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Rients E. Niks - One of the best experts on this subject based on the ideXlab platform.
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EVIDENCE OF ISOLATE-SPECIFICITY IN NON-HYPERSENSITIVE RESISTANCE IN SPRING Wheat (TRITICUM AESTIVUM) TO Wheat Leaf Rust
Pakistan Journal of Botany, 2007Co-Authors: Maqsood Qamar, Rients E. NiksAbstract:Isolate-specific aspect of non-hypersensitive resistance in Wheat to Wheat Leaf Rust was studied at seedling stage in the green house. Isolate-specific response of non-hypersensitive resistance was assessed from latency period (LP) and infection frequency (IF) of two single-pustule isolates of Puccinia triticina in 26 spring Wheat cultivars/lines. Small but significant cultivar x isolate interactions were observed for LP and IF in seedlings of host genotypes. Isolate specific effect for LP at seedling stage was consistent and reproduced in a repeated experiment; however, the interaction for IF was inconsistent and was not reproducible. The inconsistency in cultivar x isolate interaction may be due to some non-genetic origin. The result suggested that a gene-for-gene relationship could exist between non-hypersensitive resistance genes in the host and genes in pathogen.
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Morphological and molecular characterisation confirm that Triticum monococcum s.s. is resistant to Wheat Leaf Rust
Theoretical and Applied Genetics, 2001Co-Authors: C.c. Anker, J.b. Buntjer, Rients E. NiksAbstract:The three diploid Wheat species Triticum monococcum, Triticum boeoticum and Triticum urartu differ in their reaction to Wheat Leaf Rust, Puccinia triticina. In general, T. monococcum is resistant while T. boeoticum and T. urartu are susceptible. However, upon screening a large collection of diploid Wheat accessions, 1% resistant T. boeoticum accessions and 16% susceptible T. monococcum accessions were found. In the present study these atypical accessions were compared with 49 typical T. monococcum, T. boeoticum and T. urartu accessions to gain insight into the host-status of the diploid Wheat species for Wheat Leaf Rust. Cluster analysis of morphological data and AFLP fingerprints of the typical accessions clearly discriminated the three diploid species. T.monococcum and T. boeoticum had rather-similar AFLP fingerprints while T. urartu had a very different fingerprint. The clustering of most atypical accessions was not consistent with the species they were assigned to, but intermediate between T. boeoticum and T. monococcum. Only four susceptible T. monococcum accessions were morphologically and moleculary similar to the typical T. monococcum accessions. Results confirmed that T. boeoticum and T. monococcum are closely related but indicate a clear difference in host-status for the Wheat Leaf Rust fungus in these two species.
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Prehaustorial resistance to the Wheat Leaf Rust fungus, Puccinia triticina, in Triticum monococcum (s.s.)
Euphytica, 2001Co-Authors: C.c. Anker, Rients E. NiksAbstract:Diploid Wheat, Triticum monococcum s.l., is a host for the Wheat Leaf Rust fungus, Puccinia triticina . Some accessions have been reported to show a high degree of prehaustorial resistance. This is non-hypersensitivity resistance, which acts before the formation of haustoria by the pathogen. To assess the frequency of prehaustorial resistance 598 accessions of diploid Wheat were inoculated with the Wheat Leaf Rust isolate Felix. Most T. monococcum s.s. accessions (84%) were resistant whereas all T. urartu and all but three T. boeoticum accessions were susceptible. Histological components analysis revealed that a high percentage of prehaustorial resistance to P. triticina was found in only three T. monococcum accessions. No haustoria were observed in such infection units confirming the prehaustorial nature of the resistance. Prehaustorial abortion of certain infection units in an accession always coincided with posthaustorial abortion of the other infection units.
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Characterization of Lr34, a major gene conferring nonhypersensitive resistance to Wheat Leaf Rust.
