed to establish indicators and their integrated analysis was developed to assess the conservation status of forest patches and identify possible causes of shortcomings or obstacles to reach the conservation status. The study area is located in a Semidecidual Forest region, in Brazil. The methodology was developed considering plots distributed in sites within forest patches. The results allowed the identification of patches in different conditions of conservation and provided information of the factors that contribute to this status, in order to help guide and select the most appropriate measures to mitigate degradation and identify forest conservation strategies. Made available in DSpace on 2017-06-06T23:54:06Z (GMT). No. of bitstreams: 1 Forestpatch.pdf: 826756 bytes, checksum: e4a77c0b6066714b3c7373d7dbef4ef2 (MD5) Previous issue date: 2016-08-02

tBacterial endophytes are considered to have a beneficial effect on host plants, improv-ing their growth by different mechanisms. The objective of this study was to investigatethe capacity of four endophytic Bacillus strains to solubilize iron phosphate (Fe-P), pro-duce siderophores and indole-acetic acid (IAA) in vitro, and to evaluate their plant growthpromotion ability in greenhouse conditions by inoculation into pearl millet cultivated ina P-deficient soils without P fertilization, with Araxá rock phosphate or soluble triplesuperphosphate. All strains solubilized Fe-P and three of them produced carboxylate-typesiderophores and high levels of IAA in the presence of tryptophan. Positive effect of inocu-lation of some of these strains on shoot and root dry weight and the N P K content of plantscultivated in soil with no P fertilization might result from the synergistic combination ofmultiple plant growth promoting (PGP) traits. Specifically, while B1923 enhanced shoot androot dry weight and root N P content of plants cultivated with no P added, B2084 and B2088strains showed positive performance on biomass production and accumulation of N P K inthe shoot, indicating that they have higher potential to be microbial biofertilizer candidatesfor commercial applications in the absence of fertilization. Made available in DSpace on 2018-11-25T23:29:47Z (GMT). No. of bitstreams: 1 Endophyticbacillus.pdf: 467964 bytes, checksum: d0e676d68b857dee9c86841a979c4f72 (MD5) Previous issue date: 2018-11-21

Marginal soil fertility, soil acidity, aluminum toxicity, and a generalized low level of available nutrients, especially phosphorus (P), are major limiting factors to maize production in highly weathered oxisols that are prominent in the tropics. Plants have evolved several strategies to improve P acquisition, including the ability to associate with soil microorganisms that potentially enhance P uptake and plant nutrition. We investigated the effect of two maize genotypes with contrasting P use efficiency and their hybrid, grown in soils with two P levels, on bacterial and fungal community structures in the root and the rhizosphere. We found that a significant fraction of bacterial and fungal diversity could be attributed to the host genotype, but in general, the soil P level was the major driver of microbiome structure followed by plant compartment (rhizosphere versus directly root associated). Slow-growing bacterial taxa increased in the low P soil, whereas fast-growing taxa were enriched in high P soil. The low P soil had a positive effect on arbuscular mycorrhizal fungi abundance, as expected, particularly inside the root. On the other hand, our results did not support selection for microbes associated to plant growth promoting and P solubilization based on P availability. Taken together, our results expand knowledge of which microbial groups are favored in P-deficient oxisol and suggest that P fertilization significantly impacts the species composition and diversity indices of bacteria and fungi communities, both inside the roots and in the rhizosphere. Made available in DSpace on 2018-11-15T00:26:52Z (GMT). No. of bitstreams: 1 Rootassociated.pdf: 1316925 bytes, checksum: b9f7c63b9767b7ed56973f61d7f4b8b8 (MD5) Previous issue date: 2018-11-14

Secondary metabolites produced by Actinobacteria of tropical soils represent a largely understudied source of novel molecules with relevant application in medicine, pharmaceutical and food industries, agriculture, and environmental bioremediation. The present study aimed to characterize sixty-nine Actinobacteria isolated from compost and tropical soils using morphological, biochemical, and molecular methods. All the isolates showed high variation for morphological traits considering the color of pigments of the aerial and vegetative mycelium and spore chain morphology. The enzymatic activity of amylase, cellulase, and lipase was highly variable. The amylase activity was detected in 53 (76.81%) isolates. Eighteen (Streptomyces curacoi) and ACSL 6 (S. hygroscopicus) showed the highest EI values (6.44 and 6.42, respectively). The cellulase activity varied significantly (P ≤ 0.05) among the isolates. Twenty-nine isolates (42.02%) showed high cellulase activity, and the isolates ACJ 48 (S. chiangmaiensis) and ACJ 53 (S. cyslabdanicus) showed the highest EI values (6.56 for both isolates). The lipase activity varied statistically (P ≤ 0.05) with fourteen isolates (20.29%) considered good lipase producers (EI > 2.0). The isolate ACSL 6 (S. hygroscopicus) showed the highest EI value of 2.60. Molecular analysis of partial 16S rRNA gene sequencing revealed the existence of 49 species, being 38 species with only one representative member and 11 species represented by one or more strains. All species belonged to three genera, namely Streptomyces (82.61%), Amycolatopsis (7.25%), and Kitasatospora (10.14%). The present results showed the high biotechnological potential of different Actinobacteria from tropical soils. Made available in DSpace on 2017-09-23T00:13:50Z (GMT). No. of bitstreams: 1 Characterizationphylogenetic.pdf: 1195818 bytes, checksum: 92ea31e443977aea67547fa87103d811 (MD5) Previous issue date: 2017-09-21

