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Glen L Hartman - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Selected Biopesticides in Reducing Soybean Rust (Phakopsora pachyrhizi) Development.
    Plant disease, 2019
    Co-Authors: M. Twizeyimana, Glen L Hartman
    Abstract:

    The intensive use of fungicides in controlling soybean rust (SBR), a damaging foliar fungal disease of soybean caused by the obligate fungus Phakopsora pachyrhizi, may have accelerated the insensitivity of P. pachyrhizi populations to fungicides. The objective of this study was to determine the effect of selected biopesticides and their application time on reducing SBR infection. There were differences (P < 0.05) in percent rust reduction values for application times, biopesticide treatments, and their interaction in detached-leaf and whole-plant greenhouse experiments. All application times and nearly all biopesticide treatments reduced (α = 0.05) fungal infection compared with the nonfungicide control. Among the treatments, Bacillus subtilis QST 713 and acibenzolar-S-methyl often reduced fungal sporulation more than the other treatments in detached-leaf and whole-plant greenhouse experiments. The identification of biopesticides effective to P. pachyrhizi may be a valuable alternative or complement to synthetic fungicides and may be useful in integrated pest management programs for SBR control.

  • Prediction of Short-Distance Aerial Movement of Phakopsora pachyrhizi Urediniospores Using Machine Learning.
    Phytopathology, 2017
    Co-Authors: Liwei Wen, C. R. Bowen, Glen L Hartman
    Abstract:

    Dispersal of urediniospores by wind is the primary means of spread for Phakopsora pachyrhizi, the cause of soybean rust. Our research focused on the short-distance movement of urediniospores from within the soybean canopy and up to 61 m from field-grown rust-infected soybean plants. Environmental variables were used to develop and compare models including the least absolute shrinkage and selection operator regression, zero-inflated Poisson/regular Poisson regression, random forest, and neural network to describe deposition of urediniospores collected in passive and active traps. All four models identified distance of trap from source, humidity, temperature, wind direction, and wind speed as the five most important variables influencing short-distance movement of urediniospores. The random forest model provided the best predictions, explaining 76.1 and 86.8% of the total variation in the passive- and active-trap datasets, respectively. The prediction accuracy based on the correlation coefficient (r) betwee...

  • Archaeophytopathology of Phakopsora pachyrhizi, the Soybean Rust Pathogen
    Plant disease, 2015
    Co-Authors: J. S. Haudenshield, Glen L Hartman
    Abstract:

    Herbarium specimens are useful to compare attributes of the past to attributes of today and predictions into the future. In this study, herbarium specimens from 1887 to 2006 were used to identify Phakopsora pachyrhizi and P. meibomiae, the two known fungal species that cause soybean rust. Historically, these two species differed in geographic distribution, with P. pachyrhizi confined to Asia and Australia, and P. meibomiae confined to the Americas. In our analyses, herbarium specimens were used to determine whether it was possible to extract adequate useful DNA from the fungal structures. If present, quantitative PCR primers specific to P. pachyrhizi, P. meibomiae, or to a third group inclusive of many rust species could be used to speciate the fungus. Of the 38 archival specimens, 11 were positive for P. pachyrhizi, including a 1912 specimen from Japan; 15 were positive for P. meibomiae, including a 1928 specimen from Brazil and two 1923 specimens from the Philippines; and 12 (including all African acces...

  • melanin independent accumulation of turgor pressure in appressoria of Phakopsora pachyrhizi
    Phytopathology, 2014
    Co-Authors: Hao Xun Chang, Lou Ann Miller, Glen L Hartman
    Abstract:

    ABSTRACT Appressoria of some plant-pathogenic fungi accumulate turgor pressure that produces a mechanical force enabling the direct penetration of hyphae through the epidermis. Melanin functions as an impermeable barrier to osmolytes, which allows appressoria to accumulate high turgor pressure. Deficiency of melanin in appressoria reduces turgor pressure and compromises the infection process. In Phakopsora pachyrhizi, the soybean rust pathogen, the appressoria are hyaline. Our objective was to ensure the absence of a melanin layer specifically between the appressorial cell wall and plasma membrane, as well as to determine the turgor pressure of P. pachyrhizi appressoria. We demonstrated that two melanin biosynthesis inhibitors neither reduced turgor pressure nor compromised the infection process. Transmission electron microscopy also showed the absence of a melanin layer between the appressorial cell wall and plasma membrane. In addition, the turgor pressure of P. pachyrhizi appressoria was 5 to 6 MPa, ba...

