Rapid multiplication of mature Eucalyptus hybrids through macro-and-micropropagation

Eucalyptus species are globally recognized and extensively planted hardwood trees whose flexibility, growth and diversity make them popular renewable sources of fibre and energy. Across the globe, the interest to create ways to develop significant hardwoods, like eucalypts, is rapidly growing. Although micropropagation offers a means to clonally propagate the desirable cultivars, the technique is often variety-specific for eucalypts. The present study aimed to expand our understanding of root initiation through macro-and-micropropagation in difficult to propagate superior full-sib matured hybrid (7-years-old trees) of eucalypts. Analysis of Variance (ANOVA) revealed that hormonal treatment of IBA (2,000–4,000 ppm) supplemented with Enterobacter sp. (10 cfu ml) significantly increased (p < 0.05) hybrid rooting through macropropagation. Notably, root initiation with maximum root development of 10.00% ± 0.91 and 3.75% ± 0.48 was observed at 3,000 ppm of IBA for hybrid genotypes FRI-PH3 (Corymbia torelliana × C. citriodora; 2A) and FRI-PH4 (E. pellita × E. urophylla; 1D), respectively. In the case of micropropagation studies, genotype FRI-4s (coppice shoots of E. tereticornis × E. camaldulensis, 10O) showed significant differences (p < 0.01) with various hormonal combinations (BAP, Kn and TDZ); and maximum number of shoot (4.0 ± 0.82) proliferation with average shoot length of 2.5 ± 0.15 cm was recorded in 0.5 mg L BAP, ½ MS medium and 0.5 mg L Kn in accordance to Duncan Multiple Range Test (DMRT). Afterward, for in vitro rooting, ¼ MS medium fortified with 1.0 mg L IBA was proved to be the optimal medium for root induction, the maximum number of roots per explant (5.0 ± 0.91) with an average root length of 3.10 ± 0.15 cm was observed. Overall, the study signifies successful macro-and-micropropagation of mature eucalyptus hybrids through branch cuttings and nodal segments.