In the present study, we demonstrated the in vitro activity of endophytic phosphate-solubilizing bacteria (PSB). Fifty-five endophytic PSB that were isolated from sap, leaves, and roots of maize were tested for their ability to solubilize tricalcium phosphate and produce organic acid. Partial sequencing of the 16S rRNA-encoding gene showed that the isolates were from the genus Bacillus and different species of Enterobacteriaceae. The phosphate solubilization index on solid medium and phosphate solubilization in liquid medium varied significantly among the isolates. There was a statistically significant difference (P ≤ 0.05) for both, the values of phosphate-solubilizing activity and pH of the growth medium, among the isolates. Pearson correlation was statistically significant (P ≤ 0.05) between P-solubilization and pH (R = -0.38), and between the gluconic acid production and the lowering of the pH of the liquid medium at 6 (R = 0.28) and 9 days (R = 0.39). Gluconic acid production was prevalent in all the PSB studied, and Bacillus species were most efficient in solubilizing phosphate. This is the first report on the characterization of bacterial endophytes from maize and their use as potential biofertilizers. In addition, this may provide an alternative strategy for improving the phosphorus acquisition efficiency of crop plants in tropical soils.

Phosphate fertilization is a common practice in agriculture worldwide, and several commercial products are widely used. Triple superphosphate (TSP) is an excellent soluble phosphorus (P) source. However, its high cost of production makes the longterm use of crude rock phosphate (RP) a more attractive alternative in developing countries, albeit its influence on plant-associated microbiota remains unclear. Here, we compared long-term effects of TSP and RP fertilization on the structure of maize rhizosphere microbial community using next generation sequencing. Proteobacteria were dominant in all conditions, whereas Oxalobacteraceae (mainly Massilia and Herbaspirillum) was enriched in the RP-amended soil. Klebsiella was the second most abundant taxon in the RP-treated soil. Burkholderia sp. and Bacillus sp. were enriched in the RP-amended soil when compared to the TSP-treated soil. Regarding fungi, Glomeromycota showed highest abundance in RP-amended soils, and the main genera were Scutellospora and Racocetra. These taxa are already described as important for P solubilization/acquisition in RP-fertilized soil. Maize grown on TSP and RP-treated soil presented similar productivity, and a positive correlation was detected for P content and the microbial community of the soils. The results suggest changes of the microbial community composition associated to the type of phosphate fertilization. Whilst it is not possible to establish causality relations, our data highlights a few candidate taxa that could be involved in RP solubilization and plant growth promotion. Moreover, this can represent a shorter path for further studies aiming the isolation and validation of the taxa described here concerning P release on the soil plant system and their use as bioinoculants. Made available in DSpace on 2017-10-04T10:32:20Z (GMT). No. of bitstreams: 1 Longterm.pdf: 2180247 bytes, checksum: 542626c4a904bb640d2448275b260ac1 (MD5) Previous issue date: 2017-10-03 Article 1266.

