Summary of the ASD Molecular Biology Program 

Introduction

ASD Costa Rica, (Agricultural Services & Development), is an oil palm technology company whose main products are high yielding certified seeds and clones, which are marketed in the tropical regions of Asia, Africa and America .

ASD has 450 hectares for field experiments in Coto, Costa Rica and owns one of the most diverse oil palm germplasm collections in the world. The first introductions of germplasm were carried out in 1928; however, the genetic improvement program was not consolidated and intensified until 1975. The main achievements of this program have been the development of six high yielding commercial varieties, two special varieties for extreme conditions and three high density varieties.

To date, ASD has resorted to classic methods for improvement that require large land areas for field experiments and long time periods to evaluate the behavior of each new generation. Thanks to notable advances in molecular biology, technologies are now used to identify genes and their functions, allowing more effective and rapid genetic improvement. Consequently, ASD began a molecular biology program in 2006 to develop and use genomic technologies such as gene markers and sequencing either as a complement to or to eventually substitute evaluation and phenotypic selection methods in the future. Described below are the different projects that ASD is contemplating for the development of new varieties with the aid of molecular biology.

“Compact Gene” to Increase Planting Density

Any palm with slow truck growth and short leaves is called “compact”; these palms allow higher planting densities and prolong the economic life of the plantation.

In 1966, ASD identified a palm originating from a hybrid ( E. oleifera x E. guineensis ) pollinated naturally with E. guineensis pollen (open pollination) . This palm ( E. oleifera x E. guineensis) x E. guineensis, with short trunk and leaves and a composition of ¾ E. guineensis genes and ¼ E. oleifera genes, was called the original compact palm (OCP). It is believed that the compact trait of the OCP was acquired from the E. oleifera parent. This project would need to identify the compact genes using molecular markers in order to develop a linkage map to the compact trait. This identification will allow the manipulation of the trait throughout ASD germplasm. With the use of seed varieties and/or compact clones, oil productivity per hectare can probably be increased by more than 30%.

Identification Of Dura, Tenera And Pisifera Genes

Three kinds of fruits are distinguished in oil palms: dura, tenera and pisifera, which differ in the thickness of the seed shell and in mesocarp content. Dura fruits have thick shells, thin mesocarp and lower oil contents while pisifera fruits have no shell, and naturally most are sterile and have no economic importance. Tenera fruits have thin shell and more mesocarp than dura fruits, and their oil contents exceed 25%.

The characteristic of shell thickness is governed by a pair of genes with intermediate inheritance. The identification of dura, tenera and pisifera palms in the nursery stage without needing to wait four years to verify the kind of fruit will save time and lower research costs.

Virescens Gene For Improving Harvest Efficiency

A change in color is associated with fruit ripeness in oil palm. For this reason, this trait is one of the indicators usually used by field workers to help identify ripe bunches during harvest. However, sometimes this indicator is not adequate for bunches of nigrescens fruits (black color when unripe), because the color change when ripe is often subdued and the workers frequently cut bunches with sub-optimal degrees of ripeness and lower oil contents.

One alternative for improving harvest efficiency is to develop varieties with virescens fruits (green color) . The virescens bunches are quite conspicuously green when unripe and change to a bright intense orange color upon ripening, making them easily identifiable by the harvesters. It would be advantageous to place planting materials with virescens fruits on the market to allow the harvest of riper bunches with higher oil contents.

Low Dehiscence In The Bunches To Reduce Crop Losses

Oil palm fruits detach naturally from the bunches when ripe. Since the ripening process is gradual and more than 10 days may pass from when the first fruits detach until the last fruits are ripe, the harvesting of bunches with an optimal degree of ripeness is difficult. In addition, due to dehiscence, loose fruits must be collected during the harvest, which increases costs significantly.

It is estimated that if bunches ripen without detaching fruits, oil production could increase by 20 to 25%. In nature, some mutant palms occur that have bunches without abscission. In these palms, the fruits do not detach from the bunch when ripe; they remain stuck to the spikelets and rot in the bunch if not harvested. The genetics of this trait are not yet known; however, crosses have been made with these kinds of palms. The only inconvenience of a non-abscising variety is that the harvesters will not have loose fruits as an indicator of ripeness. However, this can easily be resolved with the simultaneous introduction of the virescens gene described above. ASD has identified palms and families that have bunches with low or no dehiscence of ripe fruits (hard bunches). These palms could be cloned or used to transmit the low dehiscence trait to their progenies.

Legitimacy Of Clones

The use of oil palm clones in commercial plantations is a viable reality due to technological advances in tissue culture that have allowed the reproduction of thousands of ramets. Genetically, clones should be exact copies of the tissue donor palms (ortets) in order to reproduce their genetic potential. Verification that the clones bear the same genetic load as the ortets (fingerprinting) is important as a guarantee in the marketing of the clones.

Alteration of Oil Chemical Composition

Because palm oil has high saturated fatty acid content, mainly palmitic acid (45 - 58%), alteration of its composition to make the oil more liquid and increase its oleic acid content would enhance the value of this product. There are two ways to meet this objective: i) find palms that have high unsaturated oil contents among the populations of Elaeis guineensis , Elaeis oleifera and their hybrids, to produce clones or varieties with high olein content in their oil; and ii) change the oil composition via genetic engineering.

Genetic Associations Between Different Sources Of Germplasm

Knowing on the genetic distances between the germplasm from different origins could be useful for associating genetic materials of similar origin, to manipulating them as a single population, thereby reducing the number of materials to be evaluated in the process to improve and develop new varieties. Furthermore, the costs of maintenance and data collection would also be reduced by managing fewer populations.