Richard Lee - Academia.edu (original) (raw)

Papers by Richard Lee

DergiPark (Istanbul University), Mar 1, 2004

The RNA-dependent RNA polymerase (RdRp) gene was first amplified by reverse transcription/polymer... more The RNA-dependent RNA polymerase (RdRp) gene was first amplified by reverse transcription/polymerase chain reaction (RT/PCR) from dsRNA template isolated from citrus leaves infected with citrus tristeza closterovirus (CTV). Then the RdRp was cloned into expression vector and Escherichia coli was transformed with this vector containing the RdRp gene for expression. Analysis of total protein from E. coli by polyacrylamide gel electrophoresis showed that expression of a 60 kDa CTVRdRp protein was induced at 30 min and gradually increased for 3 hr after induction. Further analysis of the protein indicated that the RdRp was not soluble, and found only in the insoluble fractions of the E. coli cells. A polyclonal antiserum was produced by injecting a rabbit with the RdRp protein expressed in E. coli a collecting antiserum from it. Western blot analysis of the total protein from E. coli expressing the RdRp with this antiserum showed that the polyclonal antibody produced was specific to the RdRp of CTV.

Journal of Citrus Pathology, 2014

Plants, 2021

Citrus huanglongbing (HLB) disease associated with the ‘Candidatus Liberibacter asiaticus’ (CLas)... more Citrus huanglongbing (HLB) disease associated with the ‘Candidatus Liberibacter asiaticus’ (CLas) bacterium has caused significant financial damage to many citrus industries. Large-scale pathogen surveys are routinely conducted in California to detect CLas early in the disease cycle by lab-based qPCR assays. We have developed an improved reference gene for the sensitive detection of CLas from plants in diagnostic duplex qPCR and analytical digital droplet PCR (ddPCR) assays. The mitochondrial cytochrome oxidase gene (COX), widely used as a reference, is not ideal because its high copy number can inhibit amplification of small quantities of target genes. In ddPCRs, oversaturation of droplets complicates data normalization and quantification. The variable copy numbers of COX gene in metabolically active young tissue, greenhouse plants, and citrus relatives suggest the need for a non-variable, nuclear, low copy, universal reference gene for analysis of HLB hosts. The single-copy nuclea...

HortScience, 2014

A test population consisting of progenies of 92 seed-source genotypes (hereafter called “parent g... more A test population consisting of progenies of 92 seed-source genotypes (hereafter called “parent genotypes”) of Citrus and Citrus relatives in the field in east–central Florida was assessed after natural freeze events in the winters of 2010 and 2011. Eight seedlings per parent genotype were planted in a randomized complete block design; however, as a result of mortality, the number of plants assessed in some genotype groups was reduced at some or all sampling dates. The citrus diseases huanglongbing and citrus canker were endemic in the planting and may have influenced tree response to cold temperatures. Unusually low temperatures (near –4 °C each winter) for east–central Florida were experienced during the trial period. Defoliation and dieback were significantly greater in the winter of 2011 than in the winter of 2010. The winter in 2011 was preceded by a period of extraordinarily low temperatures in mid-December with no period of cool temperatures to allow trees to acclimate. In 20...

HortScience, 2014

Xanthomonas citri ssp. citri (Xcc) is the causal agent of Asiatic citrus canker (ACC), a commerci... more Xanthomonas citri ssp. citri (Xcc) is the causal agent of Asiatic citrus canker (ACC), a commercially important disease in Florida citrus as well as in many other regions. In this study we evaluated occurrence of foliar lesions from ACC on progenies of 94 seed-source genotypes (hereafter called “parent genotypes”) of Citrus and Citrus relatives in the field in east–central Florida to identify the relative susceptibility to ACC. Eight seedlings per parent genotype were planted in a randomized complete block planting, but the number of plants assessed in some genotype groups was reduced by mortality at some or all sampling dates. Plants experienced ambient exposure to high Xcc inoculum pressure and plants were assessed in Sept. 2010, July 2011, Oct. 2011, May 2012, and Sept. 2012. The incidence and severity of ACC lesions were assessed and evaluated using non-parametric analyses to compare progeny from the 94 parent genotypes. Progeny of 14 parent genotypes did not exhibit ACC symptom...

