Summary: Pm1a, the first powdery mildew resistance gene described in wheat, is part of a complex resistance (R) gene cluster located in a distal region of chromosome 7AL that has suppressed genetic recombination. A nucleotide‐binding, leucine‐rich repeat (NLR) immune receptor gene was isolated using mutagenesis and R gene enrichment sequencing (MutRenSeq). Stable transformation confirmed Pm1a identity which induced a strong resistance phenotype in transgenic plants upon challenge with avirulent Blumeria graminis (wheat powdery mildew) pathogens. A high‐density genetic map of a B. graminis family segregating for Pm1a avirulence combined with pathogen genome resequencing and RNA sequencing (RNAseq) identified AvrPm1a effector gene candidates. In planta expression identified an effector, with an N terminal Y/FxC motif, that induced a strong hypersensitive response when co‐expressed with Pm1a in Nicotiana benthamiana. Single chromosome enrichment sequencing (ChromSeq) and assembly of chromosome 7A suggested that suppressed recombination around the Pm1a region was due to a rearrangement involving chromosomes 7A, 7B and 7D. The cloning of Pm1a and its identification in a highly rearranged region of chromosome 7A provides insight into the role of chromosomal rearrangements in the evolution of this complex resistance cluster.

The uncultivated species Dasypyrum breviaristatum carries novel diseases resistance and agronomically important genes of potential use for wheat improvement. The development of new wheat-D. breviaristatum derivatives lines with disease resistance provides an opportunity for the identification and localization of resistance genes on specific Dasypyrum chromosomes. The comparison of wheat-D. breviaristatum derivatives to the wheat-D. villosum derivatives enables to reveal the genomic divergence between D. breviaristatum and D. villosum. The mitotic metaphase of the wheat- D. breviaristatum partial amphiploid TDH-2 and durum wheat -D. villosum amphiploid TDV-1 were studied using multicolor fluorescent in situ hybridization (FISH). We found that the distribution of FISH signals of telomeric, subtelomeric and centromeric regions on the D. breviaristatum chromosomes was different from those of D. villosum chromosomes by the probes of Oligo-pSc119.2, Oligo-pTa535, Oligo-(GAA)7 and Oligo-pHv62-1. A wheat line D2139, selected from a cross between wheat lines MY11 and TDH-2, was characterized by FISH and PCR-based molecular markers. FISH analysis demonstrated that D2139 contained 44 chromosomes including a pair of D. breviaristatum chromosomes which had originated from the partial amphiploid TDH-2. Molecular markers confirmed that the introduced D. breviaristatum chromosomes belonged to homoeologous group 7, indicating that D2139 was a 7Vb disomic addition line. The D2139 displayed high resistance to wheat stripe rust races at adult stage plant, which may be inherited from, D. breviaristatum chromosome 7Vb. The study present here revealed that the large divergence between D. breviaristatum and D. villosum with respected to the organization of different repetitive sequences. The identified wheat- D. breviaristatum chromosome addition line D2139 will be used to produce agronomically desirable germplasm for wheat breeding.

An elite hexaploid triticale Yukuri from Australia was used as a bridge for transferring valuable genes from Secale cereale L. into common wheat for enriching the genetic variability of cultivated wheat. Non-denaturing-fluorescence in situ hybridization (ND-FISH) identified that Yukuri was a secondary triticale with a complete set of rye chromosomes and a 6D(6A) substitution. Seed protein electrophoresis showed that Yukuri had a unique composition of glutenin subunits. A set of Yukuri-derived wheat-rye introgression lines were created from a Yukuri x wheat population, and all lines were identified by ND-FISH with multiple probes and validated by diagnostic molecular marker analysis. A total of 59 wheat-rye introgression lines including modified chromosome structural variations of wheat, and new complex recombinant chromosomes of rye were detected through ND-FISH and Oligo-FISH painting based on oligonucleotide pools derived from wheat-barley genome collinear regions. Wheat lines carrying the 1R chromosome from Yukuri displayed resistance to both stripe rust and powdery mildew, while the lines carrying the 3RL and 7RL chromosome arms showed stripe rust resistance. The chromosome 1R-derived lines were found to exhibit a significant effect on most of the dough-related parameters, and chromosome 5R was clearly associated with increased grain weight. The development of the wheat-rye cytogenetic stocks carrying disease resistances and superior agronomic traits, as well as the molecular markers and FISH probes will promote the introgression of abundant variation from rye into wheat improvement programs.

Thinopyrum intermedium (JJJ^sJ^sStSt, 2n = 6x = 42), a wild relative of common wheat, possesses many desirable agronomic genes for wheat improvement. The production of wheat–Thinopyrum intermedium introgression lines is a key step for transferring these beneficial genes into wheat. In this study, we characterized three wheat–Thinopyrum intermedium introgression lines TA3681, TA5566, and TA5567 using non-denaturing fluorescence in situ hybridization, genomic in situ hybridization, PCR-based landmark unique gene, and intron targeting markers. Our results showed that TA3681 is a wheat–Thinopyrum intermedium 1St disomic addition line, TA5566 is a wheat–Thinopyrum intermedium non-Robertsonian translocation line carrying two pairs of 3A-7J^s translocation chromosomes, and that TA5567 is a wheat–Thinopyrum intermedium non-Robertsonian translocation line carrying a pair of 3A-7J^s translocation chromosomes. We developed 13, 36, and 15 Thinopyrum intermedium chromosome-specific markers for detecting the introgressed Thinopyrum chromosomes in TA3681, TA5566, and TA5567, respectively. Stem rust assessment revealed that TA3681 exhibited a high level of seedling resistance to Chinese-prevalent Puccinia graminis f. sp. tritici pathotypes, and both TA5566 and TA5567 were highly resistant to Australian P. graminis f. sp. tritici pathotypes, indicating that Thinopyrum intermedium chromosomes 1St and 7J^s might carry new stem rust resistance genes. Therefore, the new identified introgression lines may be useful for improving wheat stem rust resistance.

Global climate change, which includes drought, extreme temperatures, and adverse soil conditions such as salinity and heavy metal pollution, has had a profound impact on crop yields and quality, thereby posing a substantial threat to global food security Notwithstanding the fact that a multitude of strategies and significant genes involved in plants' responses to abiotic stress have been reported in both model and non-model plants through the application of these advanced techniques, thereby augmenting our comprehension of the mechanisms underlying the abiotic stress tolerance of major crops, there still exist lacunae in knowledge. We instituted the research topic "Advances in crop breeding for abiotic stress tolerance" with the objective of bridging these gaps. Analyzing the responses of various crops to abiotic stress, especially identifying the relatively conserved metabolic pathways or important homologous genes in different species, is of crucial importance for the improvement of stress resistance breeding in important crops. In this research topic, the U-box, Dof, Di19, bZIP, and LLRLK gene families have been identified as potentially involved in the response process of crops to abiotic stress in different species. Multiple pathways related to transcriptional regulation, hormone regulation, energy metabolism, and secondary metabolite synthesis have also been found to be closely associated with abiotic stress. The interactions among these pathways/genes may be crosstalk, synergistic, or antagonistic, all of which have a certain impact on the abiotic stress resistance of crops. In the future, more advanced technologies and analytical strategies need to be further utilized to gain a deeper understanding of the molecular responses of crops to abiotic stress and ultimately promote the breeding improvement of crop stress resistance.