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Bruce D L Fitt - One of the best experts on this subject based on the ideXlab platform.
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Phoma Stem Canker severity in controlled environment experiment.
2018Co-Authors: Yongju Huang, Georgia K. Mitrousia, Siti Nordahliawate M. Sidique, Bruce D L FittAbstract:Cultivar difference in the severity of phoma Stem Canker scored on a 0–6 scale (A) and the internal length of phoma Stem Canker symptoms (B) that had developed at 20°C by 49 days after inoculation of leaf petioles of different cultivars/lines with conidial suspensions of Leptosphaeria maculans isolates. For details of isolates, see Table 2. Error bars are standard errors of the difference. Multiple comparisons were done using the least significance difference at significance level P≤0.05. The values for phoma Stem Canker severity or the internal length of phoma Stem Canker symptoms that had different letters differed significantly at P≤0.05.
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Phoma Stem Canker symptoms that developed in a controlled environment experiment.
2018Co-Authors: Yongju Huang, Georgia K. Mitrousia, Siti Nordahliawate M. Sidique, Bruce D L FittAbstract:External (A, B, C) and internal (D, E, F) phoma Stem Canker symptoms on DH line A30 (A, D), cultivars Bilbao (B, E) and Adriana (C, F). A30 with no known Rlm resistance genes and no quantitative resistance (QR), Bilbao (Rlm4) with resistance gene Rlm4, Adriana (Rlm4 + QR) with Rlm4 and QR. Leaf petioles were inoculated with conidia of Leptosphaeria maculans isolate v23.11.9, which is virulent against Rlm4. Inoculated plants were kept at 20°C with 12h light/12h darkness and sampled at 49 days after inoculation.
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Effects of a penthiopyrad and picoxystrobin fungicide mixture on phoma Stem Canker (Leptosphaeria spp.) on UK winter oilseed rape
European Journal of Plant Pathology, 2016Co-Authors: Thomas R Sewell, Steven Moloney, Mike Ashworth, Faye Ritchie, Alla Mashanova, Henrik U. Stotz, Yongju Huang, Bruce D L FittAbstract:In the UK, fungicides are often used to control phoma Stem Canker on winter oilseed rape. Field trials were established near Boxworth, Cambridgeshire for four cropping seasons (2011/2012, 2012/2013, 2013/2014 and 2014/15) to test the efficacy of a new fungicide mixture Refinzar® (penthiopyrad + picoxystrobin) by comparison to an existing fungicide Proline 275® (prothioconazole) against phoma Stem Canker (Leptosphaeria spp.) and the effect on winter oilseed rape (cv. Catana) yield. In each season, weather data were collected from a weather station at Boxworth and the release of ascospores was monitored using a nearby Burkard spore sampler. The patterns of ascospore release differed between seasons and related to weather conditions. Fungicides penthiopyrad + picoxystrobin and prothioconazole were applied in October/November when 10 % of plants had phoma leaf spotting (T1, early), 4/8 weeks after T1 (T2, late) or at both T1 and T2 (combined). When phoma leaf spot symptoms were assessed in autumn/winter, penthiopyrad + picoxystrobin and prothioconazole both decreased numbers of phoma leaf spots caused by L. maculans; there were few leaf spots caused by L. biglobosa. Penthiopyrad + picoxystrobin and prothioconazole both reduced phoma Stem Canker severity before harvest compared to the untreated control but did not increase yield in these seasons when epidemics were not severe. In 2013/2014, the presence of L. maculans and L. biglobosa in upper Stem lesions or Stem base Cankers was determined by species-specific PCR. The proportions of Stems with L. maculans DNA were much greater than those with L. biglobosa DNA for both upper Stem lesions and basal Stem Cankers. These results suggest that both penthiopyrad + picoxystrobin and prothioconazole can decrease phoma Stem Canker severity on winter oilseed rape in severe disease seasons.