Plant Disease, 1995Co-Authors: Diego Rubiales, Rients E. NiksAbstract:Wheat Leaf Rust resistance gene Lr34 is claimed to contribute to durability of resistance in Wheat cultivars in combination with other genes for resistance. We compared the effect of Lr34 with that of Lr12 and Lr13 (all in Thatcher background) and with the partial resistance of Akabozu and BH1146. Seedlings of all lines displayed a compatible infection type. Lr34 increased latency period and decreased infection frequency, especially at low temperature. The gene caused a small but significant increase in early abortion of sporelings. The number of haustoria per sporeling 42 h after inoculation was reduced significantly, but this was not associated with papilla formation. In adult plants the effect of Lr34 was much clearer. In the flag Leaf Lr34 decreased infection frequency and increased latency period. Many infection units did not develop further than the stage in which they caused pale (nonhypersensitive) flecks. Also at the microscopic level we found no increased hypersensitivity due to Lr34. Lr34 shared features both with Lr13 and with the genes for partial resistance in Akabozu and BH1146. The main difference with Lr13 was the association of the latter with chlorosis at the macroscopic level and cell necrosis at the microscopic level. Lr34 and the partial resistance in Akabozu and BH1146 are based on reduced rates of haustorium formation in the early stages of infection, in association with no or relatively little plant cell necrosis. However, the reduction of haustorium formation in Thatcher-Lr34 appeared to be due to a low rate of intercellular hyphal development and not to papilla formation as in Akabozu and BH1146. We argue that Lr34 should be considered a major gene conferring partial resistance sensu Parlevliet.
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Inheritance of resistance to Wheat Leaf Rust (Puccinia recondita) in four accessions of diploid Wheat.
Durability of Disease Resistance, 1993Co-Authors: H. S. Zhang, Rients E. Niks, R. G. Dekens, H.h. LubbersAbstract:Diploid Wheats are almost inappropriate host (or nonhost) to the Wheat Leaf Rust fungus (Puccinia recondita f.sp. tritici): over 99% of the accessions are resistant, usually without symptoms. Histological research showed that the mechanism of resistance in diploid Wheat to Wheat Leaf Rust could be either prehaustorial or posthaustorial.
James Kolmer - One of the best experts on this subject based on the ideXlab platform.
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First report of a Wheat Leaf Rust (Puccinia triticina) phenotype with high virulence to durum Wheat in the Great Plains region of the United States.
Plant disease, 2015Co-Authors: James KolmerAbstract:Phenotypes of the Wheat Leaf Rust pathogen Puccinia triticina with high virulence to tetraploid durum Wheat (Triticum turgidum) are found regularly in Mexico (5), the Mediterranean region (1), the Middle East (3), and rarely in the Imperial Valley of California and the adjacent area in Arizona. Previous to 2013, these phenotypes had not been found in the Great Plains region of the United States where hexaploid, T. aestivum types of hard red winter Wheat, hard red spring Wheat, and durum Wheat are grown. In May 2013, collections of P. triticina, the Wheat Leaf Rust fungus identified by color, size, and shape of uredinia, were obtained from leaves of the hard red winter Wheat cultivar Overley in research plots at Hutchinson, KS. A single uredinial isolate was obtained that was used in virulence testing and molecular genotyping. Urediniospores from the initial field collection were inoculated onto seedlings of the susceptible cultivar Little Club. Subsequently, single uredinia were isolated and re-increased ...
