X. Nesme - Academia.edu (original) (raw)

Papers by X. Nesme

Genetics Selection Evolution, 2001

The reliability and the level of taxonomic resolution of the amplified fragment length polymorphi... more The reliability and the level of taxonomic resolution of the amplified fragment length polymorphism (AFLP) method were evaluated with species of pathogenic bacteria involved in human, animal and plant diseases. The method was found to be very versatile as it can be adapted to the individual genome constraints of all

Journal of Chromatography B, 2021

Opines are low-molecular-weight metabolites specifically biosynthesized by agrobacteria-transform... more Opines are low-molecular-weight metabolites specifically biosynthesized by agrobacteria-transformed plant cells when plants are struck by crown gall and hairy root diseases, which cause uncontrolled tissue overgrowth. Transferred DNA is sustainably incorporated into the genomes of the transformed plant cells, so that opines constitute a persistent biomarker of plant infection by pathogenic agrobacteria and can be targeted for crown gall/hairy root disease diagnosis. We developed a general, rapid, specific and sensitive analytical method for overall opine detection using ultra-high-performance liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-MS-QTOF), with easy preparation of samples. Based on MS, MS/MS and chromatography data, the detection selectivity of a wide range of standard opines was validated in pure solution and in different plant extracts. The method was successfully used to detect different structural types of opines, including opines for which standard compounds are unavailable, in tumors or hairy roots induced by pathogenic strains. As the method can detect a wide range of opines in a single run, it represents a powerful tool for plant gall analysis and crown gall/hairy root disease diagnosis. Using an appropriate dilution of plant extract and a matrix-based calibration curve, the quantification ability of the method was validated for three opines belonging to different families (nopaline, octopine, mannopine), which were accurately quantified in plant tissue extracts.

European Journal of Plant Pathology, 2004

Horizontal gene transfer (HGT) is considered as a major source of innovation in bacteria, and as ... more Horizontal gene transfer (HGT) is considered as a major source of innovation in bacteria, and as such is expected to drive adaptation to new ecological niches. However, among the many genes acquired through HGT along the diversification history of genomes, only a fraction may have actively contributed to sustained ecological adaptation. We used a phylogenetic approach accounting for the transfer of genes (or groups of genes) to estimate the history of genomes in Agrobacterium biovar 1, a diverse group of soil and plant-dwelling bacterial species. We identified clade-specific blocks of co-transferred genes encoding coherent biochemical pathways that may have contributed to the evolutionary success of key Agrobacterium clades. This pattern of gene co-evolution rejects a neutral model of transfer, in which neighbouring genes would be transferred independently of their function and rather suggests purifying selection on collectively coded acquired pathways. The acquisition of these syna...

Applied and Environmental Microbiology, 1987

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil... more This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the...

Two molecular methods, namely Restriction Fragment Length Polymorphism of Polymerase Chain Reacti... more Two molecular methods, namely Restriction Fragment Length Polymorphism of Polymerase Chain Reaction amplified gene fragment (PCR-RFLP) and simplified Amplified Fragment Length Polymorphism (AFLP), were tested in order to differentiate the Pseudomonas spp. strains and isolates. The isolates were identified based on the selected biochemical tests and comparing sequences of PCR amplified 16S rDNA fragments. The obtained results show that of gyrB, recA and rpoD gene fragments studied, the most useful in PCR-RFLP analysis for genotyping of Pseudomonas syringae pv. tomato and P. syringae pv. syringae was gyrB fragment. Simplified AFLP analysis allows for differentiation of three pathovars of P. syringae: P. syringae pv. tomato, P. syringae pv. syringae, P. syringae pv. lachrymans and P. savastonoi pv. phaseolicola. Simplified AFLP analysis seems to be the method, which is more effective and easier to perform than PCR-RFLP for the genetic differentiation of Pseudomonas species and pathovars.

Applied and Environmental Microbiology

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil... more This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the...

Applied and environmental microbiology

The development of competence allowing natural transformation of Ralstonia solanacearum was found... more The development of competence allowing natural transformation of Ralstonia solanacearum was found to occur during exponential growth and not in response to any excreted factors. Linear DNAs were effectively integrated by recombination requiring a minimum of 50 bp of homologous DNA. Therefore, DNA from other genera and species were ineffective.