  • First Report of Phakopsora pachyrhizi on Soybean Causing Rust in Tanzania
    Plant disease, 2014
    Co-Authors: H. M. Murithi, J. S. Haudenshield, Fen D. Beed, C.s. Madata, Glen L Hartman
    Abstract:

    Phakopsora pachyrhizi Syd. was reported on legume hosts other than soybean in Tanzania as early as 1979 (1). Soybean rust (SBR), caused by P. pachyrhizi, was first reported on soybean in Africa in Uganda in 1996 (3), and its introduction into Africa was proposed to occur through urediniospores blowing from western India to the African east coastal areas by moist northeast monsoon winds (4). The fungus rapidly spread and was reported on soybean in South Africa in 2001, in western Cameroon in 2003, and in Ghana and the Democratic Republic of the Congo in 2007 (5). A second species causing SBR on soybean, P. meibomiae, has not been reported in Africa or elsewhere, outside of the Americas. From 2012 to 2014, symptomatic leaf samples were collected in the major soybean growing areas of the Tanzanian Southern Highlands (Iringa, Mbeya, and Ruvuma regions). Symptoms of SBR included yellowing of leaves and tan sporulating lesions. These symptoms were observed at flowering through seed maturity. From fields surveye...

Reid D. Frederick - One of the best experts on this subject based on the ideXlab platform.

  • Gene expression and proteomic analysis of the formation of Phakopsora pachyrhizi appressoria
    BMC genomics, 2012
    Co-Authors: Christine L. Stone, Douglas G. Luster, M. B. Mcmahon, Laurie L. Fortis, Alberto Nuñez, Gary W Smythers, Reid D. Frederick
    Abstract:

    Background Phakopsora pachyrhizi is an obligate fungal pathogen causing Asian soybean rust (ASR). A dual approach was taken to examine the molecular and biochemical processes occurring during the development of appressoria, specialized infection structures by which P. pachyrhizi invades a host plant. Suppression subtractive hybridization (SSH) was utilized to generate a cDNA library enriched for transcripts expressed during appressoria formation. Two-dimensional gel electrophoresis and mass spectroscopy analysis were used to generate a partial proteome of proteins present during appressoria formation.

  • Characterizing Resistance to Phakopsora pachyrhizi in Soybean
    Plant disease, 2011
    Co-Authors: M. R. Miles, Reid D. Frederick, M. R. Bonde, S. E. Nester, Dana K. Berner, Glen L Hartman
    Abstract:

    Resistance in soybean to Phakopsora pachyrhizi, the cause of soybean rust, is characterized by either reddish-brown (RB) lesions or an immune response. The RB type of resistance can be incomplete, as evidenced by the presence of sporulating uredinia within lesions. Susceptibility, on the other hand, is exemplified by tan-colored (TAN) lesions, and can be expressed in gradations of susceptibility or partial resistance that are less well defined. This study evaluated traits associated with incomplete or partial resistance to P. pachyrhizi in soybean by comparing 34 soybean accessions inoculated with four P. pachyrhizi isolates. Six accessions produced RB lesions to all four isolates, while 19 accessions produced TAN lesions, including plant introduction (PI) 200492 (Rpp1) and the susceptible check ‘Williams’. Williams had among the largest area under the disease progress curve (AUDPC) values and area under the sporulating uredinia progress curve (AUSUPC) values, while eight accessions had lower AUSUPC value...