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First Detection in North America of Virulence in Wheat Leaf Rust (Puccinia triticina) to Seedling Plants of Wheat with Lr21
Plant disease, 2011Co-Authors: James Kolmer, James A. AndersonAbstract:Leaf Rust resistance gene Lr21 is present in hard red spring Wheat (Triticum aestivum) cultivars grown in Minnesota, North Dakota, South Dakota, Manitoba, and Saskatchewan. Isolates of Puccinia triticina, the causal organism of Wheat Leaf Rust, with virulence to this gene have not been previously detected in annual virulence surveys in the United States. (2). In 2010, hard red spring Wheat cvs. Faller, RB07 (1), and Glenn, all with Lr21, had 0 to 5% levels of Leaf Rust severity, which was higher than in previous years in research plots in North Dakota and Minnesota. Leaf Rust collections from Wheat cultivars and germplasm lines with Lr21 at three locations in Minnesota and North Dakota were increased on plants of the Leaf Rust susceptible Wheat Thatcher and the Thatcher line with Lr21. Single uredinia from the collections were isolated and increased on seedlings of Thatcher. The single uredinial isolates were inoculated to 7- to 8-day-old seedling plants of the set of 19 differential lines that are curren...
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Wheat Leaf Rust caused by Puccinia triticina
Molecular Plant Pathology, 2008Co-Authors: Melvin D Bolton, James Kolmer, David F. GarvinAbstract:SUMMARY Leaf Rust, caused by Puccinia triticina , is the most common Rust disease of Wheat. The fungus is an obligate parasite capable of producing infectious urediniospores as long as infected Leaf tissue remains alive. Urediniospores can be wind-disseminated and infect host plants hundreds of kilometres from their source plant, which can result in Wheat Leaf Rust epidemics on a continental scale. This review summarizes current knowledge of the P. triticina /Wheat interaction with emphasis on the infection process, molecular aspects of pathogenicity, Rust resistance genes in Wheat, genetics of the host parasite interaction, and the population biology of P. triticina . Taxonomy: Puccinia triticina Eriks.: kingdom Fungi, phylum Basidiomycota, class Urediniomycetes, order Uredinales, family Pucciniaceae, genus Puccinia . Host range: Telial/uredinial (primary) hosts: common Wheat ( Triticum aestivum L.), durum Wheat ( T. turgidum L. var. durum ), cultivated emmer Wheat ( T. dicoccon ) and wild emmer Wheat ( T. dicoccoides) , Aegilops speltoides , goatgrass ( Ae. cylindrica ), and triticale (X Triticosecale). Pycnial/aecial (alternative) hosts: Thalictrum speciosissimum (= T. flavum glaucum ) and Isopyrum fumaroides . Identification: Leaf Rust is characterized by the uredinial stage. Uredinia are up to 1.5 mm in diameter, erumpent, round to ovoid, with orange to brown uredinia that are scattered on both the upper and the lower Leaf surfaces of the primary host. Uredinia produce urediniospores that are sub-globoid, average 20 µ m in diameter and are orange‐brown, with up to eight germ pores scattered in thick, echinulate walls. Disease symptoms: Wheat varieties that are fully susceptible have large uredinia without causing chlorosis or necrosis in the host tissues. Resistant Wheat varieties are characterized by various responses from small hypersensitive flecks to small to moderate size uredinia that may be surrounded by chlorotic and/ or necrotic zones. Useful website: USDA Cereal Disease Laboratory: http:// www.ars.usda.gov/mwa/cdl
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Virulence and molecular polymorphism in international collections of the Wheat Leaf Rust fungus Puccinia triticina
Phytopathology, 2000Co-Authors: James Kolmer, J Q LiuAbstract:Kolmer, J. A., and Liu, J. Q. 2000. Virulence and molecular polymorphism in international collections of the Wheat Leaf Rust fungus Puccinia triticina. Phytopathology 90:427-436. Collections of Puccinia triticina, the Wheat Leaf Rust fungus, were obtained from Great Britain, Slovakia, Israel, Germany, Australia, Italy, Spain, Hungary, South Africa, Uruguay, New Zealand, Brazil, Pakistan, Nepal, and eastern and western Canada. All single-uredinial isolates derived from the collections were tested for virulence polymorphism on 22 Thatcher Wheat lines that are near-isogenic for Leaf Rust resistance genes. Based on virulence phenotype, selected isolates were also tested for randomly amplified polymorphic DNA (RAPD) using 11 primers. The national collections were placed into 11 groups based on previously established epidemiological zones. Among the 131 single-uredinial isolates, 105 virulence phenotypes and 82 RAPD phenotypes were described. In a modified analysis of variance, 26% of the virulence variation was due to differences in isolates between groups, with the remainder attributable to differences within groups. Of the RAPD variation, 36% was due to differences in isolates between groups. Clustering based on the average virulence distance (simple distance coefficient) within and between groups resulted in eight groups that differed significantly. Collections from Australia-New Zealand, Spain, Italy, and Britain did not differ significantly for virulence. Clustering of RAPD marker differences (1 ‐ Dice coefficient) distinguished nine groups that differed significantly. Collections from Spain and Italy did not differ significantly for RAPD variation, neither did collections from western Canada and South America. Groups of isolates distinguished by avirulent/virulent infection types to Wheat lines with resistance genes Lr1, Lr2a, Lr2c, and Lr3 also differed significantly for RAPD distance, showing a general relationship between virulence and RAPD phenotype. The results indicated that on a worldwide level collections of P. triticina differ for virulence and molecular backgrounds.