Applied and environmental microbiology

Crown gall tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, ... more Crown gall tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, yielded both tumorigenic and nonpathogenic agrobacteria. On the basis of classical diagnostic tests, the nonpathogenic strains were identified as Agrobacterium tumefaciens, whereas the tumorigenic strains could not be assigned to any of the known terrestrial Agrobacterium spp. The tumorigenic strains also differed from other members of the genus by producing more acid from mannitol. According to cluster analysis of carbon substrate oxidation (GN Microplate; Biolog, Inc.) and fatty acid content, the tumorigenic fig strains were distinct from strains of A. tumefaciens, Agrobacterium rhizogenes, Agrobacterium vitis, and Agrobacterium rubi. Furthermore, they had unusual opine metabolism, inducing tumors that synthesized nopaline and three recently discovered opines: chrysopine (d-lactone of N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-5-...

Applied and Environmental Microbiology

In order to develop a rapid and specific detection test for bacteria in soil, we improved a metho... more In order to develop a rapid and specific detection test for bacteria in soil, we improved a method based on the polymerase chain reaction (PCR). Each step of the protocol, including direct lysis of cells, DNA purification, and PCR amplification, was optimized. To increase the efficiency of lysis, a step particularly critical for some microorganisms which resist classical techniques, we used small soil samples (100 mg) and various lytic treatments, including sonication, microwave heating, and thermal shocks. Purification of nucleic acids was achieved by passage through up to three Elutip d columns. Finally, PCR amplifications were optimized via biphasic protocols using booster conditions, lower denaturation temperatures, and addition of formamide. Two microorganisms were used as models: Agrobacterium tumefaciens, which is naturally absent from the soil used and was inoculated to calibrate the validity of the protocol, and Frankia spp., an actinomycete indigenous to the soil used. Spe...

Blood

Mast cells participate in normal and pathogenic inflammatory processes, including innate host def... more Mast cells participate in normal and pathogenic inflammatory processes, including innate host defense, allergy, and asthma. Stimulation of the mast cell high-affinity IgE receptor (FcεR) by receptor cross-linking activates multiple downstream signaling pathways resulting in degranulation and de novo synthesis of multiple cytokines. However, the molecular mechanisms underlying these processes are incompletely defined. It is known that Rac2 deficient murine bone marrow derived mast cells (BMMCs) have impaired degranulation, but the downstream effectors that modulate this function are unknown. We hypothesized that p-21 activated kinase 1 (Pak1), a downstream effector of Rac proteins, is important in degranulation and de novo cytokine synthesis. Mature BMMCs from wild-type (WT) and Pak1 KO mice were sensitized with anti-DNP IgE then stimulated with DNP-HSA to stimulate FcεR. Interestingly, Pak1 KO BMMCs showed significant impairment in degranulation, as demonstrated by a 3-fold reductio...

Phytopathology

... cerasus tumefaciens Nopal i ne 5 296 111 Unknown tumefaciens Nopaline 5 449 Prunus domestica ... more ... cerasus tumefaciens Nopal i ne 5 296 111 Unknown tumefaciens Nopaline 5 449 Prunus domestica rhizogenes Agropine 5 1317 Rubus tabeas rhizogenes Nopaline .s 1804 Prunus persicae rhizogenes Nopaline 5 1840 Populus alba rhizogenes Nopaline 5 1873 Dahlia sp. ...

Trends in Colloid and Interface Science XVI, 2004

The surface chemistry and physicochemical phenomena involved in the chemical grafting process of ... more The surface chemistry and physicochemical phenomena involved in the chemical grafting process of short DNA single strands on silica or glass slides has been studied in order to be able to prepare reusable DNA-arrays (DNA-chips) with an optimum signal-to-noise ratio. Some crucial steps of the immobilisation of oligonucleotides on silica surfaces by means of their chemical grafting at their 3'

II International Rose Symposium, 1996

II International Rose Symposium, 1996

ABSTRACT

Molecular Plant-Microbe Interactions, 2015

Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) th... more Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) that are known to act as posttranscriptional regulators in plant pathogenic bacteria. sRNA-seq analyses of Agrobacterium fabrum C58 allowed us to identify 1,108 small transcripts expressed in several growth conditions that could be sRNAs. A quarter of them were confirmed by bioinformatics or by biological experiments. Antisense RNAs represent 24% of the candidates and they are over-represented on the pTi (with 62% of pTi sRNAs), suggesting differences in the regulatory mechanisms between the essential and accessory replicons. Moreover, a large number of these pTi antisense RNAs are transcribed opposite to those genes involved in virulence. Others are 5′- and 3′-untranslated region RNAs and trans-encoded RNAs. We have validated, by rapid amplification of cDNA ends polymerase chain reaction, the transcription of 14 trans-encoded RNAs, among which RNA1111 is expressed from the pTiC58. Its del...

