Potential use of polyploid eucalypt in forestry

Abstract

Polyploidy induction has been used as a strategy to select new clones, potentially increasing the genetic progress obtained by eucalypt breeding in Brazil. Genetic variation occurs among polyploids produced by the chromosome duplication of a diploid clone, which can affect their performance. The present study aimed to evaluate the performance of polyploid eucalypt clones under field conditions to verify if they are more adapted and stable for forest exploration and if polyploid performance depends on its diploid. The evaluations were performed on 80 synthetic tetraploid clones obtained, in equal number, from two diploid clones of E. grandis x E. urophylla hybrids. The experiments were conducted in four environments in São Paulo and Mato Grosso do Sul States, Brazil. Measurements of DBH (diameter at breast height) and MAI (mean annual increment) of three-year-old trees were taken. Results showed that few polyploid clones showed similar performance to their diploid of origin. On average, the diploid clone A showed performance 41.1% higher than that presented by its polyploids and the diploid clone B presented performance 75.7% higher than that obtained by the polyploids originated from it, in MAI. The clones x environments interaction was relatively expressive, although predominantly simple in many cases, indicating that the ranking of clones was similar among the evaluated sites. More adapted and stable clones were identified, although in most cases their performances were lower than diploids. The performance of polyploid clones was not affected by the performance of their diploid. The results found were important and indicate that the selection of polyploids that outperform diploid clones should be pursued, although there are still many questions regarding the use of polyploidy in eucalypt breeding.