The Sr12 region is involved in enhanced stem rust resistance in lines carrying Lr34 or SuSr-D1 mutant alleles in wheat
Citation
Colin W. Hiebert, Jyoti Saini Sharma, Tom Fetch, Brent D. McCallum, Matthew Moscou, Wolfgang Spielmeyer (2023) The Sr12 region is involved in enhanced stem rust resistance in lines carrying Lr34 or SuSr-D1 mutant alleles in wheat. International Plant and Animal Genome Conference, January 13-18, 2023, San Diego
Plain language summary
Stem rust is a potentially devastating disease of wheat. Stem rust can be controlled by developing wheat cultivars that carry effective stem rust resistance (Sr) genes. In some cases stem rust resistance can be suppressed by other genes, such as the recently identified gene SuSr-D1. In the wheat lines derived from the cultivar Thatcher, additional stem rust resistance is expressed if either SuSr-D1 is knocked-out by mutation or if the mulit-pest resistance gene Lr34 is added. Lr34 appears to negate the suppressing effect that SuSr-D1 has on stem rust resistance. Two populations were used for genetic mapping experiments and both identified the chromosome region carrying gene Sr12 as an important component of the stem rust resistance expressed when SuSr-D1 was knocked-out or Lr34 was added. An additional population confirmed these findings. It is unknown if Sr12 is the gene interacting with SuSr-D1 and Lr34 or if an associated gene is responsible for the additional resistance. Future studies focused on cloning Sr12 will help answer these questions.
Abstract
Stem rust, caused by Puccinia graminis f.sp. tritici (Pgt), is an important disease of wheat that can cause devastating grain yield losses. Genetic resistance to stem rust is a sustainable method of disease control. Wheat lines derived from Thatcher have been shown to have some stem rust resistance that is suppressed by SuSr-D1, a gene that encodes a subunit of the Mediator Complex. When SuSr-D1 is removed or knocked-out by mutagenesis these lines are resistant to some races of Pgt that are otherwise virulent. Similarly, the presence of gene Lr34 in Thatcher-derivatives appears to act as a nonsuppressor of SuSr-D1 and a gain in resistance to Pgt occurs. To study which genes contribute to stem rust resistance in Thatcher-derivatives when SuSr-D1 is knocked out or when Lr34 is present, three populations were analysed: Canthatch-NS1/Cadenza-mut-7DL which was fixed for SuSr-D1 mutant alleles, Thatcher-Lr34/Chinese Spring (Lr34 carrier) which was fixed for Lr34, and Thatcher-Lr34/RL90 (Lr34 carrier) that was fixed for Lr34. The stem rust resistance was polygenic in all populations and mapped as QTL. An important QTL for resistance on chromosome 3B corresponded to the presence of stem rust resistance gene Sr12. It is unknown if Sr12 or a linked gene interacts with SuSr-D1 and Lr34.