Bulletin de la Société Botanique de France. Lettres Botaniques, 1982

ResumeChez Rubus idaeus L., des secretions de nature hydrophile et hydrophobe peuvent etre detect... more ResumeChez Rubus idaeus L., des secretions de nature hydrophile et hydrophobe peuvent etre detectees au niveau des organes lies a la pollinisation: nectaire, stigmates et grains de pollen. Dans les fleurs en anthese, le nectaire exsude un nectar abondant; les stigmates se couvrent d'un exsudat lipo-polysaccharidique; la paroi des grains de pollen comporte, sous un epais «pollenkitt», des substances proteiques et lipidiques aisement diffusibles. Ces secretions sont liees a la nature entomogame de la pollinisation.

Phytopathology, 1994

To verify the occurrence of physiologic races in Xanthomonas populi pv. populi, the causal agent ... more To verify the occurrence of physiologic races in Xanthomonas populi pv. populi, the causal agent of oozing canker of poplar, the virulence of 19 strains was compared by inoculating five poplar clones and one willow clone was two sets of tests performed during June and September, respectively. Canker severity was measured 2 yr later by determining the lengths and the girdling index of cankers. Analysis of variance indicated a significant poplar clone-strain interaction and no significant clone-strain-inoculation date interaction for most strains, using the two variables. Five putative physiologic races were characterized. Race 3 was totally avirulent on the clone Italica, although the other races gave relatively small differences in canker severity [...]

Genetics Selection Evolution, 2001

The reliability and the level of taxonomic resolution of the amplified fragment length polymorphi... more The reliability and the level of taxonomic resolution of the amplified fragment length polymorphism (AFLP) method were evaluated with species of pathogenic bacteria involved in human, animal and plant diseases. The method was found to be very versatile as it can be adapted to the individual genome constraints of all

Journal of Chromatography B, 2021

Opines are low-molecular-weight metabolites specifically biosynthesized by agrobacteria-transform... more Opines are low-molecular-weight metabolites specifically biosynthesized by agrobacteria-transformed plant cells when plants are struck by crown gall and hairy root diseases, which cause uncontrolled tissue overgrowth. Transferred DNA is sustainably incorporated into the genomes of the transformed plant cells, so that opines constitute a persistent biomarker of plant infection by pathogenic agrobacteria and can be targeted for crown gall/hairy root disease diagnosis. We developed a general, rapid, specific and sensitive analytical method for overall opine detection using ultra-high-performance liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-MS-QTOF), with easy preparation of samples. Based on MS, MS/MS and chromatography data, the detection selectivity of a wide range of standard opines was validated in pure solution and in different plant extracts. The method was successfully used to detect different structural types of opines, including opines for which standard compounds are unavailable, in tumors or hairy roots induced by pathogenic strains. As the method can detect a wide range of opines in a single run, it represents a powerful tool for plant gall analysis and crown gall/hairy root disease diagnosis. Using an appropriate dilution of plant extract and a matrix-based calibration curve, the quantification ability of the method was validated for three opines belonging to different families (nopaline, octopine, mannopine), which were accurately quantified in plant tissue extracts.

European Journal of Plant Pathology, 2004

Horizontal gene transfer (HGT) is considered as a major source of innovation in bacteria, and as ... more Horizontal gene transfer (HGT) is considered as a major source of innovation in bacteria, and as such is expected to drive adaptation to new ecological niches. However, among the many genes acquired through HGT along the diversification history of genomes, only a fraction may have actively contributed to sustained ecological adaptation. We used a phylogenetic approach accounting for the transfer of genes (or groups of genes) to estimate the history of genomes in Agrobacterium biovar 1, a diverse group of soil and plant-dwelling bacterial species. We identified clade-specific blocks of co-transferred genes encoding coherent biochemical pathways that may have contributed to the evolutionary success of key Agrobacterium clades. This pattern of gene co-evolution rejects a neutral model of transfer, in which neighbouring genes would be transferred independently of their function and rather suggests purifying selection on collectively coded acquired pathways. The acquisition of these syna...

Applied and Environmental Microbiology, 1987

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil... more This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the...

