Molecular markers linked to the leaf rust resistance gene Lr24 in different wheat cultivars.

The aim of this study was to find molecular markers (RAPD and SCAR) for the wheat leaf rust resistance gene Lr24. A backcross line, RL 6064, possessing a single resistance gene to leaf rust (Lr24) and its recurrent parent 'Thatcher' were used to find RAPD markers linked to the Lr24 gene. Among 125 RAPD primers tested, only one (OP-H5) detected an additional band in the resistant line RL 6064. The genetic linkage of this molecular marker to Lr24 was tested on a segregating F2 population derived from a cross between the leaf rust resistant line RL 6064 and the susceptible line 'Chinese Spring'. This marker showed complete linkage to the Lr24 resistance gene. A more reliable and specific marker for this resistance gene was made by converting it into a sequence characterized amplified region (SCAR). The presence of a single amplification product allowed direct detection of the gene in the test tube by the addition of ethidium bromide. This SCAR marker linked to the leaf rust resistance gene Lr24 could be used easily in a practical breeding program.