The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Jared M. Leboldus - One of the best experts on this subject based on the ideXlab platform.
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The Correlation Between Septoria Leaf Spot and Stem Canker Resistance in Hybrid Poplar
Plant Disease, 2016Co-Authors: Kelsey L. Dunnell, Jared M. LeboldusAbstract:Sphaerulina musiva is an important fungal pathogen that causes a leaf spot and stem Canker disease of hybrid poplar. Stem Cankers are widely regarded as the greatest threat to hybrid poplar plantations because of their ability to cause tree mortality; thus, the efforts of breeding programs have been focused on stem Canker resistance. To explore the relationship between resistance to leaf spot and stem Canker in Populus nigra × P. deltoides hybrids, two experiments were conducted. Initially, comparisons among leaves of different ages indicated that younger leaves were more susceptible to leaf spot infection than older leaves. Correlations between leaf spot severity and stem Canker severity for both individual leaves and all leaves averaged together indicated that, in 10 of 11 comparisons, there were no significant correlations. The lack of correlation suggests that deploying genotypes resistant to stem Canker may not affect the pathogen population causing leaf spot disease. To our knowledge, this is the fi...
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The Correlation Between Septoria Leaf Spot and Stem Canker Resistance in Hybrid Poplar
Plant disease, 2016Co-Authors: Kelsey L. Dunnell, Jared M. LeboldusAbstract:Sphaerulina musiva is an important fungal pathogen that causes a leaf spot and stem Canker disease of hybrid poplar. Stem Cankers are widely regarded as the greatest threat to hybrid poplar plantations because of their ability to cause tree mortality; thus, the efforts of breeding programs have been focused on stem Canker resistance. To explore the relationship between resistance to leaf spot and stem Canker in Populus nigra × P. deltoides hybrids, two experiments were conducted. Initially, comparisons among leaves of different ages indicated that younger leaves were more susceptible to leaf spot infection than older leaves. Correlations between leaf spot severity and stem Canker severity for both individual leaves and all leaves averaged together indicated that, in 10 of 11 comparisons, there were no significant correlations. The lack of correlation suggests that deploying genotypes resistant to stem Canker may not affect the pathogen population causing leaf spot disease. To our knowledge, this is the first study specifically designed to test the correlation between stem Canker resistance and leaf spot resistance by inoculating whole trees with a spore suspension in a controlled environment.
Khalid Ettouil - One of the best experts on this subject based on the ideXlab platform.
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fine level genetic structure of white pine blister rust populations
Phytopathology, 1998Co-Authors: Richard C Hamelin, Mathieu Dusabenyagasani, Khalid EttouilAbstract:ABSTRACT The fine-level genetic structure of the white pine blister rust agent, Cronartium ribicola, was investigated by sampling multiple monokaryotic spermogonia directly on Cankers in four eastern Canadian white pine (Pinus strobus) plantations and assessing genetic variability, using random amplified polymorphic DNA (RAPD) markers. Ninety-eight percent of the Cankers surveyed contained a single DNA haplotype, suggesting spermogonia within Cankers are the result of clonal reproduction. A single Canker contained two haplotypes that were divided between the upper and lower parts of the Canker, suggesting it represented two confluent Cankers. In contrast, genotypic diversity was high among Cankers. Thirty-seven haplotypes were found among forty-three Cankers sampled, and an analysis of molecular variance indicated that 93% (P < 0.001) of the total genetic diversity was attributable to sampling of different Cankers, strongly suggesting that multiple infections do not take place in the white pine blister ru...
Dennis A. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Expansion of Cankers Caused by Leucostoma cincta on Sweet Cherry Trees.
Plant disease, 1997Co-Authors: Radwan M. Barakat, Dennis A. JohnsonAbstract:Wounds made in July 1987 and fresh pruning cuts made monthly from August 1989 to July 1990 on sweet cherry trees were inoculated with Leucostoma cincta. Infection occurred each month, with a higher percentage of wounds becoming infected during the spring and summer than during the winter months. Inoculation with conidia placed directly on wounds or inoculation with pruning shears contaminated with conidia and mycelia resulted in the same incidence and severity of Cankers. Canker enlargement was related to increasing monthly temperature. Greatest Canker enlargement usually occurred from April through August. The period of least Canker enlargement occurred from October through January. The largest Cankers resulted from inoculations in July, and the smallest Cankers resulted from inoculations in November, December, and January. Canker expansion curves were significantly described by cubic or quadratic equations for inoculation made during 10 of 12 months.
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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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.
William H Livingston - One of the best experts on this subject based on the ideXlab platform.
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compartmentalization process in eastern white pine pinus strobus l documented using a native fungal pathogen
Forest Ecology and Management, 2018Co-Authors: Savannah L Haines, Kara K L Costanza, William H LivingstonAbstract:Abstract Eastern white pine (Pinus strobus L.) is an historically, ecologically, and economically significant tree species throughout New England, USA. Reports of tree damage are being associated with the native, Canker-forming fungal disease Caliciopsis Canker, thought to be caused by the pathogen Caliciopsis pinea Peck. When infected with this pathogen, eastern white pine trees begin a compartmentalization process that limits fungal infection and spread in the xylem. Successful compartmentalization of C. pinea and closure of associated Cankers likely allows the tree to maintain health and vigor, while unsuccessful compartmentalization likely results in declining tree health and possible tree mortality. This study used tree-ring and image analysis software to quantify the compartmentalization and eventual closure process in eastern white pine trees, in response to this pathogen. The size of 357 individual Caliciopsis Cankers was measured, the loss of functional sapwood resulting from these Cankers was quantified, and the year of Canker formation and successful closure was recorded. Cankers were classified as successfully closed if the compartmentalization process clearly delimited the necrosis of a Canker and new sapwood formed to the exterior of the necrotic tissue. Our results indicate that eastern white pine growing in stands after silvicultural thinning have fewer and smaller Cankers. Of the 357 Cankers measured, the 147 in thinned stands were shorter, narrower, and closed faster than those in unthinned stands. However, regardless of size or extent of Cankers, functional sapwood was consistently reduced in trees with more Caliciopsis Cankers, indicating trees in declining health and vigor have reduced ability to compartmentalize. These results improve our understanding of how eastern white pine compartmentalizes Caliciopsis Canker infections, which will provide justification for improved management practices to reduce susceptibility to this pathogen. Further, these results broaden the overall knowledge of the compartmentalization process in softwoods and provide a resource for future studies on the compartmentalization of specific pathogens.
