A method for genetic transformation of germinating seeds and seedlings of Eucalyptus grandis × E. urophyllais described using the sonication-assisted Agrobacterium-mediated transformation (SAAT) system. Seeds germinated for 2 d, and 15-d-old seedlings, sonicated for 30 s, had the highest percentage of β-glucuronidase (GUS) transient expression (21.7 and 37.4%, respectively). Pre-sonication greatly enhanced the efficiency of transformation. The differential transformation of tissues was also investigated, with seeds imbibed for 2 d having over 90% of the blue sectors localised in cotyledons and in the intersection of the hypocotyls and roots, whereas in 5-d-old seedlings, 70% of GUS activity was detected in cotyledons. However, 15–17-d-old seedlings had around 60% of transformed sectors localised in the first pair of leaves. The efficiency of the method was also assessed using a chimeric construct containing the Lhcb1*2 gene of the 28 kDa chlorophyll a/b binding pea protein from the LHCII antenna. Four stable transformants were confirmed by genomic blotting.

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

No abstract

The genus Eucalyptus is currently an important source of timber, cellulose pulp, and energy in a world that is becoming increasingly more conscious of the need to use renewable resources. This chapter initially explains the importance of hybridization and cloning techniques in intensive breeding programs that occurred in Brazil during the last few decades. The strength of these programs is based on the selection of the genetic material and the evaluation of the factors that can influence the expected genetic gains in forestry breeding programs using seeds. Factors such as endogamy, floral development, pollen viability, and pollination are discussed together with seed vigor and the influence of environmental factors on correct evaluation of candidate material. The recent application of molecular markers in eucalypt breeding programs is also mentioned with particular emphasis on genetic diversity, genotyping, and their association with disease resistance. An introduction into Eucalyptus tissue culture is also given as a prelude to the current status of genetic transformation using biolistics and Agrobacterium tumefaciens in this genus. The final sections describe the current challenges, disease resistance, and wood quality for large‐scale cultivation and utilization of eucalyptus wood as prime material.