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Phillip N Miklas - One of the best experts on this subject based on the ideXlab platform.
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registration of common bacterial blight Rust and Bean common mosaic resistant great northern common Bean germplasm line abc weihing
Journal of Plant Registrations, 2008Co-Authors: Nedim Mutlu, James R Steadman, Carlos A Urrea, Dale T Lindgren, Marcial A Pastorcorrales, Phillip N Miklas, J Reiser, Anne K Vidaver, Dermot P CoyneAbstract:Great northern common Bean (Phaseolus vulgaris L.) germplasm line ABC-Weihing (Reg. No. GP-246, PI 647964) was developed by the University of Nebraska Agricultural Research Division in cooperation with USDA-ARS and released in 2006. This line, tested as NE1-05-4, was bred specifi cally for enhanced resistance to common bacterial blight (CBB), a major seed borne disease of common Bean caused by the bacterium Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp). ABC-Weihing is a great northern BC 5 F 3:6 line obtained from fi ve backcrosses ('Weihing'*5//'Chase'/XAN 159). The fi rst cross was made in spring 1997. Only BC n F 1 plants resistant to Xcp isolates Dominican Republic DR-7 and Nebraska SC4A, as determined by multiple needle leaf inoculation tests in the greenhouse, were used for successive backcrossing. In addition to phenotypic selection for CBB resistance, marker-assisted selection for the resistant QTL- linked marker SU91 was conducted in the BC 1 F 1 , BC 2 F 1 , and ABC-Weihing. When inoculated with Nebraska Xcp strains in the fi eld, ABC-Weihing exhibited resistance in both 2005 and 2006. ABC-Weihing has Ur-3 and Ur-6 genes for resistance to common Bean Rust and carries the single dominant hypersensitive I gene that provides resistance to all non-necrotic strains of the Bean common mosaic virus (BCMV). ABC-Weihing has bright white seed, blooms 45 d after planting, and is a midseason Bean maturing 92 d after planting.
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scar markers linked to the common Bean Rust resistance gene ur 13
Theoretical and Applied Genetics, 2005Co-Authors: C M S Mienie, M M Liebenberg, Z A Pretorius, Phillip N MiklasAbstract:Rust in common Bean (Phaseolus vulgaris L.) is caused by Uromyces appendiculatus Pers.:Pers. (Unger) which exhibits a high level of pathogenic diversity. Resistance to this disease is conditioned by a considerable number of genes. Pyramiding resistance genes is desirable and could be simplified by the use of molecular markers closely linked to the genes. The resistance gene Ur-13, present in the South African large seeded cultivar Kranskop, has been used extensively in the local breeding program. The purpose of this study was the development of a molecular marker linked to Ur-13. An F2 population derived from a cross between Kranskop and a susceptible (South African) cultivar Bonus was used in combination with bulked segregant analysis utilizing the amplified fragment length polymorphism (AFLP) technique. Seven AFLP fragments linked significantly to the Rust resistance and five were successfully converted to sequence characterized amplified region (SCAR) markers. The co-dominant SCAR markers derived from a 405 bp EAACMACC fragment, KB126, was located 1.6 cM from the gene. Two additional SCAR markers and one cleaved amplified polymorphic sequence marker were located further from the gene. The gene was mapped to linkage group B8 on the BAT 93/Jalo EEP 558 core map (chromosome 3).
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tagging and mapping of genes and qtl and molecular marker assisted selection for traits of economic importance in Bean and cowpea
Field Crops Research, 2003Co-Authors: James D Kelly, Phillip N Miklas, Paul Gepts, Dermot P CoyneAbstract:Bean/Cowpea Collaborative Research Support Program (B/C CRSP) scientists have successfully developed integrated consensus maps of the 11 linkage groups (LGs) in both Bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata L. Walp). The Bean map is approximately 1200 cM with some 500 markers and an additional 500 markers shared with other Bean maps. The cowpea map spans 2670 cM with over 400 markers. In addition to molecular markers, both maps include map locations of defense genes and phenotypic traits for disease and insect resistance, seed size, color and storage proteins, pod color and those traits associated with the domestication syndrome in Bean. Since the Bean and cowpea maps were developed independently, LGs with the same number probably refer to non-syntenic groups. Map locations of major resistance genes in Bean are revealing gene clusters on LGs B1, B4, B7, and B11 for resistance to Bean Rust, anthracnose, common bacterial blight and white mold. Gene tagging and marker-assisted selection for disease resistance has progressed to a point where the indirect selection for resistance to a number of major diseases is now routine in Bean breeding programs both in the US and overseas. # 2003 Elsevier Science B.V. All rights reserved.
