Lachenaud Philippe.
2005. Genetic effects of inter-tree competition in mixed cocoa stands on yield, vigour and cropping efficiency.
In : Proceedings of the International workshop on cocoa breeding for improved production systems, 19th-21th October 2003, Accra, Ghana. Bekele Frances L. (ed.), End Michelle (ed.), Eskes Albertus (ed.). INGENIC, CRIG
Résumé : A method developed to assess family competition effects (partner effects) in variety trials was applied to the cocoa tree. The study was conducted in a hybrid trial, involving twelve families of 50 trees each planted in a totally randomised single-tree plot design, at a density of 1,667 trees ha-1. The trial was thinned 10 years after planting, at a rate of two out of four rows. Competition was studied with reference to juvenile and adult vegetative vigour, to periodic and cumulative yields (number of pods, potential total pod weight and average weight of one pod), and the yield x vigour ratio or "cropping efficiency" (total pod weight divided by the trunk cross-section). At the end of the trial, after thirteen years of monitoring, competition effects were revealed which explained 8 to 10% of the residual variance after removal of the hybrid and micro-environmental effects. The competition effects, which were detectable by 18 months after planting for vigour, occurred earlier than generally acknowledged. Competition effects for yield increased with age of the plantation and decreased drastically after thinning at 10 years. Under the trial conditions, the families could be classified as "aggressive", "stimulating" or "passive" in relation to their neighbours. Vegetative vigour (trunk cross-sectional area) explained up to 34% of the competition effects affecting vegetative development- total pod production and total pod weight over the period concerned. The partner effects on the production variables could never be explained by any of the production variables themselves, hence it should be possible to select non-aggressive high-yielding families. No significant partner effect was observed for average pod weight. The improvement of the cropping efficiency, and more generally management of vegetative vigour, can follow genetic and plant husbandry pathways and these are considered in the Discussion. The genetic pathway entails the selection of hybrid or clonal material with low vigour and/or the search for dwarfing rootstocks. The plant husbandry pathway involves developing designs and techniques (such as thinning, pruning, etc...), which might decrease the competition effects between trees in a given plot situation.
Mots-clés Agrovoc : Theobroma cacao, hybride, performance de culture, compétition végétale
Classification Agris : F30 - Génétique et amélioration des plantes
Auteurs et affiliations
- Lachenaud Philippe, CIRAD-CP-CACAO (FRA)
Autres liens de la publication
Source : Cirad - Agritrop (https://agritrop.cirad.fr/527686/)
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