IDENTIFICATION OF A STS MARKER LINKED TO THE AEGILOPS SPELTOIDES-DERIVED LEAF RUST RESISTANCE GENE LR28 IN WHEAT

A sequence-tagged-site (STS) marker is reported linked to Lr28, a leaf rust resistance gene in wheat. RAPD (random amplified polymorphic DNA ) analysis of near-isogenic lines (NILs) of Lr28 in eight varietal bac kgrounds was carried out using random primers. Genomic DNA enriched fo r low-copy sequences was used for RAPD analysis to overcome the lack o f reproducibility due to the highly repetitive DNA sequences present i n wheat. Of 80 random primers tested on the enriched DNA, one RAPD mar ker distinguished the NILs and the donor parent from the susceptible r ecurrent parents. The additional band present in resistant lines was c loned, sequenced, and STS primers specific for Lr28 were designed. The STS marker (Indian patent pending: 380 De198) was further confirmed b y bulk segregation analysis of F-3 families. It was consistently prese nt in the NILs, the resistant F-3 bulk and the resistant F-3 lines, bu t was absent in recurrent parents, the susceptible Fg bulk and the sus ceptible F-3 lines.