P. Bartoš - One of the best experts on this subject based on the ideXlab platform.
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Physiologic specialization of Wheat Leaf Rust (Puccinia triticina Eriks.) in the Slovak Republic in 2005, 2006 and 2008
Czech Journal of Genetics and Plant Breeding, 2018Co-Authors: A. Hanzalová, Jozef Huszár, E. Herzová, P. BartošAbstract:In 2005, 2006 and 2008 the virulence of Wheat Leaf Rust population was studied on Thatcher nearisogenic lines with lr1, lr2a, lr2b, lr2c, lr3a, lr9, lr10, lr13, lr15, lr17, lr19, lr21, lr23, lr24, lr26 and lr28. Samples of Leaf Rust (141 in total) were obtained from different parts of Slovakia. Resistance gene lr9 was effective to all tested isolates except three isolates from 2008. No virulence was found to lr19 and genes lr24 and lr28 were also highly effective. Low incidence of virulence to lr2a was observed. Sixty-five winter Wheat cultivars registered in Slovakia were tested with seven Leaf Rust isolates in the greenhouse. Cultivar Bona Dea was the most resistant of all.
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Physiologic specialization of Wheat Leaf Rust (Puccinia triticina Eriks.) in the Slovak Republic in 2009-2011.
Czech Journal of Genetics and Plant Breeding, 2018Co-Authors: A. Hanzalová, T. Sumíková, Jozef Huszár, P. BartošAbstract:In 2009–2011 virulence of the Wheat Leaf Rust population was studied on Thatcher near-isogenic lines with Lr1, Lr2a, Lr2b, Lr2c, Lr3a, Lr9, Lr11, Lr13, Lr15, Lr17, Lr19, Lr21, Lr23, Lr24, Lr26 and Lr28. Samples of Leaf Rust were obtained from different parts of the Slovak Republic. A total of 122 Wheat Leaf Rust isolates were analysed. Resistance gene Lr19 was effective to all tested isolates. Virulence to Lr9 was found, however only in one isolate. Gene Lr24 conditioned resistance to almost all Rust collections. A lower frequency of virulence to Lr2a and Lr28 was also observed. Nineteen winter Wheat cultivars grown in Slovakia were tested with 8 Leaf Rust isolates. Winter Wheat cultivar Bona Dea was resistant to all isolates applied in the greenhouse test. Presence of Lr genes was estimated according to the reactions of the tested cultivars. Presence of Lr10, Lr26, Lr34 and Lr37 was studied by molecular markers.
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Virulence surveys of Wheat Leaf Rust in the Czech Republic and resistance genes in registered cultivars.