The Brazilian acreage planted with genetically modified (GM) maize expressing Cry genes derived from the soil bacterium Bacillus thuringiensis (Bt) has increased from 4.9% (5.0 million hectares) of total area planted in 2009 to 81.4 % (15.83 million hectares) in 2014. However, studies on the effects of Bt-maize technology on non-target microorganisms in tropical soils are incipient. Thus, a field experiment was performed to assess the physiological activity of bacterial communities associated with Bt-maize genotypes planted in tropical Dark Red Latosol of Cerrado and lowland hydromorphic soil with localized flooding. A non-transgenic hybrid (30F35) and its transgenic counterparts 30F35Y (Cry1Ab) and 30F35H (Cry1F) were planted in a randomized block design with four replicates. Rhizosphere and non-rhizosphere soils collected from plants in the flowering stage were assayed for metabolic diversity with Biolog and enzyme activities of urease, arginase, acid phosphatase and alkaline phosphatase. Rhizosphere soil showed higher microbial activity and no significant differences were detected among genotypes in all the biochemical soil parameters evaluated. The results suggested that Bt-maize does not negatively impact the microbial community of tropical soils. Keywords: Bt-maize, functional diversity, bio-indicators, soil quality, non-target organisms. ATIVIDADE MICROBIANA EM SOLOS CULTIVADOS COM MILHO TRANSGENICO EXPRESSANDO OS GENES Bacillus thuringiensis CRY1AB E CRY1F RESUMO - A area brasileira plantada com milho geneticamente modificado (GM) expressando genes Cry derivados da bacteria do solo Bacillus thuringiensis (Bt) aumentou de 4,9% (5,0 milhoes de hectares) da area total plantada em 2009 para 81,4% (15,83 milhoes de hectares) em 2014. No entanto, estudos sobre os efeitos da tecnologia Bt-milho sobre microrganismos nao alvo em solos tropicais sao incipientes. Dessa forma, foi realizado experimento de campo para avaliar a atividade fisiologica das comunidades bacterianas associadas com genotipos de milho Bt plantados em Latossolo Vermelho Escuro do Cerrado e solos hidromorficos da planicie com inundacoes localizadas. Um hibrido nao transgenico (30F35) e seus homologos transgenicos 30F35Y (Cry1Ab) e 30F35H (Cry1F) foram plantados com delineamento de blocos casualizados com quatro repeticoes. Solos rizosfericos e nao rizosfericos coletados de plantas no estadio de florescimento foram submetidos aos ensaios de diversidade metabolica com Biolog e atividades enzimaticas de urease, arginase, fosfatase acida e fosfatase alcalina. Solos rizosfericos apresentaram maior atividade microbiana e nao foram detectadas diferencas significativas entre os genotipos em todos os parâmetros bioquimicos e de solo avaliados. Os resultados sugerem que o milho Bt nao afeta negativamente a comunidade microbiana dos solos tropicais. Palavras-chave: milho Bt, diversidade funcional, bioindicadores, qualidade do solo, organismos nao alvo.

The selection of microorganisms capable of solubilizing phosphorus (P) from rock phosphates (RP) may contribute to reduce the dependence of imported fertilizers in grain crops, reducing the costs of agricultural production, and also the environmental impacts. This study tested 59 microorganisms (46 bacteria and 13 fungi) isolated from maize rhizosphere for solubilization of two RP, Araxá and Itafós phosphate in vitro (PA and PI, respectively). Among the 59 microorganisms solubilizing PA, 51% of the bacteria and 8% of fungi were classified as efficient. For PI, among 18 isolates, 50% of the bacteria and no fungi were efficient. There were significant differences in the availability of P among strains for both phosphates and most isolates evaluated for both types of rocks released more soluble P from PI than PA. Bacterial isolates CMSB58, CMSB32, CMSB20 and CMSB46 solubilized almost 20% of the P total in the PA and CMSB58, CMSB82, CMSB91 and CMSB48 solubilized more than 25% of the PI. The solubilizing activity of both phosphates was associated with a reduction of pH which suggests that the acidification of the culture medium can be one of the mechanisms involved in the solubilization of P. There was a dominance of the genera Burkholderia and Bacillus in the group of the most efficient bacteria and Talaromyces and Penicillium in the fungi group. The contribution of these strains to increasing the phosphorus nutrition of grain crops should be investigated further by in vivo experiments. RESUMO - A seleção de microrganismos capazes de solubilizarem fósforo (P) a partir de fosfatos de rocha (FR) pode contribuir para reduzir a dependência de fertilizantes importados em culturas de grãos, reduzindo os custos da produção agrícola e também os impactos ambientais. Este estudo avaliou 59 microrganismos (46 bactérias e 13 fungos), isolados da rizosfera de milho, quanto à solubilização de dois FR, Araxá e Itafós in vitro (FA e FI, respectivamente). Entre os 59 microrganismos solubilizadores de PA, 51% das bactérias e 8% dos fungos foram classificados como eficientes. Para FI, entre 18 isolados, 50% das bactérias e nenhum fungo foram eficientes. Houve diferença significativa na disponibilidade de P entre as cepas em ambos os fosfatos e a maioria dos isolados avaliados em ambos os tipos de rocha liberaram mais P solúvel de FI em comparação com FA. As bactérias CMSB58, CMSB32, CMSB20 e CMSB46 solubilizaram quase 20% do P total em FA e CMSB58, CMSB82, CMSB91 e CMSB48 solubilizaram mais que 25% de FI. A atividade de solubilização para ambos os fosfatos foi associada com a redução de pH, sugerindo que a acidificação do meio de cultura pode ser um dos mecanismos envolvidos na solubilização de P. Houve predominância dos gêneros Burkholderia e Bacillus no grupo de bactérias mais eficientes e Talaromyces e Penicillium no grupo dos fungos. A contribuição destes isolados na melhoria da nutrição de P em milho precisa ser investigada futuramente em experimentos in vivo.