Plant Cell Reports, 2003

Grapefruit (Citrus paradisi Macf. cv Duncan) plants were transformed with several sequences from ... more Grapefruit (Citrus paradisi Macf. cv Duncan) plants were transformed with several sequences from citrus tristeza closterovirus (CTV) that varied in terms of position in the CTV genome and virus strain origin in an attempt to obtain resistant plants. The sequences included the capsid protein gene from three different strains, a nontranslatable version of the capsid protein gene, the replicase (RdRp), the minor capsid protein (p27), a highly transcribed gene of unknown function (p20) and the more conserved 3′ end of the genomic RNA. Transgenic plants were generated from all of the constructs, except from the p20 and p27 genes. Southern and Western blot analyses demonstrated that stably transformed grapefruit plants were obtained and that at least some transgenes were expressed. In a first effort at virus challenge, 25 transgenic lines were graft inoculated with a severe strain of CTV. Although some transgenic plants averaged lower titers of virus than controls, there was great variability in titer in both controls and transgenic plants, and all were apparently susceptible to the virus.

Scientia Horticulturae, 2015

Citron (Citrus medica L.) is one of the three basic species of the genus Citrus L. that have cont... more Citron (Citrus medica L.) is one of the three basic species of the genus Citrus L. that have contributed to the development of cultivated citrus. We analyzed the genetic diversity of 47 citrons (32 from Yunnan Province, China; and 15 of Mediterranean origin) to understand their diversity and relationships within the species. Genetic analysis was conducted using data from microsatellite markers, single nucleotide polymorphisms generated from sequences of a nuclear malate dehydrogenase gene and a chloroplast gene, rps16. Neighbor joining and maximum parsimony analyses were conducted. All three approaches found citron to be monophyletic. Population structure analysis clustered the 47 citrons into three distinct groups. The first group consisted of wild, non-fingered citrons generally having locules, juice sacs and seeds within the fruit. The second cluster consisted mostly of fingered citrons that lacked locules, juice sacs or seeds, and some non-fingered types with smaller locules and vestigial juice sacs, but with seeds. All accessions that clustered in groups I and II originated in China. The third cluster consisted of citrons cultivated in the Mediterranean region. Genetic distance between the clusters from population structure analysis indicated considerable diversity within the species. A citron-specific microsatellite marker was identified and characterized. We observed considerable heterozygosity in certain citrons, contrary to previous reports.

Virology, 1996

The 3-terminal half of the beet yellow stunt virus (BYSV) genome, 10,545 nt, has been cloned and ... more The 3-terminal half of the beet yellow stunt virus (BYSV) genome, 10,545 nt, has been cloned and sequenced. The sequenced portion of the BYSV genome encompasses 10 open reading frames (ORFs) and 241 nt of the 3 untranslated region. The sequence spans, in the 5 to 3 direction, the C-terminal region of the replication-associated polyprotein gene (ORF 1a) which includes the set of motifs typical of helicases (HEL), the entire 53-kDa polymerase (RdRp) gene (ORF 1b), and genes encoding 30-kDa (ORF 2), 6-kDa (ORF 3), 66-kDa (ORF 4), 61-kDa (ORF 5), 25-kDa (ORF 6), 23.7-kDa (coat protein, CP) (ORF 7), 18-kDa (ORF 8), and 22-kDa (ORF 9) proteins. The double-stranded RNA ''replicative form'' of the BYSV was demonstrated to have a nontemplate G residue at the 3 terminus of the (/) strand. The RdRp of BYSV is presumably expressed via a /1 ribosomal frameshift. The five-gene module conserved among closteroviruses was identified in BYSV; it includes a gene array coding for a 6-kDa small hydrophobic protein, a 66-kDa homolog of the cellular HSP70 heat shock proteins, a 61-kDa protein, and a 25-kDa diverged copy of the CP followed by the CP gene itself. Phylogenetic analysis of the replication-associated HEL and RdRp domains as well as proteins from the five-gene module demonstrated the closest relationship between BYSV and two other closteroviruses, beet yellows (BYV) and citrus tristeza (CTV) viruses. Like CTV, the BYSV genome contains a 30-kDa protein gene between the RdRp and the 6-kDa protein genes, and like BYV it has only two genes downstream of the CP gene. The organization of the BYSV genome appears to be intermediate between BYV and CTV, which suggests that these three viruses might represent three distinct but probably close stages in the closterovirus evolution.

