Discovery of marker-trait associations for growth in Eucalyptus grandis through association mapping

PAMELA V. VILLALBA; JANET HIGGINS; NATALIA C. AGUIRRE; CINTIA ACUÑA; MARTÍN N. GARCÍA; EDUARDO P. CAPPA; JUAN GABRIEL RIVAS; MARIA C MARTÍNEZ; JAVIER OBERSCHELP; LEONEL HARRAND; JUAN LÓPEZ; MARTIN MARCÓ; H. ESTEBAN HOPP; NORMA PANIEGO; SUSANA N. MARCUCCI POLTRI

Cambridge

Encuentro; UK Plant Evolution 2016 meeting; 2016

University of Cambridge

Eucalyptus is a diverse genus of flowering trees, in the myrtle family, Myrtaceae. The trees are mostly native to Australia, however, Eucalyptus tree species and hybrids are now the most widely planted hardwoods worldwide, primarily due to their fast growth, adaptability, short rotation and high productivity. Both E. globulus and E. grandis are popular in South America for pulp and paper production. The identification of genetic factors underlying variation for growth and wood properties is important for gene discovery and forest breeding programs.Here we describe an association mapping study which has been used to identify genomic regions underlying growth and wood property phenotypes. A total of 188 individuals from an open-pollinated progeny trial in Argentina were assessed for different characteristics related to growth and quality of wood such as DBH (diameter at breast height), FORM (straightness of bole), TH (total height), PILO (estimated wood density by pilodyn), LIG TOTAL and KLASON (tenor and type of lignin), SG (ratio Syringil:Guayacil of lignin), ET EXT and EXT TOTAL (ethanolic and total extractives) and DB (basic density conventional). The population was genotyped using a high throughput array-based genotyping system of 7,680 DArT markers and a panel of 384 single nucleotide polymorphism (SNP) markers developed using the Illumina GoldenGate Genotyping assay. 3,003 high quality DArT molecular markers and 160 SNP markers were polymorphic and therefore used in the association analysis.Genetic structure, carried out using 400 randomly selected DArT markers, revealed three subpopulations consistent with the Australian origins present in the Argentine population. Marker-trait associations (MTA) were found for DBH, FORM, TH and VOL. Sequences of the markers with significant associations were mapped and annotated using the E. grandis genome. 1,930 genes were identified in silico to be located within a 600kb window surrounding the MTA regions. 53 of the genes are potentially interesting candidates for forest breeding programs as they are important MYB transcription factors, involved in the cellulose and lignin pathways or involved in the synthesis of peroxidase and laccase genes.