The worldwide expansion of hybrid breeding and clonal forestry is to meet the demands of paper pulp and bioenergy. Although India was one of the pioneers in hybrid production of eucalypts only recently the hybrid clonal forestry is gaining momentum. Inter-specific hybrids are being produced to exploit the hybrid vigor of F1 individuals. Quality control genotyping for hybrid purity and parentage confirmation at the early stage is one of the essential criteria for clonal propagation and field trails for the assessment of growth performance. Eucalyptus being a obligatory outcrossed species with potential to self pollination, possibilities of pollen contamination are high. Hence, in the present study, Eucalyptus camaldulensis × E. tereticornis inter-specific hybrids were genotyped using 25 fluorescent labeled microsatellite markers available in public domain. Multiplex loading of PCR products was performed successfully for most of the microsatellite loci. Hybrid purity index was calculated and parentage was confirmed. Hybrid purity values ranged from 85 to 100 % showed the efficiency of controlled pollination techniques. A subset of six fully informative simple sequence repeats was identified for routine quality control genotyping for these hybrids. Detection of non-essential genotypes observed among the hybrid seedlings proved the significance of hybrid purity tests and the false hybrids were removed at the seedling stage. The hybrids with proven hybridity will be used for generation of genetic linkage, discovery of quantitative trait loci and the individuals with high productivity can enter into mass clonal multiplication.

Adventitious rooting, a key step in clonal propagation is affected by tree maturation. Micropropagation followed by microcuttings propagation has the potential to rejuvenate the clones thereby enhancing the rooting potential and minimize intra clonal variation. In this study, 33 superior performing Eucalyptus camaldulensis clones were propagated by rooting of stem cuttings (SCs) and micropropagation. Micropropagated plantlets were used as stock plants for microcutting propagation. Rooting of SCs and micropropagation was carried out with the coppice shoot cuttings and axillary buds respectively, obtained from approximately fourteen year old trees that had undergone one vegetative propagation cycle. The adventitious rooting recorded was significantly higher in micropropagation (24.8-100 %) and microcuttings (43-95 %) than SCs method (9.3-75.5 %). Studies on ontogeny of adventitious rooting showed the emergence of root primordium from the phloem region and root initials were noticed within 5-9 days after auxin treatment. Further, molecular marker analysis showed genetic uniformity except for two ramets, detected using inter simple sequence repeats (ISSR) markers and suitable corrective measures were taken to avoid entry of such plantlets for mass multiplication. This study demonstrates the importance of integration of micropropagation and microcuttings production for rejuvenation and mass multiplication. Although current rejuvenation and root induction treatments favored adventitious rooting, the basic mechanisms involved in rejuvenation and adventitious rooting need to be explored for hassle free industrial rooting process, consequently cost effective propagation.

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