The Experts below are selected from a list of 7041 Experts worldwide ranked by ideXlab platform
Robert L. Gilbertson - One of the best experts on this subject based on the ideXlab platform.
-
Movement of Xanthomonas campestris pv. vitians in the stems of lettuce and Seed Contamination
Plant Pathology, 2002Co-Authors: Jeri D. Barak, Steven T. Koike, Robert L. GilbertsonAbstract:Xanthomonas campestris pv. vitians, the causal agent of bacterial leaf spot of lettuce (BLS), can be Seedborne, but the mechanism by which the bacteria contaminates and/or infects lettuce Seed is not known. In this study, the capacity of X. campestris pv. vitians to enter and translocate within the vascular system of lettuce plants was examined. The stems of 8- to 11-week-old lettuce plants were stab-inoculated, and movement of X. campestris pv. vitians was monitored at various intervals. At 4, 8, 12 and 16 h post-inoculation (hpi), X. campestris pv. vitians was recovered from 2 to 10 cm above (depending on stem length) and 2 cm below the inoculation site. Xanthomonas campestris pv. vitians was also recovered from surface-disinfested stem sections of spray-inoculated plants. Together, these results are consistent with X. campestris pv. vitians invading and moving systemically within the vascular system of lettuce plants. To investigate the mechanism of Seed Contamination, lettuce plants at the vegetative stage of growth were spray-inoculated with X. campestris pv. vitians and allowed to develop BLS. Seed collected from these plants had a 2% incidence of X. campestris pv. vitians external colonization, but no bacteria were recovered from within the Seed.
-
Seed Contamination Thresholds for Development of Carrot Bacterial Blight Caused by Xanthomonas campestris pv. carotae.
Plant disease, 1998Co-Authors: K. C. Umesh, Ryan Davis, Robert L. GilbertsonAbstract:ABSTRACT The relationship between levels of carrot (Daucus carota subsp. sativus) Seed Contamination with Xanthomonas campestris pv. carotae and (i) establishment of populations of X. campestris pv. carotae on carrot leaves and (ii) the incidence and severity of carrot bacterial blight was determined in field plots in Davis, California, in 1995 and 1996. Levels of Seed Contamination ranged from 0 to 1.5 × 105 CFU/g in 1995 and from 0 to 1.5 × 107 CFU/g in 1996. Seed Contamination levels were positively correlated with X. campestris pv. carotae populations detected on leaves and with the incidence and severity of carrot bacterial blight. The size of X. campestris pv. carotae populations on leaves was also directly related to disease incidence. In 1996, yields were significantly reduced in plots established with Seed lots having the highest levels of X. campestris pv. carotae Contamination. Under the conditions of this study (i.e., a location having low rainfall and relative humidity), the threshold of Seed...
Stephen A. Harrison - One of the best experts on this subject based on the ideXlab platform.
-
Relationship Between Flag Leaf Symptoms Caused by Xanthomonas translucens pv. translucens and Subsequent Seed Transmission in Wheat
Plant Disease, 1998Co-Authors: K. M. Tubajika, Barry L. Tillman, J. S. Russin, Christopher A. Clark, Stephen A. HarrisonAbstract:ABSTRACT The relationship between foliar disease symptoms on parent plants, Seed Contamination by the causal bacterium (Xanthomonas translucens pv. translucens), and subsequent development of bacterial leaf streak in wheat was studied in microplots and in the laboratory to determine the role of Seed transmission in disease epidemiology. Microplot experiments were carried out during the 1994-95 and 1995-96 growing seasons using Seed harvested in Baton Rouge, Louisiana, in 1994 and 1995, respectively. Treatments were Seed lots from plants with differing levels of bacterial leaf streak severity on the flag leaves of the parent tillers. X. translucens pv. translucens was detected in 1 to 20% of Seed from susceptible cultivars Florida 304 and Savannah collected from plants with leaf streak symptoms. Correlations between Seed Contamination and disease on plants that developed from this Seed were detected only when Seed came from parent tillers that expressed flag leaf disease severity ≥15 to 20% in 1994-95 and ...
Christian Bay - One of the best experts on this subject based on the ideXlab platform.
-
Non-native vascular flora of the Arctic: Taxonomic richness, distribution and pathways
Ambio, 2020Co-Authors: Pawel Wasowicz, Alexander N. Sennikov, Kristine B. Westergaard, Katie Spellman, Matthew Carlson, Lynn J. Gillespie, Jeffery M. Saarela, Steven S. Seefeldt, Bruce Bennett, Christian BayAbstract:We present a comprehensive list of non-native vascular plants known from the Arctic, explore their geographic distribution, analyze the extent of naturalization and invasion among 23 subregions of the Arctic, and examine pathways of introductions. The presence of 341 non-native taxa in the Arctic was confirmed, of which 188 are naturalized in at least one of the 23 regions. A small number of taxa (11) are considered invasive; these plants are known from just three regions. In several Arctic regions there are no naturalized non-native taxa recorded and the majority of Arctic regions have a low number of naturalized taxa. Analyses of the non-native vascular plant flora identified two main biogeographic clusters within the Arctic: American and Asiatic. Among all pathways, Seed Contamination and transport by vehicles have contributed the most to non-native plant introduction in the Arctic.
