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  • Bock, C. H.  (7)
  • Biodiversity Research  (7)
  • 1
    Online Resource
    Online Resource
    Heterokaryosis and diploid formation among Brazilian isolates of Macrophomina phaseolina
    Wiley ; 2018
    In:  Plant Pathology Vol. 67, No. 9 ( 2018-12), p. 1857-1864
    Details
    In: Plant Pathology, Wiley, Vol. 67, No. 9 ( 2018-12), p. 1857-1864
    Abstract: Heterokaryosis is the association of genetically distinct nuclei in a common hyphal cytoplasm, and is a process involved in the generation of fungal variation. The fusion of the distinct nuclei within a heterokaryotic hypha produces a heterozygous diploid nucleus and is one of the stages of the parasexual cycle. A heterokaryon's viability depends on the isolates’ genetic constitution with regard to loci called het (heterokaryon incompatibility) or vic (vegetative incompatibility). The current study evaluates for the first time the diversity of vegetative compatibility reactions in isolates of Macrophomina phaseolina from different hosts. Complementary nit (nitrate non‐utilizing) mutants of each isolate were obtained and paired in all possible combinations. Isolates were classified in vegetative compatibility groups ( VCG ) according to their ability to form viable heterokaryons. Ten VCG s were identified, two of them containing two isolates, and the remainder containing a single isolate. When grown on basal medium, heterokaryons produced both (i) auxotrophic segregants exhibiting the same phenotype as the paired mutants; and (ii) a fast‐growing sector, characterized as a heterozygous diploid sector, named D653, which showed a nit+ phenotype with a growth rate similar to the original wild isolate. When grown in the presence of benomyl, a haploidizing agent, D653 produced auxotrophic haploid segregants exhibiting the nit phenotypes of the crossed mutants. The results demonstrate for the first time the ability of M. phaseolina isolates to form viable heterokaryons and heterozygous diploid nuclei, suggesting that the parasexual cycle may be an alternative source of genetic variability in this species.
    Type of Medium: Online Resource
    ISSN: 0032-0862 , 1365-3059
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2018.67.issue-9
    DOI: 10.1111/ppa.12919
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2020845-5
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  • 2
    Online Resource
    Online Resource
    Changes in fungicide sensitivity and relative species abundance in Oculimacula yallundae and O. acuformis populations (eyespot disease of cereals) in Western Europe
    Wiley ; 2008
    In:  Plant Pathology Vol. 57, No. 3 ( 2008-06), p. 509-517
    Details
    In: Plant Pathology, Wiley, Vol. 57, No. 3 ( 2008-06), p. 509-517
    Abstract: Changing fungicide sensitivities in populations of Oculimacula yallundae and O. acuformis , the species responsible for cereal eyespot in Western Europe, were determined over a 17 year period between 1984 and 2000. The data were collected by Aventis Crop Science as part of their long‐term survey to monitor changes in sensitivity to prochloraz and the methyl benzimidazole carbamate (MBC) fungicides in eyespot populations. The results show evidence for reduced sensitivity to both fungicides over the period of the survey. The decline in MBC sensitivity is in agreement with reports of practical resistance (a detectable loss of disease control in the field) to this fungicide which were widely reported from the mid 1980s onward. Prochloraz sensitivity was more complex, with the emergence of a higher resistance category of isolates in the late 1980s and early 1990s which then decreased in frequency towards the end of the survey. This may be partly explained by the introduction and increased use of cyprodinil in the mid 1990s. Although all trends were similar across Europe, differences were observed between the two eyespot species. A higher frequency of O. yallundae isolates showed decreased sensitivity to MBC, whereas decreased sensitivity to prochloraz was at a higher frequency in O. acuformis populations. The relative abundance of the two eyespot species was influenced by their differential levels of fungicide sensitivity, with the ratio increasing toward the species with the highest level of resistance to the prevailing fungicide.