Plant Disease, 1997

Polymerase chain reaction amplification of DNA from various strains of Xylella fastidiosa with tR... more Polymerase chain reaction amplification of DNA from various strains of Xylella fastidiosa with tRNA consensus primers produced three different fingerprint groups. The citrus variegated chlorosis (CVC) and mulberry leaf scorch strains were unique and readily separated from each other and all other strains tested. Internal primers were designed based on the sequence of a DNA fragment unique to the CVC strain. An assay was developed with a mixture of these primers and those reported to detect 18 strains of X. fastidiosa. The assay was used to survey citrus in Brazil. The strain identified to be the cause of CVC was found in constant association with trees with CVC symptoms. On occasion, trees with no symptoms were found to have the CVC strain; this was presumably due to presymptomatic infections. No other strains were found in this survey, and X. fastidiosa was not associated with citrus blight.

Annual Review of Phytopathology, 1989

Annual Reviews tagline graphic. ...

HortScience, 2017

In a Fort Pierce, FL, field planting, plant growth, and Huanglongbing (HLB) severity were assesse... more In a Fort Pierce, FL, field planting, plant growth, and Huanglongbing (HLB) severity were assessed as indicators of HLB tolerance on progenies of 83 seed-source accessions of Citrus and Citrus relatives mainly from the Riverside, CA, genebank. The HLB-associated pathogen [Candidatus Liberibacter asiaticus (CLas)] and vector [asian citrus psyllid (ACP), Diaphorina citri] were abundant, and trees were naturally challenged for 6 years before metrics (leaf mottle, percent canopy mottle, overall health, canopy density, canopy width, canopy height, and trunk diameter) were collected in Oct. and Nov. 2015. The healthiest trees with low or no HLB symptoms were distant citrus relatives: Balsamocitrus dawei, Bergera koenigii, Casimiroa edulis, Clausena excavata, Murraya paniculata, and one accession of Severinia buxifolia. Within Citrus, most of the healthiest trees with densest canopies, little leaf loss, and greater growth were those with pedigrees that included Citrus medica (citron). Thes...

Journal of Citrus Pathology, 2014

Florida Entomologist, 2012

The Asian citrus psyllid, Diaphorina citri Kuwayama, was reported for the first time in Florida i... more The Asian citrus psyllid, Diaphorina citri Kuwayama, was reported for the first time in Florida in June 1998, and huanglongbing (HLB, citrus greening), vectored by D. citri, was detected in Florida for the first time in Aug 2005. In Florida, the only known HLB pathogen is 'Candidatus Liberibacter asiaticus' (Las). After HLB was known to be established in Florida, the psyllid vectors found in regulatory samples from plants for sale were tested for the pathogen by real-time qPCR. Approximately 1,200 regulatory samples were tested between Aug 2005 and Aug 2009. Samples came from venues in 44 of Florida's 67 counties. Most of the samples came from citrus, but about 11% came from Murraya exotica, a popular ornamental plant and close relative of citrus. Approximately 9.7% of the psyllid samples tested were positive for Las. Numbers of samples and proportion of positive samples varied by year and by county.

Florida Entomologist, 2010

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2000

The coat protein gene (CPG) of the citrus tristeza virus (CTV) complex known as Capão Bonito from... more The coat protein gene (CPG) of the citrus tristeza virus (CTV) complex known as Capão Bonito from Pera sweet orange was cloned and sequenced. Results indicated that there are at least two CTV strains in the source plant. These isolates were designated CB3-22 and CB3-104 and they differed in 59 nucleotides which changed 11 amino acids in the coat protein. A dendrogram was generated which grouped isolate CB3-22 with mild isolates and CB3-104 with severe isolates from other countries. In addition, hybridization results also indicated that CB3-104 titer is higher than of CB3-22 in the plant. A discussion of the ramification of these results is discussed. Index words. Capão Bonito CTV complex, 'Pera' sweet orange, coat protein gene.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2005

