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<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves /> <w:TrackFormatting /> <w:HyphenationZone>21</w:HyphenationZone> <w:PunctuationKerning /> <w:ValidateAgainstSchemas /> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF /> <w:LidThemeOther>ES-CO</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables /> <w:SnapToGridInCell /> <w:WrapTextWithPunct /> <w:UseAsianBreakRules /> <w:DontGrowAutofit /> <w:SplitPgBreakAndParaMark /> <w:DontVertAlignCellWithSp /> <w:DontBreakConstrainedForcedTables /> <w:DontVertAlignInTxbx /> <w:Word11KerningPairs /> <w:CachedColBalance /> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> <m:mathPr> <m:mathFont m:val="Cambria Math" /> <m:brkBin m:val="before" /> <m:brkBinSub m:val=" " /> <m:smallFrac m:val="off" /> <m:dispDef /> <m:lMargin m:val="0" /> <m:rMargin m:val="0" /> <m:defJc m:val="centerGroup" /> <m:wrapIndent m:val="1440" /> <m:intLim m:val="subSup" /> <m:naryLim m:val="undOvr" /> </m:mathPr></w:WordDocument> </xml><![endif]--> <p class="MsoNormal" style="text-align: justify; tab-stops: 35.4pt 70.8pt 106.2pt 141.6pt 177.0pt 212.4pt 247.8pt 283.2pt 318.6pt 354.0pt 389.4pt 424.8pt 460.2pt 495.6pt 531.0pt 566.4pt 601.8pt 637.2pt 672.6pt 708.0pt 743.4pt 778.8pt 814.2pt 849.6pt 885.0pt 920.4pt 955.8pt 991.2pt 1026.6pt 1062.0pt 1097.4pt 1132.8pt 1168.2pt 1203.6pt 1239.0pt 1274.4pt 1309.8pt 1345.2pt 1380.6pt 1416.0pt;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.0pt; font-family: " lang="EN-GB">Título en ingles: Selection and characterization of plant growth promoting rhizobacteria (PGPR’s) associated with cotton crop </span></strong><span style="font-size: 10.0pt; font-family: " lang="EN-GB">(<em style="mso-bidi-font-style: normal;">Gossypium<span style="mso-bidi-font-style: italic;"> hirsutum</span></em>)</span></p> <p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.0pt; font-family: ">Resumen: </span></strong><span style="font-size: 10.0pt; font-family: ">Como parte de las estrategias de una agricultura sostenible, se hace necesario disminuir el uso de fertilizantes nitrogenados de síntesis, mediante la utilización de los biofertilizantes. En particular, los géneros <em style="mso-bidi-font-style: normal;">Azotobacter </em>y <em style="mso-bidi-font-style: normal;">Azospirillum </em>son utilizados como agentes promotores de crecimiento vegetal debido<em style="mso-bidi-font-style: normal;"> </em>a su<em style="mso-bidi-font-style: normal;"> </em>capacidad para fijar nitrógeno atmosférico y producir hormonas de tipo indólico. Por tal razón, en este estudio se aislaron bacterias diazotróficas de los géneros <em>Azotobacter </em>y <em>Azospirillum </em>a partir de la rizósfera de cultivos de algodón en el Espinal (Tolima). Las poblaciones microbianas se caracterizaron fenotípicamente en los medios de cultivo semiespecíficos: Ashby y LG (<em>Azotobacter</em><span style="mso-bidi-font-style: italic;"> sp.)</span> y NFb, LGI y Batata (<em>Azospirillum</em><span style="mso-bidi-font-style: italic;"> sp.</span>). La promoción de crecimiento vegetal se determinó mediante la actividad de la enzima nitrogenasa por medio de la técnica de reducción de acetileno y producción de índoles por el método colorimétrico de Salkowsky. Se obtuvieron 9 aislamientos tentativos de <em style="mso-bidi-font-style: normal;">Azotobacter</em> sp. y 4 de <em style="mso-bidi-font-style: normal;">Azospirillum</em> sp. Se presentaron diferencias significativas en la prueba de reducción de acetileno con las cepas presuntivas de <em style="mso-bidi-font-style: normal;">Azotobacter </em>sp.: NAT 9 (206.43 </span><span style="font-size: 10.0pt; font-family: " lang="ES">nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="ES">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="ES">.h^-1</span><span style="font-size: 10.0pt; font-family: ">), NAT 4, (292.77 </span><span style="font-size: 10.0pt; font-family: " lang="ES">nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="ES">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="ES">.h^-1</span><span style="font-size: 10.0pt; font-family: ">), y NAT 6 (460.60 </span><span style="font-size: 10.0pt; font-family: " lang="ES">nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="ES">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="ES">.h^-1</span><span style="font-size: 10.0pt; font-family: ">) y en la producción de índoles de