Thirteen years under arid conditions: exploring marker-trait associations in Eucalyptus cladocalyx for complex traits related to flowering, stem form and growth

We present an association analysis for seven key traits related to flowering, stem form and growth in Eucalyptus cladocalyx, a tree species suitable for low rainfall sites, using a long-term progeny trial with 49 open-pollinated maternal families in the southern Atacama Desert, Chile. The progeny trial was carried out in an arid environment with a mean annual rainfall of 152 mm. Simple sequence repeats (SSR) from a full consensus map of Eucalyptus were used for genotyping 245 individual trees. Twenty-three significant marker-trait associations were identified, explaining between 5.9 and 23.7% of the phenotypic variance. The marker EMBRA101 located on LG10 at 56.5 cM was concomitantly associated with diameter at breast height and tree height. Nine SSR were significantly associated with stem forking and stem straightness, explaining between 5.9 and 14.8% of the phenotypic variation. To our knowledge, this is the first study reporting a SSR-based association mapping analysis for stem form traits in Eucalyptus. These results provide novel and valuable information for understanding the genetic base of key traits in E. cladocalyx for breeding purposes under arid conditions.