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 1993

Four isolates of citrus tristeza closterovirus (CTV) from India causing stem pitting and vein fle... more Four isolates of citrus tristeza closterovirus (CTV) from India causing stem pitting and vein flecking symptoms in lime, lemon, citron, sweet orange and grapefruit were used in this study. Two isolates caused severe stem pitting in mandarins, rough lemon and Cleopatra mandarin. The CTV coat protein gene (CPG) was selectively amplified by polymerase chain reaction from infected tissue extracts, cloned into the pUC 118 phagemid vector and sequenced. There was more than 90% similarity at the nucleotide level and above 95% at the deduced amino acid level among the sequences of these isolates. When compared to T36, a severe isolate from Florida, the same amino acid changes were found consistently at seven positions in all four Indian isolates. The coding region of the CPG of isolate B227 was expressed in E. coli BL21 (DE3) pLysS using the pETH3a vector. The identity of the E. coli expressed coat protein (ECP) was confirmed by Western blot analysis using polyclonal antibodies and MCA-13, a monoclonal antibody. Polyclonal antibodies raised against partially purified ECP expressed at 29 C reacted well with ECP and with CTV-infected tissue. The ECP can be produced in large quantities and can serve as a good source of antigen for production of antibodies and for use as a positive control in serological reactions.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2005

Symptoms induced by 266 isolates of Citrus tristeza virus (CTV) obtained from 30 countries were e... more Symptoms induced by 266 isolates of Citrus tristeza virus (CTV) obtained from 30 countries were evaluated in graft-inoculated Mexican lime, sour orange, Madam vinous sweet orange and Duncan grapefruit seedlings, and sweet orange plants budded on sour orange rootstock. Sequential tests were conducted for 16 yr in a USDA-ARS quarantine facility at Beltsville, MD using consistent protocols. Two standard isolates were included in each test for reference. The isolates tested varied markedly in their ability to induce symptoms in specific indicators as well as in the severity of symptoms. The different patterns of symptoms observed in the five indicators suggested that seedling yellows, the decline syndrome in sweet orange grafted on sour orange, stem pitting in sweet orange, and stem pitting in grapefruit are independent expressions of CTV pathogenicity and may occur in various combinations. Although some general associations between some symptoms and CTV genotypes and reaction to the selective monoclonal antibody MCA13 were observed, absolute correlations were not established.

HortScience, 2011

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a key pes... more The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a key pest in most citrus-growing regions worldwide. Adult citrus leafminers oviposit primarily on young elongating flush of Citrus as well as other Rutaceae and some ornamental plants. Larvae feed on the epidermal cell layer of developing leaves and injury to leaves provides a pathway for infection by the bacterium Xanthomonas citri subsp. citri (Hasse), the causal agent of Asiatic citrus canker. In this study, we quantified abundance of citrus leafminer larvae on progeny of 87 seed parent genotypes of Citrus and Citrus relatives (family Rutaceae) in the field in East–central Florida to identify those that have low abundance of leafminers. Progeny from the 87 parent genotypes varied in abundance of the leafminer. Progeny of 15 parent genotypes had a high mean abundance of more than six leafminers per flush shoot. All but one of these genotypes were in the Citrus genus. Progeny of 16 parent genot...

DergiPark (Istanbul University), Mar 1, 2004

The RNA-dependent RNA polymerase (RdRp) gene was first amplified by reverse transcription/polymer... more The RNA-dependent RNA polymerase (RdRp) gene was first amplified by reverse transcription/polymerase chain reaction (RT/PCR) from dsRNA template isolated from citrus leaves infected with citrus tristeza closterovirus (CTV). Then the RdRp was cloned into expression vector and Escherichia coli was transformed with this vector containing the RdRp gene for expression. Analysis of total protein from E. coli by polyacrylamide gel electrophoresis showed that expression of a 60 kDa CTVRdRp protein was induced at 30 min and gradually increased for 3 hr after induction. Further analysis of the protein indicated that the RdRp was not soluble, and found only in the insoluble fractions of the E. coli cells. A polyclonal antiserum was produced by injecting a rabbit with the RdRp protein expressed in E. coli a collecting antiserum from it. Western blot analysis of the total protein from E. coli expressing the RdRp with this antiserum showed that the polyclonal antibody produced was specific to the RdRp of CTV.

Journal of Citrus Pathology, 2014

Plants, 2021

Citrus huanglongbing (HLB) disease associated with the ‘Candidatus Liberibacter asiaticus’ (CLas)... more Citrus huanglongbing (HLB) disease associated with the ‘Candidatus Liberibacter asiaticus’ (CLas) bacterium has caused significant financial damage to many citrus industries. Large-scale pathogen surveys are routinely conducted in California to detect CLas early in the disease cycle by lab-based qPCR assays. We have developed an improved reference gene for the sensitive detection of CLas from plants in diagnostic duplex qPCR and analytical digital droplet PCR (ddPCR) assays. The mitochondrial cytochrome oxidase gene (COX), widely used as a reference, is not ideal because its high copy number can inhibit amplification of small quantities of target genes. In ddPCRs, oversaturation of droplets complicates data normalization and quantification. The variable copy numbers of COX gene in metabolically active young tissue, greenhouse plants, and citrus relatives suggest the need for a non-variable, nuclear, low copy, universal reference gene for analysis of HLB hosts. The single-copy nuclea...