Czech Journal of Genetics and Plant Breeding, 2018Co-Authors: A. Hanzalová, P. BartošAbstract:Hanzalova A., Bartos P. (2014): Virulence surveys of Wheat Leaf Rust in the Czech Republic and resistance genes in registered cultivars. Czech J. Genet. Plant Breed., 50: 241–246. The technical report presents a summary of results obtained in the Leaf Rust race surveys carried out in Czechoslovakia/Czech Republic in the years 1966–2001. The physiologic races were determined using the standard differentials Malakoff (Lr1), Carina (Lr2b), Brevit (Lr2c), Webster (Lr2a), Loros (Lr2c), Mediterranean (Lr3), Hussar (Lr11), Democrat (Lr3) and the additional differential Salzmunder Bartweizen (Lr26). Races 14, 77, 61, 53 and 2 successively dominated in the given period. They mostly appeared in two variants, avirulent and virulent to Lr26. Genes for virulence in the Leaf Rust races were compared with genes for resistance in the registered Wheat cultivars listed in the report. Most frequent were the genes Lr3 and Lr26.
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The Virulence Spectrum of the Wheat Leaf Rust Population Analyzed in the Czech Republic from 2002 to 2011
Czech Journal of Genetics and Plant Breeding, 2018Co-Authors: A. Hanzalová, P. BartošAbstract:The research report presents a summary of Wheat Leaf Rust virulence surveys in the Czech Republic from 2002 to 2011. Determination of virulence was based on infection types on Thatcher near-isogenic lines (NILs) with the resistance genes Lr1, Lr2a, Lr2b, Lr2c, Lr3a, Lr9, Lr10, Lr11, Lr13, Lr15, Lr17, Lr19, Lr21, Lr23, Lr24, Lr26 and Lr28 , respectively. Virulence for Lr9 and Lr19 occurred only sporadically in the investigated period. On average, virulence for Lr2a, Lr2b, Lr24 and Lr28 was low. The highest frequency of virulence was found for Lr3a, Lr10, Lr11, Lr13, Lr15, Lr17, Lr21, Lr23 and Lr26 . During the investigation period we recorded a shift from prevailing virulence for Lr2c and avirulence for Lr1 to avirulence for aLr2c and virulence for Lr1 . There virulences in the Leaf Rust population were compared with matching resistance genes in the registered Wheat cultivars. The most frequent resistance gene was Lr37 , while the genes Lr3a and Lr26 were less frequent.
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Pathotypes of Wheat Leaf Rust (Puccinia triticina Eriks.) and resistance of registered cultivars in the Czech Republic in 2012–2015
Czech Journal of Genetics and Plant Breeding, 2017Co-Authors: A. Hanzalová, P. Bartoš, T. SumíkováAbstract:In 2012–2015 the virulence of the Wheat Leaf Rust (Puccinia triticina Eriks.) population was studied on Thatcher near-isogenic lines with Lr1, Lr2a, Lr2b, Lr2c, Lr3a, Lr9, Lr10, Lr11, Lr13, Lr15, Lr17, Lr19, Lr21, Lr23, Lr24, Lr26 and Lr28. Samples of Leaf Rust were obtained from different parts of the Czech Republic. A total of 163 Wheat Leaf Rust isolates were analysed. No virulence for the resistance gene Lr9 was found. Virulence for Lr19 was found only in one isolate in 2015. A lower frequency of virulence to Lr24, Lr2a, 2b, 2c and Lr28 was also observed. The presence of Lr10, Lr24, Lr26, Lr28 and Lr37 in registered cultivars was detected by polymerase chain reaction (PCR) molecular markers.
Christian Lannou - One of the best experts on this subject based on the ideXlab platform.
