IDENTIFICATION OF AN RFLP MARKER TIGHTLY LINKED TO THE HT1 GENE IN MAIZE

We have identified tight linkage of an RFLP marker to the Ht1 gene of maize that confers resistance to the fungal pathogen Helminthosporium turcicum race 1. This was accomplished by the use of four pairs of near isogenic lines (NILs; B73, A619, W153R, and CM105), each differing by the presence or the absence of the gene Ht1. Since Ht1 maps to chromosome 2, 26 clones already mapped to this chromosome were labeled and probed against Southern blots of these NILs DNA digested with three restriction enzymes: EcoRI, BamHI, and HindIII. Six markers exhibited an RFLP for at least one pair of NILs. Presumptive linkage was further tested by analyzing the segregation of five of the six markers (one was monomorphic in the cross studied) and resistance to H. turcicum race 1 on 95 F2 individuals from the cross DF20 x LH146Ht. The results indicate a tight linkage between one of the DNA markers, UMC150B, and the Ht1 gene.