HortScience, 2014

A test population consisting of progenies of 92 seed-source genotypes (hereafter called “parent g... more A test population consisting of progenies of 92 seed-source genotypes (hereafter called “parent genotypes”) of Citrus and Citrus relatives in the field in east–central Florida was assessed after natural freeze events in the winters of 2010 and 2011. Eight seedlings per parent genotype were planted in a randomized complete block design; however, as a result of mortality, the number of plants assessed in some genotype groups was reduced at some or all sampling dates. The citrus diseases huanglongbing and citrus canker were endemic in the planting and may have influenced tree response to cold temperatures. Unusually low temperatures (near –4 °C each winter) for east–central Florida were experienced during the trial period. Defoliation and dieback were significantly greater in the winter of 2011 than in the winter of 2010. The winter in 2011 was preceded by a period of extraordinarily low temperatures in mid-December with no period of cool temperatures to allow trees to acclimate. In 20...

HortScience, 2014

Xanthomonas citri ssp. citri (Xcc) is the causal agent of Asiatic citrus canker (ACC), a commerci... more Xanthomonas citri ssp. citri (Xcc) is the causal agent of Asiatic citrus canker (ACC), a commercially important disease in Florida citrus as well as in many other regions. In this study we evaluated occurrence of foliar lesions from ACC on progenies of 94 seed-source genotypes (hereafter called “parent genotypes”) of Citrus and Citrus relatives in the field in east–central Florida to identify the relative susceptibility to ACC. Eight seedlings per parent genotype were planted in a randomized complete block planting, but the number of plants assessed in some genotype groups was reduced by mortality at some or all sampling dates. Plants experienced ambient exposure to high Xcc inoculum pressure and plants were assessed in Sept. 2010, July 2011, Oct. 2011, May 2012, and Sept. 2012. The incidence and severity of ACC lesions were assessed and evaluated using non-parametric analyses to compare progeny from the 94 parent genotypes. Progeny of 14 parent genotypes did not exhibit ACC symptom...

Plant Cell Reports, 2003

Grapefruit (Citrus paradisi Macf. cv Duncan) plants were transformed with several sequences from ... more Grapefruit (Citrus paradisi Macf. cv Duncan) plants were transformed with several sequences from citrus tristeza closterovirus (CTV) that varied in terms of position in the CTV genome and virus strain origin in an attempt to obtain resistant plants. The sequences included the capsid protein gene from three different strains, a nontranslatable version of the capsid protein gene, the replicase (RdRp), the minor capsid protein (p27), a highly transcribed gene of unknown function (p20) and the more conserved 3′ end of the genomic RNA. Transgenic plants were generated from all of the constructs, except from the p20 and p27 genes. Southern and Western blot analyses demonstrated that stably transformed grapefruit plants were obtained and that at least some transgenes were expressed. In a first effort at virus challenge, 25 transgenic lines were graft inoculated with a severe strain of CTV. Although some transgenic plants averaged lower titers of virus than controls, there was great variability in titer in both controls and transgenic plants, and all were apparently susceptible to the virus.

Scientia Horticulturae, 2015

Citron (Citrus medica L.) is one of the three basic species of the genus Citrus L. that have cont... more Citron (Citrus medica L.) is one of the three basic species of the genus Citrus L. that have contributed to the development of cultivated citrus. We analyzed the genetic diversity of 47 citrons (32 from Yunnan Province, China; and 15 of Mediterranean origin) to understand their diversity and relationships within the species. Genetic analysis was conducted using data from microsatellite markers, single nucleotide polymorphisms generated from sequences of a nuclear malate dehydrogenase gene and a chloroplast gene, rps16. Neighbor joining and maximum parsimony analyses were conducted. All three approaches found citron to be monophyletic. Population structure analysis clustered the 47 citrons into three distinct groups. The first group consisted of wild, non-fingered citrons generally having locules, juice sacs and seeds within the fruit. The second cluster consisted mostly of fingered citrons that lacked locules, juice sacs or seeds, and some non-fingered types with smaller locules and vestigial juice sacs, but with seeds. All accessions that clustered in groups I and II originated in China. The third cluster consisted of citrons cultivated in the Mediterranean region. Genetic distance between the clusters from population structure analysis indicated considerable diversity within the species. A citron-specific microsatellite marker was identified and characterized. We observed considerable heterozygosity in certain citrons, contrary to previous reports.