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Influence of cultivated landscape composition on variety resistance: an assessment based on Wheat Leaf Rust epidemics
The New phytologist, 2011Co-Authors: Julien Papaix, Henriette Goyeau, Hervé Monod, Philippe Du Cheyron, Christian LannouAbstract:Summary •In plant pathology, the idea of designing variety management strategies at the scale of cultivated landscapes is gaining more and more attention. This requires the identification of effects that take place at large scales on host and pathogen populations. Here, we show how the landscape varietal composition influences the resistance level (as measured in the field) of the most grown Wheat varieties by altering the structure of the pathogen populations. •For this purpose, we jointly analysed three large datasets describing the Wheat Leaf Rust pathosystem (Puccinia triticina/Triticum aestivum) at the country scale of France with a Bayesian hierarchical model. •We showed that among all compatible pathotypes, some were preferentially associated with a variety, that the pathotype frequencies on a variety were affected by the landscape varietal composition, and that the observed resistance level of a variety was linked to the frequency of the most aggressive pathotypes among all compatible pathotypes. •This data exploration establishes a link between the observed resistance level of a variety and landscape composition at the national scale. It illustrates that the quantitative aspects of the host–pathogen relationship have to be considered in addition to the major resistance/virulence factors in landscape epidemiology approaches.
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Landscape composition and cultivar resistance : Bayesian modelling of the Wheat Leaf Rust epidemiology on large scales
2010Co-Authors: Julien Papaix, Henriette Goyeau, Christian Lannou, Hervé Monod, Philippe Du CheyronAbstract:Structure and composition changes in our agricultural landscapes have made the domestication of pathogens easier. It has also made these agricultural landscapes more sensitive to epidemic risks. To regulate these phenomena in a natural way, functional diversity must be introduced. In plant epidemiology, diversity may be represented by the resistance of each cultivar to a particular disease. These resistances are limited in number, so that management strategies must be defined to avoid their erosion. In this study, assuming a homogeneous dispersion, we tried to link the cultivar composition of the landscape to the symptoms exhibited by the most grown Wheat cultivars. In order to integrate three independent datasets describing the pathosystem of the Wheat Leaf Rust - a foliar disease caused by the fungus Puccinia triticina on its strict host Triticum aestivum - we developed a hierarchical model in a Bayesian framework. We proved that, in production conditions and for large scales of time and space, the cultivar frequencies in the French Wheat landscape play a leading role on the composition of Puccinia triticina populations. As a consequence we brought to light a maladaptation of several Puccinia triticina populations to their host, which is reflected by a decrease in the Wheat Leaf Rust symptoms. Finally this work shows an investigation method to link heterogeneous datasets collected on macroscopic scales and it gives encouragement to acquire such datasets.
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Distribution of pathotypes with regard to host cultivars in French Wheat Leaf Rust populations.
Phytopathology, 2006Co-Authors: Henriette Goyeau, Robert F. Park, Brigitte Schaeffer, Christian LannouAbstract:Isolates of Wheat Leaf Rust collected from durum and bread Wheat cultivars in France during 1999-2002 were analyzed for virulence on 18 Thatcher lines with single genes for Leaf Rust resistance (Lr genes). Sampling focused on the five most widely grown bread Wheat cultivars (two susceptible and three resistant) to allow statistical comparison of diversity indexes between the cultivars. Leaf Rust populations from durum and bread Wheats were different. The diversity of the bread Wheat Leaf Rust pathotypes, as measured by the Shannon index, ranged from 2.43 to 2.76 over the 4 years. Diversity for Wheat Leaf Rust resistance was limited in the host since we postulated only seven seedling resistance genes in the 35 cultivars most widely grown during 1999-2002. Leaf Rust populations were strongly differentiated for virulence within bread Wheat cultivars, and diversity was higher on those that were resistant, mainly due to a more even distribution of virulence phenotypes than on susceptible cultivars. The pathogen population on the susceptible cv. Soissons was largely dominated by a single pathotype (073100), whereas all other pathotypes virulent on cv. Soissons either decreased in frequency or remained at a low frequency during the period studied. Several pathotypes including the most complex one were found only on resistant cultivars, even though most of them were virulent on the susceptible cv. Soissons. Specific interactions were necessary, but not always sufficient, to account for pathotype distribution and frequencies on the cultivars, suggesting that selection for virulence to host resistance genes is balanced by other selective forces including selection for aggressiveness.