Two molecular methods, namely Restriction Fragment Length Polymorphism of Polymerase Chain Reacti... more Two molecular methods, namely Restriction Fragment Length Polymorphism of Polymerase Chain Reaction amplified gene fragment (PCR-RFLP) and simplified Amplified Fragment Length Polymorphism (AFLP), were tested in order to differentiate the Pseudomonas spp. strains and isolates. The isolates were identified based on the selected biochemical tests and comparing sequences of PCR amplified 16S rDNA fragments. The obtained results show that of gyrB, recA and rpoD gene fragments studied, the most useful in PCR-RFLP analysis for genotyping of Pseudomonas syringae pv. tomato and P. syringae pv. syringae was gyrB fragment. Simplified AFLP analysis allows for differentiation of three pathovars of P. syringae: P. syringae pv. tomato, P. syringae pv. syringae, P. syringae pv. lachrymans and P. savastonoi pv. phaseolicola. Simplified AFLP analysis seems to be the method, which is more effective and easier to perform than PCR-RFLP for the genetic differentiation of Pseudomonas species and pathovars.

Applied and Environmental Microbiology

This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil... more This study focused on the natural crown gall infections occurring in a Leuce poplar nursery. Soil effects on crown gall frequency were detected, indicating that contamination was due to a resident Agrobacterium tumefaciens population, which was present before seedling plantation. The crown gall frequency on poplar progenies varied from 3 to 67%, indicating the feasibility of improvement in crown gall resistance. Of 129 tumor isolates, 128 were pathogenic. These isolates were of biotype 1 or 2. Biochemical, serological, and antibiotic resistance typing results concurred, indicating the presence of four biotype 1 and two biotype 2 resident subpopulations. No significant change was noticed in the relative proportions of subpopulations from one year to another. Pathogenic subpopulations both in vitro and in planta were susceptible to Kerr K84 (P. B. New and A. Kerr, J. Appl. Bacteriol. 90:172-179, 1972). In addition, no serological cross-reactions were found to occur between K84 and the...

Applied and environmental microbiology

The development of competence allowing natural transformation of Ralstonia solanacearum was found... more The development of competence allowing natural transformation of Ralstonia solanacearum was found to occur during exponential growth and not in response to any excreted factors. Linear DNAs were effectively integrated by recombination requiring a minimum of 50 bp of homologous DNA. Therefore, DNA from other genera and species were ineffective.

Applied and environmental microbiology

Crown gall tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, ... more Crown gall tumors, collected from branches of 1-year-old weeping fig (Ficus benjamina L.) trees, yielded both tumorigenic and nonpathogenic agrobacteria. On the basis of classical diagnostic tests, the nonpathogenic strains were identified as Agrobacterium tumefaciens, whereas the tumorigenic strains could not be assigned to any of the known terrestrial Agrobacterium spp. The tumorigenic strains also differed from other members of the genus by producing more acid from mannitol. According to cluster analysis of carbon substrate oxidation (GN Microplate; Biolog, Inc.) and fatty acid content, the tumorigenic fig strains were distinct from strains of A. tumefaciens, Agrobacterium rhizogenes, Agrobacterium vitis, and Agrobacterium rubi. Furthermore, they had unusual opine metabolism, inducing tumors that synthesized nopaline and three recently discovered opines: chrysopine (d-lactone of N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-L-glutamine, and N-1-deoxy-D-fructosyl-5-...

Applied and Environmental Microbiology

In order to develop a rapid and specific detection test for bacteria in soil, we improved a metho... more In order to develop a rapid and specific detection test for bacteria in soil, we improved a method based on the polymerase chain reaction (PCR). Each step of the protocol, including direct lysis of cells, DNA purification, and PCR amplification, was optimized. To increase the efficiency of lysis, a step particularly critical for some microorganisms which resist classical techniques, we used small soil samples (100 mg) and various lytic treatments, including sonication, microwave heating, and thermal shocks. Purification of nucleic acids was achieved by passage through up to three Elutip d columns. Finally, PCR amplifications were optimized via biphasic protocols using booster conditions, lower denaturation temperatures, and addition of formamide. Two microorganisms were used as models: Agrobacterium tumefaciens, which is naturally absent from the soil used and was inoculated to calibrate the validity of the protocol, and Frankia spp., an actinomycete indigenous to the soil used. Spe...

