Accelerating eucalypt clone selection pipeline via cloned progeny trials and molecular data

Abstract

The high productivity of Eucalyptus spp. forest plantations is mainly due to advances in silvicultural techniques and genetic improvement associated with the potential that many species of the genus have for vegetative propagation. However, long reproduction cycles for forest species pose significant challenges for genetic progress via traditional breeding programs. Furthermore, there is often poor correlation between individual (seedling) performance in initial (progeny trials) and final (clonal trials) stages of the breeding program. In this scenario, cloned progeny trials (CPT) offer an alternative to accelerate the eucalypt clone selection pipeline, combining progeny and clonal trials in a single experiment. CPT has the potential to speed up the evaluation process and increase its efficiency by developing new commercial genotypes that were tested as clones from the initial stage of the breeding program. Thus, this study aims to assess the potential of CPT to accelerate eucalypt clone selection programs by estimating the genetic parameters, analyzing responses to selection, and predicting the adequate number of ramets to be used in CPT of Eucalyptus urophylla x Eucalyptus grandis. The results show that when the number of ramets per progeny was decreased from five to one there was a reduction in the estimates of broad-sense heritability and accuracy. However, three ramets/progeny can be used without significant reductions in these estimates. CPT accelerates clonal selection by combining progeny and clonal trial methodologies, enabling an evaluation of performance as both progeny and clone. This capacity is very important for vegetatively propagated crop species such as Eucalyptus. Integrating CPT with SNP markers can offer an alternative to shorten the tree clone selection pipeline, better estimate and decompose the genetic variance components, and improve the correlation between initial and final performance for selected genotypes. This study confirms the potential of CPT to improve selection processes and accelerate genetic gains in the eucalypt clone selection pipeline.