© 2003 Heron Publishing—Victoria, Canada
Selection of a seed orchard of Eucalyptus dunnii based on genetic diversity criteria calculated using molecular markers
S. N. Marcucci Poltri (1), N. Zelener (1), J. Rodriguez Traverso (1, 2), P. Gelid (1) and H. E. Hopp (3, 4)
1. Instituto de Recursos Biológicos CIRN-CNIA-INTA, 1712 Castelar, Argentina / 2. Deceased August 30, 2001 / 3. Instituto de Biotecnología CICVyA-CNIA-INTA, 1712 Castelar, Argentina and Departamento de Ciencias Biológicas, Facultad de
Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1424 Buenos Aires, Argentina / 4. Author to whom correspondence should be addressed (ehopp@correo.inta.gov.ar) / Received June 15, 2001; accepted March 9, 2002; published online May 15, 2003
Summary
A Eucalyptus dunnii Maiden breeding population of 46 accessions originated in Australia and selected for fitness to subtropical and cold environments
was screened by Amplified Fragment Length Polymorphism (AFLP) and microsatellite markers to obtain quantitative estimates
of genetic diversity. A randomly chosen group of AFLP primers generated 205 AFLP bands that were used to fingerprint the genotypes
and to evaluate genetic relationships among accessions. Sixty-eight percent (140) of the bands were polymorphic markers. The
mean diversity index (DI) was 0.33 and about 52% of the loci had values greater than 0.4. Cluster analysis derived from similarity
indices (SI) revealed no particular grouping among accessions suggesting the absence of closely related genotypes, except
for five pairs of genotypes. Bootstrap analysis results confirmed the suitability of AFLP to describe genetic relationships
in this breeding population. In addition, four highly informative microsatellites were used to construct an identification
matrix that discriminated nearly all of the genotypes. Mean values for the number of alleles per locus, DI and SI among accessions
were 13, 0.78 and 0.19, respectively, indicating that the breeding population has high genetic diversity. However, several
genotypes showed the presence of single microsatellite bands suggesting a putatively important degree of homozygosity. Molecular
data were used to design a clonal seed orchard. To achieve this aim, the nine most divergent pairs of genotypes were chosen,
thereby retaining 95.2% of the total number of alleles from the 140 polymorphic AFLP loci and the four microsatellite loci
analyzed. Mean DI and SI for AFLP and microsatellites showed no significant differences between the original breeding population
and the selected seed orchard, confirming that a seed orchard can be designed with a limited number of individuals, which
allows similar accessions to be discarded and avoids inbreeding.
Keywords:
AFLP, forest tree breeding, germplasm, identification matrix, microsatellite, simple sequence repeats, SSR.