  • An Immunofluorescence Assay to Detect Urediniospores of Phakopsora pachyrhizi.
    Plant disease, 2008
    Co-Authors: Fulya Baysal-gurel, Melanie L. Lewis Ivey, Anne E. Dorrance, Douglas G. Luster, Reid D. Frederick, Jill Czarnecki, Michael J. Boehm, Sally A. Miller
    Abstract:

    An indirect immunofluorescence spore assay (IFSA) was developed to detect urediniospores of Phakopsora pachyrhizi, utilizing rabbit polyclonal antisera produced in response to intact nongerminated (SBR1A) or germinated (SBR2) urediniospores of P. pachyrhizi. Both antisera were specific to Phakopsora spp. and did not react with other common soybean pathogens or healthy soybean leaf tissue in enzyme-linked immunosorbent assay (ELISA). SBR1A and SBR2 bound to P. pachyrhizi and P. meibomiae urediniospores were detected with goat anti-rabbit Alexa Fluor 488-tagged antiserum using a Leica DM IRB epifluorescent microscope with an I3 blue filter (excitation 450 to 490 nm, emission 515 nm). The assay was performed on standard glass microscope slides; double-sided tape was superior to a thin coating of petroleum jelly both in retaining spores and in immunofluorescence. The IFSA was used to confirm the identity of P. pachyrhizi urediniospores captured on glass slides from passive air samplers from Georgia, Kentucky, and Ohio during 2006.

  • Development of simple sequence repeat markers for the soybean rust fungus, Phakopsora pachyrhizi.
    Molecular ecology resources, 2008
    Co-Authors: Sharon J. Anderson, Douglas G. Luster, Reid D. Frederick, Christine L. Stone, Martha Lucia Posada-buitrago, Jeffrey L. Boore, Beena Neelam, Robert M. Stephens, Kerry F. Pedley
    Abstract:

    Twenty-four simple sequence repeat markers were developed for Phakopsora pachyrhizi, a fungal pathogen of soybean (Glycine max) and other legumes. All 24 of the loci were evaluated on 28 isolates of P. pachyrhizi. Twenty-one loci were polymorphic, with allelic diversity ranging from two to eight alleles, and null alleles were observed for eight of the 24 loci. A preliminary screen with the closely related species, P. meibomiae, indicated that these primer pairs are specific to P. pachyrhizi.

  • Comparative Susceptibilities of Legume Species to Infection by Phakopsora pachyrhizi.
    Plant Disease, 2008
    Co-Authors: M. R. Bonde, Reid D. Frederick, W. F. Moore, S. E. Nester, D.k. Berner, S. Little
    Abstract:

    ABSTRACT Knowledge of the host range of Phakopsora pachyrhizi is important to agriculture in the United States because of the distinct possibility that economic losses could occur to crops other than soybean. Furthermore, it is possible that alternative hosts could provide a means of overwintering of the pathogen, providing inoculum to initiate epidemics in future years. To clarify the potential importance of soybean rust on nonsoybean legumes and their role in overwintering of the disease, multiple accessions of clover, cowpea, pea, kudzu, lima bean, snap bean, and single accessions of coffee senna, Florida beggarweed, hemp sesbania, hyacinth bean, partridge pea, and showy crotalaria were inoculated under greenhouse conditions with urediniospores of P. pachyrhizi; infected soybean plants served as a control. The four criteria used to assess susceptibility were lesion density, proportion of lesions with sporulating uredinia, average number of uredinia per lesion, and average uredinia diameter, each determ...

M. R. Miles - One of the best experts on this subject based on the ideXlab platform.

  • Characterizing Resistance to Phakopsora pachyrhizi in Soybean
    Plant disease, 2011
    Co-Authors: M. R. Miles, Reid D. Frederick, M. R. Bonde, S. E. Nester, Dana K. Berner, Glen L Hartman
    Abstract:

    Resistance in soybean to Phakopsora pachyrhizi, the cause of soybean rust, is characterized by either reddish-brown (RB) lesions or an immune response. The RB type of resistance can be incomplete, as evidenced by the presence of sporulating uredinia within lesions. Susceptibility, on the other hand, is exemplified by tan-colored (TAN) lesions, and can be expressed in gradations of susceptibility or partial resistance that are less well defined. This study evaluated traits associated with incomplete or partial resistance to P. pachyrhizi in soybean by comparing 34 soybean accessions inoculated with four P. pachyrhizi isolates. Six accessions produced RB lesions to all four isolates, while 19 accessions produced TAN lesions, including plant introduction (PI) 200492 (Rpp1) and the susceptible check ‘Williams’. Williams had among the largest area under the disease progress curve (AUDPC) values and area under the sporulating uredinia progress curve (AUSUPC) values, while eight accessions had lower AUSUPC value...