C.c. Anker - One of the best experts on this subject based on the ideXlab platform.
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Morphological and molecular characterisation confirm that Triticum monococcum s.s. is resistant to Wheat Leaf Rust
Theoretical and Applied Genetics, 2001Co-Authors: C.c. Anker, J.b. Buntjer, Rients E. NiksAbstract:The three diploid Wheat species Triticum monococcum, Triticum boeoticum and Triticum urartu differ in their reaction to Wheat Leaf Rust, Puccinia triticina. In general, T. monococcum is resistant while T. boeoticum and T. urartu are susceptible. However, upon screening a large collection of diploid Wheat accessions, 1% resistant T. boeoticum accessions and 16% susceptible T. monococcum accessions were found. In the present study these atypical accessions were compared with 49 typical T. monococcum, T. boeoticum and T. urartu accessions to gain insight into the host-status of the diploid Wheat species for Wheat Leaf Rust. Cluster analysis of morphological data and AFLP fingerprints of the typical accessions clearly discriminated the three diploid species. T.monococcum and T. boeoticum had rather-similar AFLP fingerprints while T. urartu had a very different fingerprint. The clustering of most atypical accessions was not consistent with the species they were assigned to, but intermediate between T. boeoticum and T. monococcum. Only four susceptible T. monococcum accessions were morphologically and moleculary similar to the typical T. monococcum accessions. Results confirmed that T. boeoticum and T. monococcum are closely related but indicate a clear difference in host-status for the Wheat Leaf Rust fungus in these two species.
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Prehaustorial resistance to the Wheat Leaf Rust fungus, Puccinia triticina, in Triticum monococcum (s.s.)
Euphytica, 2001Co-Authors: C.c. Anker, Rients E. NiksAbstract:Diploid Wheat, Triticum monococcum s.l., is a host for the Wheat Leaf Rust fungus, Puccinia triticina . Some accessions have been reported to show a high degree of prehaustorial resistance. This is non-hypersensitivity resistance, which acts before the formation of haustoria by the pathogen. To assess the frequency of prehaustorial resistance 598 accessions of diploid Wheat were inoculated with the Wheat Leaf Rust isolate Felix. Most T. monococcum s.s. accessions (84%) were resistant whereas all T. urartu and all but three T. boeoticum accessions were susceptible. Histological components analysis revealed that a high percentage of prehaustorial resistance to P. triticina was found in only three T. monococcum accessions. No haustoria were observed in such infection units confirming the prehaustorial nature of the resistance. Prehaustorial abortion of certain infection units in an accession always coincided with posthaustorial abortion of the other infection units.
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Prehaustorial and posthaustorial resistance to Wheat Leaf Rust in diploid Wheat
2001Co-Authors: C.c. AnkerAbstract:In modern Wheat cultivars, resistance to Wheat Leaf Rust, Puccinia triticina , is either based on hypersensitivity resistance or on partial resistance. Hypersensitivity resistance in Wheat is monogenic, often complete and posthaustorial: it is induced after the formation of a haustorium by the pathogen in the plant cell. The localised plant cell death that follows prevents the uptake of nutrients by the pathogen. Although this type of resistance is widely used in Wheat breeding, it is in general not durable as the pathogen overcomes the resistance with new variants. Partial resistance is mono- or polygenic, has a quantitative expression with a susceptible infection type and is assumed to be durable. A small proportion of the infection units in partially resistant Wheat is aborted prehaustorially, before the formation of haustoria by the fungus, whereas the other infection units continue to grow and form pustules. Partial resistance is not associated with necrosis. Diploid Wheat is a close relative of tetra- and hexaploid cultivated Wheats and can be used as a donor species in Wheat breeding. Certain diploid Wheat accessions show complete resistance to Wheat Leaf Rust based on a high level of prehaustorial resistance as compared to hexaploid