Genetic mapping of the Glu-1Dx5 transgene in maize (Zea mays L.)
Six events (7, 17, 18, 35, 38, 42) of the inserted wheat Glu-1 Dx5 transgene were mapped in the maize (Zea mays L.) genome using SSR markers at known loci. Twelve mapping populations, two for each event, were created by co-bombarding Glu-1 Dx5 and bar on separate plasmids into Hi-II embryogenic tissue. Secondary objectives of determining and analyzing the segregation ratios for Glu-1 Dx5, bar, 1DX5 protein, and herbicide response from bar expression were also performed. The hypotheses are that the segregation ratios will be 3:1 within the ten selfed (F2) populations and 1:1 within the two backcross (BC1) populations. Chi-square tests were implemented to assess for deviation from the hypothesized segregation ratios. Significant deviations from the expected segregation ratios were detected in one of the selfed populations (9) within event 17 for each gene and phenotype analyzed. Other significant deviations were detected in a selfed population (6) from event 17 for 1DX5 protein and a selfed population (26) from event 38 for herbicide response. The ability to use herbicide response as a surrogate test for the presence of Glu-1 Dx5 was also accessed. A high level of herbicide resistance conference from bar expression was discovered in all twelve populations. Coupled with the strong linkage that was detected between Glu-1 Dx5 and bar in all twelve populations, it is concluded that herbicide resistance can be used as a high throughput method to test for the presence of Glu-1 Dx5. Linkage of Glu-1 Dx5 to SSRs was detected and genetic map placement was attained for five of the six events. Event 17 was placed on chromosome 1, 35 on chromosome 6, 38 on chromosome 8, and 7 and 18 on chromosome 9. No linkage was detected between Glu-1 Dx5 and the SSR loci that were genotyped within the mapping populations of event 42.