las cepas </span><span style="font-size: 10.0pt; font-family: " lang="ES">NAT 19 (19.87 </span><span style="font-size: 10.0pt; font-family: ">μg.mL^-1</span><span style="font-size: 10.0pt; font-family: " lang="ES">) y NAT 13 (20.08 </span><span style="font-size: 10.0pt; font-family: ">μg.mL^-1</span><span style="font-size: 10.0pt; font-family: " lang="ES">)<span style="mso-bidi-font-weight: bold;">. Por su eficiencia <em style="mso-bidi-font-style: normal;">in vitro</em> en la promoción de crecimiento vegetal se seleccionaron las cepas NAT9, NAT4, NAT6, NAT19 y NAT13 para ser evaluadas como principio activo en futuros inoculantes para el algodón en esta zona del departamento del Tolima.</span></span><span style="font-size: 10.0pt; font-family: " lang="ES"> </span></p> <p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.0pt; font-family: ">Palabras clave:</span></strong><span style="font-size: 10.0pt; font-family: "> fijación biológica de nitrógeno; producción de índoles; promoción del crecimiento vegetal; <span style="mso-spacerun: yes;"> </span>biofertilizantes.</span></p> <p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.0pt; font-family: " lang="EN-GB">Abstract: </span></strong><span style="font-size: 10.0pt; font-family: " lang="EN-GB">As part of strategies for sustainable agriculture, it is necessary to reduce the use of synthetic nitrogen fertilisers through the use of biofertilisers. In particular, the genera <em style="mso-bidi-font-style: normal;">Azotobacter</em> and <em style="mso-bidi-font-style: normal;">Azospirillum</em> are used as plant growth promoters because of their ability to fix atmospheric nitrogen and indolic type hormones. For this reason, in this study were isolated diazotrophic bacteria of the genera <em style="mso-bidi-font-style: normal;">Azotobacter </em>and<em style="mso-bidi-font-style: normal;"> Azospirillum</em> from the rhizosphere of cotton crops in Espinal (Tolima). The microbial populations were characterized phenotypically </span><span style="font-size: 10.0pt; font-family: " lang="EN-US">in specific semi culture media</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">: Ashby and LG (<em style="mso-bidi-font-style: normal;">Azotobacter</em> sp.) and NFb, LGI and Batata (<em style="mso-bidi-font-style: normal;">Azospirillum </em>sp.). The promotion of plant growth was determined by the enzyme nitrogenase activity through acetylene reduction technique and production of indoles by the salkowsky colorimetric method. 9 isolates were obtained tentative <em style="mso-bidi-font-style: normal;">Azotobacter</em> sp. and 4 of <em style="mso-bidi-font-style: normal;">Azospirillum </em>sp. Significant differences in acetylene reduction test with presumptive strains of <em style="mso-bidi-font-style: normal;">Azotobacter </em>sp.: NAT 9 (206.43 nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="EN-GB">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="EN-GB">.h^-1</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">), NAT, 4, (292.77 nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="EN-GB">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="EN-GB">.h^-1</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">), and NAT 6 (460.60 nmol C₂H₂ mL</span>^{<span style="font-size: 10.0pt; font-family: " lang="EN-GB">-1</span>}<span style="font-size: 10.0pt; font-family: " lang="EN-GB">.h^-1</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">) and indole production strains NAT 19 (19.87 </span><span style="font-size: 10.0pt; font-family: ">μ</span><span style="font-size: 10.0pt; font-family: " lang="EN-US">g.mL^-1</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">) and NAT 13 (20.08 </span><span style="font-size: 10.0pt; font-family: ">μ</span><span style="font-size: 10.0pt; font-family: " lang="EN-US">g.mL^-1</span><span style="font-size: 10.0pt; font-family: " lang="EN-GB">). <em style="mso-bidi-font-style: normal;">In vitro</em> efficiency in promoting plant growth were selected strains NAT9, NAT4, NAT6, NAT19 and NAT13 to be evaluated as active in future inoculants on cotton in this part of the department of Tolima.</span></p> <p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 10.0pt; font-family: " lang="EN-GB">Keywords:</span></strong><span style="font-size: 10.0pt; font-family: " lang="EN-GB"> biological nitrogen fixation; indole production; plant growth-promoting; biofertilisers.</span></p>