Responses of soil microbial biomass and enzyme activity to herbicides imazethapyr and flumioxazin

The use of herbicides is important for controlling weeds in crops. However, they can present impacts on soil properties, such as biological properties. In this study, we evaluated the responses of soil microbial biomass and enzymes activity to the application of the herbicides imazethapyr and flumioxazin and their mixture in an experiment under laboratory conditions, using soils with a different history of use. Soil microbial biomass C (MBC) decreased, while microbial biomass N (MBN) was not affected after the application of the herbicides as compared to the control. Soil respiration, respiratory quotient, and dehydrogenase (DHA) activity increased significantly after the application of the herbicides compared to the control. The hydrolysis of fluorescein diacetate (FDA) was not significantly different between the control and the herbicide treatments. The principal response curve showed the largest initial effects for the flumioxazin, followed by imazethapyr and their mixture. Flumioxazin had a different influence on soil respiration and respiratory quotient than imazethapyr and their mixture. Finally, the effects of herbicides on soil microbial biomass and enzymes are short-term as we observed recovery in the biological parameters over time.</p

Diversity of plant growth-promoting bacteria associated with sugarcane

The sugarcane (Saccharum spp) presents economic importance, mainly for tropical regions, being an important Brazilian commodity. However, this crop is strongly dependent on fertilizers, mainly nitrogen (N). This study assessed the plant growth-promoting bacteria (PGPB) associated with sugarcane that could be used as a potential inoculant to the crop. We evaluated the genetic diversity of PGPB in the plant tissue of sugarcane varieties (RB 867515, RB 1011, and RB 92579). The primer BOX-A1R was used to differentiate the similar isolated and further sequencing 16S rRNA ribosomal gene. The 16S rRNA gene showed the presence of seven different genera distributed into four groups, the genus Bacillus, followed by Paenibacillus (20%), Burkholderia (14%), Herbaspirillum (6%), Pseudomonas (6%), Methylobacterium (6%), and Brevibacillus (3%). The molecular characterization of endophytic isolates from sugarcane revealed a diversity of bacteria colonizing this plant, with a possible biotechnological potential to be used as inoculant and biofertilizers

Current knowledge and future prospects of lima bean (Phaseolus lunatus)-rhizobia symbiosis

Lima bean (Phaseolus lunatus) is an important species of the genus Phaseolus for human consumption in tropical regions. The seeds are important source of protein for people from South America, Africa and Mexico. In addition, as a legume plant, lima bean presents the ability to perform the biological nitrogen fixation (BNF) through the symbiosis with nitrogen-fixing bacteria. The studies about diversity and efficiency of lima bean-rhizobia symbiosis have increased worldwide, mainly in Latin America. These studies have shown Bradyrhizobium and Rhizobium as the main symbionts, although Sinorhizobium, Mesorhizobium and Allorhizobium have been found associated with lima bean. Also, there is a large variation in the efficiency of N fixation by the current isolates of rhizobia and some rhizobia have presented high capability for fixing N. This review aims to explore the studies about diversity and efficiency of rhizobia in symbiosis with lima bean.Lima bean (Phaseolus lunatus) is an important species of the genus Phaseolus for human consumption in tropical regions. The seeds are important source of protein for people from South America, Africa and Mexico. In addition, as a legume plant, lima bean presents the ability to perform the biological nitrogen fixation (BNF) through the symbiosis with nitrogen-fixing bacteria. The studies about diversity and efficiency of lima bean-rhizobia symbiosis have increased worldwide, mainly in Latin America. These studies have shown Bradyrhizobium and Rhizobium as the main symbionts, although Sinorhizobium, Mesorhizobium and Allorhizobium have been found associated with lima bean. Also, there is a large variation in the efficiency of N fixation by the current isolates of rhizobia and some rhizobia have presented high capability for fixing N. This review aims to explore the studies about diversity and efficiency of rhizobia in symbiosis with lima bean

Isolation and Characterization of Plant Growth-Promotion Diazotrophic Endophytic Bacteria Associated to Sugarcane (Saccharum officinarum L.) Grown in Paraíba, Brazil

