03427naa a2200253 a 450000100080000000500110000800800410001902400550006010000240011524501200013926000090025952026440026865000150291265000110292765000180293865000140295665000350297070000220300570000210302770000200304870000170306870000250308577300630311021392292022-01-21       2021    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1016/j.indcrop.2021.1139062DOI1 aCASTRO, C. A. de O.  aAccelerating Eucalyptus breeding strategies through top grafting applied to young seedlings.h[electronic resource]  c2021  aThe genetic improvement of tree species takes time. The breeding cycles are long and this makes the process difficult. However, the selection and recombination cycles can be reduced considerably by speeding up the recommendation of new clones using a top grafting method in young seedlings. Eucalyptus top grafting is very promising since this graft technique can induce ultra-early flowering, making the use of the Genome-Wide Selection effective. Thus, the aim of this study was to establish a standard methodology for top grafting of young seedlings in order to enable flowering in Eucalyptus progenies. In this sense, 384 top graftings were performed with seedlings originating from 3 different crossings among Eucalyptus urophylla S.T. Blake and Eucalyptus grandis W. Hill ex Maiden species. The progenies? seeds from each crossing were separated, sown, and conducted as seedlings until they reached 60?90 days and 150?180 days of development. The graftings were performed at two different periods of the year: July and October (six and three months before the natural flowering of the species). In addition to the mentioned effects, the efficiency of paclobutrazol in stimulating flowering was analyzed from its application on each rootstock genotype. At three-month intervals, the live top grafting samples were evaluated on flower production (bud and fruit account) and scion development (survival rate and canopy area measurement). The differences between treatments and the interactions were detected using variance analysis and the Scott-Knott test (p-value&lt 0.05). Top grafting proved to be effective in inducing very early flowering in Eucalyptus, as it produced enough flower buds to carry out the next recombination cycle in progenies of the crossing between Eucalyptus urophylla × Eucalyptus grandis. The flowering was observed three months after the graft procedure. After one year of periodic measurements, the top grafting of 150?180 day old seedlings showed better results in all evaluated effects. Paclobutrazol application favored flowering, since all blooming graftings were in rootstocks in which the regulator was applied. The best time to graft young seedlings is six months before natural flowering, since it has resulted in greater flower production and growth of canopy area. Considering these results, top grafting of young Eucalyptus seedlings can guarantee fast production of flower buds and fruits. Thus, it will become possible to perform consecutive recombination cycles in selected progenies by Genome-Wide Selection in breeding programs, making this technique quite effective in the forestry sector.  aEucalyptus  aGenome  aPaclobutrazol  aEucalipto  aMelhoramento Genético Vegetal1 aSANTOS, G. A. dos1 aTAKAHASHI, E. K.1 aNUNES, A. C. P.1 aSOUZA, G. A.1 aRESENDE, M. D. V. de  tIndustrial Crops and Productsgv. 171, n. 1, 113906, 2021.