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The adult‐plant leaf rust resistant gene Lr22a confers broadly effective resistance against the fungal pathogen Puccinia triticina Eriks. (Pt) in wheat that has not been extensively utilized in wheat cultivars. The objective of this study was to develop robust functional molecular markers using the Lr22a gene sequence to facilitate integration of Lr22a in breeding programmes. The Lr22a coding sequence was used to identify isolated SNPs and four kompetitive allele specific polymerase chain reaction (PCR) (KASP) markers were developed. For marker testing, a F2:3 population was developed by crossing a near‐isogenic line RL4495 (Lr22a carrier) with Thatcher and phenotyped with Pt race TDBJ and genotyped with a 90K iSelect SNP array, four KASP markers and two SSR markers. A linkage map of chromosome arm 2DS that included Lr22a was constructed. The KASP markers co‐segregated with Lr22a and were validated for cross‐applicability on a panel of wheat lines. KASP markers Kwh636, Kwh637 and Kwh638 reliably detected the presence or absence of Lr22a. The markers developed in this study will facilitate Lr22a selection in breeding programmes. [ABSTRACT FROM AUTHOR]

Leaf, stem and stripe rust caused by Puccinia triticina, P. graminis f. sp. tritici and P. striiformis f. sp. tritici, respectively, are common wheat diseases. The deployment of complex rust resistance sources is likely to contribute to their durability. In this study, wheat varieties and experimental plants (F2), with different rust resistance gene combinations, were characterised using molecular markers, phenotypic evaluation and quantification of fungal biomass accumulation. The experimental wheat plants were developed from six donor parental varieties that in combination carry seven known rust resistance genes/quantitative trait loci (QTL). A timeline study revealed that quantification of fungal biomass accumulation for the rusts, 10‐day postinoculation (dpi), can successfully distinguish between resistant and susceptible wheat varieties. Phenotypic evaluation included seedling infection types and adult‐plant response types that were determined 15 dpi. Data obtained from the three methods were in support of each other and in combination successfully distinguished between rust‐resistant and susceptible experimental wheat plants. Resistance genes/QTL evaluated in this study, when deployed in combination, may lower the risk of rust outbreaks. [ABSTRACT FROM AUTHOR]

Wheat leaf rust (LR), caused by the obligate biotrophic fungus Puccinia triticina ( Pt), is a destructive foliar disease of common wheat ( Triticum aestivum L.) worldwide. The most effective, economic means to control the disease is resistant cultivars. The Romanian wheat line Fundulea 900 showed high resistance to LR in the field. To identify the basis of resistance to LR in Fundulea 900, a population of 188 F2:3 lines from the cross Fundulea 900/'Thatcher' was phenotyped for LR severity during the 2010-2011, 2011-2012 and 2012-2013 cropping seasons in the field at Baoding, Hebei Province. Bulked segregant analysis and simple sequence repeat markers were used to identify the quantitative trait loci ( QTLs) for LR adult-plant resistance in the population. Three QTLs were detected and designated as QLr.hebau-1 BL, QLr.hebau-2 DS and QLr.hebau-7 DS. Based on the chromosome positions and molecular marker tests, QLr.hebau-1 BL is Lr46, and QLr.hebau-7 DS is Lr34. QLr.hebau-2 DS was derived from 'Thatcher' and was close to Lr22. This result suggests that Lr22b may confer residual resistance on field nurseries when challenged with isolates virulent on Lr22b, or another gene linked to Lr22b confers this resistance from 'Thatcher'. This study confirms the value of Lr34 and Lr46 in breeding for LR resistance in China; the contribution of the QTL to chromosome 2D needs further validation. [ABSTRACT FROM AUTHOR]

With 1 figure and 4 tables Abstract A leaf rust resistance gene (temporarily designated LrARK0;) was identified in the Swiss spelt wheat 'Altgold Rotkorn' and mapped to chromosome 2A. The gene was located 2 cM distal to marker Xgwm614 (co-segregating with markers Xbarc124, Xbarc212, XE34M48-103 and XE38M53-334) on chromosome 2AS. This map location is similar to that of LrAlt identified in the same germplasm in a previous study. Based on gene location, allelism tests and pathogen specificity, this leaf rust resistance gene wa s designated Lr65. A single gene stock (AUS 91455) in a Triticum aestivum background was developed and registered for utilization and research purposes. The gene was widely effective against Australian and German isolates of Puccinia triticina. [ABSTRACT FROM AUTHOR]

With 2 figures and 2 tables The recessive adult plant leaf rust resistance (APR) gene Lr48 in CSP44 was tagged using simple sequence repeat (SSR) markers. The population was phenotyped under controlled conditions using pathotype 77‐5 (121R63‐1) at both seedling and adult plant stages. Four microsatellite markers Xwmc175, Xwmc332, Xwmc627 and Xwmc149 were linked to Lr48 and mapped to chromosome 2BL with distances of 10.3, 2.5, 12.6 and 20.7 cM from Lr48 covering a length of 31 cM. Lr48 was placed between markers Xwmc175 and Xwmc332. The earlier reported location of Lr48 on 2BS could not be confirmed. The markers were validated on another population and the closest SSR marker, Xwmc332, was specific to resistance allele Lr48 and did not amplify in wheat lines carrying other resistance genes, thus enabling breeders to pyramid Lr48 with other leaf rust resistance genes. [ABSTRACT FROM AUTHOR]