Sugarcane is an important Brazilian commodity, being usually cultivated in soils with low natural fertility. This study aimed to isolate diazotrophic endophytes from sugarcane tissues and evaluate the morphological and physiological characteristics of their colonies as well as their plant growth-promoting (PGP) traits in select diazotrophic endophytic bacteria. Fifty-six bacterial isolates were identified in the sugarcane tissues, and these isolates presented distinct morphological and physiological traits. A total of thirty-five bacterial isolates were biochemically evaluated. Overall, Bacillus was the dominant genus. Isolates of Methylobacterium spp. and Brevibacillus agri were present only in leaves, while Herbaspirillum seropedicae occurred only in stems. Except to IPA-CF45A, all isolates were nitrogenase positive. All endophytes exhibit production of indol 3-acetic acid. Over 50% of endophytes solubilize phosphate, release N-acyl homoserine lactones, and present the activity of 1-aminocyclopropane-1-carboxylic acid deaminase, catalase, lipase and protease. The network analysis showed that isolates belonged to Burkholderia, Herbaspirillum, and Methylobacterium interact with Bacillus. Bacterial endophytes exhibited distinct morphological, physiological, and PGP traits that are useful for sustainable agriculture, highlighting the isolates IPA-CC33, IPA-CF65, IPA-CC9 and IPA-CF27. Further studies on the effects of these diazotrophic endophytes and their potential for providing microbial inoculants for improving sugarcane fields will provide valuable information to maintain the sustainability and environment quality.National Council for Scientific and Technological Development 426655/2018-

Bacteria diazotrophic endophytic in sugar cane : strategy for sustainable agriculture

