Regeneration and Agrobacterium-mediated genetic transformation of twelve Eucalyptus species

Eucalyptus is a genus of over 900 species and hybrids,and many of them are valuable fast-growing hardwoods.Due to its economic importance,Eucalyptus is one of the early tree species whose genomes were deciphered.However,the lack of efficient genetic transformation systems severely restricts the functional genomic research on the plant.The success of Eucalyptus regeneration and transformation depends greatly on the genotypes and explants.In this study,we systematically screened 26 genotypes from 12 Eucalyptus species in an attempt to obtain Eucalyptus genotypes with high regeneration potential.We developed two common regeneration media that can be applied to most tested Eucalyptus genotypes for both seeding hypocotyls and cloned internodes as explants.We then implemented DsRed2 as a visual marker for genetic transformation efficiency test.Our results suggest that E.camaldulen and E.robusta are amenable for genetic transformation.Finally,we successfully set up a stable Agrobacterium-mediated genetic transformation procedure for both E.camaldulen and E.robusta using seeding hypocotyls and cloned internodes respectively.Taken together,our study provides valuable means for vegetative propagation,gene transformation,CRISPR based gene mutagenesis,activation and suppression,as well as functional characterization of genes in Eucalyptus.

Genetic variation and selection of 10-year-old Eucalyptus camaldulensis based on wind damage index and wood properties

Typhoons are becoming frequent and intense with ongoing climate change,threatening ecological security and healthy forest development in coastal areas.Eucalyptus of a predominant introduced species in southern China,faces significant growth challenges because of typhoon.Therefore,it is vital to investigate the variation of related traits and select superior breeding materials for genetic improvement.Variance,genetic parameter,and correlation analyses were carried out on wind damage indices and eight wood proper-ties in 88 families from 11 provenances of 10-year-old Euca-lyptus camaldulensis.The selection index equation was used for evaluating multiple traits and selecting superior prov-enances and family lines as future breeding material.The results show that all traits were highly significantly differ-ent at provenance and family levels,with the wind damage index having the highest coefficient of genetic variation.The heritability of each trait ranged from 0.48 to 0.87,with the wind damage index,lignin and hemicellulose contents,and microfibril angle having the highest heritabilities.The wind damage index had a positive genetic correlation with wood density,a negative correlation with lignin content,a negative phenotypic correlation and a negative genetic correlation with microfibril angle.Wind damage index and genetic progress in the selection of eight wood traits varied from 7.2%to 614.8%.Three provenances and 12 superior families were selected.The genetic gains of the wind damage index were 10.2%and 33.9%for provenances and families,and these may be starting material for genetic modification for wind resistance in eucalyptus and for their dissemination to typhoon-prone coastal areas of southern China.