Genetic architecture of vegetative propagation traits in Eucalyptus hybrids

Vegetative propagation constitutes a bottleneck in Eucalyptus globulus genetic improvement programs. This species has excellent properties for pulp production but poor adventitious rooting. Eucalyptus tereticornis is frequently used in hybrid crosses to improve E. globulus adventitious rooting ability. Although environment is important in rooting success, there is still need for genetic improvement.; We have used amplified fragment length polymorphic (AFLP) markers, 73 F1 progeny and a two-way pseudo-test cross strategy to construct two genetic linkage maps. In the E. tereticornis map, 268 markers were ordered in fourteen linkage groups (919 cM). The E. globulus map had 200 markers in sixteen linkage groups (967 cM). Results from the PGRI software were compared with MAPMAKER. Framework markers were ordered with 90% average confidence level.; Vegetative propagation traits were evaluated in this F1 family in 1995 and 1996. The inheritance of AFLP markers was assessed in a selected and a random sample of F1 individuals. Quantitative trait loci (QTL) analyses were performed using chi-square tests, single marker analysis, interval mapping and composite interval mapping. Three QTL were hypothesized to influence mortality, nine adventitious rooting, four petrification, one sprouting ability and four the instability of adventitious rooting. Most putative QTL were detected in successive years, accounting for 2.6--17.0% of the phenotypic variance of a trait (R2). Estimated standardized gene substitution effects varied between 0.13 and 0.49 phenotypic standard deviations (sigmap).; Heterologous amplification of codominant microsatellite markers developed from E. grandis and E. urophylla was successful in 78% loci screened in the E. tereticornis x E. globulus F1 family. Thirty eight microsatellite loci were mapped to E. tereticornis and 28 to E. globulus . Eleven microsatellite loci heterozygous in the four species allowed us to propose homeologies among eleven linkage groups in E. tereticornis , ten in E. globulus, eight in E. grandis and six in E. urophylla. Putative QTL for vegetative propagation were detected on homeologous linkage groups. Our findings indicate high transferability of microsatellite markers between related eucalypt species and establish foundations for the investigation of synteny in this genus.; Genomic research will emphasize the comparison of genes across species using map-based and sequence-based tools.