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phoma Stem Canker disease on oilseed rape brassica napus in china is caused by leptosphaeria biglobosa brassicae
European Journal of Plant Pathology, 2014Co-Authors: Bruce D L Fitt, A O Latundedada, Ze Liu, Avice HallAbstract:Phoma Stem Canker of oilseed rape (Brassica napus) is a globally important disease that is caused by the sibling ascomycete species Leptosphaeria maculans and L. biglobosa. Sixty fungal isolates obtained from oilseed rape Stems with phoma Stem Canker disease symptoms collected from four provinces in China in 1999, 2005 and 2006 were all identified as Leptosphaeria biglobosa, not L. maculans, by PCR diagnostics based on species-specific primers. There were no differences in cultural characteristics (e.g. pigmentation and in vitro growth) between these L. biglobosa isolates from China and those of 37 proven L. biglobosa isolates from Europe or Canada. In studies using amplified fragment length polymorphism (AFLP) markers, Chinese L. biglobosa populations were genetically more similar to European L. biglobosa populations than to the more diverse Canadian L. biglobosa populations. Sequencing of gene fragments of β-tubulin, actin and the internal transcribed spacer (ITS) region of rDNA from L. biglobosa isolates from China, Europe, Australia and Canada showed a closer taxonomic similarity of Chinese L. biglobosa to the European L. biglobosa ‘brassicae’ than to Canadian L. biglobosa ‘canadensis’ or to the Australian L. biglobosa ‘occiaustralensis’ or ‘australensis’ subclades. These results suggest that the Chinese L. biglobosa population in this study is in the same subclade as European L. biglobosa ‘brassicae’ populations.
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assessing quantitative resistance against leptosphaeria maculans phoma Stem Canker in brassica napus oilseed rape in young plants
PLOS ONE, 2014Co-Authors: Yongju Huang, Graham J W King, Aiming Qi, Bruce D L FittAbstract:Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of Canker symptoms on the Stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the Stem by leaf lamina inoculation; stage 2, growth in Stem tissues to produce Stem Canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of Stem Canker and amount of L. maculans DNA in Stem tissues. GFP-labelled L. maculans spread more quickly from the Stem cortex to the Stem pith in A30 than in C119. Stem Canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases.
Veronique Souchere - One of the best experts on this subject based on the ideXlab platform.
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A participatory approach to design spatial scenarios of cropping syStems and assess their effects on phoma Stem Canker management at a regional scale
Environmental Modelling and Software, 2013Co-Authors: L. Hossard, Marie-hélène Jeuffroy, Elise Pelzer, Xavier Pinochet, Veronique SouchereAbstract:Phoma Stem Canker is a worldwide disease of oilseed rape, responsible for major economic losses. The main control methods are the use of resistant cultivars, cropping practices and spatial territory organization, involving large-scale spatial processes. A participatory approach can be useful for dealing with this problem, which requires stakeholders' coordination as regards to the timing and spatial layout of cropping practices. The scenario concept is used to plan possible future cropping syStems and to reveal their main drivers. In this paper, we test a method to build quantitative land use scenarios and to test them with an existing spatially-explicit model to assess the effects of various scenarios on phoma Stem Canker management. It was built from previous participatory methods. The method we tested is composed of six steps: stakeholder identification, building with them a common vision of the disease behaviour, collective scenario design, and discussion with stakeholders of model-based scenario evaluations. We tested this method on a regional case study application in France. This application revealed benefits of the method with respect to the diversity of the designed scenarios (predictive and exploratory scenarios; driven by local or global context change) and the diversity of results on phoma Stem Canker management. Based on this application, recommendations for participation improvement and model acceptance are made: (1) build a partnership with a key local stakeholder; (2) describe and discuss precisely model functioning with stakeholders (avoid the ''black box''); and (3) facilitate interpretation of scenario assessment by adapting model outputs. This method, combining a participatory approach (qualitative and quantitative construction of scenarios and their evaluation with an existing model) highlights the potential benefits of involving stakeholders in attempting to solve a local problem, in this case, phoma Stem Canker management.
