Produtividade e diluição isotópica de 15N em cana-de-açúcar inoculada com bactérias diazotróficas

Abstract

Resumo -O objetivo deste trabalho foi avaliar a produtividade e a diluição do isótopo 15 N de duas variedades de cana-de-açúcar, inoculadas ou não com bactérias diazotróficas. Dois experimentos foram realizados nas regiões Sudeste e Nordeste do Brasil, durante três safras (2007/2008, 2008/2009 e 2009/2010): o primeiro em Argissolo Vermelho eutrófico, de textura argilosa, e o segundo em Planossolo Háplico distrófico, de textura média. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições. As variedades testadas foram a RB867515 e a RB72454, cultivadas com inoculação com bactérias diazotróficas (cinco estirpes combinadas no inoculante para cana-de-açúcar) ou com adubação de 120 kg ha -1 de N, além do controle experimental sem inoculação e sem adubação. Avaliaram-se a produtividade de colmos e a diluição isotópica de 15 N nas folhasbandeira. A variedade RB72454 foi mais responsiva aos tratamentos, nos ciclos de cana-planta e na segunda soca. A abundância natural de 15 N nas folhas-bandeira diminui ao longo dos anos, o que indica aumento da fixação biológica de N na medida em que a disponibilidade de N do solo vem sendo reduzida.Termos para indexação: Saccharum, bactérias endofíticas, fixação biológica de N, inoculante para cana-deaçúcar. Productivity and N isotope dilution of sugarcane inoculated with diazotrophic bacteriaAbstract -The objective of this work was to evaluate the productivity and 15 N isotope dilution of two sugarcane varieties inoculated or not with diazotrophic bacteria. Two experiments were carried out in the Southeast and Northeast regions of Brazil, during three cropping seasons (2007/2008, 2008/2009 e 2009/2010): the first one on a clayey Acrisol, and the second one on a medium-textured Planosol. A randomized complete block design, with four replicates was used. The varieties RB867515 and RB72454 were tested with inoculation of diazotrophic bacteria (five strains combined in the inoculant for sugarcane) or fertilization with 120 kg ha -1 N, besides the control treatment without inoculation and nitrogen fertilization. Stalk yield and 15 N isotope dilution of the flag-leaves were evaluated. The RB72454 variety showed greater response to the treatments during the plant-cane cycle and the second ratoon.15 N natural abundance in the flag-leaves decreases over the years, which suggests the increase of biological N fixation when N availability in soil reduces.Index terms: Saccharum, endophytic bacteria, N biological fixation, inoculant for sugarcane. IntroduçãoA cana-de-açúcar (Saccharum sp.) é uma das espécies mais estudadas quanto à nutrição nitrogenada nos últimos anos. De maneira geral a fertilização nitrogenada apresenta baixa eficiência na cultura, com pequeno aproveitamento do N aplicado, principalmente no ciclo de cana-planta (Vitti el al., 2008; Schultz et al., 2012). Nas socas, as respostas à adubação nitrogenada são mais frequentes; entretanto, as diferenças entre as doses aplicadas e a quantidade de N acumulado pela cultura ainda são expressivas. Atualmente no Brasil, são a...

Changes in metabolic profiling of sugarcane leaves induced by endophytic diazotrophic bacteria and humic acids

“…Mixed inoculum containing Gluconacetobacter diazotrophicus strain PAL5 and Herbaspirillum seropedicae strain HRC54 was used in this experiment, both originally isolated from sugarcane in Brazil and characterized as endophytic diazotrophs ( Cavalcante & Dobereiner, 1988 ; Olivares et al., 1996 ), and being part of the five-species inoculant recommended for sugarcane in Brazil ( Schultz et al., 2016 ). For pre-inoculum preparation, both bacteria species were grown in 5 mL liquid DIGYS medium at 30 °C for 36 h at 140 rpm in rotatory shaker ( Baldani et al., 2014 ).…”

Peer Review #2 of "Changes in metabolic profiling of sugarcane leaves induced by endophytic diazotrophic bacteria and humic acids (v0.2)"

“…The HAs were titrated to a pH of 7.0 with 0.1 mol L -1 KOH then dialyzed against deionized water using a 1 kD cutoff membrane (Thomas Scientific, Swedesboro, NJ) before they were lyophilized. Mixed inoculum containing Gluconacetobacter diazotrophicus strain PAL5 and Herbaspirillum seropedicae strain HRC54 was used in this experiment, both originally isolated from sugarcane in Brazil and characterized as endophytic diazotrophs (Cavalcante and Dobereiner, 1988;Olivares et al, 1996), and being part of the five-species inoculant recommended for sugarcane in Brazil (Schultz et al, 2016). For pre-inoculum preparation, both bacteria species were grown in 5mL liquid DIGYS medium at 30 °C for 36 hours at 140 rpm in rotatory shaker (Baldani et al, 2014).…”

Biotechnological Potential of Endophytic Bacteria to Improve the Micropropagated Seedling of Variety RB92579 Sugarcane (<i>Saccharum officinarum L.</i>)

“…Current evidence indicates that the BNF process performed by diazotrophic bacteria may contribute up to 60% to the sugarcane's N uptake [2], and that it depends on the plant genotype and on its interaction with various associative bacteria genera [44].…”

“…It is one of the highest costs for farmers. Since fertilizer is not subsidized in Brazil, most commercially used genotypes were chosen aiming to obtain a high productivity with low levels of soil N, favoring; even indirectly, the selection of varieties that are capable of covering part of the need for N by the association with diazotrophic bacteria [2].…”