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...

O gênero Ceratocystis contempla diversas espécies distribuídas em vários lugares do mundo. Uma planta infectada com este fungo apresenta como sintomas primários o escurecimento do sistema vascular e como sintomas secundários murcha, seca e morte da planta, decorrentes do colapso do xilema, causando pelo fungo. Estes sintomas são típicos de estresse hídrico e ocorre em plantas doentes como resultado do desenvolvimento do patógeno no interior de seus vasos e também por mecanismos de defesa da planta que bloqueiam vasos do xilema. O presente trabalho teve como objetivo realizar as análises das reações estruturais e bioquímicas que possam estar ligadas a resistência de plantas de eucalipto a Ceratocystis. Para observação das reações estruturais e bioquímicas das plantas de eucalipto à colonização do fungo, plantas de eucalipto de Eucalyptus grandis (Clone C3 resistente ao fungo e Clone C10 suscetível ao fungo) foram inoculadas com um isolado de C. fimbriata. Após a inoculação, fragmentos dos caules das plantas inoculadas foram coletados (7 e 21 dias após inoculação), fixados em "Karnovsky" e processadas para polimerização em historesina. Foram usadas diferentes técnicas para visualização de gomas e géis, grãos de amido, arginina, ligninas e tiloses. As tiloses, os géis e gomas foram observados em todas as plantas inoculadas com Ceratocystis. O acumulo de lignina foi observado somente em plantas resistentes. O amido e a arginina foram observados em todas as plantas trabalhadas. Estes resultados sugerem que a resistência de eucalipto ao fungo Ceratocystis pode estar ligada a capacidade de acumulo de ligninas nas células, já que esta estrutura somente foi visualizada em plantas resistentes inoculadas com o fungo.

We compared the anatomy, density, chemical contents, and bioenergy values of Eucalyptus grandis and hybrids of Eucalyptus grandis x Eucalyptus urophylla wood originating from diploids, triploids and tetraploids. We hypothesize that Eucalyptus grandis and hybrids of Eucalyptus grandis x Eucalyptus urophylla with different degrees of ploidy have variations as a result of different sets of chromosomes producing different phenotypic expressions and chemical constituents, such as variation in cell size and frequency, which would directly influence wood quality. Twenty-year-old trees were cut, eight for each ploidy: diploids and tetraploids are E. grandis; triploids are E. grandis x E. urophylla. We use standardized techniques. Our hypothesis was confirmed. Triploid and tetraploid trees presented wider trunks, taller trees with longer stems and wider crowns compared to diploid trees. Wood density showed significant radial variation only in diploids, while triploid and tetraploid trees were more homogeneous. In polyploid trees, the anatomical features did not clearly present a radial pattern. Triploid and tetraploid trees presented higher density wood than diploid trees. The chemical constituents varied from pith to bark in the three ploidies, but no differences between ploidies were found. For energy generation purposes, diploid and triploid trees are more desirable than tetraploid trees.

ABSTRACT.Eucalyptus urophylla is an important species in the Brazilian forest sector due to its rapid growth rates and resistance to disease. The aim of this study was to verify Mendelian inheritance, genetic linkage, and genotypic disequilibrium for 15 microsatellite loci, with the goal of producing a robust set of genetic markers. Mendelian inheritance and genetic linkage analyses were carried out using genotypes from maternal trees, and their open-pollinated seeds and genotypic disequilibrium were assessed using adult trees. By comparing heterozygous maternal genotypes and their seeds, we found no significant deviations from the expected 1:1 Mendelian segregation and the expected 1:1:1:1 segregation hypothesis for pairwise loci. For adult trees, we did not find strong evidence of genotypic imbalance for pairwise loci. Our results indicated that the analyzed set of microsatellite loci could be used to carry out analyses of genetic diversity, mating system, and parentage in E. urophylla.