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Mutations induced by radiation are widely used for developing new varieties of plants. To better understand the frequency and pattern of irradiation-induced chromosomal rearrangements, we irradiated the dry seeds of Chinese Spring (CS)-Dasypyrum villosum nullisomic-tetrasomic (6A/6D) addition (6V) line (2n = 44), WD14, with 60Co-γ-rays at dosages of 100, 200, and 300 Gy. The M0 and M1 generations were analyzed using Feulgen staining and non-denaturing fluorescence in situ hybridization (ND-FISH) by using oligonucleotide probes. Abnormal mitotic behavior and chromosomes with structural changes were observed in the M0 plants. In all, 39 M1 plants had structurally changed chromosomes, with the B genome showing the highest frequency of aberrations and tendency to recombine with chromosomes of the D genome. In addition, 19 M1 plants showed a variation in chromosome number. The frequency of chromosome loss was considerably higher for 6D than for the alien chromosome 6V, indicating that 6D is less stable after irradiation. Our findings suggested that the newly obtained γ-induced genetic materials might be beneficial for future wheat breeding programs and functional gene analyses.

The unique 75 K γ-secalins encoded by Sec2 loci in Secale species is composed of almost half rye storage proteins. The chromosomal location of Sec2 loci in wild Secale species, Secale africanum, was carried out by the wheat—S. africanum derivatives, which were identified by genomic in situ hybridization and multi-color fluorescence in situ hybridization. The Sec2 gene-specific PCR analysis indicated that the S. cereale Sec2 was located on chromosome 2R, while the S. africanum Sec2 was localized on chromosome 6Rafr of S. africanum. A total of 38 Sec2 gene sequences were isolated from S. africanum, S. cereale and S. sylvestre by PCR-based cloning. Phylogenetic analysis showed that S. africanum Sec2 diverged from S. cereale Sec2 approximately 2–3 million years ago. The illegitimate recombination of chromosome 2R–6R involving the Sec2 loci region may accelerate sequence variation during evolutionary process from wild to cultivated Secale species.

A new wheat-Thinopyrum translocation line CH13-21 was selected from the progenies derived from a cross between wheat-Th. intermedium partial amphiploid TAI7047 and wheat line Mianyang11. CH13-21 was characterized by using genomic in situ hybridization (GISH), multicolor-GISH (mc-GISH), multicolor-fluorescence in situ hybridization (mc-FISH) and chromosome-specific molecular markers. When inoculated with stripe rust and powdery mildew isolates, CH13-21 displayed novel resistance to powdery mildew and stripe rust which inherited from its Thinopyrum parent. The chromosomal counting analyses indicated that CH13-21 has 42 chromosomes, with normal bivalent pairing at metaphase I of meiosis. GISH probed by Th. intermedium genomic DNA showed that CH13-21 contained a pair of wheat-Th. intermedium translocated chromosomes. Sequential mc-FISH analyses probed by pSc119.2 and pAs1 clearly revealed that chromosome arm 6BS of CH13-21 was replaced by Thinopyrum chromatin in the translocation chromosome. The molecular markers analysis further confirmed that the introduced Th. intermedium chromatin in CH13-21 belonged to the long arm of homoeologous group 6 chromosome. Therefore, CH13-21 was a new T6BS.6Ai#1L compensating Robertsonian translocation line. It concludes that CH13-21 is a new genetic resource for wheat breeding programs providing novel variation for disease resistances.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating fungal diseases of wheat worldwide. It is essential to discover more sources of stripe rust resistance genes for wheat breeding programs. Specific locus amplified fragment sequencing (SLAF-seq) is a powerful tool for the construction of high-density genetic maps. In this study, a set of 200 recombinant inbred lines (RILs) derived from a cross between wheat cultivars Chuanmai 42 (CH42) and Chuanmai 55 (CH55) was used to construct a high-density genetic map and to identify quantitative trait loci (QTLs) for stripe rust resistance using SLAF-seq technology. A genetic map of 2828.51 cM, including 21 linkage groups, contained 6732 single nucleotide polymorphism markers (SNP). Resistance QTLs were identified on chromosomes 1B, 2A, and 7B; Qyr.saas-7B was derived from CH42, whereas Qyr.saas-1B and Qyr.saas-2A were from CH55. The physical location of Qyr.saas-1B, which explained 6.24−34.22% of the phenotypic variation, overlapped with the resistance gene Yr29. Qyr.saas-7B accounted for up to 20.64% of the phenotypic variation. Qyr.saas-2A, a minor QTL, was found to be a likely new stripe rust resistance locus. A significant additive effect was observed when all three QTLs were combined. The combined resistance genes could be of value in breeding wheat for stripe rust resistance.

