Reducing the size of an alien segment carrying leaf rust and stripe rust resistance in wheat

Abstract

Background: Leaf and stripe rusts are two major wheat diseases, causing significant yield losses. The preferred way for protecting wheat from rust pathogens is by introgression of rust resistance traits from wheat-related wild species. To avoid genetic drag due to replacement of large wheat chromosomal segments by the alien chromatin, it is necessary to shorten the alien chromosome segment in primary recombinants. Results: Here we report on shortening of an alien chromosome segment in wheat that carries leaf and stripe rust resistance from Sharon goatgrass (Aegilops sharonensis). Rust resistant wheat introgression lines were selected and the alien region was mapped using genotyping by sequencing. Single polymorphic nucleotides (SNP) were identified and used to generate diagnostic PCR markers. Shortening of the alien fragment was achieved by induced homoeologous pairing and lines with shortened alien chromosome were identified using the PCR markers. Further reduction of the segment was achieved in tertiary recombinants without losing the rust resistance. Conclusions: Alien chromatin in wheat with novel rust resistance genes was characterized by SNP markers and shortened by homoeologous recombination to avoid deleterious traits. The resulting wheat lines are resistant to highly virulent races of leaf and stripe rust pathogens and can be used as both resistant wheat in the field and source for gene transfer to other wheat lines/species.

Genome sequences of three Aegilops species of the section Sitopsis reveal phylogenetic relationships and provide resources for wheat improvement

“…Furthermore, some species in the secondary and tertiary gene pools of wheat (including Aegilops longissima and Aegilops sharonensis) cause chromosome breakage and preferential transmission of undesired gametes in wheat hybrids through the presence of so-called gametocidal genes, which restrict interspecific hybridization (Finch et al 1984;Tsujimoto, 1994). Therefore, introgression requires complex cytogenetic manipulations (Khazan et al, 2020;Kilian et al, 2011) and extensive backcrossing to recover the desired agronomic traits of the recipient wheat cultivar. These limitations can be overcome by using gene editing and genetic engineering technologies, which are not limited by plant species and can augment genetic crosses and substantially expedite the transfer of new traits into elite wheat cultivars (Arora et al, 2019;Luo et al, 2021;Uauy et al, 2017).…”

Genome sequences ofAegilopsspecies of section Sitopsis reveal phylogenetic relationships and provide resources for wheat improvement

“…For example, the Ae. sharonensis genome encodes resistance against a wide range of diseases that also attack wheat ( 10, 27, 48,49, 50 ). To better evaluate the genetic diversity and potential of disease-resistance genes in the three species, we cataloged and analyzed their NLR complements, the major class of genes encoded by plant disease-resistance genes.…”

“…longissima) cause chromosome breakage and preferential transmission of undesired gametes in wheat hybrids due to the presence of so-called gametocidal genes, which restrict interspecific hybridization (7,8). Therefore, introgression requires complex cytogenetic manipulations (9,10) and extensive backcrossing to recover the desired agronomic traits of the recipient wheat cultivar. These limitations can be overcome by using gene editing and genetic engineering technologies, which are not limited by plant species and can substantially expedite transfer of new traits into elite wheat cultivars (11,12).…”

Whole genome sequencing uncovers the structural and transcriptomic landscape of hexaploid wheat/Ambylopyrum muticum introgression lines

“…Segments in these lines that confer phenotypes of interest can be identified. Lines with overlapping segments can then be crossed to break down large segments (13), resulting in genes of interest captured in short introgressed segments with reduced linkage drag, ready to be crossed into elite lines and deployed in breeding programmes.…”