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A participatory approach to design spatial scenarios of cropping syStems and assess their effects on phoma Stem Canker management at a regional scale
Environmental Modelling and Software, 2013Co-Authors: L. Hossard, Marie-hélène Jeuffroy, Elise Pelzer, Xavier Pinochet, Veronique SouchereAbstract:Phoma Stem Canker is a worldwide disease of oilseed rape, responsible for major economic losses. The main control methods are the use of resistant cultivars, cropping practices and spatial territory organization, involving large-scale spatial processes. A participatory approach can be useful for dealing with this problem, which requires stakeholders' coordination as regards to the timing and spatial layout of cropping practices. The scenario concept is used to plan possible future cropping syStems and to reveal their main drivers. In this paper, we test a method to build quantitative land use scenarios and to test them with an existing spatially-explicit model to assess the effects of various scenarios on phoma Stem Canker management. It was built from previous participatory methods. The method we tested is composed of six steps: stakeholder identification, building with them a common vision of the disease behaviour, collective scenario design, and discussion with stakeholders of model-based scenario evaluations. We tested this method on a regional case study application in France. This application revealed benefits of the method with respect to the diversity of the designed scenarios (predictive and exploratory scenarios; driven by local or global context change) and the diversity of results on phoma Stem Canker management. Based on this application, recommendations for participation improvement and model acceptance are made: (1) build a partnership with a key local stakeholder; (2) describe and discuss precisely model functioning with stakeholders (avoid the "black box"); and (3) facilitate interpretation of scenario assessment by adapting model outputs. This method, combining a participatory approach (qualitative and quantitative construction of scenarios and their evaluation with an existing model) highlights the potential benefits of involving stakeholders in attempting to solve a local problem, in this case, phoma Stem Canker management. (C) 2013 Elsevier Ltd. All rights reserved.
Febina M Mathew - One of the best experts on this subject based on the ideXlab platform.
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quantitative pcr assays developed for diaporthe helianthi and diaporthe gulyae for phomopsis Stem Canker diagnosis and germplasm screening in sunflower helianthus annuus
Plant Disease, 2020Co-Authors: Taylor R Elverson, Samuel G Markell, Brian Kontz, Robert M Harveson, Febina M MathewAbstract:Phomopsis Stem Canker of sunflower is caused by two fungal pathogens, Diaporthe helianthi and Diaporthe gulyae, in the United States. In this study, two quantitative PCR (qPCR) assays were developed to detect and quantify D. helianthi and D. gulyae in sunflower. The two assays differentiated the two fungi from each other, other species of the genus Diaporthe, and pathogens, and they have high efficiency (>90%). The qPCR assays detected the two pathogens on plant samples exhibiting Phomopsis Stem Canker symptoms sampled from commercial sunflower fields in Minnesota, Nebraska, North Dakota, and South Dakota. Furthermore, the assays were used to screen cultivated sunflower accessions for resistance to D. helianthi and D. gulyae. The disease severity index (DSI) of the accessions significantly correlated (P < 0.0001) with the amount of pathogen DNA from the qPCR assays. The qPCR assays identified PI664232 and PI561918 to be significantly less susceptible (P ≤ 0.05) to D. helianthi and D. gulyae, respectively, when compared with the susceptible check cultivar HA 288, and this was in agreement with the DSI. These results suggest that the qPCR assays for D. helianthi and D. gulyae can be used as a reliable tool to diagnose Phomopsis Stem Canker and screen sunflower germplasm for disease resistance.
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Phomopsis Stem Canker of sunflower in North America: correlation with climate and solutions through breeding and management
OCL, 2019Co-Authors: Brent S. Hulke, Samuel G Markell, Nolan C. Kane, Febina M MathewAbstract:Climate change is occurring in the central US and is interacting with agroecological factors to increase biotic stress in sunflower. Certain species of Diaporthe cause Phomopsis Stem Canker in sunflower and other dicotyledonous weeds and crops. The increase in precipitation already observed in the states of North Dakota, South Dakota, and Minnesota have increased the chances of outbreaks of necrotrophic pathogens, like Diaporthe . We discuss how climate trends, combined with technological, management, and economic interactions, are correlated with increasing incidence of Phomopsis Stem Canker in these and adjacent areas in North America. Further, we discuss management options and the role of improved sunflower genetics in reducing Phomopsis Stem Canker outbreak risk.