Alguns estados brasileiros, especialmente da região Nordeste, têm sua economia baseada na cultura da cana-de-açúcar, que depende do êxito dessa atividade para o consequente desempenho de sua economia. Nesse contexto, é prioritário realizar trabalhos de prospecção de bactérias diazotróficas e de pesquisas que avaliem a potencialidade da fixação biológica do nitrogênio (FBN) na cana-de-açúcar, sob condição regional, aplicando tecnologias que permitam a produção sustentável desta cultura. Com isso, objetivou-se isolar e efetuar caracterizações morfofisiológica, bioquímica e molecular de bactérias diazotróficas endofíticas de colmos e folhas de três cultivares de cana-de-açúcar (RB1011, RB92579 e RB867515), assim como avaliar a resposta da cana-de-açúcar quanto ao potencial de FBN, a eficiência da inoculação destas bactérias quanto à produtividade de colmos e qualidades tecnológicas de cana-de-açúcar nos ciclos da cana-planta, cana-soca e cana-ressoca como suporte a uma produção sustentável da cultura. Foram obtidos 56 isolados endofíticos, sendo 62,5% do colmo e 37,5% da folha. Utilizou-se a técnica molecular de BOX-PCR que permitiu diferenciar os isolados em 34 perfis de bandas, pela formação de cinco agrupamentos distintos, que foram selecionadas para os testes bioquímicos e/ou fisiológicos. Desses isolados, 66 % apresentaram capacidade de solubilizar fosfato inorgânico; 26 % de produzirem urease, 34 % de produzirem proteases; 17 % de produzirem amilase; 68 % de produzirem lipase; 14 % de produzirem quitinase; 17 % de produzirem sideróforo; 71 % de produzirem ACC deaminase; 54 % de produzirem N-acil-homoserina lactona (AHL); 51 % de produzirem catalase e 23 % apresentaram capacidade hidrolitica de degradarem a gelatina; 97 % reduziram acetileno (ARA) com valores entre 4,14 e 7,84 nmol C2H4/hora. Para o sequenciamento do gene 16S rRNA ribosomal, foi verificado a presença de sete diferentes gêneros, 46% de identidade com o gênero Bacillus , 20% com Paenibacillus, 14% com Burkholderia, 6 % com Herbaspirillum, Pseudomonas e Methylobacterium e 3% com Brevibacillus. A caracterização bioquímica e molecular dos isolados endofíticos de colmo e folha de cana-de-açúcar revelou uma diversidade de bactérias colonizando esta planta, com potencial biotecnológico para serem usadas como biofertilizantes. Foram selecionados três isolados pela atividade da nitrogenase e em conjunto com as respostas dos testes bioquímicos para compor o inoculante microbiano que foi avaliado em campo durante três anos compreendendo os ciclos da cana planta, soca e ressoca na variedade de cana-de-açúcar RB 92579. Utilizou-se o delineamento experimental em blocos casualizados, em esquema fatorial 10x3, constituído de dez tratamentos (IPA-CC9 (Herbaspirillum seropedicae), IPACC33(Pseudomonas sp.), IPA-CF65 (Bacillus Megaterium), IPA-CC9 + IPA-CC33, IPACC9 + IPA-CF65, IPA-CC33 + IPA-CF65, IPA-CC9 + IPA-CC33 + IPA-CF65, Mistura Embrapa (BR1140 (Azospirillum amazonense), BR11175 (H. seropedicae), BR11192 (H. rubrisubalbicans), BR11284 (Gluconacetobacter diazotrophicus) e BR11364 (Burkholderia tropica), testemunha nitrogenada (TN) e testemunha absoluta ( TA)), três ciclos de cultivo (cana-planta, cana-soca e cana-ressoca) com quatro repetições, totalizando 40 parcelas por cultivo. Foram avaliados os seguintes parâmetros: altura de plantas, diâmetro do colmo, massa seca da parte aérea, nitrogênio total das folhas +3, produtividade do colmo fresco, rendimento de açúcar por hectare (TPH), teor de sólidos solúveis totais (°Brix), fibra, açúcar total recuperável (ATR) e estimativa da contribuição da FBN na nutrição da cana-de-açúcar pela técnica de abundância natural do isótopo 15N. A inoculação promoveu ganhos significativos em comparação a TA para o diâmetro do colmo e ATR, para o cultivo canaressoca. A contribuição da FBN nos tratamentos inoculados foi de até 57,31%. Constatou-se incrementos na produtividade do colmo fresco de até 14 Mg.ha-1 em comparação a TN, porém não diferenciando estatisticamente dos outros tratamentos. O comportamento semelhante dos tratamentos inoculados com a TN que recebeu 60 kg.ha‑1 de N, infere em baixo custo econômico e ecológico, e ganha importância pela necessidade para o desenvolvimento de práticas agrícolas mais sustentáveis para melhorar a qualidade de vida da população.Some Brazilian states, especially the Northeast, has its economy based on the cultivation of sugarcane, which depends on the success of this activity for the subsequent performance of its economy. In this context, priority is performing prospecting work diazotrophs and research to evaluate the potential of biological nitrogen fixation (BNF) in sugarcane under regional condition, applying technologies that enable the sustainable production of this crop. With that aimed to isolate and make characterizations morphophysiological, biochemistry and molecular endophytic bacteria stems and leaves of three varieties of sugarcane (RB1011, RB92579 and RB867515) and to evaluate the response of the cane sugar and the potential of BNF, the efficiency of inoculation of these bacteria as the productivity of stalks and technological qualities of sugarcane in the cycles of plant cane, cane ratoon and cane ressoca as support for sustainable crop production. 56 isolates were endophytic, being 62.5% and 37.5% of the stem of the leaf. We used molecular BOX-PCR technique that allows to differentiate into isolated sections 34 bands, for the formation of five distinct clusters that were selected for biochemical and / or physiological tests. These isolates, 66% were able to solubilize inorganic phosphate; 26% to produce urease, proteases produce 34%; 17% amylase to produce; 68% to produce lipase; 14% to produce chitinase; 17% of producing siderophore; 71% of produce ACC deaminase; 54% to produce N-acyl homoserine lactone (AHL); 51% to produce catalase and 23% showed hydrolytic ability to degrade gelatin; 97% reduced acetylene (ARA) with values between 4.14 and 7.84 nmol C2H4 / hour. To sequence the 16S rRNA ribosomal the presence of seven different genres, 46% identity was observed with the genus Bacillus, 20% to Paenibacillus, 14% Burkholderia, 6% Herbaspirillum, Pseudomonas and Methylobacterium and 3% Brevibacillus . Biochemical and molecular characterization of endophytic isolates stem and leaf of sugarcane revealed a diversity of bacteria colonizing this plant, with biotechnological potential to be used as biofertilizers. Three isolated by the nitrogenase activity and together with the responses of biochemical tests were selected to compose the microbial inoculant that was tested in the field for three years comprising the cycles of sugar cane plant, soca and ressoca the variety of sugarcane RB 92579 . We used the experimental randomized block design in a factorial 10x3, consisting of ten treatments (IPACC9 (Herbaspirillum seropedicae), IPA-CC33 (Pseudomonas sp.), IPA-CF65 (Bacillus Megaterium), IPA-CC9 + IPA-CC33, IPA-CC9 + IPA-CF65, IPA-CC33 + IPA-CF65, IPACC9 + IPA-CC33 + IPA-CF65, mix Embrapa (BR1140 (Azospirillum amazonense) BR11175 (H. seropedicae) BR11192 ( H. rubrisubalbicans) BR11284 (Gluconacetobacter diazotrophicus) and BR11364 (Burkholderia tropica), nitrogen witness (TN) and absolute control (TA)), three crop cycles (plant cane, cane and ratoon cane ressoca) with four replications totaling 40 plots for cultivation were evaluated the following parameters:.plant height, stem diameter, shoot dry weight, total nitrogen leaves +3, fresh stalk yield, sugar yield per hectare (TPH) content solids (° Brix) soluble fiber, total recoverable sugar (ATR) and estimation of the contribution of BNF nutrition of sugarcane by the technique of natural abundance of 15N isotope. Inoculation promoted significant gains compared to TA for the inoculated treatments was up to 57.31%. It found increases in productivity fresh stalk of up to 14 Mg ha-1 compared to TN, but not statistically differing from the other treatments. The similar behavior of the treatments inoculated with TN who received 60 kg ha-1 N, infers in low economic and environmental cost, and gains importance by the need to develop more sustainable agricultural practices to improve the quality of life of the population.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESConselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNP

