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Preservation, multiplication and characterisation of amazonian Hevea germplasm"
A project entitled "Preservation, multiplication and
characterisation of amazonian Hevea germplasm" led by D. Nicolas,
of the 'Centre de Coopération Internationale en recherche
Agronomique pour le Dévelopement, Institut de Recherches sur le
Caoutchouc, (CIRAD-IRCA), France, in partnership with other
research institutions in the Ivory Coast and Belgium, was carried
out under the European Union (D.G. XII) STD2 scientific programme.
The ultimate aim of the project is the genetic improvement of Hevea
and the release of new clones adapted to various environmental
conditions. The current Hevea varieties all came out from a single
population, called Wickham, bred in Asia, and there is a need to
enlarge the genetic basis for Hevea breeding. In order to achieve
it, a research was conducted in a large germplasm collection, from
Bimbresso research station, Ivory Coast. The collection consists of
3352 genotypes, mostly of Hevea brasiliensis, and includes both
selected (domesticated) clones coming from Africa, Asia and South
America and unselected (wild) clones collected in brasilian,
peruvian and colombian Amazonia.
An agronomic evaluation of the collection was performed in small
scale field trials. Wild germplasm showed a poor growth, an
irregular crown architecture and a very low latex yield when
compared with domesticated germplasm. However, it proved to be a
very interesting source of resistances to leaf diseases, in
particular to Microcyclus ulei.
Crosses between wild and domesticated germplasm were made in order
to provide progeny tests for the wild germplasm and to evaluate the
chances of Hevea breeding through genetic recombination between the
two kinds of germplasm. The good correlation between phenotypic
value and combining ability found in wild germplasm clearly
indicates that selection within amazonian germplasm will be
effective in order to obtain a better and smaller population, more
suitable to the development of further crosses with domesticated
material. The recombination between wild and domesticated clones
proved to be a promising breeding strategy; in particular,
heterotic effects in growth were observed.
Molecular markers - isoenzymes, nuclear and cytoplasmic RFLP - were
used in order to better characterise the genetic diversity of
amazonian germplasm. The analyses of fourteen isoenzymic loci
provided the separation of amazonian germplasm into three groups:
the South group and the Southwest group in brasilian Amazonia, and
the Northwest group in colombian Amazonia. Besides, amazonian
germplasm provided a very important increase of the enzymatic
polymorphisms known in Hevea till now. RFLP analysis is still in
course, but the results available so far allowed the individuation
of subgroups within the main geographical groups. Furthermore, a
gene library of 600 unique sequences, constructed within the
research programme, will provide further probes for DNA
polymorphism analysis.
The results of the research project clearly provided new tools for
the breeders: the different genetic groups within the amazonian
germplasm, individuated by molecular markers, shall enter a
programme of recurrent selection for genetic recombination between
populations. In the meantime, selecting among wild clones and
crossing them with domesticated tester clones may provide, in the
short term, clones of amazonian origin to enter a programme of
Wickham population breeding.
Within this project several publications have been issued.
For further information please contact:
D. Nicolas
Centre de Coopération Internationale en recherche Agronomique pour
le Dévelopement, Institut de Recherches sur le Caoutchouc,
(CIRAD-IRCA)
42, Rue Scheffer
75116 Paris, France
Phone +33-1-47 04 32 15
Fax +33-1-47 27 33 66
+33-1-47 64 09 75
Contract number TS2-A-161