A combination of humic substances and Herbaspirillum seropedicae inoculation enhances the growth of maize (Zea mays L.) |
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Authors: | Luciano Pasqualoto Canellas Dariellys Martínez Balmori Leonardo Oliveira Médici Natália Oliveira Aguiar Eliemar Campostrini Raul C C Rosa Arnoldo R Façanha Fábio Lopes Olivares |
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Institution: | 1. Núcleo de Desenvolvimento de Insumos Biológicos para a Agricultura (NUDIBA), Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, 28013-602, Rio de Janeiro, Brazil 2. Departamento de Ciências Fisiológicas, Universidade Federal Rural do Rio de Janeiro, km7 BR 467, Seropédica, Rio de Janeiro, Brazil 3. Laboratório de Melhoramento Genético Vegetal, Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, 28013-602, Rio de Janeiro, Brazil 4. Embrapa Mandioca e Fruticultura, Rua Embrapa, s/no., CEP 44380-000, Cruz das Almas, BA, Brasil
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Abstract: | Background Endophytic diazotrophic bacteria colonize several non-leguminous plants and promote plant growth. Different mechanisms are involved in bacteria-induced plant growth promotion, including biological nitrogen fixation (BNF), mineral solubilization, production of phytohormones, and pathogen biocontrol. Herbaspirillum seropedicae is a broad-host-range endophyte that colonizes sugarcane, rice, wheat, sorghum, and maize, and has been used as a biofertilizer. Contrasting results between greenhouse and field experiments have prompted efforts to improve the consistency of the plant response to microbial stimulation. Aims The aim of this study was to evaluate the effect of the presence of humic substances on inoculation of maize (Zea mays L.) with H. seropedicae. Methods Two experiments were conducted: one in the greenhouse using sand and nutrient solution and the other a field trial in soil with low natural fertility and to which was applied N in the form of urea (50 kg ha?1). In the greenhouse, pre-emerging seeds were inoculated with a solution of H. seropedicae (109 cells mL?1) in the presence of humic substances isolated from vermicompost (10, 20, or 30 mg C?L?1); in the field trial, bacteria combined with humate were added as a foliar spray (450 L?ha?1). Results At early stages (7 and 45 days old) in the greenhouse, the treatment activated plant metabolism including enhancement of plasma membrane H+-ATPase activity, alteration of sugar and N metabolism, and greater net photosynthesis. The number of viable bacterial cells was higher in root tissues when inoculation was in the presence of soluble humic substances. Foliar application of endophytic diazotrophic bacteria and humic substances increased maize grain production 65 % under field conditions. These results show a promising use of humic substances to improve the benefit of endophytic diazotrophic inoculation. |
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