Chromosome and chromosomal arm locations of genes for resistance to Septoria glume blotch in wheat cultivar Cotipora

Summary Septoria glume blotch, caused by Stagonospora nodorum, is an important disease of wheat (Triticum aestivum). Separate genetic mechanisms were found to control flag leaf and spike resistance. Genes for resistance to S. nodorum were located on different chromosomes in the few wheat cultivars studied. These studies only partially agree on the chromosome locations of gene in wheat for resistance to S. nodorum, and chromosomal arm locations of such genes are not known. The objectives of this study were to determine the chromosome and chromosomal arm locations of genes that significantly influence resistance to S. nodorum in wheat cultivar Cotipora. Monosomic analysis showed that flag leaf resistance was controlled by genes on chromosomes 3A, 4A, and 3B whereas the spike resistance was controlled by genes on chromosomes 3A, 4A, 7A, and 3B (P=0.01). Additionally, genes on chromosomes 6B and 5A influenced the susceptibility of the flag leaf and spike reactions, respectively (P=0.01). Telocentric analysis showed that genes on both arms of chromosome 3A, and the long arms of chromosomes 4A and 3B were involved in the flag leaf resistance whereas genes on both arms of chromosome 4A, the short arm of chromosome 3A, and the long arm of chromosome 3B conferred spike resistance.     

Cytogenetical studies in wheat XVI. Chromosome location of a new gene for resistance to leaf rust in a Japanese wheat-rye translocation line

Summary A leaf rust resistant wheat-rye translocation stock, ST-1, introduced from Japan, comprised distinct morphological types. One type possessed a T1BL·1RS chromosome with genes Lr26, Yr9 and Sr31. A second type carried a new gene, Lr45, located in a large segment of rye chromosome translocated to wheat chromosome 2A. Its structure was identified as T2AS-2RS·2RL. Despite the homoeology of the 2A and 2R chromosomes and the high level of compensation provided by the translocation, Lr45 was not normally inherited and is probably associated with agronomic deficiencies that will prevent its exploitation in agriculture.Contribution No. 94-509-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, USA.     

Characterization of stem rust resistant derivatives of wheat cultivar Amigo

Summary Originally developed for resistance to greenbug derived from Insave rye, Amigo wheat carries two genes for resistance to stem rust. One of these genes is associated with a rye chromosome 1RS segment carrying the Sec-1 protein marker and presumably greenbug resistance. The second gene which is genetically linked to leaf rust resistance is associated with an Agropyron-derived segment. Rust tests in Canada confirmed that these genes were Sr24 and Lr24. In contrast to Agent and certain 3D/Ag derivatives from Dr. E.R. Sears, the Amigo source of Sr24/Lr24 freely recombined with white seed colour during backcrossing.     

Control and inheritance of resistance to yellow rust in Triticum aestivum-Lophopyrum elongatum chromosome substitution lines

A set of T. aestivum-L. elongatum chromosome substitution lines was tested for yellow rust resistance at the seedling stage. Inheritance of the resistance and esterase-5 (Est-5) variation were studied. The results demonstrated that L.elongatum carried a new gene(s) conferring yellow rust resistance. This gene was dominant and located on chromosome 3E of L. elongatum. The biochemical locus encoding Est-5was also located on chromosome 3E, and co-segregated with theYr gene(s) in the wheat background. The transmission frequencies of chromosome 3E in 3E(3A) × CS, 3E(3B) × CS and 3E(3D) × CS hybrids were scored.None of the hybrids transmitted the alien chromosome at thetheoretical maximum rate, but the transmission frequencies ofchromosome 3E in F₂ populations of 3E(3A) × CS and 3E(3D) × CS were significantly higher than in thatof 3E(3B) × CS.     