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phomopsis Stem Canker a reemerging threat to sunflower helianthus annuus in the united states
Phytopathology, 2015Co-Authors: Febina M Mathew, Kholoud M Alananbeh, James G Jordahl, Scott M Meyer, Lisa A Castlebury, T J Gulya, Samuel G MarkellAbstract:Phomopsis Stem Canker causes yield reductions on sunflower (Helianthus annuus L.) on several continents, including Australia, Europe, and North America. In the United States, Phomopsis Stem Canker incidence has increased 16-fold in the Northern Great Plains between 2001 and 2012. Although Diaporthe helianthi was assumed to be the sole causal agent in the United States, a newly described species, D. gulyae, was found to be the primary cause of Phomopsis Stem Canker in Australia. To determine the identity of Diaporthe spp. causing Phomopsis Stem Canker in the Northern Great Plains, 275 infected Stems were collected between 2010 and 2012. Phylogenetic analyses of sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-α, and actin gene regions of representative isolates, in comparison with those of type specimens, confirmed two species (D. helianthi and D. gulyae) in the United States. Differences in aggressiveness between the two species were determined using the Stem-...
Samuel G Markell - One of the best experts on this subject based on the ideXlab platform.
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quantitative pcr assays developed for diaporthe helianthi and diaporthe gulyae for phomopsis Stem Canker diagnosis and germplasm screening in sunflower helianthus annuus
Plant Disease, 2020Co-Authors: Taylor R Elverson, Samuel G Markell, Brian Kontz, Robert M Harveson, Febina M MathewAbstract:Phomopsis Stem Canker of sunflower is caused by two fungal pathogens, Diaporthe helianthi and Diaporthe gulyae, in the United States. In this study, two quantitative PCR (qPCR) assays were developed to detect and quantify D. helianthi and D. gulyae in sunflower. The two assays differentiated the two fungi from each other, other species of the genus Diaporthe, and pathogens, and they have high efficiency (>90%). The qPCR assays detected the two pathogens on plant samples exhibiting Phomopsis Stem Canker symptoms sampled from commercial sunflower fields in Minnesota, Nebraska, North Dakota, and South Dakota. Furthermore, the assays were used to screen cultivated sunflower accessions for resistance to D. helianthi and D. gulyae. The disease severity index (DSI) of the accessions significantly correlated (P < 0.0001) with the amount of pathogen DNA from the qPCR assays. The qPCR assays identified PI664232 and PI561918 to be significantly less susceptible (P ≤ 0.05) to D. helianthi and D. gulyae, respectively, when compared with the susceptible check cultivar HA 288, and this was in agreement with the DSI. These results suggest that the qPCR assays for D. helianthi and D. gulyae can be used as a reliable tool to diagnose Phomopsis Stem Canker and screen sunflower germplasm for disease resistance.
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Phomopsis Stem Canker of sunflower in North America: correlation with climate and solutions through breeding and management
OCL, 2019Co-Authors: Brent S. Hulke, Samuel G Markell, Nolan C. Kane, Febina M MathewAbstract:Climate change is occurring in the central US and is interacting with agroecological factors to increase biotic stress in sunflower. Certain species of Diaporthe cause Phomopsis Stem Canker in sunflower and other dicotyledonous weeds and crops. The increase in precipitation already observed in the states of North Dakota, South Dakota, and Minnesota have increased the chances of outbreaks of necrotrophic pathogens, like Diaporthe . We discuss how climate trends, combined with technological, management, and economic interactions, are correlated with increasing incidence of Phomopsis Stem Canker in these and adjacent areas in North America. Further, we discuss management options and the role of improved sunflower genetics in reducing Phomopsis Stem Canker outbreak risk.
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phomopsis Stem Canker a reemerging threat to sunflower helianthus annuus in the united states
Phytopathology, 2015Co-Authors: Febina M Mathew, Kholoud M Alananbeh, James G Jordahl, Scott M Meyer, Lisa A Castlebury, T J Gulya, Samuel G MarkellAbstract:Phomopsis Stem Canker causes yield reductions on sunflower (Helianthus annuus L.) on several continents, including Australia, Europe, and North America. In the United States, Phomopsis Stem Canker incidence has increased 16-fold in the Northern Great Plains between 2001 and 2012. Although Diaporthe helianthi was assumed to be the sole causal agent in the United States, a newly described species, D. gulyae, was found to be the primary cause of Phomopsis Stem Canker in Australia. To determine the identity of Diaporthe spp. causing Phomopsis Stem Canker in the Northern Great Plains, 275 infected Stems were collected between 2010 and 2012. Phylogenetic analyses of sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-α, and actin gene regions of representative isolates, in comparison with those of type specimens, confirmed two species (D. helianthi and D. gulyae) in the United States. Differences in aggressiveness between the two species were determined using the Stem-...
