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Eucalyptus genetic improvement in Madagascar

Lebot V., Ranaivoson L.. 1994. Forest Ecology and Management, 63 : p. 135-152.

DOI: 10.1016/0378-1127(94)90107-4

Eucalyptus improvement was initiated 20 years ago in Madagascar and aimed at selecting species and provenances adapted to the very diverse climatic conditions of the island. The present paper reviews the results obtained by interspecific, provenance, and progeny tests. The good adaptation of Eucalyptus grandis and Eucalyptus robusta was confirmed by various experiments. Malagasy provenances of both species exhibited poorer performance than those recently introduced from Australia. This is thought to be the result of a narrow genetic base and inbreeding. The results obtained from tests conducted in diverse environments indicate that E. grandis provenances are already well per-forming but exhibit limited variation. Provenances and progenies performances appear to be quite irregular and unpredictable on the basis of site as shown by the results presented here. Significant genetic differences exist among provenances of E. robusta tested for growth parameters. The analysis of variance revealed that genetic gain in volume production is possible through provenance selection. However, it is suggested to introduce a wider range of provenances of E. grandis and E. robusta for further evaluation and to select plus-trees within provenance rather than search for superior provenance. Tremendous variation in growth rate among trees offers great opportunity for further genetic improvement. It appears that there are remarkable provenance X site and progeny X site interactions. Future reafforested areas need to be planted with genetically improved material. Smallholder's ideo-types require that priority should be given to a few major selection criteria: growth rate and volume production, juvenile performance, coppicing ability and fire resistance. The priorities of the Madagascar genetic improvement programme are to pursue provenance introduction and progeny evaluation and to produce genetically improved material to be distributed on a large scale to village communities. It is suggested that these priorities be combined for cost efficiency. Evaluation of different provenances and progenies in diverse ecological areas, individual selection, and large-scale production of genotypes with a broad base is presently conducted in breeding seedling orchards to satisfy national needs for Eucalyptus spp. seeds using synthetic varieties.

Mots-clés : eucalyptus; amélioration des plantes; eucalyptus grandis; eucalyptus robusta; méthode statistique; essai de provenances; peuplement semencier; descendance; madagascar

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