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Comparisons of agronomic and resistance traits for the international clone trial

Eskes A.. 2011. In : Eskes Albertus (ed.). Collaborative and participatory approaches to cocoa variety improvement : final report of the CFC/ICCO/Biodiversity international project on "Cocoa productivity and quality improvement: a participatory approach" (2004-2010). Amsterdam : CFC, p. 124-127. (CFC Technical paper, 59).

The stability of agronomic and resistance traits for the International Clone Trial over eight countries was compared through linear regression analyses. The number of clones compared varied over the sites from 8 to 18. For average yield, the majority of the coefficients of correlation were positive and significant, showing reasonable stability of this trait over sites. For plant vigour measured by stem girth, the coefficients of correlation were generally positive but rarely significant, indicating interaction between sites and clones. Incidence of witches' broom (WB) disease was compared for four sites (Brazil, Ecuador, Trinidad and Venezuela). Correlations for the total number of brooms, for the number of vegetative brooms and for the number of cushion brooms per tree were positive but not always significant, suggesting some interaction between clones and sites for resistance to WB. In Ecuador, the total number of brooms per tree was significantly correlated with the average weight of the brooms. The numbers of cushion brooms and vegetative brooms were significantly correlated for three out of four sites. For vascular streak dieback (VSD) severity, the coefficient of correlation between two sites in Papua New Guinea was significant, but the correlations between these sites and Malaysia were not significant. The consequences of these findings for breeding are discussed. (Résumé d'auteur)

Mots-clés : theobroma cacao; amélioration des plantes; stabilité génétique; caractère agronomique; résistance aux maladies; vigueur; rendement des cultures; qualité; clone; oncobasidium theobromae; moniliophthora; essai de variété; trinité-et-tobago; Équateur; venezuela (république bolivarienne du); brésil; papouasie-nouvelle-guinée; côte d'ivoire; ghana; malaisie; moniliophthora perniciosa

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