    Type of Medium: Online Resource
    ISSN: 0032-0862 , 1365-3059
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2008.57.issue-3
    DOI: 10.1111/j.1365-3059.2007.01786.x
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 2020845-5
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  • 3
    Online Resource
    Online Resource
    Short-distance dispersal of splashed bacteria of Xanthomonas citri subsp. citri from canker-infected grapefruit tree canopies in turbulent wind : Dispersal plume of Xanthomonas citri subsp. citri
    Wiley ; 2012
    In:  Plant Pathology Vol. 61, No. 5 ( 2012-10), p. 829-836
    Details
    In: Plant Pathology, Wiley, Vol. 61, No. 5 ( 2012-10), p. 829-836
    Type of Medium: Online Resource
    ISSN: 0032-0862
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2012.61.issue-5
    DOI: 10.1111/j.1365-3059.2011.02588.x
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2020845-5
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  • 4
    Online Resource
    Online Resource
    A comparison of UP ‐ PCR and RAPD markers to study genetic diversity of F usicladium effusum (G. Winter), cause of pecan scab
    Wiley ; 2014
    In:  Forest Pathology Vol. 44, No. 4 ( 2014-08), p. 266-275
    Details
    In: Forest Pathology, Wiley, Vol. 44, No. 4 ( 2014-08), p. 266-275
    Abstract: Fusicladium effusum infects pecan causing yield loss, but no information is available on the genetic diversity of F. effusum . Randomly amplified polymorphic DNA s ( RAPD s) and universally primed polymerase chain reaction ( UP ‐ PCR ) were compared to detect polymorphisms on a group of 20 isolates of F. effusum from 11 geographical locations in the southeastern USA . Two tests (run 1 and 2) of both the RAPD and UP ‐ PCR s were conducted to assess the repeatability of the methods, and the markers scored on agarose gels. In addition, the UP ‐ PCR markers from run 1 were scored using an automated capillary system. Both RAPD s and UP ‐ PCR markers detected a high level of polymorphism among the scored markers (92 and 91% of RAPD markers, and 86 and 87% of manually scored UP ‐ PCR markers in run 1 and 2 were polymorphic, respectively; 93% of UP ‐ PCR markers were polymorphic when scored using the automated system). Unweighted paired group method of arithmetic averages ( UPGMA ) analysis showed both RAPD s and UP ‐ PCR markers individually identified each isolate, producing three groupings, but only the groupings based on run 1 and 2 of the UP ‐ PCR contained the same isolates. Bootstrap analysis based on the Dice coefficient produced phenograms from the UP ‐ PCR data with weak to moderate node support (≥54) for the primary branch, but no support for the RAPD s data (≤34). A Mantel test of runs 1 and 2 using RAPD s or UP ‐ PCR showed good agreement ( r  = 0.8761 and 0.8289, p  〈  0.0001), but poor agreement between RAPD s and UP ‐ PCR . UP ‐ PCR results based on the interisolate Dice coefficients showed a weak to strong association with distance. Based on these results, both RAPD s and UP ‐ PCR markers were capable of demonstrating polymorphisms and identifying relationships among isolates of F. effusum ; however, UP ‐ PCR markers appear to be more reliable.
    Type of Medium: Online Resource
    ISSN: 1437-4781 , 1439-0329
    URL: Issue
    URL: Article
    DOI: 10.1111/efp.2014.44.issue-4
    DOI: 10.1111/efp.12090
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2020304-4
    detail.hit.zdb_id: 2232646-7
    SSG: 23
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Development of Oculimacula yallundae and O. acuformis (eyespot) lesions on stems of winter wheat in relation to thermal time in the UK
    Wiley ; 2009
    In:  Plant Pathology Vol. 58, No. 1 ( 2009-02), p. 12-22
    Details
    In: Plant Pathology, Wiley, Vol. 58, No. 1 ( 2009-02), p. 12-22
    Abstract: Relationships between development of eyespot, caused by Oculimacula yallundae (OY) or O. acuformis (OA) on stems of winter wheat (cv. Avalon), and thermal time (°C days after sowing) were investigated in field experiments in 1985/86, 1986/87 and 1987/88 (two experiments). In all experiments, the incidence and severity of stem eyespot (uninoculated plots, OY‐ and OA‐inoculated plots) were linearly related to accumulated thermal time after sowing. There were ca. 600–800°C days from the time of the first sample when eyespot lesions were recorded on stems to the time when maximum eyespot incidence or severity was recorded. Relationships between stem eyespot incidence or severity and thermal time differed between seasons, with more severe eyespot in 1986/87 and 1987/88 than 1985/86. Both the severity and volume of stem lesions were initially greater in OY‐inoculated plots than OA‐inoculated plots in spring but differences were less by harvest in all seasons. The percentage of plants with stems colonized by OY or OA over all plots (including uninoculated) showed a consistent pattern in 1986/87 and 1987/88 (two experiments), with the percentage colonized by OY greater initially and the percentage colonized by OA gradually increasing with time towards harvest.