This study was undertaken to understand the inheritance of leaf rust resistance in line TM16 of Triticum monococcum ssp. monococcum var. macedonicum Papag. which is the source of resistance transferred into hexaploid triticale lines (Tcl/Tm). Thirty-two secondary tetraploid genotypes were analysed cytologicaly to identify substitutions of Am-genome chromosomes by their homoeologous A-genome chromosomes from a leaf rust susceptible hexaploid triticale accession. Plants with one (or more) substituted chromosomes were inoculated with leaf rust at two growth stages. The disease phenotypes of these lines indicated that a major resistance gene was located on the short arm of T. monococcum chromosome 2Am. An additional gene on chromosome 6Am had complementary effects in enhancing the effects of the gene on chromosome 2Am. [ABSTRACT FROM AUTHOR]

An Aegilops peregrina (Hackel in J. Fraser) Maire & Weiller accession that showed resistance to mixed leaf rust ( Puccinia triticina Eriks.) inoculum was crossed with, and backcrossed to, hexaploid wheat ( Triticum aestivum L.). During backcrossing a chromosome segment containing a leaf rust resistance gene (here designated Lr59) was spontaneously translocated to wheat chromosome 1A. Meiotic, monosomic and microsatellite analyses suggested that the translocated segment replaced most of, or the complete, 1AL arm, and probably resulted from centromeric breaks and fusion. The translocation, of which hexaploid wheat line 0306 is the appropriate source material, provided seedling leaf rust resistance against a wide range of South African and Canadian pathotypes. [ABSTRACT FROM AUTHOR]

A genetic analysis of the landrace-derived wheat accessions Americano 25e, Americano 26n, and Americano 44d, from Uruguay was conducted to identify the leaf rust resistance genes present in these early wheat cultivars. The three cultivars were crossed with the leaf rust susceptible cultivar ‘Thatcher’ and approximately 80 backcross (BC1) F2 families were derived for each cross. The BC1F2 families and selected BC1F4 lines were tested for seedling and adult plant leaf rust resistance with selected isolates of leaf rust, Puccinia triticina. The segregation and infection type data indicated that Americano 25e had seedling resistance genes Lr3, Lr16, an additional unidentified seedling gene, and one adult plant resistance gene that was neither Lr12 nor Lr13, and did not phenotypically resemble Lr34. Americano 26n was postulated to have genes Lr11, Lr12, Lr13, and Lr14a. Americano 44d appeared to have two possibly unique adult plant leaf rust resistance genes. [ABSTRACT FROM AUTHOR]

A set of bread wheat and durum wheat cultivars adapted to Spanish conditions was tested for resistance against leaf rust caused by different pathotypes of Puccinia triticina in field trials and in growth chamber studies. Lower levels of resistance were found in durum wheat than in bread wheat. The most frequent Lr genes found in bread wheat were Lr1, Lr10, Lr13, Lr20, Lr26 and Lr28. In durum wheat, additional resistance genes that differed from the known Lr genes were identified. The level of partial resistance to leaf rust was in general low, although significant levels were identified in some bread wheat and durum wheat cultivars. [ABSTRACT FROM AUTHOR]

The tendency of unpaired meiotic chromosomes to undergo centric misdivision was exploited to translocate leaf rust and stripe rust resistance genes from an Aegilops kotschyi addition chromosome to a group 2 chromosome of wheat. Monosomic and telosomic analyses showed that the translocation occurred to wheat chromosome arm 2DL. The introgressed region did not pair with the corresponding wheat 2DL telosome during meiosis suggesting that a whole arm may have been transferred. Female transmission of the resistance was about 55% whereas male transmission was strongly preferential (96%). The symbols Lr54 and Yr37 are proposed to designate the new resistance genes. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the leaf rust resistance introduced into introgressive triticale lines with Triticum monococcum genes, and to study the expression of these genes at the hexaploid level. The introgressive lines were developed by incorporating diploid wheat ( T. monococcum s.s.) genes into hexaploid triticale LT 522/6 using the synthetic allotetraploid T. monococcum/Secale cereale (AmAmRR) as a bridging form. A group of 44 those lines, parental stocks and check cultivars were inoculated at the seedling stage (in a greenhouse) and at the adult-plant stage (in the field) with four pathotypes of Puccinia triticina. At the seedling stage the assessment of infection type showed that four lines had resistance to all pathotypes as high as in the T. monococcum donor. Adult plant examinations showed some introgressive lines with complete resistance and also lines with partial resistance, expressed in area under the disease progress curve (AUDPC) calculations as slow rusting. Some lines comprise low AUDPC with complete resistance at seedling stage. [ABSTRACT FROM AUTHOR]

