Oil palm genetic improvement program

Oil palm cultivation in America is linked to the history of the United Fruit Company, which introduced and disseminated this species throughout tropical America in the early 20th century. This is how the ASD oil palm genetic improvement program was born in Costa Rica. It is now more than 50 years old and during this time it has formed and enriched a diverse germplasm bank of Elaeis guineensis and E. oleifera. This genetic wealth has allowed the creation of new varieties that are increasingly productive, which also perform very well in new particular environments.

Efforts to improve oil palm at ASD have been concentrated in three areas: i) the development of E. guineensis varieties, ii) the selection of oleifera palms for the production of interspecific hybrids, and iii) the development of composite materials or gene mixtures of E. guineensis and E. oleifera.

The fruits of this program have been the consolidation of ten varieties, with which more than 1.85 million hectares have been planted in the main palm-growing regions of the world. Likewise, the program has created high density varieties and clones, characterized by their short leaves and slow trunk growth. ASD has also offered the market new varieties that are tolerant to adverse weather conditions, such as low temperatures and water deficits. Part of this effort also led to the creation of an innovative OxG hybrid (Amazon), which has agronomic and spear rot tolerance traits that are superior to other hybrids on the market.

ensayo cuckra 2010

ASD's genetic resource

In the past, ASD participated in an aggressive genetic material exchange program with leading oil palm research centers in Asia and Africa. Some of the materials acquired during this exchange are the following:

  1. Deli dura palms, from the genetic improvement stations of Chemara, Harrison & Crosfield, Banting, SOCFIN (Societé Financiere de Caoutchouc), Malaysian Agricultural Research and Development Institute (now the Malaysian Palm Oil Board) in Malaysia, and Dami, Papua New Guinea.
  2. AVROS pisifera sources (Algemene Vereniging van RubberplantersOostkust van Sumatra) from Harrison & Crosfield (Malaysia), Ekona of Unilever (Cameroon), Ghana and Nigeria from the Kade Station (Ghana) and the NIFOR station (Nigerian Institute for Oil Palm Research, formerly WAIFOR-West African Institute for Oil Palm Research), and La Mé and Yangambi from IRHO (Institut de Recherches pour les Huiles et Oléagineux in the Ivory Coast).

This exchange program was strengthened with the introduction of wild palm seeds from the highlands of Bamenda (Cameroon) and Tanzania, and from several regions of Sierra Leone, Uganda, Zambia and Malawi.

To obtain some 'guineensis' materials, ASD gave germplasm from the American oil palm, which breeders considered a species with great potential at that time. The E. oleifera germplasm collection was initiated between 1960 and 1970, and has introductions from several regions of Honduras, Nicaragua, Costa Rica, Panama, Colombia, Suriname and Brazil. This collection was complemented with introductions from the Taisha region in Ecuador.

The total number of guineensis, compact and oleifera mother palms that are currently used for seed production at ASD is 6,468; of which 3,946 are of Deli origin, 1,689 are compact palms derived from the second and third cycles of backcrossing, 312 have Bamenda and Tanzania origins, and 521 are oleifera.

ASD's genetic improvement strategy

The development of new oil palm varieties aims to consolidate the high density types and improve the adaptability of new ones to marginal areas with high water deficits, and/or low temperatures.

For commercial seed production of tenera type (DxP) oil palms, two populations of genetically advanced palms are used. The so-called 'mother palms' are characterized by producing few very large bunches, with dura type fruits (fruits with a thick shell and little mesocarp). These palms are crossed with others known as pisiferas (pollen sources), which produce numerous bunches of fruits with no shell that are normally infertile and are usually aborted. The crossing scheme is illustrated in the figure below:

2 foto de mejoramiento genetico

Diagram of DxP crossing for commercial seed production

The selection of dura ‘mother palms’ is based on the results of DxP progeny trials, which are crosses of dura palms with several sources of pollen. This allows choosing those palms that give rise to the most productive progenies with the desired growth traits (high overall combinatorial ability). The subsequent selection of individual palms focuses on highly heritable bunch traits such as mesocarp content in the fruit and oil in the mesocarp, which is complemented with information on bunch production and growth (trunk height and leaf length).

The standards used in Malaysia by SIRIM (Standards and Industrial Research Institute of Malaysia) are a benchmark for determining the quality of the mother palms. The oil production potential of the population of ASD dura Deli superior mother palms exceeds the standards established by SIRIM. The Tanzania guineensis mother palms and those of compact origin also exceed SIRIM standards.