Effect of alien 5R(5A) chromosome substitution on ear-emergence time and winter hardiness in wheat-rye substitution lines

Ear emergence time and response to vernalization were investigated in 12 alien substitution lines in which a pair of chromosomes 5A of recipient spring wheat cultivars was replaced by a pair of chromosomes 5R of Siberian spring rye ‘Onokhoiskaya’. The recipients were 12 spring cultivars of common wheat, each carrying different Vrn genes. Spring rye ‘Onokhoiskaya’ had the Sp1 (now called Vrn-R1) gene for spring growth habit located on chromosome 5R, but its expression was weaker. The Vrn-R1 gene had no effect on growth habit, ear emergence time and response to vernalization in wheat-rye substitution lines. Ears emerged significantly later in the 5R(5A) alien substitution lines than in the recipient wheat cultivars with the Vrn-A1/Vrn-B1/vrn-D1 or Vrn-A1/vrn-B1/Vrn-D1 genotypes. No difference in ear emergence time was found between most of the 5R(5A) alien substitution lines and the cultivars carrying the recessive vrn-A1 gene. The presence of the Vrn2a and Vrn2b alleles at the Vrn2 (now called Vrn-B1) locus located on wheat chromosome 5B was confirmed.The replacement of chromosome 5A by chromosome 5R in wheat cultivars ‘Rang’ and ‘Mironovskaya Krupnozernaya’, which carries the single dominant gene Vrn-A1, converted them to winter growth habit. In field studies near Novosibirsk the winter hardiness of 5R(5A) wheat–rye substitution lines of ‘Rang’ and ‘Mironovskaya Krupnozernaya’ was increased by 20–47% and 27–34%, respectively, over the recurrent parents.     

Development and characterization of a new 1BL.1RS translocation line with resistance to stripe rust and powdery mildew of wheat

The 1BL.1RS wheat-rye translocation from Petkus rye has contributed substantially to the world wheat production. However, following the breakdown of disease resistance genes in 1RS, its importance for wheat improvement decreased. We have developed a new 1BL.1RS line, R14, by means of crossing rye inbred line L155, selected from Petkus rye to several wheat cultivars. One new gene each, for stripe rust and powdery mildew resistance, located on 1RS of the line R14, are tentatively named YrCn17 and PmCn17. YrCn17 and PmCn17 confer resistance to Puccinia striiformis f. sp. tritici pathotypes that are virulent on Yr9, and Blumeria graminis f. sp. tritici pathotypes virulent on Pm8. These two new resistances, YrCn17 and PmCn17, are now available for wheat improvement programs. The present study indicates that rye cultivars may carry yet untapped variations as potential sources of resistance.     

Monosomic analyses of stripe rust and leaf rust resistance genes in winter wheat varieties Lüquyu and Yantar

Summary A set of 21 monosomics of Novosadska Rana-1 was used to locate the rust resistance genes of Lüqiyu, a stripe rust resistant line developed by BAU and Yantar, a leaf rust resistant wheat introduced from Bulgaria. The resistance of the former to p. striiformis race C25 was conditioned by a dominant gene located on chromosome 2B, whereas that of the latter to P. recondita race CL3 was controlled by two complementary dominant genes located on chromosomes 5A and 1D, respectively. The relationship of the stripe rust resistance gene in Lüqiyu to Yr5, Yr7 or Yr _Suwon' all located on chromosome 2B is unknown. The two complementary leaf rust resistance factors in Yantar appear to be new.     

Isolation, chromosomal location, and expression analysis of putative powdery mildew resistance genes in wheat (Triticum aestivum L.)

Special and degenerate primers are designed according to the conservative sequence of barley powdery mildew resistance genes Mla1, Mla6, and Mla13. Two wheat Mla-like orthologs, TaMla-2 and TaMla-3 are cloned and sequenced from the cDNA of wheat resistant-powdery mildew line TAM104R by RT-PCR method. TaMla-2 and TaMla-3 encode distinct but highly related coiled-coil nucleotide-binding site leucine-rich repeat type (NBS-LRR) resistant disease proteins and both reveal about 74 and 81% identity with amino acid sequence of Mla1, respectively. They are multiple copies in wheat genomes, one copy of them is mapped on wheat chromosome 1AL and two on 1BL using Chinese Spring nulli-tetra-somic lines and ditelosomic lines of 1A, 1B and 1D in southern analysis. This result suggests that may be the two Mla-like genes originated from the two diploid ancestral genomes, respectively. The expression pattern analysis of semi-quantitative PCR shows the TaMla genes are mainly expressed in leaf and sheath, and expression level is enhanced in organs infected by Erysiphe graminis, suggesting that TaMla-2 and TaMla-3 are powdery mildew resistance related-genes in wheat. Electronic Supplementary Material Supplementary material is available for this article at     