Virology, 1996

The 3-terminal half of the beet yellow stunt virus (BYSV) genome, 10,545 nt, has been cloned and ... more The 3-terminal half of the beet yellow stunt virus (BYSV) genome, 10,545 nt, has been cloned and sequenced. The sequenced portion of the BYSV genome encompasses 10 open reading frames (ORFs) and 241 nt of the 3 untranslated region. The sequence spans, in the 5 to 3 direction, the C-terminal region of the replication-associated polyprotein gene (ORF 1a) which includes the set of motifs typical of helicases (HEL), the entire 53-kDa polymerase (RdRp) gene (ORF 1b), and genes encoding 30-kDa (ORF 2), 6-kDa (ORF 3), 66-kDa (ORF 4), 61-kDa (ORF 5), 25-kDa (ORF 6), 23.7-kDa (coat protein, CP) (ORF 7), 18-kDa (ORF 8), and 22-kDa (ORF 9) proteins. The double-stranded RNA ''replicative form'' of the BYSV was demonstrated to have a nontemplate G residue at the 3 terminus of the (/) strand. The RdRp of BYSV is presumably expressed via a /1 ribosomal frameshift. The five-gene module conserved among closteroviruses was identified in BYSV; it includes a gene array coding for a 6-kDa small hydrophobic protein, a 66-kDa homolog of the cellular HSP70 heat shock proteins, a 61-kDa protein, and a 25-kDa diverged copy of the CP followed by the CP gene itself. Phylogenetic analysis of the replication-associated HEL and RdRp domains as well as proteins from the five-gene module demonstrated the closest relationship between BYSV and two other closteroviruses, beet yellows (BYV) and citrus tristeza (CTV) viruses. Like CTV, the BYSV genome contains a 30-kDa protein gene between the RdRp and the 6-kDa protein genes, and like BYV it has only two genes downstream of the CP gene. The organization of the BYSV genome appears to be intermediate between BYV and CTV, which suggests that these three viruses might represent three distinct but probably close stages in the closterovirus evolution.

Plant Disease, 1997

Polymerase chain reaction amplification of DNA from various strains of Xylella fastidiosa with tR... more Polymerase chain reaction amplification of DNA from various strains of Xylella fastidiosa with tRNA consensus primers produced three different fingerprint groups. The citrus variegated chlorosis (CVC) and mulberry leaf scorch strains were unique and readily separated from each other and all other strains tested. Internal primers were designed based on the sequence of a DNA fragment unique to the CVC strain. An assay was developed with a mixture of these primers and those reported to detect 18 strains of X. fastidiosa. The assay was used to survey citrus in Brazil. The strain identified to be the cause of CVC was found in constant association with trees with CVC symptoms. On occasion, trees with no symptoms were found to have the CVC strain; this was presumably due to presymptomatic infections. No other strains were found in this survey, and X. fastidiosa was not associated with citrus blight.

Annual Review of Phytopathology, 1989

Annual Reviews tagline graphic. ...

HortScience, 2017

In a Fort Pierce, FL, field planting, plant growth, and Huanglongbing (HLB) severity were assesse... more In a Fort Pierce, FL, field planting, plant growth, and Huanglongbing (HLB) severity were assessed as indicators of HLB tolerance on progenies of 83 seed-source accessions of Citrus and Citrus relatives mainly from the Riverside, CA, genebank. The HLB-associated pathogen [Candidatus Liberibacter asiaticus (CLas)] and vector [asian citrus psyllid (ACP), Diaphorina citri] were abundant, and trees were naturally challenged for 6 years before metrics (leaf mottle, percent canopy mottle, overall health, canopy density, canopy width, canopy height, and trunk diameter) were collected in Oct. and Nov. 2015. The healthiest trees with low or no HLB symptoms were distant citrus relatives: Balsamocitrus dawei, Bergera koenigii, Casimiroa edulis, Clausena excavata, Murraya paniculata, and one accession of Severinia buxifolia. Within Citrus, most of the healthiest trees with densest canopies, little leaf loss, and greater growth were those with pedigrees that included Citrus medica (citron). Thes...

