Conference Paper


Conference: XII Seminario Nacional de Sanidad Vegetal


RESUMEN El presente trabajo tuvo por finalidad evaluar la resistencia de clones de cacao amazónico al hongo Ceratocystis fimbriata. Se evaluaron 43 clones de la colección Chalmers y 54 clones de Allen, usando la técnica de inoculación de secciones de ramillas de cacao, incluyendo un testigo resistente y uno susceptible. Las ramillas se inocularon con una suspensión conteniendo 3 x 10 4 unidades infectivas/ml, dispuestas dentro de una cámara húmeda construida de madera y forradas de polietileno, al cuarto día se realizó la lectura del desarrollo de micelio y peritecios usando una escala de 0 a 4. Destacaron los clones AMA 10, EBC 122, EBC 138, EBC 142, EBC 148 y LCT-EEN 73, los cuales se comportaron como moderadamente resistentes frente a desarrollo de micelio y, resistentes para formación de peritecios. Los clones AMA 4, AMA 14, AMA 9, CUR 3, LCT-EEN 57 y LCT-EEN 382, resultaron susceptibles para la colonización por el hongo sin embargo, presentaron resistencia a su reproducción. Estos materiales originarios de la región amazónica ecuatoriana, constituyen nuevas fuentes de resistencia al Mal del machete del cacao en Ecuador. ABSTRACT The present research work had the objetive of evaluate the resistance of cocoa amazonic accesions against Ceratocystis fimbriata. Forty three and fifty four clones from Chalmers and Allen collections were evaluated, using the inoculation of section of branches of cocoa technique, including a resistant and a susceptible check. The branches were inoculated using a suspension containing 3 x 10 4 infective units /mL, placed in a wood box covered with polietilene which serve as a humid chamber, at the fourth day the mycelium and perithecium development were scored with a scale ranged from 0 to 4. The clones AMA 10, EBC 122, EBC 138, EBC 142, EBC 148 and LCT-EEN 73, behave as moderately resistant for mycelium formation and resistant for perithecium formation. The clones AMA 4, AMA 14, AMA 9, CUR 3, LCT-EEN 57 and LCT-EEN 382, were susceptible for mycellium development and resistant for perithecium formation. All this ecuadorian amazonic clones constitute new sources of resistance against Ceratocystis wilt of cacao in Ecuador.

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    • "Methods to study the response of cacao to C. cacaofunesta inoculation have been used, allowing a sufficient recognition of resistant genotypes under local conditions (Mata 1991; Delgado 2003). Most of that work employed a classical method developed by Delgado and Echandi (1965) that is based upon application of propagule suspensions on sections of branches and evaluation of perithecial development. "
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    ABSTRACT: Ceratocystis wilt of cacao (caused by Ceratocystis cacaofunesta) is a dangerous disease and results in the death of the plant. This fungus was recently identified in the major cacao-producing regions of Brazil, and was observed to be more aggressive than isolates from other geographical locations. The objective of this study was to develop and test a consistent method to assess cacao genotype response to C. cacaofunesta, based on young plants (seedlings or cuttings). The fungus was inoculated by the deposition of propagule suspensions on cut stems. The parameters to assess disease progress were (a) disease incidence, (b) differences in mortality between the most contrasting cacao genotypes for resistance and susceptibility, (c) disease index, (d) consistency of response over time and (e) relative lesion heights. When seedlings were used for the analyses, the ICS-1 and TSH-1188 genotypes proved to be useful as genetic standards for susceptibility and resistance to C. cacaofunesta, respectively. Inoculum concentrations between 104 and 105 propagules ml−1 and the moment at which the disease incidence stabilized provided appropriate conditions for genotypic comparison. When ten cacao genotypes propagated by cuttings (clones) were assessed, the results confirmed TSH-1188 as the reference genotype for resistance to C. cacaofunesta, while the remaining clones could be grouped as resistant (CEPEC-2008), moderately resistant (CEPEC-2002, CEPEC-2007) and susceptible (CEPEC-2009, CCN-10, CCN-51, HW-25, PH-16, SJ-02). The analytical concepts and results were discussed in terms of their application in breeding programmes aimed at developing genetic resistance to Ceratocystis wilt of cacao.
    Full-text · Article · Nov 2008 · European Journal of Plant Pathology