International audienceAbstract Key messageThe identification of an anomaly with deleterious effect and Mendelian segregation (3 normal: 1 abnormal) allowed the detection of a marker linked to a locus for the anomalous phenotype. This marker could be useful in marker-assisted breeding programs and for understanding this anomaly. ContextDue to the mixed mating systems in Eucalyptus genera, outcrossing populations exhibit low inbreeding depression (abnormalities). In this study, we identified a developmental anomaly in a controlled cross of Eucalyptus grandis, with Mendelian segregation. The anomaly was characterized by branching, reduced height, smaller individual leaf area, and asymmetrical leaf shape. Aims and methodsTo investigate and evaluate the anomaly detected, we performed morphological and molecular analysis. The genitors and bulks of normal and abnormal individuals were screened with random primers. The polymorphic markers that co-segregated with the anomalous phenotype were selected, validated, converted into SCAR markers and analyzed in silico. ResultsMorphological analysis showed significant differences between normal and abnormal phenotypes. The co-segregating marker was present in one genitor, in all abnormal individuals, and in 31 % of normal individuals (recombinants). In silico analyses revealed a mutation of two base pairs between the contrasting phenotypes and identified the marker in an intergenic region presenting partial identity with an expressed sequence tag (EST) of Bet v1-like genes. ConclusionA marker was developed to identify the recessive allele for the anomaly in E. grandis. This will be important for management of crosses in eucalypt breeding programs and in anomaly studies

About 95% of Eucalyptus species present an organ known as a lignotuber, a basal woody swelling that holds a large number of dormant buds in a protected position along with carbohydrates and other nutrients. The importance of this trait in Eucalyptus species relates to its regenerative capacity, particularly in the context of coppicing practices and survival in regions of high abiotic stress, especially fire. In this study, we identified and characterized a genomic region associated with the lignotuber trait in commercially important Eucalyptus species by developing a polymorphic marker that co-segregates with lignotuber presence. The marker was then converted into a SCAR (Sequence Characterized Amplified Region) marker, validated in four other Eucalyptus species and hybrids and analyzed in silico. Our investigation presents a marker (ELig) that is effective in identifying individuals with lignotuber. In silico and Southern blot analyses show that the marker is present in a single copy region and is related to auxilin/cyclin-G associated kinase, containing a DnaJ domain. The ELig marker is an important tool that can be used to manage crosses in Eucalyptus breeding programs and inform studies involving lignotuber development and genetics. Eucalyptus is a widely planted tree genus due to its ability to adapt, grow, and produce quality wood that can be used for multiple end purposes 1,2. In Brazil, Eucalyptus plantations are extremely important as they comprise more than 71% of the total forest plantation area (5.56 million ha), making the country a leader in the forestry sector 3. In this context, researchers and foresters seek to implement tree improvement programs, advance silvicultural practices to increase productivity, introduce desirable traits, and reduce the environmental impacts of eucalypt plantations 4-6. A common practice in Eucalyptus management is coppicing, which offers an initial sprout growth rate greater than planting seedlings and is enhanced by the presence of an organ known as a lignotuber 7-9. Natural conditions in Australia led to the evolution of the Eucalyptus genus which is strongly associated with the occurrence of fire. Trees have been both survivors and promoters of fire over millions of years, leading to the development of a series of regeneration strategies including lignotubers 10. Lignotubers are basal, woody swellings that can form rapidly during the seedling stage 11-13. They hold a large number of dormant buds in a protected position, along with carbohydrates and nutrients necessary for bud development 11,12,14. Under normal conditions, the buds remain dormant, but they can be activated by stress factors, such as defoliation 14 , fire and coppicing 9,15 , and nutrient and water deficiencies 13,16 , underscoring the importance of the lignotuber for tree survival. These organs are present in 95% of all Eucalyptus species, including E. urophylla, E. brassiana, and E. saligna; however, some commercial species, such as E. grandis, E. regnans, E. delegatensis, E. pilularis, and E. niten...

Flowering time is an important trait for tree breeding because it determines the speed of generation turnover and therefore the rapidity of genetic gains, and it is of particular interest in Eucalyptus species. In this work, we used simple sequence repeats (SSRs), random amplified polymorphic DNA (RAPD) analysis and specific markers for flowering to evaluate early flowering segregation in a full-sibling family of Eucalyptus grandis and to identify molecular markers associated with the control of flowering time. A cross between a normal flowering tree (wild-type) and early flowering tree resulted in 118 progeny with a 1:1 Mendelian segregation ratio for flowering time (χ2 = 0.5424, P > 0.05), which suggested the action of one main gene in a locus named Early flowering in Eucalyptus grandis (PFEg). The SSR marker EMBRA 02 was related to the QTL PFEg, and identified this region as a candidate for trait control. These maps may be used as the basis for a study in which can be inserted new markers in an attempt to find more loci related to early flowering characteristic on eucalyptus.

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