Isolamento, caracterização e identificação de rizobactérias com habilidades para promover o crescimento de plantas
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2020-12-16
Autores
Santos, Roberta Mendes dos
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Universidade Estadual Paulista (Unesp)
Resumo
As rizobactérias promotoras de crescimento de plantas têm o potencial para melhorar a produtividade das culturas. Os principais mecanismos pelos quais essas bactérias podem estimular o crescimento das plantas incluem, a produção de fitormônios, disponibilização de nutrientes e produção de compostos orgânicos voláteis e antimicrobianos, tais como antibióticos, enzimas líticas e sideróforos. Vários isolados bacterianos são relatados com o potencial de estimular o crescimento em diferentes culturas e sob diversos sistemas de produção agrícola e vêm sendo utilizados como inoculantes na agricultura, com a finalidade de melhorar a produtividade das culturas. Neste contexto, o presente estudo teve o objetivo isolar, caracterizar e identificar bactérias provenientes da rizosfera de cana-de-açúcar e analisar seu potencial de crescimento em plantas de cana-de-açúcar e milho. O isolamento das rizobactérias foi realizado a partir de solo rizosférico de seis diferentes variedades de cana-de-açúcar, coletado nas cidades de Jaboticabal – SP, Pirajuba – MG e Frutal – MG. A seleção das cepas bacterianas ocorreu a partir da realização de testes in vitro qualitativos e quantitativos de fixação biológica de nitrogênio, produção de ácido indolacético, atividade celulolítica e solubilização de fosfatos e potássio. Os isolados selecionados foram identificados a partir da extração e amplificação do rDNA 16S. Enquanto que, o potencial de promoção de crescimento e colonização de sete isolados foi avaliado a partir de testes em casa de vegetação com cana-de-açúcar e milho. Foi avaliado altura, massa seca, teores de fósforo e nitrogênio nas plantas e contagem de unidades formadoras de colônias nas plantas e no solo. Foram isoladas 167 cepas bacterianas que apresentaram habilidades de promoção de crescimento, destas, sete cepas foram selecionadas e identificadas pertencendo aos gêneros, Staphylococcus, Enterobacter, Bacillus e Achromobacter. Cinco isolados conseguiram proporcionar o crescimento em cana-de-açúcar, Enterobacter sp. IP11, Enterobacter sp. IP14, Bacillus anthracis IP17, B. thuringiensis IP21, Achromobacter spanius IP23. Na cultura do milho, somente Enterobacter sp. IP14, B. anthracis IP17 e B. thuringiensis IP21 promoveram o crescimento. A maioria das cepas bacterianas isoladas da rizosfera de cana-de-açúcar tiveram uma preferência pela mesma cultura. Entretanto, é possível e foi verificado com esse estudo, que rizobactérias isoladas de cana-de-açúcar podem também ser capazes de promover o crescimento e o desenvolvimento vegetal do milho.
Plant growth-promoting rhizobacteria have the potential to improve crop productivity. The main mechanisms by which these bacteria can stimulate plant growth include the production of phytohormones, availability of nutrients, and production of volatile organic compounds and antimicrobials, such as antibiotics, lytic enzymes, and siderophores. Several bacterial isolates are reported with the potential to stimulate growth in different crops and under different agricultural production systems and have been used as inoculants in agriculture, with the purpose of improving crop productivity. In this context, the present study aimed to isolate, characterize, and identify bacteria from the sugarcane rhizosphere and to analyze their growth potential in sugarcane and maize plants. The rhizobacteria isolation was carried out from rhizospheric soil of six different sugarcane varieties, collected in the cities of Jaboticabal - SP, Pirajuba - MG, and Frutal - MG. The selection of bacterial strains occurred through the performance of qualitative and quantitative in vitro tests for biological nitrogen fixation, indoleacetic acid production, cellulolytic activity, and phosphate and potassium solubilization. The selected isolates were identified from the extraction and amplification of the 16S rDNA. The potential for promoting growth and colonization of seven isolates was evaluated using greenhouse tests with sugarcane and maize. Height, dry mass, phosphorus, and nitrogen levels in plants, and counting of colony-forming units in plants and soil were evaluated. 167 bacterial strains that showed growth promotion abilities were isolated, of these, seven strains were selected and identified belonging to the genera, Staphylococcus, Enterobacter, Bacillus, and Achromobacter. Five isolates were able to provide growth in sugarcane, Enterobacter sp. IP11, Enterobacter sp. IP14, Bacillus anthracis IP17, B. thuringiensis IP21, Achromobacter spanius IP23. In maize, only Enterobacter sp. IP14, B. anthracis IP17, and B. thuringiensis IP21 promoted growth. Most bacterial strains isolated from the sugarcane rhizosphere preferred the same culture. However, it is possible and it has been verified with this study, that rhizobacteria isolated from sugarcane may also be able to promote the growth and plant development of maize.
Plant growth-promoting rhizobacteria have the potential to improve crop productivity. The main mechanisms by which these bacteria can stimulate plant growth include the production of phytohormones, availability of nutrients, and production of volatile organic compounds and antimicrobials, such as antibiotics, lytic enzymes, and siderophores. Several bacterial isolates are reported with the potential to stimulate growth in different crops and under different agricultural production systems and have been used as inoculants in agriculture, with the purpose of improving crop productivity. In this context, the present study aimed to isolate, characterize, and identify bacteria from the sugarcane rhizosphere and to analyze their growth potential in sugarcane and maize plants. The rhizobacteria isolation was carried out from rhizospheric soil of six different sugarcane varieties, collected in the cities of Jaboticabal - SP, Pirajuba - MG, and Frutal - MG. The selection of bacterial strains occurred through the performance of qualitative and quantitative in vitro tests for biological nitrogen fixation, indoleacetic acid production, cellulolytic activity, and phosphate and potassium solubilization. The selected isolates were identified from the extraction and amplification of the 16S rDNA. The potential for promoting growth and colonization of seven isolates was evaluated using greenhouse tests with sugarcane and maize. Height, dry mass, phosphorus, and nitrogen levels in plants, and counting of colony-forming units in plants and soil were evaluated. 167 bacterial strains that showed growth promotion abilities were isolated, of these, seven strains were selected and identified belonging to the genera, Staphylococcus, Enterobacter, Bacillus, and Achromobacter. Five isolates were able to provide growth in sugarcane, Enterobacter sp. IP11, Enterobacter sp. IP14, Bacillus anthracis IP17, B. thuringiensis IP21, Achromobacter spanius IP23. In maize, only Enterobacter sp. IP14, B. anthracis IP17, and B. thuringiensis IP21 promoted growth. Most bacterial strains isolated from the sugarcane rhizosphere preferred the same culture. However, it is possible and it has been verified with this study, that rhizobacteria isolated from sugarcane may also be able to promote the growth and plant development of maize.
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Palavras-chave
Inoculantes, Promoção do crescimento de plantas, Rizosfera, Saccharum spp., Sustentabilidade, Zea mays, Inoculants, Plant-growth promotion, Rhizosphere, Sustainability, Sugarcane, Maize