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bacterial fungal and viral disease resistance loci mapped in a recombinant inbred common Bean population dorado xan 176
Journal of the American Society for Horticultural Science, 2000Co-Authors: Phillip N Miklas, James R Steadman, Richard Delorme, Valerie Stone, Mark J Daly, Rennie J Stavely, Mark J Bassett, James S. BeaverAbstract:Understanding the genomic associations among disease resistance loci will facilitate breeding of multiple disease resistant cultivars. We constructed a genetic linkage map in common Bean ( Phaseolus vulgaris L.) containing six genes and nine quantitative trait loci (QTL) comprising resistance to one bacterial, three fungal, and two viral pathogens of Bean. The mapping population consisted of 79 F 5:7 recombinant inbred lines (RILs) derived from a 'Dorado'/XAN 176 hybridization. There were 147 randomly amplified polymorphic DNA (RAPD) markers, two sequence characterized amplified region (SCAR) markers, one intersimple sequence repeat (ISSR) marker, two seedcoat color genes R and V, the Asp gene conditioning seed brilliance, and two Rust ( Uromyces appendiculatus var. appendiculatus (Pers.:Pers) Unger) resistance genes: one conditioning resistance to Races 53 and 54 and the other conditioning resistance to Race 108. These markers mapped across eleven linkage groups, one linked triad, and seven linked pairs for an overall map length of 930 cM (Kosambi). Genes conditioning resistance to anthracnose ( Co-2) (Colletotrichum lindemuthianum (Sacc. and Magnus) Lams.-Scrib.), Bean Rust (Ur-5), and Bean common mosaic virus (I and bc-3) (BCMV) did not segregate in this population, but were mapped by inference using linked RAPD and SCAR markers identified in other populations. Nine previously reported quantitative trait loci (QTL) conditioning resistance to a variety of pathogens including common bacterial blight (Xanthomonas campestris pv. phaseoli (Smith) Dye), ashy stem blight (Macrophomina phaseolina (Tassi) Goid.), and Bean golden mosaic virus (BGMV), were located across four linkage groups. Linkage among QTL for resistance to ashy stem blight, BGMV, and common bacterial blight on linkage group B7 and ashy stem blight, BGMV, and Rust resistance loci on B4 will complicate breeding for combined resistance to all four pathogens in this population. opment of multiple disease resistant cultivars is often compli- cated by repulsion (trans) linkages among desired resistance genes and QTL used to control different pathogens in a particular production region (Kelly and Miklas, 1998). The development of an integrated map of resistance loci is just beginning, however, as many loci have yet to be mapped and the genomic relationships among several mapped loci are still unknown; thus, a comprehen-
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coupling and repulsion phase rapds for marker assisted selection of pi 181996 Rust resistance in common Bean
Theoretical and Applied Genetics, 1995Co-Authors: Elizabeth S Johnson, J R Stavely, Phillip N Miklas, Juan Carlos MartinezcruzadoAbstract:The Guatemalan black Bean (Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the Bean Rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20490 tightly linked (no recombinants) in coupling phase and OAE19890 linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 Rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC4F2 (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC4F2 and 57 BC4F3 individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20490 and OAE19890 was investigated in a diverse group of common Bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20490. A RAPD similar in size to OAC20490, observed in some susceptible common Bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20490. Use of the RAPDs OAC20490 and OAE19890 in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BCnF1individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F2 or later-segregating generations.
James R Steadman - One of the best experts on this subject based on the ideXlab platform.