  • Hosts of Phakopsora pachyrhizi Identified in Field Evaluations in Florida
    Plant Health Progress, 2008
    Co-Authors: T. L. Slaminko, James J. Marois, M. R. Miles, David L. Wright, Glen L Hartman
    Abstract:

    Phakopsora pachyrhizi, the causal organism of soybean rust, was first found on Glycine max in the continental United States in 2004, and subsequently on Pueraria lobata, Desmodium tortuosum, three Phaseolus species, and Erythrina herbacea in the field. The pathogen has been reported to occur on over 150 legume species worldwide, and it is likely to infect native and introduced legume species in the USA. The objective of this study was to determine if USA-native or -naturalized legume species could become infected with P. pachyrhizi in field conditions. A total of 80 accessions representing 52 species in 29 genera were infected in the field trials. Crotalaria retusa, Lathyrus latifolius, Phaseolus angustissimus, P. polystachios, and Robinia hispida are new hosts. This is the first report showing the broad host range of P. pachyrhizi based on field infections in the USA. Some of these hosts grow in the southern USA, and could, like kudzu, overwinter P. pachyrhizi.

  • New Legume Hosts of Phakopsora pachyrhizi Based on Greenhouse Evaluations.
    Plant disease, 2008
    Co-Authors: T. L. Slaminko, Reid D. Frederick, M. R. Miles, M. R. Bonde, Glen L Hartman
    Abstract:

    Phakopsora pachyrhizi, the causal organism of soybean rust, was first found in the continental United States in 2004 and has been found on soybean, kudzu, Florida beggarweed, and three Phaseolus species in the field. The pathogen has been reported to occur on more than 90 legume species worldwide and it is likely to infect native and introduced legume species in the United States. The objective of this study was to determine if 176 species representing 57 genera of legumes, the majority of which are either native or naturalized to soybean-growing areas of the United States, could be hosts of P. pachyrhizi. Between one and three accessions of each species, a total of 264 accessions, were inoculated with a mixture of four isolates of P. pachyrhizi. Severity and sporulation were rated on a 1-to-5 scale at 14 and 28 days after inoculation. P. pachyrhizi was confirmed by the presence of sporulating uredinia and/or immunological assay on 65 new species in 25 genera; 12 of these genera have not been reported previously as hosts. Many of the newly identified hosts grow in the southern United States, and like kudzu, could serve as overwintering hosts for P. pachyrhizi.

  • Differential Response of Common Bean Cultivars to Phakopsora pachyrhizi
    Plant disease, 2007
    Co-Authors: M. R. Miles, Glen L Hartman, M. A. Pastor-corrales, Reid D. Frederick
    Abstract:

    Soybean rust (Phakopsora pachyrhizi) has been reported on common bean (Phaseolus vulgaris) in Asia, South Africa, and the United States. However, there is little information on the interaction of individual isolates of Phakopsora pachyrhizi with common bean germplasm. A set of 16 common bean cultivars with known genes for resistance to Uromyces appendiculatus, the causal agent of common bean rust, three soybean accessions that were sources of the single gene resistance to P. pachyrhizi, and the moderately susceptible soybean 'Ina' were evaluated using seedlings inoculated with six isolates of P. pachyrhizi. Among the common bean cultivars, Aurora, Compuesto Negro Chimaltenango, and Pinto 114, were the most resistant to all six P. pachyrhizi isolates, with lower severity, less sporulation, and consistent reddish-brown (RB) lesions associated with resistance in soybean. A differential response was observed among the common bean cultivars, with a cultivar-isolate interaction for both severity and sporulation levels, as well as the presence or absence of the RB lesion type. This differential response was independent of the known genes that condition resistance to U. appendiculatus, suggesting that resistance to P. pachyrhizi was independent of resistance to U. appendiculatus.

