Detection and location of Lr11 and other leaf rust resistance genes in the durably resistant wheat cultivar Buck Poncho

Abstract

Three race-specific genes were identified in a cross between the durably leaf rust resistant wheat cultivar Buck Poncho (BP) and leaf rust susceptible cultivar Purple Straw (P). Two seedling resistance genes, temporarily named LrBP1 and LrBP2, and one adult plant resistance gene named LrBP3 were identified. Multi-pathotype tests on seedlings of BP and Thatcher near-isogenic lines carrying single resistance genes indicated that Lr10 and Lr11 were candidates for LrBP1 and LrBP2, respectively. The identification of LrBP1 as Lr10 was corroborated by markers previously reported to be linked to Lr10. LrBP2 was linked to 12 markers located on the short arm of chromosome 2D, the closest of which was SCAR32/35 at 0.3 cM. Lr11 was previously located in chromosome 2A, but monosomic analysis and telocentric mapping indicated that Lr11 was distally located in chromosome 2DS. The presence of the expected PCR fragment of SCAR32/35 in BP and wheat lines carrying Lr11, and results from an allelism test between a stock carrying LrBP2 with one carrying Lr11, indicated that these two genes are most likely the same. Thirteen markers located in chromosome 6A were loosely linked to LrBP3. Lines carrying the three resistance genes were evaluated for leaf rust response in the field. None of the gene combinations showed infection severities as low as BP, indicating that the three genes only partially explained the observed level of resistance in BP.