THE ROLE OF LR10, LR13, AND LR34 IN THE EXPRESSION OF ADULT-PLANT RESISTANCE TO LEAF RUST IN THE WHEAT CULTIVAR ERA

Elucidation of the genetic basis of the highly effective resistance in Era wheat to Puccinia recondita f. sp. tritici could assist breeders in reconstructing similar Lr gene combinations in other cultivars. Att empts to relate the presence of Lr10, Lr13, and Lr34 with the expressi on of adult-plant resistance showed that a combination of these genes did not necessarily confer high levels of resistance to pathotype UVPr t8 of P. r. f. sp. tritici. The most resistant adult F-2 plant derived from a cross between Era and line RL6058 was homozygous for Lr10, Lr1 3, and Lr34, but other F-2 plants exhibiting intermediate levels of ad ult-plant resistance also appeared homozygous for all three genes. In the leaf rust-susceptible background of Line E, no clear relationship between Lr13 and expression of adult-plant resistance derived from Era was observed. Limited evidence was obtained that Lr10 in association with an unknown gene or Lr13 interacted with Lr34 to confer an improve d level of resistance to leaf rust in certain plants. Mostly results i ndicated a lack of interaction among Lr10, Lr13, and Lr34. It seems un likely that wheat breeders will be able to reconstruct a similar Era-t ype of leaf rust resistance by combining Lr10, Lr13, and Lr34.