  • First Report of Phakopsora pachyrhizi, Cause of Soybean Rust, on Neonotonia wightii in Paraguay.
    Plant disease, 2007
    Co-Authors: W. Morel, M. R. Miles, J. R. Hernández, C. L. Stone, Reid D. Frederick
    Abstract:

    Phakopsora pachyrhizi Syd. & P. Syd., the cause of soybean rust, was first observed on soybean (Glycine max (L.) Merr.) in South America in the district of Itapua in Paraguay during March, 2001 (2). The disease is now widespread in soybean-production areas in South America on soybean and kudzu (Pueraria lobata (Willd.) Ohwi). On 15 March 2006, leaves of the perennial legume Neonotonia wightii (Graham ex Wight & Arn.) Lackey with lesions and rust sori were observed in the Reserva Biologica de Itabo, Departamento Alto Parana. Lesions were scattered, most contained a single uredinium, mostly hypophyllous, and appeared to be new infections. Lesions with several uredinia, which are indicative of older infections on soybean, were also observed. Sori (Malupa-type) contained hyaline, peripheral, cylindric to clavate paraphyses measuring 24 to 45 × 6 to 13 μm and urediniospores that were hyaline, ovoid to globose, and measuring 20 to 40 × 14 to 25 μm with an echinulate spore wall, characteristics typical of a Phak...

Douglas G. Luster - One of the best experts on this subject based on the ideXlab platform.

  • Gene expression and proteomic analysis of the formation of Phakopsora pachyrhizi appressoria
    BMC genomics, 2012
    Co-Authors: Christine L. Stone, Douglas G. Luster, M. B. Mcmahon, Laurie L. Fortis, Alberto Nuñez, Gary W Smythers, Reid D. Frederick
    Abstract:

    Background Phakopsora pachyrhizi is an obligate fungal pathogen causing Asian soybean rust (ASR). A dual approach was taken to examine the molecular and biochemical processes occurring during the development of appressoria, specialized infection structures by which P. pachyrhizi invades a host plant. Suppression subtractive hybridization (SSH) was utilized to generate a cDNA library enriched for transcripts expressed during appressoria formation. Two-dimensional gel electrophoresis and mass spectroscopy analysis were used to generate a partial proteome of proteins present during appressoria formation.

  • Novel Phakopsora pachyrhizi extracellular proteins are ideal targets for immunological diagnostic assays.
    Applied and environmental microbiology, 2012
    Co-Authors: Douglas G. Luster, Melanie L. Lewis Ivey, Sally A. Miller, M. B. Mcmahon, Herb Edwards, Britney L. Boerma, Anne E. Dorrance
    Abstract:

    ABSTRACT Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), continues to spread across the southeast and midsouth regions of the United States, necessitating the use of fungicides by producers. Our objective in this research was to identify ASR proteins expressed early during infection for the development of immunodiagnostic assays. We have identified and partially characterized a small gene family encoding extracellular proteins in the P. pachyrhizi urediniospore wall, termed PHEPs (for Phakopsoraextracellular protein). Two highly expressed protein family members, PHEP 107 and PHEP 369, were selected as ideal immunodiagnostic targets for antibody development, after we detected PHEPs in plants as early as 3 days postinfection (dpi). Monoclonal antibodies (MAbs; 2E8E5-1 and 3G6H7-3) generated against recombinant PHEP 369 were tested for sensitivity against the recombinant protein and extracts from ASR-infected plants and for specificity against a set of common soybean pathogens. These antibodies should prove applicable in immunodiagnostic assays to detect infected soybeans and to identify ASR spores from sentinel surveillance plots.

  • proteomic analysis of germinating urediniospores of Phakopsora pachyrhizi causal agent of asian soybean rust
    Proteomics, 2010
    Co-Authors: Douglas G. Luster, Laurie L. Fortis, Michael B Mcmahon, Melissa L Carter, Alberto Nuñez
    Abstract:

    Phakopsora pachyrhizi is an obligate pathogen that causes Asian soybean rust. Asian soybean rust has an unusually broad host range and infects by direct penetration through the leaf cuticle. In order to understand the early events in the infection process, it is important to identify and characterize proteins in P. pachyrhizi. Germination of the urediniospore is the first stage in the infection process and represents a critical life stage applicable to studies with this obligate pathogen. We have applied a 2-DE and MS approach to identify 117 proteins from the National Center of Biotechnology Information nonredundant protein database and a custom database of Basidiomycota EST sequences. Proteins with roles in primary metabolism, energy transduction, stress, cellular regulation and signaling were identified in this study. This data set is accessible at http://world-2dpage.expasy.org/repository/database=0018.