Chromosome location of resistance to septoria leaf blotch and common bunt in wheat-barley addition lines

Septoria leaf blotch and common bunt are important diseases of wheat to which Hordeum vulgare is resistant. Addition lines of H. vulgare in wheat were utilized to determine which H. vulgare chromosomes carry resistance genes. Resistance to septoria leaf blotch was conferred by gene(s) present all over the barley genome, but more strongly by those located on chromosomes 7 and 4. Almost complete resistance to common bunt was conferred by gene(s) present in chromosomes 6 and a slight but significant level of resistance was conferred by chromosome 7. This revised version was published online in August 2006 with corrections to the Cover Date.     

Molecular mapping and detection of the yellow rust resistance gene Yr26 in wheat transferred from Triticum turgidum L. using microsatellite markers

Yellow rust (stripe rust), caused by Puccinia striiformis Westend f. sp. tritici, is one of the most devastating diseases of wheat throughout the world. Wheat-Haynaldia villosa 6AL.6VS translocation lines R43, R55, R64 and R77, derived from the cross of three species, carry resistance to both yellow rust and powdery mildew. An F₂ population was established by crossing R55 with the susceptible cultivar Yumai 18. The yellow rust resistance in R55 was controlled by a single dominant gene, which segregated independently of the powdery mildew resistance gene Pm21 located in the chromosome 6VS segment, indicating that the yellow rust resistance gene and Pm21 are unlikely to be carried by the same alien segment. This yellow rust resistance gene was considered to beYr26, originally thought to be also located in chromosome arm 6VS. Bulked Segregation Analysis and microsatellite primer screens of the population F₂ of Yumai 18 × R55 identified three chromosome 1B microsatellite locus markers, Xgwm11, Xgwm18 and Xgwm413, closely linked to Yr26. Yr26 was placed 1.9 cM distal of Xgwm11/Xgwml8, which in turn were 3.2 cM from Xgwm413. The respective LOD values were 21 and 36.5. Therefore, Yr26 was located in the short arm of chromosome 1B. The origin and distribution of Yr26 was investigated by pedigree, inheritance of resistance and molecular marker analysis. The results indicated that Yr26 came from Triticum turgidum L. Three other 6AL.6VS translocation lines, R43, R64 and R77, also carried Yr26. These PCR-based microsatellite markers were shown to be very effective for the detection of the Yr26 gene in segregating populations and therefore can be applied in wheat breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Screening for resistance to take-all in wheat,triticale and wheat-triticale hybrid lines

Summary Fifteen triticale and wheat-triticale hybrid lines were evaluated for resistance to the take-all fungus Gaeumannomyces graminis var. tritici and compared with five wheat and two rye lines in inoculated field and pot trials. The triticale and wheat-triticale hybrid lines varied in rye chromosome number and degree of resistance expressed. One line, Venus with seven pairs of rye chromosomes consistently showed levels of resistance intermediate between wheat and rye. A trend was observed where increasing rye chromosome content led to greater resistance but exceptions showed that variation within triticales could not be ascribed to rye chromosome content alone.     

Isolation of a new repetitive DNA sequence from Secale africanum enables targeting of Secale chromatin in wheat background

A genome specific DNA sequence that detects Secale africanum chromatin incorporated into wheat was developed in this study. Random amplified polymorphic DNA (RAPD) analysis was used to search for genome specific DNA sequences of S. africanum in lines, R111, “mianyang11” (MY11) and wheat-rye 1RS/1BL translocations R25 and R57. A high copy rye-specific DNA segment pSaD15₉₄₀ of the S. africanum genome was obtained. The sequence of pSaD15 did not show any significant homology to other reported sequences in databases and it is therefore a new repetitive sequence of Secale. PCR primers were designed for pSaD15₉₄₀, which amplify a clear 887 bp fragment in S. africanum but not in any wheat. The primers also amplified an 887 bp fragment in other accessions of rye, Chinese Spring-Imperial rye chromosome additions and a diverse range of material carrying different rye chromosomes or chromosomal segments. In situ hybridization showed that probe pSaD15₉₄₀ was specifically hybridized throughout all rye chromosomes arms except for the terminal regions. The advantage of the rye-specific probe developed herein compared to those of previous reports is that it has been shown to be widely applicable to other Secale species. The probe will be useful as a molecular marker for the introgression of S. africanum and other rye chromosome segments into the wheat genome.     

