Isolation of wheat–rye 1RS recombinants that break the linkage between the stem rust resistance gene SrR and secalin

Abstract

Chromosome 1R of rye is a useful source of genes for disease resistance and enhanced agronomic performance in wheat. One of the most prevalent genes transferred to wheat from rye is the stem rust resistance gene Sr31. The recent emergence and spread of a stem rust pathotype virulent to this gene has refocused efforts to find and utilize alternative sources of resistance. There has been considerable effort to transfer a stem rust resistance gene, SrR, from Imperial rye, believed to be allelic to Sr31, into commercial wheat cultivars. However, the simultaneous transfer of genes at the Sec-1 locus encoding secalin seed storage proteins and their association with quality defects preclude the deployment of SrR in some commercial wheat breeding programs. Previous attempts to induce homoeologous recombination between wheat and rye chromosomes to break the linkage between SrR and Sec-1 whilst retaining the tightly linked major loci for wheat seed storage proteins, Gli-D1 and Glu-D3, and recover good dough quality characteristics, have been unsuccessful. We produced novel tertiary wheat-rye recombinant lines carrying different lengths of rye chromosome arm 1RS by inducing homoeologous recombination between the wheat 1D chromosome and a previously described secondary wheat-rye recombinant, DRA-1. Tertiary recombinant T6-1 (SrR+ Sec-1-) carries the target gene for stem rust resistance from rye and retains Gli-D1 but lacks the secalin locus. The tertiary recombinant T49-7 (SrR- Sec-1+) contains the secalin locus but lacks the stem rust resistance gene. T6-1 is expected to contribute to wheat breeding programs in Australia, whereas T49-7 provides opportunities to investigate whether the presence of secalins is responsible for the previously documented dough quality defects.

Targeted Introgression of a Wheat Stem Rust Resistance Gene by DNA Marker-Assisted Chromosome Engineering

“…Thus far, it has been a challenge to transfer a small amount of alien chromatin containing the gene of interest from one genome to another nonhomologous genome. Only a few genes have been isolated from large alien chromosomal segments, such as Sr26 (Dundas et al 2007) and SrR (Anugrahwati et al 2008) for stem rust resistance and Pm21 (Chen et al 1995) for powdery mildew (Erysiphe graminis DC. f. sp.…”

Introgression of chromosome segments from multiple alien species in wheat breeding lines with wheat streak mosaic virus resistance

“…intermedium alien wheat introgression lines tested. It is generally thought that rye itself is probably susceptible to WSMV and that 1RS in wheat-rye translocation does not confer resistance, but that rye can resist colonisation of both greenbug and Figure 4 Diagrammatic representation of most likely marker positions and translocation BPs along the recombinant 1B lines N02Y5018, N02Y5019, N02Y2016, N02Y5163, N02Y5003, N02Y5149 and N02Y5156 based on published marker order for 1BS and 1RS (Anugrahwati et al, 2008;Reddy et al, 2008; and references and data from Supplementary Table S1). White bars represent wheat 1BS, black represents rye 1RS and red bars represent the distal 1B alien chromatin that may be rye or Th.…”

“…intermedium genomic DNA can cross-hybridise to the distal tandem repeats present at the telomere of a normal 1RS (Figures 2d and f). Detection of very small alien chromatin segments can be difficult both cytologically and with molecular markers: GISH screening using labelled rye genomic DNA probe and wheat DNA as a block failed to visualise the presence of rye chromatin in known recombinants that carried the SrR gene (Anugrahwati et al, 2008) and negative PCR results have been reported for several wheat-rye translocation lines that contained 1RS chromatin (Mago et al, 2002;Anugrahwati et al, 2008).…”

New molecular markers and cytogenetic probes enable chromosome identification of wheat-Thinopyrum intermedium introgression lines for improving protein and gluten contents

“…The previously effective resistance genes Sr31, Yr9, Pm8 and Lr26 were derived from Petkus rye, transferred to wheat as the 1BL.1RS translocation chromosome and used widely around the world commercial cultivars (Bartos 1993;Pretorius et al 2000;Hurni et al 2014). Furthermore, the recently cloned stem rust resistance gene Sr50 (=SrR) also on chromosome 1RS but derived from Imperial rye, shows promise as a replacement for the now ineffective Sr31 for stem rust resistance (Anugrahwati et al 2008;Mago et al 2015). The genes located on chromosome 1E of Th.…”