Wild barley eibi1 mutant with HvABCG31 gene mutation has low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. To better understand how such a mutant plant survives, we performed a genome-wide gene expression analysis. The leaf transcriptomes between the near-isogenic lines eibi1 and the wild type were compared using the 22-k Barley1 Affymetrix microarray. We found that the pleiotropic effect of the single gene HvABCG31 mutation was linked to the co-regulation of metabolic processes and stress-related system. The cuticle development involved cytochrome P450 family members and fatty acid metabolism pathways were significantly up-regulated by the HvABCG31 mutation, which might be anticipated to reduce the levels of cutin monomers or wax and display conspicuous cuticle defects. The candidate genes for responses to stress were induced by eibi1 mutant through activating the jasmonate pathway. The down-regulation of co-expressed enzyme genes responsible for DNA methylation and histone deacetylation also suggested that HvABCG31 mutation may affect the epigenetic regulation for barley development. Comparison of transcriptomic profiling of barley under biotic and abiotic stresses revealed that the functions of HvABCG31 gene to high-water loss rate might be different from other osmotic stresses of gene mutations in barley. The transcriptional profiling of the HvABCG31 mutation provided candidate genes for further investigation of the physiological and developmental changes caused by the mutant.

The objective of this research was to characterize the high level of resistance to stripe that has been observed in the released wheat cultivar, Chuanmai45. A combination of classic genetic analysis, molecular and cytogenetic methods were used to characterize resistance in an F2 population derived from Chuanmai45 and the susceptible Chuanmai42. Inheritance of resistance was shown to be conferred by two genes in Chuanmai45. Fluorescence in situ hybridization (FISH) was used along with segregation studies to show that one gene was located on a 1RS.1BL translocation. Molecular markers were employed to show that the other locus was located on chromosome 4B. The defeated gene, Yr24/26, on chromosome 1BL was present in the susceptible parent and lines that recombined this gene with the 1RS.1BL translocation were identified. The germplasm, loci, and associated markers identified in this study will be useful for application in breeding programs utilizing marker-assisted selection.

Mutations induced by radiation are widely used for developing new varieties of plants. To better understand the frequency and pattern of irradiation-induced chromosomal rearrangements, we irradiated the dry seeds of Chinese Spring (CS)-Dasypyrum villosum nullisomic-tetrasomic (6A/6D) addition (6V) line (2n = 44), WD14, with 60Co-γrays at dosages of 100, 200, and 300 Gy. The M0 and M1 generations were analyzed using Feulgen staining and non-denaturing fluorescence in situ hybridization (ND-FISH) by using oligonucleotide probes. Abnormal mitotic behavior and chromosomes with structural changes were observed in the M0 plants. In all, 39 M1 plants had structurally changed chromosomes, with the B genome showing the highest frequency of aberrations and tendency to recombine with chromosomes of the D genome. In addition, 19M1 plants showed a variation in chromosome number. The frequency of chromosome loss was considerably higher for 6D than for the alien chromosome 6V, indicating that 6D is less stable after irradiation. Our findings suggested that the newly obtained γ-induced genetic materials might be beneficial for future wheat breeding programs and functional gene analyses. [ABSTRACT FROM AUTHOR]

Wild barley eibi1 mutant with HvABCG31 gene mutation has low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. To better understand how such a mutant plant survives, we performed a genome-wide gene expression analysis. The leaf transcriptomes between the near-isogenic lines eibi1 and the wild type were compared using the 22-k Barley1 Affymetrix microarray. We found that the pleiotropic effect of the single gene HvABCG31 mutation was linked to the co-regulation of metabolic processes and stress-related system. The cuticle development involved cytochrome P450 family members and fatty acid metabolism pathways were significantly up-regulated by the HvABCG31 mutation, which might be anticipated to reduce the levels of cutin monomers or wax and display conspicuous cuticle defects. The candidate genes for responses to stress were induced by eibi1 mutant through activating the jasmonate pathway. The down-regulation of co-expressed enzyme genes responsible for DNA methylation and histone deacetylation also suggested that HvABCG31 mutation may affect the epigenetic regulation for barley development. Comparison of transcriptomic profiling of barley under biotic and abiotic stresses revealed that the functions of HvABCG31 gene to high-water loss rate might be different from other osmotic stresses of gene mutations in barley. The transcriptional profiling of the HvABCG31 mutation provided candidate genes for further investigation of the physiological and developmental changes caused by the mutant. [ABSTRACT FROM AUTHOR]