  • An Immunofluorescence Assay to Detect Urediniospores of Phakopsora pachyrhizi.
    Plant disease, 2008
    Co-Authors: Fulya Baysal-gurel, Melanie L. Lewis Ivey, Anne E. Dorrance, Douglas G. Luster, Reid D. Frederick, Jill Czarnecki, Michael J. Boehm, Sally A. Miller
    Abstract:

    An indirect immunofluorescence spore assay (IFSA) was developed to detect urediniospores of Phakopsora pachyrhizi, utilizing rabbit polyclonal antisera produced in response to intact nongerminated (SBR1A) or germinated (SBR2) urediniospores of P. pachyrhizi. Both antisera were specific to Phakopsora spp. and did not react with other common soybean pathogens or healthy soybean leaf tissue in enzyme-linked immunosorbent assay (ELISA). SBR1A and SBR2 bound to P. pachyrhizi and P. meibomiae urediniospores were detected with goat anti-rabbit Alexa Fluor 488-tagged antiserum using a Leica DM IRB epifluorescent microscope with an I3 blue filter (excitation 450 to 490 nm, emission 515 nm). The assay was performed on standard glass microscope slides; double-sided tape was superior to a thin coating of petroleum jelly both in retaining spores and in immunofluorescence. The IFSA was used to confirm the identity of P. pachyrhizi urediniospores captured on glass slides from passive air samplers from Georgia, Kentucky, and Ohio during 2006.

  • Development of simple sequence repeat markers for the soybean rust fungus, Phakopsora pachyrhizi.
    Molecular ecology resources, 2008
    Co-Authors: Sharon J. Anderson, Douglas G. Luster, Reid D. Frederick, Christine L. Stone, Martha Lucia Posada-buitrago, Jeffrey L. Boore, Beena Neelam, Robert M. Stephens, Kerry F. Pedley
    Abstract:

    Twenty-four simple sequence repeat markers were developed for Phakopsora pachyrhizi, a fungal pathogen of soybean (Glycine max) and other legumes. All 24 of the loci were evaluated on 28 isolates of P. pachyrhizi. Twenty-one loci were polymorphic, with allelic diversity ranging from two to eight alleles, and null alleles were observed for eight of the 24 loci. A preliminary screen with the closely related species, P. meibomiae, indicated that these primer pairs are specific to P. pachyrhizi.

J. S. Haudenshield - One of the best experts on this subject based on the ideXlab platform.

  • Archaeophytopathology of Phakopsora pachyrhizi, the Soybean Rust Pathogen
    Plant disease, 2015
    Co-Authors: J. S. Haudenshield, Glen L Hartman
    Abstract:

    Herbarium specimens are useful to compare attributes of the past to attributes of today and predictions into the future. In this study, herbarium specimens from 1887 to 2006 were used to identify Phakopsora pachyrhizi and P. meibomiae, the two known fungal species that cause soybean rust. Historically, these two species differed in geographic distribution, with P. pachyrhizi confined to Asia and Australia, and P. meibomiae confined to the Americas. In our analyses, herbarium specimens were used to determine whether it was possible to extract adequate useful DNA from the fungal structures. If present, quantitative PCR primers specific to P. pachyrhizi, P. meibomiae, or to a third group inclusive of many rust species could be used to speciate the fungus. Of the 38 archival specimens, 11 were positive for P. pachyrhizi, including a 1912 specimen from Japan; 15 were positive for P. meibomiae, including a 1928 specimen from Brazil and two 1923 specimens from the Philippines; and 12 (including all African acces...

