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Latex clonal typology of Hevea brasiliensis : Physiological modelling of yield potential and clonal response to ethephon stimulation

Gohet E., Chantuma P., Lacote R., Obouayeba S., Dian K., Clément-Demange A., Dadang Kurnia, Eschbach J.M.. 2003. In : IRRDB Workshop on Exploitation Technology, 15 -18 December 2003, Kottayam, India. s.l. : s.n., 14 p.. IRRDB Workshop on Exploitation Technology, 2003-12-15/2003-12-18, Kottayam (Inde).

Multi-clonal tapping experiments set up in Côte d'Ivoire and in Thailand have confirmed that clonal yield potential of Hevea brasiliensis (Pmax) can be accurately estimated, when using reduced tapping frequencies like d/3 or d/4, as a linear combination of Po (Production observed without ethephon stimulation, representing metabolic component of the yield potential) and [SUCpo] (latex sucrose concentration without stimulation, representing the sugar loading component of the yield potential): Pmax = Po + [alpha][SUCpo]. Whereas the first yield component (Po) describes the clonal latex metabolic activity, also correlated to inorganic phosphorus latex concentration ([Pio]), the second yield component ([alpha][SUCpo]) reflects the capability of the clone to sustain any further intensification of exploitation, especially regarding its possible response to ethephon stimulation. Classification of Hevea brasiliensis clones in a 2 dimensions-matrix (Latex Clonal Typology) containing five different metabolic types (low, low-medium, medium, medium-high and high) and three different latex sugar loading types (low, medium and high) allows to describe the response of any clone to ethephon stimulation: stimulation intensity should increase when clonal latex metabolic activity decreases and/or when clonal latex sugar loading capacity increases. Conversely, stimulation intensity should decrease when clonal latex metabolic activity increases and/or when clonal latex sugar loading capacity decreases. Latex Clonal Typology therefore greatly simplifies stimulation recommendations, as only five different levels of stimulation intensity (very high, high, medium, low and very low) provide accurate stimulation recommendations to all physiological types of clones, depending on their respective position in the matrix. Stimulation recommendations based on this principle are currently applied on a large rubber plantation of North Sumatra, Indonesia. Latex Clonal Typology provides as well accurate information regarding clonal susceptibility to tapping panel dryness (TPD), clonal adaptation to different tapping frequencies (high or reduced) and clonal yield potential. It is also of major interest for rubber breeding programmes, in order to enhance integration of clonal physiological profiles in Hevea brasiliensis genetic selection schemes.

Mots-clés : clone; hevea brasiliensis; Éthéphon; substance de croissance végétale; saignée; méthode; latex; métabolisme; composante de rendement; côte d'ivoire; thaïlande

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