K. C. Umesh - One of the best experts on this subject based on the ideXlab platform.
-
Seed Contamination Thresholds for Development of Carrot Bacterial Blight Caused by Xanthomonas campestris pv. carotae.
Plant disease, 1998Co-Authors: K. C. Umesh, Ryan Davis, Robert L. GilbertsonAbstract:ABSTRACT The relationship between levels of carrot (Daucus carota subsp. sativus) Seed Contamination with Xanthomonas campestris pv. carotae and (i) establishment of populations of X. campestris pv. carotae on carrot leaves and (ii) the incidence and severity of carrot bacterial blight was determined in field plots in Davis, California, in 1995 and 1996. Levels of Seed Contamination ranged from 0 to 1.5 × 105 CFU/g in 1995 and from 0 to 1.5 × 107 CFU/g in 1996. Seed Contamination levels were positively correlated with X. campestris pv. carotae populations detected on leaves and with the incidence and severity of carrot bacterial blight. The size of X. campestris pv. carotae populations on leaves was also directly related to disease incidence. In 1996, yields were significantly reduced in plots established with Seed lots having the highest levels of X. campestris pv. carotae Contamination. Under the conditions of this study (i.e., a location having low rainfall and relative humidity), the threshold of Seed...
Kerstin Wydra - One of the best experts on this subject based on the ideXlab platform.
-
Multiplication and movement of Xanthomonas axonopodis pv. vignicola and Seed Contamination in cowpea (Vigna unguiculata) genotypes
Journal of Plant Diseases and Protection, 2011Co-Authors: Rachidatou Sikirou, Kerstin WydraAbstract:The multiplication and systemic distribution of two Xan-thomonas axonopodis pv. vignicola strains from Benin differing in virulence were monitored after inoculation via leaf infiltration until 25 days post inoculation (dpi) in the susceptible cowpea genotype IT84E-124. The virulent strain multiplied fast in leaves to yield a final population density of about 109 colony forming units (cfu) cm^−2 of leaf, spread through the whole aerial part of the plant within two weeks (10^6 cfu g^−1 of stem) and caused blight, also on non-inoculated leaves at 15 dpi. In contrast, the less virulent strain multiplied slowly in leaves with a final population of about 10^2 cfu cm^−2 of leaf and did not spread through the whole plant until 25 dpi, colonising only the lower stem portion with 2.4 × 10^4 cfu g^−1 of stem. Comparing cowpea genotypes IT84E-124 (susceptible), IT86D-715 (moderately resistant) and IT86D-719 (resistant), considerable differences in bacterial numbers were obtained after infection. At 15 dpi, bacteria had spread in high densities through the whole plant in genotype IT84E-124, in leaves and occasionally in stems in genotype IT86D-715, but in genotype IT86D-719 bacteria were limited to the inoculated leaves. In genotypes IT86D-715 and IT86D-719, bacteria moved predominantly upwards through stems from the point of onset of the inoculated leaf. Contamination of Seeds derived from infected plants, varied with the resistance level of cowpea genotypes. There was no relationship between Contamination and disease severity. Lower bacteria densities were found in Seeds from plants with low disease severity, and no bacteria were detected in Seeds of genotypes with high or low disease severity. Most bacteria were concentrated on the Seed surface, and only few were found inside the Seed under the Seed coat. Typical ‘water soaked spots’ appeared on 17% of Seedlings emerging from contaminated Seeds of genotype IT86D-472. In conclusion, movement of bacteria on or into Seeds depended on genotypes, and Seed Contamination did not always result in Seedling infection. In breeding for resistance, the Contamination of Seeds and infection of Seeds in symptomless plants in apparently resistant genotypes should be determined and considered.
-
Multiplication and movement of Xanthomonas axonopodis pv. vignicola and Seed Contamination in cowpea ( Vigna unguiculata ) genotypes
Journal of Plant Diseases and Protection, 2011Co-Authors: Rachidatou Sikirou, Kerstin WydraAbstract:The multiplication and systemic distribution of two Xan-thomonas axonopodis pv. vignicola strains from Benin differing in virulence were monitored after inoculation via leaf infiltration until 25 days post inoculation (dpi) in the susceptible cowpea genotype IT84E-124. The virulent strain multiplied fast in leaves to yield a final population density of about 109 colony forming units (cfu) cm−2 of leaf, spread through the whole aerial part of the plant within two weeks (106 cfu g−1 of stem) and caused blight, also on non-inoculated leaves at 15 dpi. In contrast, the less virulent strain multiplied slowly in leaves with a final population of about 102 cfu cm−2 of leaf and did not spread through the whole plant until 25 dpi, colonising only the lower stem portion with 2.4 × 104 cfu g−1 of stem.