  • First Report of Phakopsora pachyrhizi on Soybean Causing Rust in Tanzania
    Plant disease, 2014
    Co-Authors: H. M. Murithi, J. S. Haudenshield, Fen D. Beed, C.s. Madata, Glen L Hartman
    Abstract:

    Phakopsora pachyrhizi Syd. was reported on legume hosts other than soybean in Tanzania as early as 1979 (1). Soybean rust (SBR), caused by P. pachyrhizi, was first reported on soybean in Africa in Uganda in 1996 (3), and its introduction into Africa was proposed to occur through urediniospores blowing from western India to the African east coastal areas by moist northeast monsoon winds (4). The fungus rapidly spread and was reported on soybean in South Africa in 2001, in western Cameroon in 2003, and in Ghana and the Democratic Republic of the Congo in 2007 (5). A second species causing SBR on soybean, P. meibomiae, has not been reported in Africa or elsewhere, outside of the Americas. From 2012 to 2014, symptomatic leaf samples were collected in the major soybean growing areas of the Tanzanian Southern Highlands (Iringa, Mbeya, and Ruvuma regions). Symptoms of SBR included yellowing of leaves and tan sporulating lesions. These symptoms were observed at flowering through seed maturity. From fields surveye...

  • First Report of Soybean Rust (Phakopsora pachyrhizi) on Florida Beggarweed (Desmodium tortuosum) in Alabama
    Plant disease, 2012
    Co-Authors: Mary A. Delaney, J. S. Haudenshield, Edward J. Sikora, Dennis P. Delaney, M. E. Palm, Glen L Hartman
    Abstract:

    Soybean rust (SBR), caused by the fungus Phakopsora pachyrhizi, was detected on Florida Beggarweed (Desmodium tortuosum) for the first time in Alabama in November, 2009. The pathogen was not observed in 2010 or 2011, probably because of the exceptionally dry, hot weather in the region. The pathogen was observed on multiple mature leaves of plants, evenly distributed through a field at the Wiregrass Research and Extension Center in Headland, Alabama, located in the southeast region of the state. Florida Beggarweed can serve as an overwintering host for SBR. Symptoms on leaves were consistent with SBR symptoms previously described on soybeans (1). Sori in multiple pustules were observed on the undersurface of the leaves. Urediniospores and paraphyses were observed microscopically and identified as P. pachyrhizi. Symptomatic leaves from 20 plants were analyzed using an Envirologix monoclonal antibody strip test kit at the Auburn University Plant Diagnostic Laboratory. A subsample of 20 plants were positive f...

  • Genetic structure and diversity of Phakopsora pachyrhizi isolates from soyabean
    Plant Pathology, 2011
    Co-Authors: M. Twizeyimana, Ranajit Bandyopadhyay, Peter S. Ojiambo, J. S. Haudenshield, Gustavo Caetano-anollés, Kerry F. Pedley, Glen L Hartman
    Abstract:

    Simple sequence repeat (SSR) markers were used to classify 116 isolates of Phakopsora pachyrhizi, the cause of soyabean rust, collected from infected soyabean leaves in four agroecological zones in Nigeria. A high degree of genetic variation was observed within the sampled populations of P. pachyrhizi. Eighty-four distinct genotypes were identified among three of the four agroecological zones. Nei’s average genetic diversity across geographical regions was 0·22. Hierarchical analysis of molecular variance showed low genetic differentiation among all populations of P. pachyrhizi. The majority (> 90%) of the genetic diversity was distributed within each soyabean field, while approximately 6% of the genetic diversity was distributed among fields within geographic regions. Low population differentiation was indicated by the low FST values among populations, suggesting a wide dispersal of identical genotypes on a regional scale. Phylogenetic analysis indicated a strictly clonal structure of the populations and five main groups were observed, with group II accounting for 30% of the entire population. Because of the asexual reproduction of P. pachyrhizi, single-step mutations in SSR genotypes are likely to account for the genetic differences within each group.

  • Movement of Phakopsora pachyrhizi (soybean rust) spores by non-conventional means
    European Journal of Plant Pathology, 2008
    Co-Authors: Glen L Hartman, J. S. Haudenshield
    Abstract:

    Soybean, caused by the rust fungus Phakopsora pachyrhizi, is the most important foliar pathogen infecting soybean. Historically, the disease was important only in the Eastern Hemisphere, but since 1994 the disease has been reported in many countries in Africa and the Americas. In the U.S.A., soybean rust has been perceived as a threat to soybean production and monitoring of the disease occurs throughout the country where soybean is grown. The objectives of this study were to show conclusive evidence that soybean rust spores can be transported by non-conventional means such as clothing. The implication may affect how researchers approach monitoring this disease in research and sentinel plots.