Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2000
Publication Date: N/A
Interpretive Summary: We conducted genetic linkage tests with two transgenic plants and a genetic marker line of cotton. The transgenic plants contained the bacterial gene that confirmed resistance to 2,4-D. The two transgenic plants were the result of separate gene insertion events that are considered random events. Both transgenes were linked to the same marker gene, naked seed. Linkage valves were similar but consistently different. The tests could not determine if the locations were close or the same. Additional test materials and tests are required to determine the exact site.
Technical Abstract: We found genetic linkage of two independent gene insertions with a single marker locus. The bacterial gene (2,4-D monooxygenase (tfdA)] was introduced into cotton to provide resistance to 2,4-dichlorophenoxyacetic acid (2,4-D). The gene was inserted by Agrobacterium tumefaciens mediated transformation, and multiple cell lines with the gene insertion were produced. Transformed cell lines were verified first to contain the introduced DNA, and transgenic plants were evaluated for expression of resistance to 2,4-D. Transgenic plants that survived the screening were then progeny tested for inheritance and level of expression of the gene insertion. Separate germlines that exhibited monogenic dominance for resistance to 2,4-D were retained, and we selected two for linkage analysis. Multiple marker lines T582 and T586 were crossed with the two 2,4-D resistant lines. Fl, P2, and backcross/testcross progeny were produced and evaluated for segregation of resistance to 2,4-D and the marker loci. Linkage was found between 2,4-D resistance of both transgenic lines and the Naked seed-1 morphological marker. Only two-point linkage tests were possible, so the orientations on the chromosome with respect to the marker could not be determined. Linkage values from the two transformants were consistently different but not statistically significant. Both transgenes were inserted into the same chromosome, but we are not able to determine the specific site(s). Preliminary data suggests close but different locations. Crosses have been made to produce segregating progeny that will be able to distinguish independence of the insertion sites and chromosome orientation.