Peter Gladders - One of the best experts on this subject based on the ideXlab platform.
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Geostatistical analysis of the distribution of Leptosphaeria species causing phoma Stem Canker on winter oilseed rape (Brassica napus) in England
Plant Pathology, 2010Co-Authors: J F Stonard, Peter Gladders, Akinwunmi O. Latunde-dada, Neal Evans, Ben P. Marchant, M. R. Eckert, Bruce D L FittAbstract:In June/July 2001, 2002, 2003 and 2006, regional variation in distribution of the pathogens Leptosphaeria maculans and L. biglobosa that are causally associated with phoma Stem Canker was surveyed on winter oilseed rape crops in England. In 2001-2003, when isolates from basal Cankers were visually identified as L. maculans or L. biglobosa based on cultural morphological characteristics, 70% were L. maculans and 30%L. biglobosa. In 2001, 2002, 2003 and 2006, when amounts of DNA of each species in basal Cankers were determined by quantitative PCR, the abundance of L. maculans DNA was greater than that of L. biglobosa DNA in 77% of samples. When regional differences in amounts of L. maculans and L. biglobosa DNA were mapped geostatistically, quantities of L. maculans DNA were greater in Cankers from southern England and those of L. biglobosa DNA were greater in northern England. A comparison with geostatistically mapped predictions made using a weather-based model describing stages in development of phoma Stem Canker epidemics suggested that these differences in Leptosphaeria populations may have been a consequence of differences in temperature after onset of leaf spotting between northern and southern England. Both PCR and morphological evidence suggested that the abundance of L. maculans in England has increased since the last surveys in the 1980s. Implications of these surveys for control of phoma Stem Canker are discussed.
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Effects of Stem Canker (Leptosphaeria maculans) and light leaf spot (Pyrenopeziza brassicae) on yield of winter oilseed rape (Brassica napus) in southern England
Plant Pathology, 2000Co-Authors: Yilin Zhou, Neal Evans, Bruce D L Fitt, S. J. Welham, Peter GladdersAbstract:The relationships between yield loss and incidence or severity of Stem Canker and light leaf spot in winter oilseed rape were analysed by correlation and regression analyses, using data from experiments at Rothamsted, England in 1992/93, 1994/95 and 1995/96. Growth stages (GS) 6,3/6,4 and 4,0/4,5 were identified as the critical points for relating percentage yield loss to Stem Canker and light leaf spot (on Stems), respectively. Critical point (CP) and area under disease progress curve (AUDPC) models relating percentage yield loss to combined incidence or severity of Stem Canker and light leaf spot (Stems) in each experiment were constructed by linear regression. There were no differences in the CP models for incidence between 1992/93, 1994/95 and 1995/96 experiments, or in the AUDPC models for incidence between 1992/93 and 1994/95 experiments. Therefore, a general CP model relating percentage yield loss (ΔY) to combined incidence of Stem Canker (Si) at GS 6,3/6,4 and light leaf spot (Stems) (Li) at GS 4,0/4,5 was constructed using data from the three experiments: ΔY = 0·85 + 0·079Si + 0·065Li (R2 = 43·7%, P
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Epidemiology of Leptosphaeria maculans in relation to forecasting Stem Canker severity on winter oilseed rape in the UK
Annals of Applied Biology, 1999Co-Authors: Jon S. West, J.e. Biddulph, Bruce D L Fitt, Peter GladdersAbstract:SUMMARY In the UK, ascospores of Leptosphaeria maculans first infect leaves of oilseed rape in the autumn to cause phoma leaf spots, from which the fungus can grow to cause Stem Cankers in the spring. Yield losses due to early senescence and lodging result if the Stem Cankers become severe before harvest. The risk of severe Stem Canker epidemics needs to be forecast in the autumn when the pathogen is still in the leaves, since early infections cause the greatest yield losses and fungicides have limited curative activity. Currently, the most effective way to forecast severe Stem Canker is to monitor the onset of phoma leaf spotting in winter oilseed rape crops, although this does not allow much time in which to apply a fungicide. Early warnings of risks of severe Stem Canker epidemics could be provided at the beginning of the season through regional forecasts based on disease survey and weather data, with options for input of crop-specific information and for updating forecasts during the winter. The accuracy of such forecasts could be improved by including factors relating to the maturation of ascospores in pseudothecia, the release of ascospores and the occurrence of infection conditions, as they affect the onset, intensity and duration of the phoma leaf spotting phase. Accurate forecasting of severe Stem Canker epidemics can improve disease control and optimise fungicide use.