Localization of Genes in Rye that Restore Male Fertility to Hexaploid Wheat with timopheevi Cytoplasm

Four sets of wheat-rye addition lines were screened to localize genes in rye that restore male fertility to hexaploid wheat with timopheevi cytoplasm. One gene, designated Rfc3, was physically located in the distal 40 % of the long arm of chromosome 6R. No allelic variation at Rfc3 was found; normal male fertility was consistently observed in all F₁ hybrid combinations tested. A second gene, designated Rfc4, was located on the long arm of chromosome 4R. Variation between chromosomes 4R in the level of restoration was observed; fertility in hybrids ranged from 0 % to about 50 % of normal. Attempts to genetically map Rfc4 were inconclusive but suggested it was located 16.1 cM from the telomere of the long arm and at least 8.0 cM from the centromere. These restorers, particularly Rfc3, may have potential in hybrid wheat breeding programs and can be manipulated for production of male sterile triticale lines.     

Development and Validation of SCAR Markers Co-Segregating with an Agropyron Elongatum Derived Leaf Rust Resistance Gene Lr24 in Wheat

Summary An Agropyron elongatum-derived leaf rust resistance gene Lr24 located on chromosome 3DL of wheat was tagged with six random amplified polymorphic DNA (RAPD) markers which co-segregated with the gene. The markers were identified in homozygous resistant F₂ plants taken from a population segregating for leaf rust resistance generated from a cross between two near-isogenic lines (NILs) differing only for Lr24. Phenotyping was done by inoculating the plants with pathotype 77-5 of Puccinia triticina. To enable gene-specific selection, three RAPD markers (S1302₆₀₉, S1326₆₁₅ and OPAB-1₃₈₈) were successfully converted to polymorphic sequence characterized amplified region (SCAR) markers, amplifying only the critical DNA fragments co-segregating with Lr24. The SCAR markers were validated for specificity to the gene Lr24 in wheat NILs possessing Lr24 in 10 additional genetic backgrounds including the Thatcher NIL, but not to 43 Thatcher NILs possessing designated leaf rust resistance genes other than Lr24. This indicated the potential usefulness of these SCAR markers in marker assisted selection (MAS) and for pyramiding leaf rust resistance genes in wheat.     

Cytogenetical studies in wheat XIX. Location and linkage studies on gene Yr27 for resistance to stripe (yellow) rust

The stripe (yellow) rust resistance gene Yr27 was located in wheat (Triticum aestivum L.) chromosome 2B and shown to be closely linked to the leaf (brown) rust resistance genes Lr13 and Lr23 in the proximal region of the short arm. Gene Yr27 was genetically independent of Lr16, which is distally located in the same arm. While Yr27 was often difficult to score in segregating seedling populations, it is apparently quite effective in conferring resistance to avirulent cultures under field conditions. The occurrence of Yr27 in Mexican wheat germplasm and the current over-dependence on Yr27 for crop protection in Asia are discussed.     

Chromosome locations of leaf rust resistance genes in selected tetraploid wheats through substitution lines

Langdon durum D-genome disomic substitution lines were used to study the chromosome locations of adult-plant leaf rust resistance genes identified from tetraploid wheat accessions. The accessions are 104 (Triticum turgidum subsp. dicoccum var. arras) and 127 (T. turgidum subsp. durum var. aestivum). The complete sets of the substitution lines were crossed as female parents with the accessions and F₁ double monosomic individuals selected at metaphase I. Segregating F₂ individuals were inoculated during the flag leaf stage with pathotype UVPrt2 of Puccinia triticina. The substitution analysis involving accession 104 showed that the gene for leaf rust resistance is located on chromosome 6B. The analysis with accession 127 indicated that chromosome 4A carries a gene for leaf rust resistance. The two novel genes are temporarily designated as Lrac104 and Lrac127, respectively from accessions 104 and 127.     