The ‘oleifera’ mother palms have bunch traits inferior to the standards indicated above, which is inherent in this species, whose oil production capacity is lower than that of guineensis. However, the production of fruit bunches in the selected ‘oleifera’ palms is higher than the SIRIM standard. In addition, the ‘oleifera’ species has tolerance to some phytosanitary problems (spear rots in particular) and the fruits have an oil that is less saturated than that of ‘guineensis’.

Historically, ASD has used traditional quantitative genetics methods. However, the company recently launched operations in a modern molecular biology laboratory, to mark genes of interest and sequence them.

The development of Elaeis guineensis varieties

The Deli dura population, with very good agronomic traits, has been the basis to create high fruit production varieties that have excellent performance under suitable climate, soil and agronomic management conditions. Other wild dura populations, obtained in areas with limiting climatic conditions, have been the basis for obtaining varieties with better tolerance to abiotic stress and some phytosanitary problems.

The Deli duras have been chosen by the majority of commercial seed production programs around the world, as these palms are characterized by producing large bunches, fruits with a high percentage of mesocarp and high oil content. At ASD, emphasis has been placed on gradually increasing oil content in the bunch, which has been achieved through four cycles of mother palm selection.

The initial work for the selection of the Deli dura progenies was consolidated in Costa Rica with the production of seeds from the classic Deli x AVROS variety, which is very popular in Asia. This variety was initially used locally and later offered on the international market in 1975. The main weaknesses of Deli x AVROS are its narrow genetic base (which limits improvement), its excessively vigorous vegetative growth and low tolerance to stress and some phytosanitary problems. Other alternative varieties were Deli x Ekona and Deli x Yangambi, which although they had some advantages over Deli x AVROS, they also had a vigorous growth. Since 2001, new varieties have been launched on the market that have far exceeded the weaknesses indicated above.

The new generation of ASD commercial varieties

The inheritance of many of the traits of economic importance in oil palm is additive, which is why it is expected that the greatest genetic contribution for the development of new varieties comes from the pollen sources (pisiferas or teneras) and not from the Deli dura mother palms with their narrow genetic base.

Nigeria origin pisiferas stand out for passing on to their progeny high precocity, high bunch and oil production potential and less vegetative development. Ghana origin fathers transmit high oil production, short leaves and tolerance to stress (low luminosity, water stress and low temperatures). Other composite Dami pisiferas give their progenies high oil production and less vegetative development. This information is the basis for the commercial production of varieties such as Deli x Nigeria, Deli x Ghana and Evolution.

The Deli x Nigeria variety can be pure nigrescens, with fruits that are shiny black when immature, or pure virescens, with bright green fruits when immature that turn orange when ripe. The virescens trait is very helpful in avoiding the harvesting of bunches that have not yet reached the optimum degree of ripeness; whereas ripeness is not so conspicuous in nigrescens bunches.

segunda foto 1 cuadro Palm of the Deli x Nigeria variety showing virescens fruits that are green when they are immature and orange when ripe. This variety along with Deli x Ghana are produced by ASD and are very popular for their exceptional performance in terms of precocity and fruit and oil production.

Stress tolerant varieties

Several wild dura and tenera populations introduced to Costa Rica from the cold highlands of West Africa have allowed the development of new lines of mother palms with an oil production potential similar to the Deli duras, but with the ability to tolerate adverse weather conditions such as water deficits, low temperatures and low solar radiation.

In progeny trials, the majority of the offspring whose female parents are of Bamenda, Tanzania and Angola origins have generally shown high fruit production, reduced vegetative development and a high percentage of oil in the bunch. Progenies of Tanzania origin have excelled, not only because of their high oil content in the mesocarp, but also because of the high percentage of kernel in the bunch. ASD now has Tanzania x Ekona and Bamenda x Ekona varieties on the market, which, apart from their tolerance to the aforementioned stress factors, also show tolerance to spear rots.

3 foto segundo cuadroWild palm in Tanzania. (2008) at more than 1100 masl, exhibiting high tolerance to water stress and low temperatures.

Compact varieties

Varieties with short leaves and trunks help increase productivity, since they can be planted at higher densities (160 or more palms/ha vs. the standard density of 143 palms/ha) than the traditional long-leaf varieties such as Deli x AVROS or Deli x Ekona. Small producers find that these materials give them an opportunity to increase their production and make better use of scarce land resources.

