The oil palm is a monocotyledon belonging to the species Elaeis. It is a perennial tree crop and the highest oil producing plant, yielding an average of 3.7 t of oil per hectare per year in Malaysia. The crop is unique in that it produces two types of oil. The ¯eshy mesocarp produces palm oil which is used mainly for edible purposes and the kernel produces palm kernel oil which has wide application in the oleochemical industry. The genus Elaeis comprises two species, namely E. guineensis and Elaeis oleifera. E. guineensis originates in West Africa and the commercial planting material is mainly of this species. E. oleifera is a stumpy plant of South American origin and its oil is characterised by a high oleic acid content.

Palm oil became the world's second most important vegetable oil after soybean oil in 1980 [1]. The oil may be designated as Malaysian, Indonesian, Nigerian, Ivory Coast or by its other sources. The origin of the oil often gives an indication of its identity and quality characteristics. Currently, most of the world's production of palm oil comes from south-east Asia, in particular Malaysia and Indonesia. Malaysian crude palm oil production increased from 8.3 million t in 1998 to 10.6 million t in 1999, maintaining the country's position as the world's largest supplier of the oil. Currently oil palm accounts for 13% of the total world production of oils and fats and is expected to overtake soybean oil as the most important vegetable oil.

E. guineensis originates from West Africa. It was first introduced to Brazil and other tropical countries in the fifteenth century by the Portuguese. However, its propagation did not take off until the nineteenth century when the Dutch brought seeds from West Africa to Indonesia resulting in the four seedlings planted in Bogor, Indonesia in 1848. The palms were dura and the progenies from these seedlings were planted as ornamentals in Deli and became known as Deli Dura. From there the oil palm was sent to the Botanical Gardens in Singapore in 1875, and subsequently brought to Malaya (as West Malaysia was then known) in 1878. The oil palm was initially planted in Malaya as an ornamental and the first commercial planting was only in 1917.

E. oleifera originates from South America. The mesocarp oil of E. oleifera has higher oleic and linoleic acid content and lower content of palmitic and other saturated acids. The iodine value (IV) ranges from 70±80. The current main interest in E. oleifera is in the potential of transmitting its useful characters to interspecific hybrids with E. guineensis. Both E. guineensis and E. oleifera have the same somatic chromosome number of 32 and hybridise easily [2]. The advantages of the F1 hybrids over E. guineensis are a more unsaturated oil and a lower height increment.

The oil palm fruit is a drupe, which forms in a tight bunch. The pericarp comprises three layers, the exocarp (skin), mesocarp (outer pulp containing palm oil) and endocarp (a hard shell enclosing the kernel (the endosperm) which contains oil and carbohydrate reserves for the embryo).

Shell thickness is controlled by a single gene [3]. The homozygote dura (sht sht) is thick-shelled and the homozygote pisifera (shÿ, shÿ) does not have a shell. A cross between dura and pisifera results in the heterozygote tenera which h thin shell surrounded by a fibre ring in the mesocarp. The thinner shell of the tenera results in more oil-bearing mesocarp. Since 1961, most of the planting materials have been tenera (dura  pisifera). The pisifera is not used as a commercial planting material as it is mostly infertile.