A blog maintained by Tevita Kete, PGR Officer
Secretariat of the Pacific Community (SPC), Suva, Fiji Islands
This weblog documents the activities of Pacific Agricultural Genetic Resources Network (PAPGREN), along with other information on plant genetic resources (PGR) in the Pacific.
The myriad varieties found within cultivated plants are fundamental to the present and future productivity of agriculture. PAPGREN, which is coordinated by the Land Resources Division of the Secretariat of the Pacific Community (SPC), helps Pacific countries and territories to conserve their crop genetic diversity sustainably, with technical assistance from the Bioversity International (BI) and support from NZAID and ACIAR.
SPC also hosts the Centre of Pacific Crops and Trees (CEPaCT). The CEPaCT maintains regional in vitro collections of crops important to the Pacific and carries out research on tissue culture technology. The CEPaCT Adviser is Dr Mary Taylor (MaryT@spc.int), the CEPaCT Curator is Ms Valerie Tuia (ValerieT@spc.int).
PAPGREN coordination and support
Mr William Wigmore
Mr Adelino S. Lorens
Dr Lois Englberger
Mr Apisai Ucuboi
Dr Maurice Wong
Mr Tianeti Beenna Ioane
Mr Frederick Muller
Mr Herman Francisco
Ms Rosa Kambuou
Ms Laisene Samuelu
Mr Jimi Saelea
Mr Tony Jansen
Mr Finao Pole
Mr Frazer Bule Lehi
Interested in GIS?
Sunday, July 10, 2005
Posted 5:40 PM by Luigi
Root Crops Agrobiodiversity Project in Vanuatu
Funded by FFEM (Fonds Français pour l’Environnement Mondial) MQAFF and CIRAD, this project is now off the ground. Dr Vincent Lebot of CIRAD says that two researchers arrived in april. They have completed work in two villages in Malo and Santo (178 vars of taro and 83 of yams in one village) . In July they are in Tanna, then Erromango. In August they will do Epi and Ambrym, in Sept. will do Pentecost and Ambae, in October Malekula and in November Vanua Lava. The first survey will be completed in December followe dby SSR fingerprinting of approximately 1000 accessions. Details of the project are as follows.
Introduction, Background and Rationale
Vanuatu has found great difficulty in sustaining the conservation and genetic improvement of lesser root crops, mostly aroids (Alocasia macrorrhizos, Amorphophallus campanulatus, Colocasia esculenta, Cyrtosperma chamissonis, Xanthosoma sagittifolium) and yams (Dioscorea alata, D. bulbifera, D. cayenensis-rotundata, D. esculenta, D. nummularia, D. pentaphylla, D. transversa, D. trifida). The persistent attempts to collect and conserve germplasm and to make use of the resources over more than 30 years are evidence of this. Aroids and yams have also become the neglected crops of the international community, although locally important as staples and/or reserve foods used in times of need, as rich sources of vitamins, dietary fibre and minerals or as folk medicines. Invariably, they are grown or left to grow without the addition of fertilisers or pesticides. As a group, these species are efficient food plants and if marginal land is to be brought into production to support burgeoning populations, the potential of these crops is interesting.
In Vanuatu and elsewhere in the tropics, their conservation is fraught with difficulty: ex situ collections are expensive to maintain and methods for “on-farm” conservation have not been studied. Numerous collections have been made and lost several times in Vanuatu (and in many other tropical countries). In response to the problems of maintaining ex situ field collections, some countries have established in vitro collections without significant results. Cryopreservation, although attractive, has not proven to be practical. Furthermore, the storage of true botanical seeds is still problematical for most root crops species.
In Vanuatu, collections have been assembled and described using conventional approaches, involving agro-morphological descriptions and molecular tools, but they have been poorly utilised in genetic improvement programmes. Since Independence in 1980, the various Vanuatu governments have shown repeatedly the desire to improve their production but have been unable to maintain the technical capacity required over the long term. The consequence for the lack of interest in root crops species is now that they are loosing their competitive position in traditional cropping systems as diets are changing rapidly.
Similarities shared by root crop species in Vanuatu
All cultivars are vegetatively propagated and they share a narrow genetic base. Their flowering is erratic, they have variable ploidy levels, are predominantly allogamous, highly heterozygous and are, of course, cultivated for the interesting chemical compositions of their underground organs. Some of these biological characteristics are not specific to these root crops but they often present all of them together. Unlike most crops, they are not cultivated for the characteristics of their sexual organs (i.e., fruits and seeds). In fact, in many cases, flowers and true botanical seeds are virtually unknown to farmers. Many cultivars are clones of edible wild forms and a few putative wild forms are probably feral plants escaped from cultivation. Some cultivars are also clones of hybrids between wild forms and feral or cultivated plants. It is also possible to observe a deterioration of the attractive traits exhibited by a cultivar when it becomes feral. The physico-chemical characteristics of the under-ground organs deteriorate rapidly if the soil texture is not improved regularly and/or if the plant is not subjected to a periodic sexual propagation and selection.
Most of the allelic diversity is found within the wild gene pool, although most of the agro-morphological variation is found within the cultivars. Compared to cultivars, wild forms present limited morphological variation. Cultivars share a narrow genetic base but present numerous variable morphotypes which are probably the result of past sexual recombinations and clonal selections of somatic mutants. Root crop growers can select variants for the sake of increasing the number of distinct morphotypes preserved in their varietal portfolio. In Vanuatu, the national cultivars collections are therefore assembling limited allelic diversity. This has been observed for cultivars of taro and for D. alata.
In Vanuatu, farmers often give the priority to taste rather than yield and yield potential is never reached in farmers’ fields. Yam tubers and aroid corms do not present a uniform shape at harvest, thus making it difficult for mechanical peeling and marketing. Internal colour ranges from white to dark purple and may include combinations of two or more colours. Their texture varies after cooking and there is a lack of information on the physico-chemical characteristics of the starches that hinders utilisation. Among the priority breeding objectives are corms and tubers with acceptable quality, i.e., an appropriate dry matter content, a good cooking texture, taste, and no oxidation (rate of enzymatic browning).
We can therefore draw some practical guidelines for the preservation and use of root crops genetic resources in Vanuatu.
We know that the genetic bases of these crops are narrow, vulnerable to introduced pathogens and that it must be broadened if the crop is to be able to respond to rapid environmental changes. However, in order to be acceptable to farmers, and to be kept as part of their varietal portfolio, any new genotypes must exhibit an interesting attribute or perform better than those presently cultivated. Also, for them to be useful in the future, these genotypes need to have sexual reproductive potential, which means that their ploidy levels, crossability and genetic make-up must be understood. Considering the economic situation of minor root crop producers and the low-input cultivation systems which are often involving different cultivars, an appropriate approach could be to increase farmers' long-term access to useful genes. This could be done via the geographical distribution of allelic diversity and is probably a practical alternative to present conservation activities.
The geographical distribution of allelic diversity follows a three steps approach:
Distribution of genotypic diversity
Selection of villages (communities)
This will constitute a record of the situation at time 0, the beginning of the project.
Year four: surveys will be conducted to assess the potential changes at the village level in farmers’ portfolio and study the causes for adoption or rejection of the genotypes introduced. An assessment of the preservation stage of local genotypes will be conducted. Monographs will be produced and distributed to villages (communities) to present the situation in year 4 of the project.
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