The history of compact palms began in 1966 with the discovery of a wild plant of hybrid origin (OxG: Elaeis oleifera x E. guineensis) that presented, in addition to a short trunk, relatively short leaves. This plant was backcrossed naturally to guineensis and in the progeny an exceptional plant with a short trunk and leaves was found, which was called the 'original compact palm' (OCP). From the OCP, several crossing programs were developed to conserve the desired vegetative growth traits and improve oil production potential. The figure below summarizes the development of compact populations during the period 1978 to 2008.

foto17 2 1 fotoDevelopment of compact populations at ASD from 1978 to 2008, from the original compact palm (OCP), RC = backcrossing, F = filial generation

The current compact varieties can originate in two ways: compact mothers with guineensis fathers (Ghana and Nigeria populations) and guineensis mothers (Deli dura) with compact fathers; however, the diversity of compact populations allows other alternatives to be exploited as progenitors. The most recent compact progenitors (populations planted in 2008) have a low rate of increase in trunk height (35 - 40 cm/year), short leaves (> 6 m) and high oil in the bunch (25 - 32% in teneras and 18 - 25% in duras).

1 foto 3 cuadro esta
Comparison of compact palms growth with a Deli x Avros cross (Foreground) of the same age. Photo taken 2010 of a 1999. Beautiful compact palm showing a large load of bunches.                                                                    

The OxG AMAZON Hybrid

The management of spear rots, including the most destructive of all, pudrición de cogollo (PC), requires making improvements in the agronomic management of the plantations, particularly in soil aeration and nutrition, and the possibility of using varieties that are tolerant of this disorder. Resistance or tolerance genes can be found in some 'guineensis' populations and particularly in 'oleifera'x'guineensis' interspecific hybrids. Despite the tolerance of some of the OxG hybrids to PC, these present some important agronomic limitations, such as vigorous vegetative growth and the need to perform assisted pollination for bunch production. In addition to this, the oil content in the bunch is relatively low compared to the 'guineensis' varieties.

Improvement of the original 'oleifera' populations and the compact ones, was the basis for creating a new OxG hybrid, called Amazon, which is a cross between oleiferas of Manaus origin with Compact pisiferas. This hybrid overcomes several of the limitations noted above, since its vegetative development is similar to the 'guineensis' varieties, in terms of leaf length and petiole thickness, and its tolerance to spear rots is comparatively greater than other hybrids. A particular feature of Amazon is the greater proportion of Elaeis oleifera genes in its genome (>50%), compared with other traditional OxG hybrids, which possess only 50% 'oleifera' genes.

1 foto cuarto cuadro segunda foto 4 cuadro
Palm 26 months of age of the OxG Amazon hybrid from the second generation.                    
   Palm 17 year of age from the Amazon first generation.

Development improvement programs

Some 'guineensis' descendants of Nigeria origin segregate virescens color fruits and this trait is associated with a population that exhibits high precocity. The objective is to select pisiferas whose descendants show high production and 100% virescens fruit color. To establish the virescens gene, dura x tenera crosses were carried out to evaluate the productive potential of the selected virescens teneras.

Tolerance to common arrow rot / leaf arcing

The syndrome called crown disease/common spear rot (CD/CSR), which produces severe deformations of the leaves and delays in production, affects young palms, which is why it is also called ‘young palm disease'. The expression of this condition has a strong genetic component, and it is possible to control it by making a meticulous selection of the mother palms and the pollen source using progeny tests. In field experiments it has been observed that the incidence of CD is very high in plants that grew in soils with greater aeration limitations (poor drainage); which also occurred in families that had shown tolerance to CD in other more favorable soil conditions. When the tolerance was partial, the soil effect became less relevant. The careful selection of progenitors may in the near future eliminate to a large extent the appearance of CD/CSR in commercial plantations.

Symptoms of Boron Deficiency

The high precocity of modern oil palm varieties and the genetic origin of some of them, make mineral deficiencies manifest more intensely, particularly the tissue deformations associated with a boron deficiency.

The results in a new population of compact palms that was planted in 2008 have been particularly relevant. In this test the parents were selfed and at the same time the descendants were evaluated in crosses with guineensis and compact x compact. In a group of three progeny tests, there was a high correspondence between the incidence of severe boron deficiencies in parents and offspring, which could indicate that severe boron deficiencies could be associated with a dominant and relatively easy to control trait.

Improvement of OxG hybrids

There are new alternatives to continue the genetic improvement of OxG hybrids, trying to develop varieties with lower vegetative growth and an oil content similar to guineensis seed varieties. The improvement of oleifera mothers depends on the genetic variability existing in natural or advanced populations; but it also depends on the ability of breeders to combine populations with distinctive traits, to concentrate desirable genes in a few individuals, such as a smaller proportion of rachis in the bunch, high average fruit weight, high percentage of mesocarp in the fruit, and high oil content in the bunch.


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Palm of 26 months of the second generation hybrid OxG Amazon.