Selection of oil palm male parents for optimal planting density estimated from mature crown surface

Abstract

Our study on selecting pisifera male parents aims at determining yield per palm as well as the optimal planting density of the tenera offspring. The data pattern came from dura x pisifera testcrosses, planted at 135 and 160 palms ha-1 in North Sumatra, Indonesia, from which the breeding values of 15 pisifera parents of Ghana origin are estimated. Optimal palm densities were assessed from the leaf surface at mature canopy, obtained from the product of number of green leaves with the (asymptotic) maximum leaf area (0.95 L-max), inferred from a logistic growth curve fitted through leaf area values versus palm age. The time to reach the optimum values ranged between 5.5 to 7.9 years after planting. Amount of light under the palms, measured by the vigor of Mucuna cover crop, scored 50 and 67 months after planting (cc-score), considerably varied among pisifera. The clear negative correlation between yield and cc-score reveals that male parents selected for yield during the early years of production may generate tenera offspring palms that are highly light-competitive later on. To circumvent this drawback, this study suggests to select pisifera parents for yield per hectare at optimal palm density instead of yield per palm.