| Summary |
The overall goal of our research is to increase Christmas tree production in the eastern region of North Carolina. One strategy is to identify species that can tolerate heat and drought, and to multiply genetic selections using micropropagation procedures. A second strategy is to identify and characterize drought tolerance genes, which subsequently could be used to transform drought tolerant species and enhance their tolerance to drought even more. I hypothesized that: micropropagation procedures established for pine species can be adapted to fir species: a drought-responsive gene (clT) isolated from allepo pine can improve drought tolerance, and Nordmann fir is more drought-tolerant than other fir species. My objectives were: (1) to develop clonal propagation procedures for selected fir Christmas trees, (2) to identify and characterize a pine drought-induced gene and (3) to evaluate the growth and survival of five fir species on a drought-prone field site. Clonal propagation procedures tested on four fir species were organogenesis, embryogenesis and lateral bud development. Balsam fir shoots were obtained from hypocotyls and cotyledon explants and were transplanted into root induction media. Organogenesis procedures could not be established for other fir species due to bacterial and/or fungal contamination. Embryogenesis procedures were tested with Fraser fir using cones harvested over three summers as a source of immature zygotic embryo explants. With each summer trial, improvements were made to the procedures. Embryogenic calli were established, but they deteriorated and were then discarded. Stimulation of lateral bud development was accomplished with Nordmann fir using seedlings maintained in the greenhouse and sprayed with a benzyladenine solution accompanied by three different excision treatments. Significant increases in bud development were obtained with all the treatments; BA-no cuts, BA-decap (apical and lateral buds clipped) and BA-stump (1/2 the height clipped) compared to the non-sprayed treatment. The c17 gene from Allepo pine was sequenced and a blast search suggests that it is similar to a family of cyclophilins, proteins which are involved in stress responses and development. Trees of six fir Christmas tree species (Nordmann, Canaan, Turkish, Fraser, Balsam and Momi) were planted on a drought-prone site in Pitt County, North Carolina. With replicated plots and irrigation and non-irrigation treatments, the five species were evaluated for their tolerance to drought by determining tree growth and survival over one growing season. Nordmann fir, Turkish fir and Momi fir had the highest survival with 40- 50% survival; Nordmann and Turkish also had the highest increase in new growth with 0.4 to 0.6 cm increase. All three of the procedures for clonal propagation are significant for multiplication of fir species in order to increase yield for the North Carolina Christmas tree industry. Because c17 identifies with a cyclophilin that responds to stress, it could be transferred to fiir species and increase their survival in eastern North Carolina. Nordmann fir field survival and height growth data in a stressful environment suggests that more evaluation of this species could be worthwhile. These studies can be used to determine the efficacy of introducing exotic Christmas tree species into eastern North Carolina. |
