Artificially induced protogyny (AlP) is a new technique for the controlled pollination of Eucalyptus, without emasculation. AlP involves cutting off the tip of the operculum of the mature flower bud just prior to an thesis, with the cut positioned so as to remove the stigma, and then applying the target pollen to the exposed cutsurface of the upper style.In trials in Brazil and Australia, rates of capsule retention and seed yield, and therefore yields of seeds per bud pollinated, have been very similar for AlP and one-stop pollination (OSP). However, AlP has achieved a 3-18-fold increase in productivity over OSP and conventional (three-visit) methods, in terms of seed produced per operator hour.Contamination levels in the Brazilian experiment ranged from 3.75% in buds pollinated at the ripe/yellow stage, to 0.77% in buds pollinated at the immature/green stage. The yield of2.0 seeds per bud pollinated with AlP at the immature/green stage was unacceptably low compared with 17.2 seeds per bud at the ripe/ yellow stage. Molecular genetic analysis of seedlings produced from one of the E. grand is x E. camaldulensis crosses in Australia confirmed that all 20 seedlings were from the target cross.The high operator productivity and relatively low levels of contamination achieved with AlP, across several eucalypt species, make it a potentially attractive technique for operational crossing. Our experiments were carried out in indoor clone banks that contained very few potential insect pollinators, so self-pollination is likely to be the main source of the contamination observed in the Brazilian experiments. Higher levels of contamination from non-target outcross pollen may occur following AlP on trees exposed to normal levels of pollinator activity.

Repeated pruning of stock plants is a common approach to delaying maturation and maintaining the propagation ability of cuttings, but little is known about the hormonal or anatomical basis for this phenomenon. We tested the effect of two different stock-plant pruning heights (15 cm and 30 cm) on shoot production, rooting capacity and rooted cutting vigour of six clones of the eucalypt Corymbia torelliana × C. citriodora. We determined whether differences in rooting potential were related to indole-3-acetic (IAA) and abscisic acid (ABA) concentrations, or the degree of lignification or sclerification, of the cuttings. Maintaining stock plants at 15 cm height sometimes reduced the production of stem cuttings. However, it often increased the ensuing percentage of cuttings that formed roots, with mean rooting across all clones increasing from 30%-53%. Therefore, the number of rooted cuttings produced by short stock plants was similar to, or higher than, the number produced by tall stock plants. Cuttings from shorter stock plants had faster root elongation and occasionally greater root dry mass, shoot dry mass or shoot height than cuttings from tall stock plants. These differences in rooting potential were generally not related to differences in IAA or ABA concentrations of the cuttings or to differences in their stem anatomy. Pruning at the lower height was more effective in maintaining clonal juvenility, supporting previous OPEN ACCESSForests 2015, 6 3764 findings that stock plant maturation is a limiting factor in clonal propagation of Corymbia torelliana × C. citriodora.

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Near infrared spectra obtained from leaf surfaces of Eucalyptus grandis seedlings were calibrated against physiological measurements of plant water stress, namely: relative water content, leaf water potential and stomatal conductance. In a controlled environment facility, spectral data were obtained from both abaxial and adaxial leaf surfaces as well as upper and lower leaves in the stem. The strongest coefficients of determination using cross-validation were r 2 CV = 0.85 for relative water content, r 2 CV = 0.74 for leaf water potential and r 2 CV = 0.80 for stomatal conductance. The use of a portable NIR instrument enabled the rapid assessment of physiological status of seedlings and would enable in situ, non-destructive, high-throughput monitoring of drought and recovery in the field. This would be particularly useful for non-destructive measurement in longitudinal studies.