Micropropagation and horticultural potential of native Tasmanian Liliaceae and Iridaceae

A study encompassing a range of botanical research areas was undertaken to determine the horticultural potential of some members of the native Tasmanian Liliaceae and Iridaceae. Six main species were studied: Blandfordia punicea, Dianella tasmanica and Milligania densiflora from the Liliaceae as well as Diplarrena moraea, Diplarrena latifolia and Isophysis tasmanica from the Iridaceae. With the exception of D. tasmanica and D. moraea, all species are endemic to Tasmania. Seed germination trials were carried out to assess the viability of this method of propagation. The natural germination percentages were extremely high for B. punicea (93-100%), D. moraea (97%) and I. tasmanica (90-100%) and reasonably high for D. latifolia (76%). For D. tasmanica and M. densiflora they were much lower (38% and 48%, respectively). The germination percentage of M. densiflora could be increased to 88% simply by germinating the seed in vitro; it could be increased further to 90% by disinfesting seeds for 35 min and growing them on a 1/2 MS medium. However, for D. tasmanica there are dormancy mechanisms present which proved more difficult to overcome. The most promising methods for this species were smoke treatments and partial removal of the testa. The percentage of seeds germinating increased with increasing smoke extract concentration; however, 100% smoke inhibited germination. Removal of part of the testa and growth in vitro was the best treatment, with 90% germination achieved. In vitro propagation was achieved for all species studied. Successful protocols were devised for disinfestation, shoot initiation and multiplication, rooting and transplanting to ex vitro conditions. Not all explant types investigated were suitable for all species, with the major problem being contamination. Meristematic regions originating underground were more difficult to disinfest than the immature floral explant types that originated above-ground. In general, a MS or 1/2 MS medium was suitable for growth of all species studied and BAP (at 8-32µM) was generally successful for shoot multiplication. Roots often grew on shoots on multiplication media, or could be induced to form on a medium containing NAA (or less successfully, IAA or IBA) or by placing them on a medium free of plant growth regulators. Transplanting was successful for all species, with a high percentage of plantlets surviving. However, they were susceptible to damping off if too much water was applied. Experiments were also performed to examine the possibility of forcing D. tasmanica plants to flower out-of-season. By manipulation of temperature and photoperiod plants could be forced to flower earlier. The fire-related treatments of smoke and foliage removal also increased the percentage of flowering plants compared to the control.