Expression of barley yellow dwarf virus and Russian wheat aphid resistance genes in and fertility of spring wheat × triticale hybrids and backcross lines

Summary The Barley Yellow Dwarf Virus disease (BYDV) and the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) have caused significant losses to wheat and barley in several areas of the world. Important sources of resistance to both BYDV and RWA have been found in Triticale. Different generations of interspecific wheat x Triticale crosses were produced and the progenies were screened for BYDV and RWA tolerance. Plants with equal chromosome numbers showed different levels of fertility. A significant correlation was observed between pollen fertility and seed set in primary florets (r=0.57). In generaL, pollen fertility, seed set and the number of euploid plants (2n=42) increased from one generation to the next. The expression of BYDV tolerance varied from population to population. Additive effects were predominant in F₁ and some backcross populations. A dominant effect of rye tolerance genes was also observed in few populations. A monogenic trait or a quantitative (polygenic) character would not agree with the observed segregation patterns. The heritability of this oligogenic tolerance was quite different between populations and in many populations the tolerance genes were only partially expressed. Some transgressive segregation for tolerance and sensitivity was demonstrated. The genes controlling tolerance to RWA in Triticale lines, Muskox 658 and Nord Kivu were not expressed in advanced lines resistant to BYDV. This indicates that tolerance genes for BYDV and RWA in these lines are located on different chromosomes.     

Cytological identification of 1B/1R wheat-rye translocations in winter wheat breeding lines

Summary The incorporation of rye (S. cereale L.) chromatin into winter wheat (T. aestivum L.) cultivars is often achieved via hybridization of unadapted wheat-rye translocation lines with adapted wheat germplasm. Identification of progenies possessing the translocated chromosome has traditionally involved phenotypic screening for the desired rye characteristics. In this study, the Giemsa N-banding technique was evaluated as a potential screening tool for detection of 1B/1R wheat-rye translocations. Five breeding lines were examined from the pedigree Aurora/2^*TAM W-101. The differential banding patterns of chromosome 1B contributed by TAM W-101 and chromosome 1B/1R contributed by Aurora allowed unequivocal identification of translocation genotypes. Three of the lines were found to be heterogeneous, whereby plants were homozygous for either the normal 1B or the translocated 1B/1R chromosome. The remaining two lines were observed to be homozygous and homogeneous for the translocated 1B/1R chromosome. The implication of N-banding chromosomal analyses to wheat breeding is presented.Contribution No. J-5172, Department of Agronomy, Oklahoma Agriculture Experiment Station, Oklahoma State University, Stillwater, OK74078.     

The introduction into bread wheat of a major gene for resistance to powdery mildew from wild emmer wheat

Summary A new source of resistance to wheat powdery mildew caused by Erysiphe graminis has been transferred to hexaploid bread wheat, Triticum aestivum, from the wild tetraploid wheat, Triticum dicoccoides. The donor was crossed to bread wheat and the pentaploid progeny was then self-pollinated. Plants having a near stable hexaploid chromosome complement were selected in the F₃ progeny and topcrossing and backcrossing of these to a second wheat cultivar to improve the phenotype was undertaken. Monosomic analysis of early backcross lines showed the transferred gene to be located on chromosome 4A. The gene has been designated Pm16.     

Use of a synthetic hexaploid Triticum miguschovae for transfer of leaf rust resistance to common wheat

Summary Triticum miguschovae, a genome addition synthetic, was used as a source for transfer of leaf rust (Puccinia recondita tritici) resistance to common wheat. This synthetic, developed from two wild species Triticum militinae and Aegilops squarrosa, proves a valuable donor of the genes for leaf rust resistance. Leaf rust resistance was transferred from T. miguschovae by both dominant and recessive genes. Stable lines phenotypically similar to their recurrent parents Kavkaz and Bezostaya 1 but differing from them in a high level of leaf rust resistance were obtained. The genes for resistance in 3 selected lines differed from each other and from the known effective genes Lr9, Lr19, and Lr24. The resistance of one of them (line 1229) is controlled by two complementary interacting genes located on chromosome 7B and 1D was revealed by monosomic analysis.