Blood

Mast cells participate in normal and pathogenic inflammatory processes, including innate host def... more Mast cells participate in normal and pathogenic inflammatory processes, including innate host defense, allergy, and asthma. Stimulation of the mast cell high-affinity IgE receptor (FcεR) by receptor cross-linking activates multiple downstream signaling pathways resulting in degranulation and de novo synthesis of multiple cytokines. However, the molecular mechanisms underlying these processes are incompletely defined. It is known that Rac2 deficient murine bone marrow derived mast cells (BMMCs) have impaired degranulation, but the downstream effectors that modulate this function are unknown. We hypothesized that p-21 activated kinase 1 (Pak1), a downstream effector of Rac proteins, is important in degranulation and de novo cytokine synthesis. Mature BMMCs from wild-type (WT) and Pak1 KO mice were sensitized with anti-DNP IgE then stimulated with DNP-HSA to stimulate FcεR. Interestingly, Pak1 KO BMMCs showed significant impairment in degranulation, as demonstrated by a 3-fold reductio...

Phytopathology

... cerasus tumefaciens Nopal i ne 5 296 111 Unknown tumefaciens Nopaline 5 449 Prunus domestica ... more ... cerasus tumefaciens Nopal i ne 5 296 111 Unknown tumefaciens Nopaline 5 449 Prunus domestica rhizogenes Agropine 5 1317 Rubus tabeas rhizogenes Nopaline .s 1804 Prunus persicae rhizogenes Nopaline 5 1840 Populus alba rhizogenes Nopaline 5 1873 Dahlia sp. ...

Trends in Colloid and Interface Science XVI, 2004

The surface chemistry and physicochemical phenomena involved in the chemical grafting process of ... more The surface chemistry and physicochemical phenomena involved in the chemical grafting process of short DNA single strands on silica or glass slides has been studied in order to be able to prepare reusable DNA-arrays (DNA-chips) with an optimum signal-to-noise ratio. Some crucial steps of the immobilisation of oligonucleotides on silica surfaces by means of their chemical grafting at their 3'

II International Rose Symposium, 1996

II International Rose Symposium, 1996

ABSTRACT

Molecular Plant-Microbe Interactions, 2015

Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) th... more Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) that are known to act as posttranscriptional regulators in plant pathogenic bacteria. sRNA-seq analyses of Agrobacterium fabrum C58 allowed us to identify 1,108 small transcripts expressed in several growth conditions that could be sRNAs. A quarter of them were confirmed by bioinformatics or by biological experiments. Antisense RNAs represent 24% of the candidates and they are over-represented on the pTi (with 62% of pTi sRNAs), suggesting differences in the regulatory mechanisms between the essential and accessory replicons. Moreover, a large number of these pTi antisense RNAs are transcribed opposite to those genes involved in virulence. Others are 5′- and 3′-untranslated region RNAs and trans-encoded RNAs. We have validated, by rapid amplification of cDNA ends polymerase chain reaction, the transcription of 14 trans-encoded RNAs, among which RNA1111 is expressed from the pTiC58. Its del...

Bulletin de la Société Botanique de France. Lettres Botaniques, 1982

ResumeChez Rubus idaeus L., des secretions de nature hydrophile et hydrophobe peuvent etre detect... more ResumeChez Rubus idaeus L., des secretions de nature hydrophile et hydrophobe peuvent etre detectees au niveau des organes lies a la pollinisation: nectaire, stigmates et grains de pollen. Dans les fleurs en anthese, le nectaire exsude un nectar abondant; les stigmates se couvrent d'un exsudat lipo-polysaccharidique; la paroi des grains de pollen comporte, sous un epais «pollenkitt», des substances proteiques et lipidiques aisement diffusibles. Ces secretions sont liees a la nature entomogame de la pollinisation.

Phytopathology, 1994

To verify the occurrence of physiologic races in Xanthomonas populi pv. populi, the causal agent ... more To verify the occurrence of physiologic races in Xanthomonas populi pv. populi, the causal agent of oozing canker of poplar, the virulence of 19 strains was compared by inoculating five poplar clones and one willow clone was two sets of tests performed during June and September, respectively. Canker severity was measured 2 yr later by determining the lengths and the girdling index of cankers. Analysis of variance indicated a significant poplar clone-strain interaction and no significant clone-strain-inoculation date interaction for most strains, using the two variables. Five putative physiologic races were characterized. Race 3 was totally avirulent on the clone Italica, although the other races gave relatively small differences in canker severity [...]