Genetic studies were conducted to gain an understanding of the inheritance of adult plant resistance (APR) to leaf rust in six common wheat varieties. The Australian varieties `Cranbrook' and `Harrier' each carry two genes for APR to leaf rust. These genes are genetically independent of the seedling resistance genes Lr23 and Lr17b , carried by the respective varieties. Adult plant resistance in `Suneca' was conferred by at least two genes, in addition to the seedling genes Lr1 and Lr13 . It is likely that the APRs in `Cranbrook', `Harrier' and `Suneca' are conferred by uncharacterized gene(s). Tests of allelism confirmed that seedling resistances in the varieties `Avocet R', `Hereward', `Moulin' and `Pastiche' are conferred by Lr13 . Adult plant resistance in the variety `Hereward' was inherited monogenically, whereas varieties `Moulin' and `Pastiche' each carried two dominant genes. On the basis of rust specificity and pedigree analysis, it would seem likely that the APR genes in `Hereward', `Moulin' and `Pastiche' are also currently uncharacterized. [ABSTRACT FROM AUTHOR]

There is worldwide interest in adult plant resistance (APR) because of greater durability of APR to the cereal rusts. Peruvian bread wheat genotype 'CPAN (Coordinated Project Accession Number) 1842' (LM 50-53) has shown leaf rust resistance in disease screening nurseries since its introduction in 1977. However, it is susceptible at the seedling stage to several Puccinia triticina (Pt) pathotypes including the widely prevalent 77-5 (121R63-1) that infects bread wheat. Inheritance studies showed that CPAN 1842 carried a dominant gene for APR to pathotype 77-5, which was different from Lr12, Lr13, Lr22a, Lr34, Lr35, Lr37, Lr46, Lr48, Lr49 and Lr68, based on the tests of allelism; and from Lr67, based on genotyping with the closely linked SSR marker cfd71. This gene should also be different from Lr22b as the latter is totally ineffective against pathotype 77-5. CPAN 1842 therefore appears to be a new promising source of leaf rust resistance. Also having resistance to stem rust and stripe rust, this line can contribute to breeding for multiple rust resistances in wheat. [ABSTRACT FROM AUTHOR]

The gene Lr34 has contributed to durable resistance to leaf rust caused by Puccinia triticina in wheat worldwide. The closely associated leaf tip necrosis is generally used as the gene's marker. Lr34 has been postulated in many Indian bread wheat cultivars including ‘C 306’, based on the associated leaf tip necrosis and a few other field and glasshouse observations. The present study showed monogenic control of adult-plant resistance in ‘C 306’ to leaf rust pathotype 77-5 (121R63-1). The F2 segregation in the crosses between ‘C 306’ and the two known carriers of Lr34, ‘Line 897’ and ‘Jupateco 73’‘R’ fitted a digenic ratio. The F3 families derived from the susceptible F2 segregants were true breeding for susceptibility, proving the absence of Lr34 in ‘C 306’. The cross between ‘Line 897’ and ‘Jupateco 73’‘R’ did not segregate for susceptibility. Resistance in the cross ‘Agra Local’ (susceptible) × ‘C 306’ was associated with leaf tip necrosis, showing that the leaf rust resistance gene in ‘C 306’ was associated with leaf tip necrosis, but was different from Lr34. This gene is being temporarily designated as Lr‘C 306’. Hence, leaf tip necrosis cannot be considered as an exclusive marker for selecting Lr34 in wheat improvement. [ABSTRACT FROM AUTHOR]

The bread wheat cultivar ‘Thatcher’ is documented to carry the gene Lr22b for adult-plant resistance to leaf rust. Seedling-resistance to leaf rust caused by Puccinia triticina in the bread wheat cultivar ‘Thatcher’, the background parent of the near-isogenic lines for leaf rust resistance genes in wheat, is rare and no published information could be found on its genetic basis. The F2 and F3 analysis of the cross ‘Agra Local’ (susceptible) × ‘Thatcher’ showed that an apparently incompletely dominant gene conditioned seedling-resistance in ‘Thatcher’ to the three ‘Thatcher’-avirulent Indian leaf rust pathotypes – 0R8, 0R8-1 and 0R9. Test of allelism revealed that this gene (temporarily designated LrKr1) was derived from ‘Kanred’, one of the parents of ‘Thatcher’. Absence of any susceptible F2 segregants in a ‘Thatcher’ × ‘Marquis’ cross confirmed that an additional gene (temporarily designated LrMq1) derived from ‘Marquis’, another parent of ‘Thatcher’, was effective against pathotype 0R9 alone. These two genes as well as a second gene in ‘Kanred’ (temporarily designated LrKr2), which was effective against all the three pathotypes, but has not been inherited by ‘Thatcher’, seem to be novel, undocumented leaf rust resistance genes. [ABSTRACT FROM AUTHOR]