    Type of Medium: Online Resource
    ISSN: 0032-0862 , 1365-3059
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2009.58.issue-1
    DOI: 10.1111/j.1365-3059.2008.01942.x
    Language: English
    Publisher: Wiley
    Publication Date: 2009
    detail.hit.zdb_id: 2020845-5
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  • 6
    Online Resource
    Online Resource
    Development of Oculimacula yallundae and O. acuformis (eyespot) on leaf sheaths of winter wheat in the UK in relation to thermal time
    Wiley ; 2005
    In:  Plant Pathology Vol. 54, No. 2 ( 2005-04), p. 144-155
    Details
    In: Plant Pathology, Wiley, Vol. 54, No. 2 ( 2005-04), p. 144-155
    Abstract: In a controlled environment (15/10°C) (day/night) container experiment on winter wheat (cv. Avalon), eyespot incidence (percentage of plants affected) and number of leaf sheaths penetrated after 6 weeks increased with inoculum concentration (10 2 −10 6 conidia mL −1 ) of Oculimacula yallundae (OY) or Oculimacula acuformis (OA), but there was no difference between the two species. In an outdoor container experiment, seedlings inoculated with OY 2 weeks after sowing had a greater incidence of eyespot than those inoculated with OA, when assessed 7 weeks after inoculation. Seedlings inoculated with OA at 10 or 20 weeks after sowing developed more severe eyespot by maturity than those inoculated with OY. In an experiment at 15/10°C with seedlings inoculated with OY + OA 2 weeks after sowing, more leaf sheaths were penetrated by OY (3·0 per plant) than OA (2·3 per plant) 6 weeks after inoculation. Field experiments with winter wheat consistently showed leaf sheath production, leaf sheath death, and number of leaf sheaths infected or penetrated by OA or OY were related linearly to thermal time (°C days) after sowing. Depending on cultivar, season and sample, a new leaf sheath was produced in 116–216°C days; a leaf sheath died in 221–350°C days; and infection of a new leaf sheath occurred in 129–389°C days. The mean number of living leaf sheaths infected differed between samples, cultivars and seasons for both OY and OA. Regression analysis of the 1985/86 data suggested that OY progressed more rapidly than OA through the leaf sheaths, and that both the pathogens progressed more rapidly than the rate of leaf sheath death, but more slowly than the rate at which leaf sheaths were produced. It also suggested that OA progressed more slowly than the rate at which leaf sheaths died in 1987/88, but OY did not.
    Type of Medium: Online Resource
    ISSN: 0032-0862 , 1365-3059
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2005.54.issue-2
    DOI: 10.1111/j.1365-3059.2005.01165.x
    Language: English
    Publisher: Wiley
    Publication Date: 2005
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  • 7
    Online Resource
    Online Resource
    A comparison between visual estimates and image analysis measurements to determine septoria leaf blotch severity in winter wheat
    Wiley ; 2015
    In:  Plant Pathology Vol. 64, No. 2 ( 2015-04), p. 355-364
    Details
    In: Plant Pathology, Wiley, Vol. 64, No. 2 ( 2015-04), p. 355-364
    Abstract: Methods to estimate disease severity vary in accuracy, reliability, ease of use and cost. Severity of septoria leaf blotch ( SLB , caused by Z ymoseptoria tritici ) was estimated by four raters and by image analysis (assumed actual values) on individual leaves of winter wheat in order to explore accuracy and reliability of estimates, and to ascertain whether there were any general characteristics of error. Specifically, the study determined: (i) the accuracy and reliability of visual assessments of SLB over the full range of severity from 0 to 100%; (ii) whether certain 10% ranges in actual disease severity between 0 and 100% were more prone to estimation error compared with others; and (iii) whether leaf position affected accuracy within those ranges. Lin's concordance correlation analysis of all severities (0–100%) demonstrated that all raters had estimates close to the actual values (agreement: ρ c  = 0·92–0·99). However, agreement between actual SLB severities and estimates by raters was less good when compared over short 10% subdivisions within the 0–100% range (ρ c  = −0·12 to 0·99). Despite common rater imprecision at estimating low and high SLB severities, individual raters differed considerably in their accuracy over the short 10% subdivisions. There was no effect of leaf position on accuracy or precision of severity estimate on separate leaves (L1–L3). Pursuing efforts in understanding error in disease estimation should aid in improving the accuracy of assessments, making visual estimates of disease severity more useful for research and applied purposes.
    Type of Medium: Online Resource
    ISSN: 0032-0862 , 1365-3059
    URL: Issue
    URL: Article
    DOI: 10.1111/ppa.2015.64.issue-2
    DOI: 10.1111/ppa.12252
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2020845-5
    SSG: 12
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