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prevalence and variability of the common Bean Rust in uganda
African Journal of Agricultural Research, 2016Co-Authors: Blessing Adanta Odogwu, Stanley T Nkalubo, Clare Mugisha Mukankusi, Pamela Paparu, Rubaihayo Patrick, James D Kelly, James R SteadmanAbstract:Uganda is the second largest producer of dry Beans (Phaseolus vulgaris L.) in Africa, but common Bean Rust caused by Uromyces appendiculatus (Pers. Unger), is negatively impacting the production of the crop. There is little information on the occurrence and identity of the Rust pathotypes present in the country. Consequently, a field survey was carried out during the 2015 second planting season in fifteen districts, representing the areas of high Beans production in Uganda. High common Bean Rust incidence and severity were observed in the low altitudes and the South-Western Highlands of Uganda. Wakiso and Hoima districts had the highest Rust disease incidence 72 and 76% respectively and severity rates of 6 and 5.5, respectively. Rust disease incidence was uniformly high on commercial genotypes and landraces. Similarly, high Rust disease incidence and severity were observed in the Bean-maize–groundnut cropping system. Twenty-three single Rust isolates were collected in Uganda and inoculated on 11 Bean Rust differentials and Ouro Negro (Ur-14) genotypes. Six Rust pathotypes were identified and these included 2-0, 4-0, 50-0, 5-1, 4-33 and 63-19. Five of the pathotypes were of Andean origin and only pathotype 4-33 was of Mesoamerican origin. The Rust pathotype 63-19 showed similar pathogenic characteristics with the Puerto Rico Rust race 19-63. This study provides critical baseline information to integrate breeding and crop protection in the efforts to develop an overall strategy for the management of common Beans in Uganda. Key words: Phaseolus vulgaris, Uromyces appendiculatus, Rust differentials, co-evolution, disease severity.
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registration of great northern common Bean cultivar coyne with enhanced disease resistance to common bacterial blight and Bean Rust
Journal of Plant Registrations, 2009Co-Authors: Carlos A Urrea, James R Steadman, M A Pastorcorrales, Dale T Lindgren, J P VenegasAbstract:Great northern common Bean (Phaseolus vulgaris L.) 'Coyne' (Reg. No. CV-287, PI 655574) was developed by the dry Bean breeding program at the University of Nebraska Agricultural Research Division and released in 2008. It was bred specifi cally for adaptation to Nebraska growing conditions and for enhanced resistance to common bacterial blight (CBB), a major disease of common Bean caused by the seed-borne bacterium Xanthomonas campestris pv. phaseoli (Smith) Dye, and Bean common Rust Uromyces appendiculatus (Pers.:Pers) Unger. Coyne is a great northern F 7 : 8 line derived from a three-way cross (G95023/Weihing//BelMiNeb-RMR-11). The fi rst cross was made in winter 2003. The F 7:8 was tested in advanced yield trials at Scottsbluff and Mitchell, NE, and in growers' fi elds in Nebraska. Yield of Coyne was only 47 kg ha -1 lower than 'Marquis' in Morrill and Scotts Bluff, NE, counties. Reaction of Coyne to CBB under fi eld conditions was consistent across 3 yr at the West Central Research and Extension Center, North Platte, NE, where fi eld disease ratings of 3.2, 3.5, and 4.4 were recorded in 2005, 2006, and 2007, respectively. Coyne has the Ur-3 and Ur-6 genes for resistance to common Bean Rust and carries the single dominant hypersensitive I gene that provides resistance to all non-necrotic strains of Bean common mosaic virus. Coyne has bright white seed, blooms 44 d after planting, and is a midseason Bean, maturing 91 d after planting.
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virulence diversity of the common Bean Rust pathogen within and among individual Bean fields and development of sampling strategies
Plant Disease, 2008Co-Authors: C N Jochua, James R Steadman, M I V Amane, X Xue, Kent M EskridgeAbstract:There is a dearth of information on pathogen variation within an individual field. In this study, virulence diversity of Uromyces appendiculatus, cause of Bean Rust, within individual fields was investigated. From six Bean fields in the United States, Honduras, Dominican Republic, and South Africa, 380 U. appendiculatus isolates were differentiated into 65 virulence phenotypes on Bean lines containing Andean- and Middle American-derived Rust resistance genes. Race variation among Bean Rust isolates from different geographic regions was found, and virulence phenotypes found in fields from tropical and subtropical regions were more virulent and diverse than those found in fields from temperate regions. The variance components between fields was greater than the variance within a field based on mean disease score on 12 differentials but the variance components within a field were greater than the variances between fields based on number of virulence phenotypes. This is the first report that multiple site samples are needed to represent the fungal virulence diversity in a diseased field. In developing sampling plans, the entire cost of sampling one field is higher than the cost of taking more samples; therefore, to estimate virulence diversity variation, we recommend selecting fewer fields and collecting more samples per field.