Wheat. The remaining infection units are aborted in association with hypersensitivity. Transferred to cultivated Wheat, the high level of prehaustorial resistance from diploid Wheat might provide an interesting and possibly durable alternative for posthaustorial resistance in Wheat breeding. The occurrence of resistance in diploid Wheat, the level of prehaustorial resistance and the inheritance of prehaustorial resistance are the subject of this thesis. Diploid Wheat comprises three species, T. monococcum , T. boeoticum and T. urartu , that can be distinguished based on morphological and molecular characteristics. The frequency of resistance in diploid Wheat was assessed by determining the reaction of about 200 accessions per species to the Wheat Leaf Rust isolate Felix. Resistance and susceptibility to Wheat Leaf Rust was almost perfectly associated with species identity. T. monococcum was almost completely resistant (98%), whereas T. boeoticum and T. urartu were completely susceptible. The percentage of early aborted infection units without and with necrosis in resistant T. monococcum accessions was determined to assess the level of pre- and posthaustorial resistance, respectively. Resistant accessions with a truly high level of prehaustorial resistance were scarce. Two percent of the accessions had a level of early abortion without necrosis of 50% or more in the seedling stage. The percentage of early abortion without necrosis in resistant seedlings ranged from 0% to 80% and all remaining infection units were aborted with necrosis. The association between species identity and Leaf Rust reaction in diploid Wheat and the combination of pre- and posthaustorial resistance in T. monococcum resemble nonhost resistance of cereals to inappropriate Rust species, suggesting that T. monococcum is a nonhost for Puccinia triticina . To elucidate the inheritance of prehaustorial resistance, two mapping populations were studied for their reaction to Wheat Leaf Rust. One population consisted of 72 recombinant inbred lines (RILs, F 6 ) of the resistant T. monococcum DV92 and the susceptible T. boeoticum G3116. The other mapping population was an F 2 of 118 plants of the susceptible T. boeoticum Tb1486 and the resistant T. monococcum Einkorn. Both resistant parents had a relatively high level of prehaustorial resistance to Wheat Leaf Rust. For the RIL population an F 2 -based RFLP linkage map already existed to which AFLPs were added and for the F 2 population a maternal and paternal AFLP map were produced. Two quantitative trait loci (QTLs) were identified: one on chromosome 5 of all three maps and one on chromosome 4 of the maternal F 2 map. The QTLs had a pleiotropic effect, governing prehaustorial as well as posthaustorial resistance, and were effective in the first and the fifth Leaf stage. In addition, two putative QTLs, for pre- and posthaustorial resistance, effective in the first Leaf stage only, were identified: one on chromosome 3 of the RIL map and one on linkage group 5 (unassigned) of the paternal F 2 map. It is remarkable that the two different resistance mechanisms in diploid Wheat are controlled by the same QTLs. In barley and cultivated Wheat, genes for prehaustorial resistance and hypersensitivity resistance represent two different classes that map to distinct locations on the respective genomes. The QTLs from diploid Wheat, identified in this study, might represent a third class of genes for Wheat Leaf Rust resistance. The pleiotropic effect of the QTLs for prehaustorial resistance from diploid Wheat may prevent the introgression into cultivated Wheat of prehaustorial resistance alone. Still, the resistance from diploid Wheat accessions with a high level of prehaustorial resistance, such as Einkorn and DV92, could prove useful in Wheat breeding, conferring a possibly durable resistance similar to nonhost resistance. Anker CC, Niks RE (2000) Genetics of prehaustorial resistance to Wheat Leaf Rust in diploid Wheat. Acta Phytopath Entomol Hungarica 35: 23-30 Anker CC, Niks RE (2001) Prehaustorial resistance to Wheat Leaf Rust in Triticum monococcum (s.s.) Euphytica 117: 209-215 Anker CC, Buntjer JP, Niks RE (in press) Morphological and molecular characterisation confirm that Triticum monococcum s.s. is resistant to Wheat Leaf Rust. Theor Appl Genet
