COMPARING INOCULATION METHODS TO EVALUATE THE GROWTH OF Xanthomonas axonopodis pv. manihotis ON CASSAVA PLANTS
Authors: Muñoz Bodnar Alejandra , Cruz Gómez Leidy Mariel , Bernal Adriana , Szurek Boris , López Carrascal Camilo Ernesto 
Published: May 2015

<p class="ecxmsonormal"><em>Xanthomonas axonopodis </em>pv. manihotis (<em>Xam</em>) is the causal agent of cassava bacterial blight (CBB), a major disease for cassava crops in South America and Africa. Until now the development of the disease is measured via AUDPC (Area Under Disease Progress Curve) but no reliable quantitative methods are available probably due to high variability of bacterial growth <em>in planta</em>. To establish an accurate method for bacterial quantification during the course of <em>Xam</em> infection within the host tissues, we analyzed bacterial populations upon stem and leaf-puncturing as well as leaf-clipping of cassava varieties MCOL1522 and SG107-35 challenged with the virulent <em>Xam</em> strain CIO151. Here, we show that the movement of bacteria along the tissues and especially in leaves is stochastic. Moreover, we were able to demonstrate differential growth of virulent <em>Xam</em> strain CIO151 upon stem-puncturing and quantification of bacteria 6 cm. away from the inoculation point of two varieties displaying contrasting levels of susceptibility.</p><p class="ecxmsonormal"><strong>RESUMEN</strong></p><p class="ecxmsonormal"><!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:AllowPNG/> </o:OfficeDocumentSettings> </xml><![endif]--></p><p class="msocomoff" align="left"><!--[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> 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lang="X-NONE">Xanthomonas axonopodis </span></em><span lang="X-NONE">pv. manihotis<em style="mso-bidi-font-style: normal;"> (Xam)</em> es el agente causal del tizón bacteriano de la yuca, una de las principales enfermedades de los cultivos de yuca en América del Sur y África. Hasta ahora, el desarrollo de la enfermedad se mide a través de AUDPC <em style="mso-bidi-font-style: normal;">(Area<span style="mso-spacerun: yes;">  </span>Under Disease Progress curve)</em>, pero no hay disponibles métodos cuantitativos fiables,<span style="mso-spacerun: yes;">  </span>esto debido posiblemente a la alta variabilidad del crecimiento bacteriano en la planta. Para establecer un método exacto para la cuantificación bacteriana durante el curso de la infección <em style="mso-bidi-font-style: normal;">Xam </em>dentro de los tejidos del huésped, se analizaron las poblaciones de bacterias sobre tallo y hojas, así como corte de hojas de las <a style="mso-comment-reference: as_1; mso-comment-date: 20141102T2035;">variedades de yuca</a></span><span lang="X-NONE">MCOL1522 y SG107-35 con la cepa virulenta CIO151 <em style="mso-bidi-font-style: normal;">Xam.</em> <a style="mso-comment-reference: as_2; mso-comment-date: 20141102T2035;">En esta investigación se </a></span><span lang="X-NONE">muestra que el movimiento de las bacterias a lo largo de los tejidos y especialmente en las hojas es estocástico. Por otra parte, hemos podido demostrar el crecimiento diferencial de la cepa virulenta<span style="mso-spacerun: yes;">  </span><em style="mso-bidi-font-style: normal;">Xam</em> CIO151 tras la punción al tallo y la cuantificación de la bacteria a 6 cm de distancia del punto de inoculación de dos variedades que presentan niveles contrastantes de susceptibilidad.</span></p><p class="ecxmsonormal"> </p>