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registration of common bacterial blight Rust and Bean common mosaic resistant great northern common Bean germplasm line abc weihing
Journal of Plant Registrations, 2008Co-Authors: Nedim Mutlu, James R Steadman, Carlos A Urrea, Dale T Lindgren, Marcial A Pastorcorrales, Phillip N Miklas, J Reiser, Anne K Vidaver, Dermot P CoyneAbstract:Great northern common Bean (Phaseolus vulgaris L.) germplasm line ABC-Weihing (Reg. No. GP-246, PI 647964) was developed by the University of Nebraska Agricultural Research Division in cooperation with USDA-ARS and released in 2006. This line, tested as NE1-05-4, was bred specifi cally for enhanced resistance to common bacterial blight (CBB), a major seed borne disease of common Bean caused by the bacterium Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp). ABC-Weihing is a great northern BC 5 F 3:6 line obtained from fi ve backcrosses ('Weihing'*5//'Chase'/XAN 159). The fi rst cross was made in spring 1997. Only BC n F 1 plants resistant to Xcp isolates Dominican Republic DR-7 and Nebraska SC4A, as determined by multiple needle leaf inoculation tests in the greenhouse, were used for successive backcrossing. In addition to phenotypic selection for CBB resistance, marker-assisted selection for the resistant QTL- linked marker SU91 was conducted in the BC 1 F 1 , BC 2 F 1 , and ABC-Weihing. When inoculated with Nebraska Xcp strains in the fi eld, ABC-Weihing exhibited resistance in both 2005 and 2006. ABC-Weihing has Ur-3 and Ur-6 genes for resistance to common Bean Rust and carries the single dominant hypersensitive I gene that provides resistance to all non-necrotic strains of the Bean common mosaic virus (BCMV). ABC-Weihing has bright white seed, blooms 45 d after planting, and is a midseason Bean maturing 92 d after planting.
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development of a coupling phase scar marker linked to the ur 7 Rust resistance gene and its occurrence in diverse common Bean lines
Crop Science, 2008Co-Authors: Soon O Park, Dermot P Coyne, James R Steadman, Kevin M CrosbyAbstract:Bean Rust, caused by Uromyces appendiculatus (Pers.: Pers.) Unger, is an important disease of common Bean (Phaseolus vulgaris L.). A coupling-phase random amplified polymorphic DNA (RAPD) marker OAD12.550 previously was identified to be linked (no recombination) to Ur-7 of Middle American (MA) origin for specific Rust resistance in the common Bean cross of Great Northern (GN) 1140 x GN Nebr. #1. However, a sequence characterized amplified region (SCAR) marker for Ur-7 present in GN1140 has not been reported. Our objectives were to convert the RAPD marker OAD12.550 most tightly linked to Ur-7 to a SCAR marker SOAD12.537 for use as a marker-assisted selection tool, and survey the presence or absence of the SCAR marker SOAD12.537 in 90 MA and Andean Bean genotypes for determining the genetic relationship of Ur-7 with Ur-6. The coupling-phase SCAR marker SOAD12.537 based on a specific forward (5'-AAGAGGGCGTGAGATCGTCG-3') and reverse (5'-AAGAGGGCGTCTTGAAGGTT-3') primer pair showed no recombination with Ur-7 in an F 2 population of the GN1140 x Nebr. #1 cross. The SCAR marker was also present in pinto US-5 from which the Rust resistance of GN1140 was derived and in the closely related pinto US-14. The cosegregating SCAR marker identified MA pinto Bean cultivars/lines Olathe, Bill Z, Apache, Montrose, BelDak-RR-1 and-2, and CO 12783 that have Rust resistance gene Ur-6 and also have Ur-7, identified in earlier literature as Ur c , due to presence of the marker. Other cultivars/lines with Ur-6 such as Weihing, Burke, Kodiak, Topaz, Golden Gate Wax, BelMiNeb 1-13, BelDakMi 1-23, and other Colorado breeding lines lack Ur-7 because of absence of the SCAR marker for the MA gene. This SCAR marker linked to Ur-7 on linkage group 11 of the core P. vulgaris linkage map can identify a phenotypically hidden resistance gene, and along with markers for other Rust resistance genes, can be utilized to pyramid multiple genes for more durable Rust resistance.
