Towards more efficient selection for oil yield in the oil palm (Elaeis guineensis Jacquin)

Detailed studies are made of the variability and heritability of a number of components of oil yield in the oil palm using published data of the breeding programme of the NIFOR in Nigeria and results of a number of experiments carried out at the OPRC in Ghana during the period 1965-1971. Estimations of h2n for oil yield components are presented. Values are very high for some of the fruit quality components. A fairly high negative genetic correlation (r A = -0.58) was found to exist between the two most important components, number of bunches and single bunch weight. Maximum selection progress for increased bunch yield may be obtained by intercrossing widely divergent subpopulations. Experimental evidence is produced of the nature of inheritance of the ratios shell to fruit and mesocarp to fruit in oil palm fruits. Consequently, selection for these components requires considerable revision. The efficiency of determinations of the oil-to-mesocarp ratio, an important oil yield component with a rather low heritability, can be enhanced considerably by applying a modified indirect method based on the fact that the dry fibre-to-mesocarp ratio has a high heritability. The effect of different periods of water stress on bunch yield and its two components, as well as on vegetative growth of the oil palm was investigated. The implications of the results of these studies for oil palm selection are discussed in detail and outlines of a modified breeding programme assuring continued selection progress are given. Essential are (1) the re-establishment of new, genetically highly variable and very divergent subpopulations, (2) the estimation of genotypic values of all components of oil yield from the first 3-4 years of production when the disturbing influence of competition for light between palms is still negligible, (3) information from special plant density-progeny trials about the optimum combination of genotype and spacing in a particular environment, required for a continued high production level beyond the first four years.