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Identification of RFLP markers for the Ht1 gene by comparison of inbreds and their Ht1-conversions --Manju Gupta, F. Dale Park, Bradley Hoo, Matthew Frome, David Zaitlin, Yan-San Chyi, William D. Banks and Philip Filner Fifteen RFLP (restriction fragment length polymorphism) probes which detect loci on chromosome 2L were used for comparing the occurrences of RFLPs in 8 inbred/Ht1-converted line pairs--A632, A635, B37, B73, N28, Mo17, A619 and Oh43. Five restriction enzymes were used: EcoRI, EcoRV, HindIII, BglII and BamHI. Correlations between 3 RFLP markers and the Ht1 gene for resistance to Bipolaris turcicum (Pass.) Shoemaker were detected. When DNA was digested with the restriction enzyme EcoRI, RFLPs were detected with the probe SGCR506 in 8 out of 8 cases. The RFLP patterns in the Ht1-converted lines fell into 2 classes, which is consistent with the use of 2 Ht1 gene donors--Ladyfinger popcorn and GE440. Thus there was a 100% correlation between presence of Ht1 and presence of an RFLP detected by SGCR506. With EcoRV and probe SGCR507, RFLPs were detected in 6 out of 8 cases. With BglII and probe SGCR25, RFLPs were detected in 6 out of 8 cases. The order of the loci detected by these RFLP probes is SGCR507 - SGCR506 - SGCR25, proceeding away from the centromere. The map distance between SGCR507 and SGCR25 is approximately 14cM, which indicates that a surprisingly large and distinct chromosomal segment, not merely a locus, has been transferred when Ht1 has been introgressed. From these results, the Ht1 gene is probably within the 14cM fragment, and in the vicinity of the RFLP locus detected by SGCR506. Data from segregating populations are being analyzed to determine the genetic linkages of these loci.

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