June 2009

A tough nut to crack: PC in tropical America

ASD is committed to the search for long-term sustainable solutions to several phytosanitary problems of the oil palm, particularly in tropical America. Spear rot (PC = pudrición del cogollo) is one of those conditions where an easy and practical solution has been hard to develop.

A frontal attack on any possible pathogen that could be involved in this syndrome has not yet been fruitful or practical. Research for more than 30 years seems to indicate that a sustainable solution will only come from a combination of adequate agronomic practices and the use of tolerant or resistant varieties.

ASD has been actively working on both fronts. First, we have found through research that palms show a marked predisposition to the problem when the radical system has been adversely affected for some time by conditions such as poor soil aeration or prolonged drought. Within this line of research, we have also found that opportune, sufficient and balanced nutrition is a key aspect in preventing the problem or reducing its severity. The nutritional aspect must consider the yield potential of each particular site, so that plants will not be expected to produce more than the environment can support.

The search for tolerance/resistance to PC has also been a priority for ASD, and we are pioneering the idea that stress tolerance (water deficit or poor soil aeration for example) is related to PC tolerance. This hypothesis is being tested in a series of field experiments where stress-tolerant crosses have been planted in specific sites where PC has been prevalent (Fig. 1). Besides this, ASD has also produced two inter-specific OxG hybrids (Amazon and Brunca: see ASD in a Nutshell, No.1), that show high tolerance to PC, providing them to growers in affected areas.

Previous and contemporary events to the onset of first PC (spear rot) symptom

Research to find the causes and factors associated with spear rot (PC) in oil palm has included studies on the previous events to the onset of the so-called first symptoms (partial yellowing of some sectors of young leaves with rotting or not of spears). Among other things, it was found that the radical system (particularly the fine root system) is significantly less profuse and can be highly deteriorated in palms that eventually show the first symptoms of the disorder. On the other hand, some variables, such as rachis length, first increased and then markedly reduced its growth rate before the first symptoms appeared. This behavior clearly indicates some degree of predisposition (stress) for the final onset of such destructive symptoms that characterize the PC in tropical America. More details on this work are being published in our journal ASD Oil Palm Papers.

Accompanying these morphological studies, we also conduct research on the physiology of the plant previous and contemporary to the onset of those so-called first symptoms. This research was taken as part of a Ph. D. thesis that is being carried out in the region of Tumaco, Colombia.

New developments in clone hardening

Several of the clones commercialized by ASD have performed well in both the nursery and the field, fully demonstrating the great potential of these materials. The major advantage of these clones is their compact nature (short stem and leaves) that permits to use much higher plant densities than normally used.

However, some lots of certain clones previously commercialized by ASD suffered important losses during the hardening phase, and besides this, many of the surviving plantlets, lacked vigorousness and if taken to the field had a substandard performance. To solve these problems, we have been looking for alternative procedures to pre harden the plantlets before they are sent to the grower and so reducing the losses and increasing considerably the chances that only premium plants eventually are taken to the field.

The acclimatization or hardening grossly consists in gradually exposing the laboratory plantlets to the external environment, and it is here where some growers have found important problems to successfully complete this phase. The solution we are looking for is to sell clones previously hardened. The first results of our work (done with great dedication by agronomist Karla Salas) have been very encouraging, by planting directly in some inert media and given a special nutrition to the plantlets. At the end of this prehardening process, the roots of the plants are washed, treated with fungicides and packet for shipment. Once some details are completed, we hope, this will be the preferable method to sent clones overseas.

Physiology: the door to new knowledge of yield potential

The study of plant physiology helps us to understand the yield potential of a variety and the reasons for its fluctuations in different environments. We have studied some of the vegetative and physiological characteristics of the new compact clones and seed varieties, and have found that compact clones show some important differences (besides just their short leaves and stems) with vigorous traditional seed varieties (such as Deli x AVROS), and this may help to explain their interesting yield potential.

An important detail learned is that some of the procedures (to estimate leaf area and leaf weight for example) developed for vigorous seed varieties, such as Deli x AVROS do not apply to compact materials, and must be somehow modified. Other important feature of some compact clones (with "guineensis blood”) is leaflet orientation and arrangement that could give them an edge when intercepting photo synthetically active radiation (PAR). Other details of this research were published in volume 32 of ASD Oil Palm Papers.

Molecular biology: a window into the future

To maintain a winning edge for a company like ASD de Costa Rica means to invest in new technologies that permit to develop innovative planting materials. Molecular biology offers new possibilities unthinkable in the past to achieve this goal. ASD started exploring this new field by creating a program led by Ing. Emmanuel Araya, under the direction of the head of the plant breeding department. This program is aimed at developing tools, through the use of genetic markers, in order to make more efficient the selection of superior genetic materials with outstanding characteristics.

The program just started in the year 2006, but some important progress have been already made, such as the generation of the compact clones’ finger printing, the association of microsatellites with fruit type, the study of the relationships and diversity of different populations of Elaeis oleifera, and the search of markers linked to the compact character (short stems and leaves). Some of the outputs of this effort will be to be able to legitimate ASD compact clones and finger printing will allow registering this valuable germplasm.

In the future, we will continue looking for markers linked to the compact character, higher yields, and a better oil composition within populations of compact origin and pure "oleiferas". Besides this, the acquisition of state of the art equipment will permit to select palms that produce higher contents of palmitic and oleic oil. Other desirable characteristics, such as the fixation of the "virescens" character will have an impact on harvest efficiency; since no unripe bunches have to be cut. Finally, tolerance to the most important diseases of the crop is something that theoretically can also be achieved through the use of the techniques of molecular biology.

Training courses for our clients

ASD has a long tradition organizing training courses on oil palm cultivation and management of commercial plantations. Such courses have been offered mainly in Costa Rica and several other countries as well. The last training course on agronomy was offered in Costa Rica in July 2006, and we are now preparing the next one for July 2009. Details on this new course are now posted on our web site http://www.asd-cr.com/curso