Roger Arditi - One of the best experts on this subject based on the ideXlab platform.
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Spatially mixed crops to control the stratified dispersal of airborne fungal diseases
Ecological Modelling, 2010Co-Authors: Natalia Sapoukhina, Yuri Tyutyunov, Ivan Sache, Roger ArditiAbstract:Intraspecific crop diversification is thought to be a possible solution to the disease susceptibility of mono-cultured crops We modelled the stratified dispersal of an airborne pathogen population in order to identify the spatial patterns of cultivar mixtures that could slow epidemic spread driven by dual dispersal mechanisms acting over both short and long distances We developed a model to simulate the propagation of a fungal disease in a 2D field including a reaction-diffusion model for short-distance disease dispersal and a stochastic model for long-distance dispersal The model was fitted to data for the spatio-temporal spread of faba Bean Rust (caused by Uromyces viciae-fabae) through a discontinuous field The model was used to compare the effectiveness of eight different planting patterns of cultivar mixtures against a disease spread by short-distance and stratified dispersal Our combined modelling approach provides a reasonably good fit with the observed data for the spread of faba Bean Rust Similar predictive power could be expected for the management of resource-mediated invasions by other airborne fungi If a disease spreads by short-distance dispersal random mixtures can be used to slow the epidemic spread since their spatial irregularity creates a natural barrier to the progression of a smooth epidemic wave In the context of stratified dispersal heterogeneous patterns should be used that include a minimum distance between susceptible units which decreases the probability of infection by long-distance spore dispersal We provide a simple framework for modelling the stratified dispersal of disease in a diversified crop The model suggests that the spatial arrangement of components in cultivar mixtures has to accord with the dispersal characteristics of the pathogen in order to Increase the efficiency of diversification strategies in agro-ecosystems and forestry It can be applied in low Input agriculture to manage pathogen invasion by intercropping and cultivar mixtures and to design sustainable systems of land use (C) 2010 Elsevier B V All rights reserved
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Spatially mixed crops to control the stratified dispersal of airborne fungal diseases
'Elsevier BV', 2010Co-Authors: Natalia Sapoukhina, Yuri Tyutyunov, Ivan Sache, Roger ArditiAbstract:Intraspecific crop diversification is thought to be a possible solution to the disease susceptibility of monocultured crops. We modelled the stratified dispersal of an airborne pathogen population in order to identify the spatial patterns of cultivar mixtures that could slow epidemic spread driven by dual dispersal mechanisms acting over both short and long distances. We developed a model to simulate the propagation of a fungal disease in a 2D field, including a reaction-diffusion model for short-distance disease dispersal, and a stochastic model for long-distance dispersal. The model was fitted to data for the spatio-temporal spread of faba Bean Rust (caused by Uromyces viciae-fabae) through a discontinuous field. The model was used to compare the effectiveness of eight different planting patterns of cultivar mixtures against a disease spread by short-distance and stratified dispersal. Our combined modelling approach provides a reasonably good fit with the observed data for the spread of faba Bean Rust. Similar predictive power could be expected for the management of resource-mediated invasions by other airborne fungi. If a disease spreads by short-distance dispersal, random mixtures can be used to slow the epidemic spread, since their spatial irregularity creates a natural barrier to the progression of a smooth epidemic wave. In the context of stratified dispersal, heterogeneous patterns should be used that include a minimum distance between susceptible units, which decreases the probability of infection by long-distance spore dispersal. We provide a simple framework for modelling the stratified dispersal of disease in a diversified crop. The model suggests that the spatial arrangement of components in cultivar mixtures has to accord with the dispersal characteristics of the pathogen in order to increase the efficiency of diversification strategies in agro-ecosystems and forestry. It can be applied in low input agriculture to manage pathogen invasion by intercropping and cultivar mixtures, and to design sustainable systems of land use
J V Groth - One of the best experts on this subject based on the ideXlab platform.
