Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/12/1996
Publication Date: N/A
Technical Abstract: Our present method of inserting a new gene (eg. Bt) into cotton consists of infecting cotton hypocotyls with modified strains of Agrobacterium containing the gene of interest, selecting transformed callus from these infected hypocotyls, reducing this selected callus mass into single cells or small cell clumps, further screening of these cells for the presence of the new gene through the use of a linked marker gene, and regenerating new plants from those cells that carry the new gene via somatic embryogenesis. This approach has been highly successful, but several inherent problems are associated with the procedure. Our new approach does not include the use of tissue culture (i.e. development of callus or the regeneration of plants from single cells). The approach includes the use of an Agrobacterium system to insert new genes directly into meristematic cells. Agrobacterium infects plant tissues if they are physically or chemically damaged. Through hthis process of infection, new genes that have been specifically engineere in the bacterium are transferred to cells of the infected plant. Cotton has a very unique germination process in that the terminal meristem in the ungerminated seed is very immature. This can be seen by the extended period of time required for a cotton seedling to initiate its first true leaves (not the cotyledons). The newly germinated seedling develops its terminal growing point after it imbibes water. In the ungerminated seed, the terminal growing point consist of a few cells that will, upon germination, divide and become the terminal meristem. If the immature meristem is conditioned or treated, so that Agrobacterium successfully infects one or more of these cells, then it is possible to insert a new gene during the early stages of germination.