CARACTERIZAÇÃO DE RIZOBIOS NODULADORES DE FEIJÃO-FAVA EM SOLOS DE TRÊS ESTADOS DO NORDESTE BRASILEIRO

The aim of this study was to characterize lima bean nodulating rhizobial from soils of northeastern Brazil. Soil samples were collected in regions with production of lima bean in the Ceara, Piaui and Maranhao states. The experiment was conducted in pots containing soil from each region, sowed with lima bean. Nodules were sampled for isolation and characterization at 35 days after plant emergence. A total of 75 isolates were found and submitted to morphological and physiological characterization. Morphologically, the majority of isolates exhibited circular and convex colonies with entire border and smooth surface. Physiologically, all isolated presented fast growth, and the majority of isolates presented acid reaction, moderate ability to produce mucus with gummy consistency and colonies with cream coloration. The isolates found in this study presented similar characteristics to genera Rhizobium, Sinorhizobium,Allorhizobium eMesorhizobium.O objetivo deste estudo foi caracterizar isolados de rizóbios noduladores de feijão-fava oriundos de solos dos estados do Ceará, Piauí e Maranhão. Amostras de solos foram coletadas de áreas produtoras de feijão-fava nos estados do Ceará, Piauí e Maranhao. O experimento foi realizado em vasos, contendo solo de cada local, semeados com feijão-fava.&nbsp; A coleta dos nódulos para isolamento e caracterização foi realizada aos 35 dias após a emergência das plantas. O total de 75 isolados foram obtidos e submetidos a caracterização morfológica e fisiológica. Morfologicamente, a maioria dos isolados exibiram colônias circulares, convexas, com bordas inteiras e de superfície lisa. Fisiologicamente, todos os isolados apresentaram crescimento rápido e a maioria apresentou reação ácida, habilidade moderada de produzir muco com consistência gomosa e colônias com coloração creme. Os isolados encontrados nestes solos apresentaram características morfológicas e fisiológicas similares àquelas encontradas nos gêneros Rhizobium, Sinorhizobium, AllorhizobiumeMesorhizobium

Bacillus subtilis improves maize tolerance to salinity

ABSTRACT: The aim of this study was to evaluate the biochemical responses of maize, under saline stress, inoculated with Bacillus subtilis. Four levels of salinity were assessed: 0mM, 50mM, 100mM, and 200mM of sodium chloride (NaCl). Saline conditions influenced negatively maize growth. However, the inoculation of B. subtilis improved the plant growth at highest level of NaCl. Chlorophyll content decreased while proline increased in inoculated plants submitted to highest salt levels. Also, B. subtilis increased the relative water content in leaves. B. subtilis improves the plant growth under salinity and ameliorates the biochemical damages in maize

Eficiência simbiótica de isolados de rizóbio noduladores de feijão-fava (Phaseolus lunatus L.)

Em leguminosas tropicais, a cuidadosa seleção de estirpes de rizóbio, entre outros fatores, é fundamental para a eficiência da fixação biológica de N2 (FBN). Essa seleção deve ser feita para as leguminosas de interesse social e econômico, entre elas o feijão-fava (Phaseolus lunatus L.). O objetivo deste trabalho foi avaliar a eficiência simbiótica de rizóbios nativos de duas regiões do Piauí produtoras de feijão-fava. Foram avaliados 17 isolados e duas estirpes de referência (CIAT 899 e NGR 234), em casa de vegetação, utilizando-se vasos de Leonard autoclavados, no delineamento experimental inteiramente ao acaso, com três repetições. O genótipo de feijão-fava utilizado foi o UFPI-468. A inoculação foi feita por ocasião do plantio. A coleta foi realizada aos 34 dias após o plantio, sendo avaliadas as seguintes características: matéria seca da parte aérea (MSPA), da raiz (MSR) e dos nódulos (MSN); relação MSPA/MSR; N acumulado (Nac) na MSPA e a eficiência da fixação de N2. Foi observada diferença significativa entre os isolados em todas as características, exceto em MSR. Em geral, os isolados ISO-18, ISO-23, ISO-24, ISO-25, ISO-30, ISO-32, ISO-35, ISO-36, ISO-43 e ISO-45 apresentaram os melhores índices de MSPA, MSR, MSPA/MSR, Nac e eficiência da fixação de N2, em relação aos isolados ISO-2, ISO-9, ISO-16, ISO-40 e testemunha absoluta. As características avaliadas foram suficientes para discriminar e selecionar isolados eficientes na nodulação em feijão-fava, contribuindo para a efetividade da FBN. Os melhores isolados apresentaram bom desempenho no fornecimento de N às plantas, podendo ser recomendados para testes de eficiência agronômica