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non mendelian and skewed segregation of dna markers in wide crosses of the Bean Rust fungus uromyces appendiculatus
Current Genetics, 1996Co-Authors: J P Martinez, J V Groth, Nevin D YoungAbstract:The inheritance of DNA markers was investigated in 27 F2 progeny from a single F1 hybrid derived from a wide cross inUromyces appendiculatus. This cross was unusual because asexual spores were used to fertilize sexual fruiting structures. Sixty percent of the DNA markers failed to segregate according to simple Mendelian ratios. Segregation bias was evident, in that F2 progeny inherited on average 91 % of maternal bands and 52% of paternal bands, which deviates significantly from the expected value for each of 75% for dominant markers. Because of these distortions, linkage mapping was not possible with this population. Evaluation of two F1s from a second wide cross, reciprocals obtained by normal fertilization, also showed non-Mendelian inheritance of one of three co-dominant RFLPs and five of six isozyme markers, indicating that the method of crossing was probably not responsible for the abnormal segregation patterns in the first cross. Either genetic incompatibility, similar to that of an interspecific cross, or selection of particular genotypes could explain the genetic anomalies reported here.
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virulence and isozyme diversity of sexual versus asexual collections of uromyces appendiculatus Bean Rust fungus
Heredity, 1995Co-Authors: J V Groth, John W Mccain, Alan P RoelfsAbstract:Virulence and isozyme diversity of sexual versus asexual collections of Uromyces appendiculatus (Bean Rust fungus)
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inter and intrapopulation isozyme variation in collections from sexually reproducing populations of the Bean Rust fungus uromyces appendiculatus
Mycologia, 1992Co-Authors: John W Mccain, J V Groth, Alan P RoelfsAbstract:Previous studies of isozyme banding patterns in Uromyces appendiculatus compared one isolate per population or location. In this study, five or more isolates were surveyed from each of 12 field collections to estimate genetic variation within and between the source populations. Five enzymes stained in polyacrylamide slab gels produced 10-21 bands grouped as 10 markers (putative loci); 14 of these bands were present in >72% of the isolates. Six markers indicated heterozygous loci. Marker I of phosphoglucomutase was the most diverse across the collections; three markers were fixed. One marker pattern was predominant for each enzyme, and one multi-isozyme phenotype occurred in 11 of the 12 collections and 21 of the 66 isolates. A 1986 collection from west-central Minnesota, denoted P24, had the lowest Shannon Diversity Index, the highest proportion of simple (homozygote-like) band patterns, the highest mean number of marker differences from isolates of the other collections, and no phenotypes in common with any other collection. Nei's Coefficient of Genetic Identity averaged 0.952 among 11 of the collections but only 0.791 between P24 and the other collections. Collection P24 may represent a late-season epidemic population of asexually produced spores.
Alan P Roelfs - One of the best experts on this subject based on the ideXlab platform.
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virulence and isozyme diversity of sexual versus asexual collections of uromyces appendiculatus Bean Rust fungus
Heredity, 1995Co-Authors: J V Groth, John W Mccain, Alan P RoelfsAbstract:Virulence and isozyme diversity of sexual versus asexual collections of Uromyces appendiculatus (Bean Rust fungus)
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inter and intrapopulation isozyme variation in collections from sexually reproducing populations of the Bean Rust fungus uromyces appendiculatus
Mycologia, 1992Co-Authors: John W Mccain, J V Groth, Alan P RoelfsAbstract:Previous studies of isozyme banding patterns in Uromyces appendiculatus compared one isolate per population or location. In this study, five or more isolates were surveyed from each of 12 field collections to estimate genetic variation within and between the source populations. Five enzymes stained in polyacrylamide slab gels produced 10-21 bands grouped as 10 markers (putative loci); 14 of these bands were present in >72% of the isolates. Six markers indicated heterozygous loci. Marker I of phosphoglucomutase was the most diverse across the collections; three markers were fixed. One marker pattern was predominant for each enzyme, and one multi-isozyme phenotype occurred in 11 of the 12 collections and 21 of the 66 isolates. A 1986 collection from west-central Minnesota, denoted P24, had the lowest Shannon Diversity Index, the highest proportion of simple (homozygote-like) band patterns, the highest mean number of marker differences from isolates of the other collections, and no phenotypes in common with any other collection. Nei's Coefficient of Genetic Identity averaged 0.952 among 11 of the collections but only 0.791 between P24 and the other collections. Collection P24 may represent a late-season epidemic population of asexually produced spores.