Jerry Pullman, Professor of the Practice
Ph.D., Plant Pathology, University of California at Davis
Office: IPST 590
Plant embryo and seed development for coniferous species, somatic embryogenesis, clonal propagation, plant tissue culture for rare and endangered species
Forest productivity can be increased by planting tree farms with fast-growing high-value trees. To take better advantage of long-term breeding programs and genetic engineering advances that produce more lumber, pulp and paper, energy, or chemicals from renewable tree biomass, methods to propagate large numbers of superior trees are needed. As demands for forest products grow and the land base to produce trees shrinks, it will become difficult for the U.S. forest products industry to remain globally competitive. Clonal propagation by somatic embryogenesis can help capture benefits of breeding or genetic engineering to improve wood quantity, quality, and uniformity.
Loblolly pine is the major species planted across the Southern U.S. with 1 to 1.5 billion trees planted annually. Forest productivity can be increased by planting tree farms with large numbers of elite, high-value trees. Sexual production of trees yields trees with variable characteristics. Methods to propagate large numbers of genetically superior conifer trees are needed. Clonal propagation technology is expected to play a major role in future reforestation of loblolly pine and other coniferous species if costs are acceptable and if a high-enough percentage of high-value genotypes can be successfully propagated and established in the plantation setting.
The research interests of Jerry and his team are in the areas of culture and manipulation of plant stem cells, conifer seed physiology, multiplication of high-value trees through somatic embryogenesis, understanding the fundamental physical and chemical factors driving plant embryo development, understanding interactions between medium and plant cell growth in vitro and the creation of tissue culture systems necessary for the genetic engineering of forest trees. We are also interested in culture and storage of rare and endangered plant species for conservation.
Over one-fifth of the world's plants are becoming rare and endangered due to loss of habitat, over-collection, diseases, competition from exotic and invasive species, and global warming. We can help to save these species for the future by preserving them in seed banks, at safekeeping sites like botanical gardens, and by multiplying the rarest plants using plant tissue culture techniques. Several projects in partnership with the Atlanta Botanical Gardens are working to clone highly endangered plants using plant tissue culture techniques.
Torreya taxifolia Arn., an ancient evergreen tree, is considered to be on the brink of extinction. Less than 1000 native trees are known in the wild. A small number of rooted cuttings are propagated for dispersal to conservation groups but cuttings may carry unknown pathogens responsible for the decline of this species. In nature, many plants produce multiple embryos in their seeds. When one embryo succeeds and outgrows the rest, the others will terminate, allowing the leader to fill the seed. We have worked out methods of somatic embryogenesis to keep this natural multiplication process going in culture resulting in multiple plant copies. This technology has the potential to decrease seedling costs, allow protection and long-term storage of valuable genetic resources in cryostorage and to provide clean planting stock for conservation and restoration. We have developed a somatic embryogenesis tissue culture system that produces somatic seedlings and stores cultures cryogenically.
The genus Sarracenia forms a group of carnivorous pitcher plants found in bog environments mainly in North America. Pitcher plants use deep fluid filled cavities to attract and capture prey helping the plant to compete in the nutrient-poor habitat where they live. Insects are attracted to the cavity, usually by visual lures such as anthocyanin pigments and secretions of sweet-smelling nectar. Pitcher plant structure further creates a natural snare. Its pitcher is shaped like a tube containing slick side and brim surfaces, usually containing hairs, grooved in a downward fashion all of which are designed to ensure that the insects cannot climb out. Fluids within the cavity of the leaves (pitchers) has been shown to contain a wetting agent to help sink prey and coniine, a narcotic that helps subdue prey. Insects are drowned and their bodies are gradually dissolved by the low pH, enzymes and an invertebrate community that helps to shred and mineralize prey in some pitcher plants. The resulting solution of amino acids, peptides, phosphates, ammonium, and urea facilitates uptake of nitrogen and phosphorus.
With habitat destruction many pitcher plants have become rare and endangered. Three species of this genus, S. leucophylla, S. oreophila and S. purpurea are considered endangered in Georgia and S. oreophila is listed as federally endangered. In vitro techniques can be used to multiply rare or endangered plants. Once enough plants are available they can be used to supplement old populations or to establish new planting sites for conservation, research, education or recreational purposes. In addition, in vitro-grown plants can be sold to collectors decreasing the collection pressures on wild populations. We are working to develop in vitro propagation systems from seed, meristems, and rhizomes to multiply the number of endangered pitcher plants.
Wu, D., C. Sullards, D.D. Oldham, L. Gelbaum, G.S. Pullman and S.W. May. 2012. Myo-inositol hexakisphosphate, isolated from female gametophyte tissue of loblolly pine, inhibits growth of early-stage somatic embryos. New Phytologist 193: 313-326.
Northcutt, C., D. Davies, R. Gagliardo, K. Bucalo, R. O. Determann, J. M. Cruse-Sanders and G.S. Pullman. 2012. Germination in vitro, micropropagation, and cryogenic storage for three rare pitcher plants: Sarracenia oreophila (Kearney) Wherry (federally endangered), S. leucophylla Raf., and S. purpurea spp. venosa (Raf.) Wherry. HortScience 47: 74-80.
Johnson, T., J.M. Cruse-Sanders, G.S. Pullman. 2012. Micropropagation and seed cryopreservation of the critically endangered species Tennessee yellow-eye grass, Xyris tennesseensis Kral. In Vitro Cell. Dev. Biol - Plant. Online first: DOI 10.1007/s11627-011-9420-1.
Ma, X., K. Bucalo, R.O. Determann, J.M. Cruse-Sanders and G.S. Pullman. 2012. Somatic embryogenesis, plant regeneration and cryopreservation for Torreya taxifolia, a highly endangered coniferous species. In Vitro Cell. Dev. Biol - Plant. Online first: DOI: 10.1007/s11627-012-9433-4
Pullman, G.S and K. Bucalo. 2011. Techniques and protocol on pine somatic embryogenesis using zygotic embryos as explant materials. In: Plant Embryo Culture: Methods and Protocols, T. Thorpe and E. Young, eds. Humana Press. Pp. 267-291.
K. Namjoshi, S. Johnson, P. Montello, and G. S. Pullman. 2010. Assay and identification of bacteria associated with recycled containerboard. Journal of Applied Microbiology, 108: 416-427.
Pullman GS, Chase KM, Skryabina A, Bucalo K. Conifer embryogenic tissue initiation: improvements by supplementation of medium with D-xylose and D-chiro-inositol. Tree Physiol. 2009 Jan;29(1):147-56. Epub 2008 Dec 5.
Pullman GS, Johnson S. Osmotic measurements in whole megagametophytes and embryos of loblolly pine (Pinus taeda) during seed development. Tree Physiol. 2009 Jun;29(6):819-27.
Pullman GS, Johnson S. Loblolly pine (Pinus taeda) female gametophyte and embryo pH changes during seed development. Tree Physiol. 2009 Jun;29(6):829-36.
De Silva V, Bostwick D, Burns KL, Oldham CD, Skryabina A, Sullards MC, Wu D, Zhang Y, May SW, Pullman GS. Isolation and characterization of a molecule stimulatory to growth of somatic embryos from early stage female gametophyte tissue of loblolly pine. Plant Cell Rep. 2008 Apr;27(4):633-46.