PRELIMINARY PHYSICAL CHARACTERISATION OF THE MAIZE Rp1 DISEASE RESISTANCE LOCUS

¹ IACR-Long Ashton Research Station, University of Bristol, Bristol BS41 9AF, UK

² Kansas State University, Dept. of Plant Pathology, Throckmorton Hall, Manhattan, Kansas, USA

In maize, the major genes which encode resistance to Puccinia sorghi are called the Rp genes and are known to reside mostly on the short arm of chromosome ten. The Rp locus is important, not just because of its economic importance, but also because the high rate frequency of non-parental variants, suggests an elevated frequency of recombination. It is therefore possible that the locus, which covers several centiMorgans, could be contained with a few hundred kb. The Rp genomic region could provide an insight into the mechanism by which unequal recombination can produce new allelic variants in a disease resistance locus. Using the Rp1 probe to screen our maize YAC library, we have identified seven clones, ranging in size from 60 to 250 kb, which appear to contain between one and three copies of Rp1 related sequences in two non-overlapping contigs. Further screening of the YAC library with YAC end sequences, from some of the original clones, has also lead to the production of a number of overlapping clones. We will present our preliminary data on the organisation of the Rp1 contig and discuss our future work plans.