Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 127

Palms (Arecaceae) form one of the most distinctive of all plant families and are emblematic of the tropical regions of the world, in which most of their natural biodiversity is concentrated. According to the most recent estimates, the palm family contains nearly 2500 species. A large number of them are exploited in some way for human purposes; indeed, the Arecaceae have been recognized as being one of the three most important plant families in terms of human usage (Tregear et al., 2011). Although a handful of species such as date palm (Phoenix dactylifera), oil palm (E. guineensis) and coconut (Cocos nucifera) occupy a particularly high profile due to their economic importance, many members of the Arecaceae have uses that extend far beyond their natural habitat.

Elaeis oleifera is a species in the oil palm genus along with the commercial E. guineensis which occurs naturally in South-Central America, from Honduras to Colombia and in the Amazon region. There are three oil palm (E. guineensis) varieties, namely dura, pisifera and tenera which are distinguished by the thickness of the fruit shell and the ratio of mesocarp to fruit. Dura is the thick-shelled variety (2–8 mm) with low to medium mesocarp content (35–55%) while pisifera is the shell-less variety. Tenera fruit has a thin shell (0.5–4 mm) and a medium to high mesocarp content (60–96%). Beirnart and Vanderweyen (1941) revealed the simple Mendelian inheritance of the fruit shell thickness trait and provided the basis of modern oil palm breeding and hybrid seed production programmes: the thick shell dura being homozygous dominant, the shell-less pisifera homozygous recessive, and the thin-shelled tenera heterozygous. The gene responsible for the inheritance has been elucidated by Singh et al. (2013a).

There is a single terminal meristem in the oil palm, which produces an average of two leaves per month. Vertical growth rates can vary from 30 to 75 cm per annum, depending on the genotype. The root system is composed of a large number of fasciculate adventive roots. Oil palm grows preferentially in rich and temporarily damp alluvial soils (Corley and Tinker, 2016). It can reach 30 m in height, with a crown of 4–5 opened palmate leaves of 10–16 m in diameter, and therefore requires a large area for growth. The standard density in industrial plantations is generally 143 palms/ha. The oil palm is a temporal dioecious species (Cruden, 1988), which displays alternate male and female flowering cycles throughout the life of the plant.