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Effects of Severity and Timing of Stem Canker (Leptosphaeria maculans) Symptoms on Yield of Winter Oilseed Rape (Brassica napus) in the UK
European Journal of Plant Pathology, 1999Co-Authors: Yilin Zhou, Peter Gladders, Bruce D L Fitt, S. J. Welham, C. E. Sansford, Jon S. WestAbstract:The relationships between yield loss and incidence (% plants with Stems affected) or severity (mean Stem score, 0–4 scale) of Stem Canker in winter oilseed rape were analysed using data from experiments at Rothamsted in 1991/92, Withington in 1992/93, Boxworth in 1993/94 and Rothamsted in 1997/98. Critical point models and area under disease progress curve (AUDPC) models were better than multiple point models for describing relationships between yield (t ha−1) and incidence or severity of Stem Canker for the four experiments. Since yield is influenced by many factors other than disease, % yield loss was calculated and critical point models and AUDPC models relating % yield loss to Stem Canker were constructed. The critical point models for % yield loss on Stem Canker incidence for three of the four experiments were similar, but differed from that for Rothamsted in 1991/92. There were also no differences between models of % yield loss on AUDPC of both incidence and severity for these three experiments. Therefore, general models of % yield loss (L) against AUDPC of incidence (X) or severity (S) of Stem Canker from growth stages 4.8 to 6.4 were derived from the combined data sets for the three experiments: L=−0.76+0.0075X (R2=35%, p
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effects of severity and timing of Stem Canker leptosphaeria maculans symptoms on yield of winter oilseed rape brassica napus in the uk
European Journal of Plant Pathology, 1999Co-Authors: Yilin Zhou, Peter Gladders, Bruce D L Fitt, S. J. Welham, C. E. Sansford, Jon S. WestAbstract:The relationships between yield loss and incidence (% plants with Stems affected) or severity (mean Stem score, 0–4 scale) of Stem Canker in winter oilseed rape were analysed using data from experiments at Rothamsted in 1991/92, Withington in 1992/93, Boxworth in 1993/94 and Rothamsted in 1997/98. Critical point models and area under disease progress curve (AUDPC) models were better than multiple point models for describing relationships between yield (t ha−1) and incidence or severity of Stem Canker for the four experiments. Since yield is influenced by many factors other than disease, % yield loss was calculated and critical point models and AUDPC models relating % yield loss to Stem Canker were constructed. The critical point models for % yield loss on Stem Canker incidence for three of the four experiments were similar, but differed from that for Rothamsted in 1991/92. There were also no differences between models of % yield loss on AUDPC of both incidence and severity for these three experiments. Therefore, general models of % yield loss (L) against AUDPC of incidence (X) or severity (S) of Stem Canker from growth stages 4.8 to 6.4 were derived from the combined data sets for the three experiments: L=−0.76+0.0075X (R2=35%, p<0.001), L=0.26+0.53S (R2=37%, p<0.001). The relationships between % yield loss and % plants with different Stem Canker severity scores at different growth stages were also analysed; the greatest yield losses were generally associated with the largest severity scores, for plants assessed at the same crop growth stage, and were also associated with the early development of Stem lesions. Further analyses showed that % yield loss was related to incidence or severity of both basal Stem Cankers and upper Stem lesions in experiments at Boxworth in 1993/94 and at Rothamsted in 1997/98.
