By R. Bourdeix, 2018
The Polymotu concept is to use the geographical isolation of special sites for conservation and reproduction of individual varieties of coconut, other plant species even animals. By combining ancestral Polynesian practices with the recent progress made in social and biological social sciences, a rational strategy for the conservation of genetic resources and associated traditional knowledge could be implemented.
The harsh constraints of ex situ coconut conservation are explained hereunder. The alternative Polymotu conservation concept is then described in the framework of multifunctional landscape management.
In classical coconut ex situ genebanks, coconut cultivars are conserved as accessions, generally planted close together in the same fields. Each accession generally counts 75 to 100 coconut palms from the same cultivar. For reproducing accessions in ex situ genebanks, the technique of controlled pollination with bagging of the inflorescence is used (Konan et al. 2008). For coconuts, this technique is very costly. It requires a well-equipped laboratory, well-trained technicians able to climb the palms and a huge amount of manpower. Not all the gene banks can afford this.
The lifespan of such accessions is only 25 to 30 years. After this period, most non-dwarf coconut varieties reach 15 m high or more. At this stage, it becomes difficult to climb the palms. It is therefore necessary to rejuvenate the accessions before the inflorescences become inaccessible. In the Côte d’Ivoire African genebank, workers use costly triple ladders that can reach a height of only 14 metres. In many other places, palms are climbed mainly manually, which is risky. Rejuvenation programmes require climbing roughly 75 palms each about 15-20 times. Production of the 200 seednuts requested for the duplication of only accession will demand one and half year's preparation; and it will cost more than 1,600 USD in a context of low salaries in Côte d’Ivoire. Only scientists with healthy research budgets can afford to order varieties from classical ex situ coconut genebanks. Almost all farmers cannot afford this.
Alternatively, the coconut palms could be planted in geographical and reproductive isolation, as it was done in the traditional conservatoires located in Tonga and Solomon Islands. For instance, when a small isolated island is planted with one variety only of coconut palm, breeding occurs only within this variety and certified seednuts are naturally produced for farmers.
In this way, the constraints linked to the heights and ages of the palms are removed. Instead of climbing the palms for making controlled pollination, people only have to wait for the coconut to fall naturally to the ground. Open-pollination will provide true-to-type and cheap seednuts. Thus, the same accession can be kept as long as a sufficient number of palms remain alive in the field. In most cases, the duration of a coconut accession will then be extended to 75 to 100 years. Even if some of the palms die, there is no need to remove the remainder, as is done in a classical genebank. Dead palms can be replaced by new ones, without removing the old palms remaining alive. Extending the lifespan of a coconut accession from 25-30 years to 75-100 years represents a huge saving of time, manpower and money.
The Polynesian practice used for traditional conservatoire is to plant only one coconut variety on each small island. This practice served as a basis for defining a new conservation concept called Polymotu. Many information about this concept and its implementation can be found in Polymotu website. When compared to the initial Polynesian model, the Polymotu concept has evolved in several ways (Bourdeix et al. 2012b):
- The sites were extended to any place where reproductive isolation can be obtained; they may be islands but also small isolated valleys, cities, or inland designs with pollen barriers made of coconut palms or other tree species, be they wild (forest) or cultivated (rubber, oil palm..)
- The species conserved may be coconut, together with other species of plant or even animals; In Polynesia, it is envisioned to conserve varieties of kofai (Sesbania coccinea subsp. atollensis) and coconut crab (Birgus latro) on the same islands than coconut for an economy of scale.
- It is recommended to plant up to three coconut varieties in the same site and to identify the different kinds of seedlings using phenotypic markers at the nursery stage. In Samoa, a green Tall and two red dwarfs will be planted together in order to conserve both Tall and Dwarfs and to produce seedlings of Tall, Dwarfs and Dwarf x Tall hybrids for farmers.
