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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