Novel Applications of Plant Tissue Culture

INTRODUCTION In 1902 Gottleib Haberlandt proposed the idea of growing individual plant cells on artificial medium. While Haberlandt never realized his idea, the 105 years since has seen the concept evolve into a powerful tool utilized throughout the plant sciences. Plant tissue culture broadly refers to growing plant cells, tissues, organs, seeds, or other plant parts in a sterile environment on a nutrient medium. Tissue culture is being used for an increasing variety of purposes. Originally used largely for fundamental research to study cell division, plant growth, and biochemistry, the technology has grown and is being widely implemented on a more applied scale. In many cases, protocols have been developed and refined so that they have become a standard and commercially viable practice for propagating many important horticultural crops. The key to the successful application of tissue culture is the manipulation of media compositions to achieve desired outcomes (Benson, 2000; Gamborg, 2002). By altering media components, tissue can be induced to produce shoots, roots, callus, or somatic embryos or inhibit growth for long-term storage. The most common application of tissue culture is micropropagation, which usually involves growing plants in an agar solidified nutrient media. Micropropagation can facilitate the rapid production and propagation of plant species. Somatic embryogenesis also has become an important technique for plant regeneration and multiplication. Somatic embryogenesis refers to the initiation of embryos from previously differentiated somatic cells. This process usually involves two distinct steps. The first step, induction of embryonic cells or proembryoids, is required to initiate cell division and establish a new polarity in the somatic cells. The second step involves the development of the proembryoid cells into embryos (McKersie and Brown, 1996; Jiménez, 2005). As plants are often regenerated from a single or a small number of cells, this approach may provide a powerful mechanism to induce polyploidy, recover mutations, or stabilize chimeras. Several other specialized tissue culture techniques have been developed to overcome barriers associated with conventional breeding. For example, embryo rescue and ovule culture techniques may be used to alleviate problems associated with post fertilization barriers such as triploid blocks (Mohapatra and Rout, 2005; Olsen, et al., 2006). At the North Carolina State University, Mountain Horticultural Crops Research and Extension Center, in Mills River, North Carolina, tissue culture has become an integral part of the nursery crops breeding program. Here we present an overview of some of the novel approaches used in our program.