Rooting and Acclimatization of Bunchberry In Vitro-Derived Propagules

This study evaluated the effects of nutrient salt formulations combined with auxin concentrations on subsequent in vitro adventitious root proliferation and the effects of different greenhouse propagation media combined with ex vitro auxin concentrations for acclimatization of bunchberry (Cornus canadensis L.).  A factorial combination of nutrient salt formulations (MS, LP, and ½ Macro MS) ranging from high to low salt concentrations and auxin, indole-3-butryic acid potassium salt (0, 5, 10 µM IBA), concentration were evaluated to determine a suitable medium for in vitro adventitious root proliferation.  Stage II multiplication propagules (callus-derived with average of 3 adventitious shoots) were transferred to the in vitro rooting factorial treatments.  Rooting data was collected at 4 and 8 weeks after transfer to rooting media treatments.  There were no significant factorial combination with respect to in vitro rooting.  The presence of indole-3-butryic acid potassium salt in the medium did have a significant effect on root number with 10 µM IBA having the highest success with adventitious root proliferation as compared to 0 and 5 µM IBA.  A factorial combination of greenhouse propagation media (perlite, fine grade vermiculite, and peatlite growing mix) and ex vitro rooting hormone concentrations (100% Talc, 0.1, and 0.3% IBA) were evaluated to determine a suitable ex vitro rooting and acclimatization protocol.  Stage II multiplication propagules, as previously described, were transferred to the ex vitro rooting/acclimatization factorial treatments.  Propagules were places in cell packs (37 mm² x 65 mm) and were placed under intermittent mist (mist interval of 6 s every 6 min) within a glass-covered greenhouse under natural photoperiod.  Data was taken on survival and root number 4 weeks after transfer to rooting/acclimatization treatments.  There were no significant factorial combination with respect to ex vitro adventitious root proliferation and plantlet survival based on acclimatization.  Treatments affecting acclimatization survivability were not significantly different.  The higher level of auxin, 0.3% was inhibitory to ex vitro root proliferation.  There were no differences with respect to root proliferation with 100% talc and 0.1% IBA.  Propagules growing in fine grade vermiculite had significantly fewer adventitious roots as compared to perlite and peatlite media.  In conclusion, bunchberry has shown successful adventitious in vitro root proliferation with the addition of 10 µM IBA to the nutrient salt medium.  Ex vitro adventitious rooting and acclimatization were successful achieved with the use of perlite or peatlite greenhouse propagation medium and 100% talc or 0.1% IBA supplemented at time of transplanting.