Journal of Citrus Pathology, 2014

Florida Entomologist, 2012

The Asian citrus psyllid, Diaphorina citri Kuwayama, was reported for the first time in Florida i... more The Asian citrus psyllid, Diaphorina citri Kuwayama, was reported for the first time in Florida in June 1998, and huanglongbing (HLB, citrus greening), vectored by D. citri, was detected in Florida for the first time in Aug 2005. In Florida, the only known HLB pathogen is 'Candidatus Liberibacter asiaticus' (Las). After HLB was known to be established in Florida, the psyllid vectors found in regulatory samples from plants for sale were tested for the pathogen by real-time qPCR. Approximately 1,200 regulatory samples were tested between Aug 2005 and Aug 2009. Samples came from venues in 44 of Florida's 67 counties. Most of the samples came from citrus, but about 11% came from Murraya exotica, a popular ornamental plant and close relative of citrus. Approximately 9.7% of the psyllid samples tested were positive for Las. Numbers of samples and proportion of positive samples varied by year and by county.

Florida Entomologist, 2010

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2000

The coat protein gene (CPG) of the citrus tristeza virus (CTV) complex known as Capão Bonito from... more The coat protein gene (CPG) of the citrus tristeza virus (CTV) complex known as Capão Bonito from Pera sweet orange was cloned and sequenced. Results indicated that there are at least two CTV strains in the source plant. These isolates were designated CB3-22 and CB3-104 and they differed in 59 nucleotides which changed 11 amino acids in the coat protein. A dendrogram was generated which grouped isolate CB3-22 with mild isolates and CB3-104 with severe isolates from other countries. In addition, hybridization results also indicated that CB3-104 titer is higher than of CB3-22 in the plant. A discussion of the ramification of these results is discussed. Index words. Capão Bonito CTV complex, 'Pera' sweet orange, coat protein gene.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2005

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 1993

Four isolates of citrus tristeza closterovirus (CTV) from India causing stem pitting and vein fle... more Four isolates of citrus tristeza closterovirus (CTV) from India causing stem pitting and vein flecking symptoms in lime, lemon, citron, sweet orange and grapefruit were used in this study. Two isolates caused severe stem pitting in mandarins, rough lemon and Cleopatra mandarin. The CTV coat protein gene (CPG) was selectively amplified by polymerase chain reaction from infected tissue extracts, cloned into the pUC 118 phagemid vector and sequenced. There was more than 90% similarity at the nucleotide level and above 95% at the deduced amino acid level among the sequences of these isolates. When compared to T36, a severe isolate from Florida, the same amino acid changes were found consistently at seven positions in all four Indian isolates. The coding region of the CPG of isolate B227 was expressed in E. coli BL21 (DE3) pLysS using the pETH3a vector. The identity of the E. coli expressed coat protein (ECP) was confirmed by Western blot analysis using polyclonal antibodies and MCA-13, a monoclonal antibody. Polyclonal antibodies raised against partially purified ECP expressed at 29 C reacted well with ECP and with CTV-infected tissue. The ECP can be produced in large quantities and can serve as a good source of antigen for production of antibodies and for use as a positive control in serological reactions.

International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2005

Symptoms induced by 266 isolates of Citrus tristeza virus (CTV) obtained from 30 countries were e... more Symptoms induced by 266 isolates of Citrus tristeza virus (CTV) obtained from 30 countries were evaluated in graft-inoculated Mexican lime, sour orange, Madam vinous sweet orange and Duncan grapefruit seedlings, and sweet orange plants budded on sour orange rootstock. Sequential tests were conducted for 16 yr in a USDA-ARS quarantine facility at Beltsville, MD using consistent protocols. Two standard isolates were included in each test for reference. The isolates tested varied markedly in their ability to induce symptoms in specific indicators as well as in the severity of symptoms. The different patterns of symptoms observed in the five indicators suggested that seedling yellows, the decline syndrome in sweet orange grafted on sour orange, stem pitting in sweet orange, and stem pitting in grapefruit are independent expressions of CTV pathogenicity and may occur in various combinations. Although some general associations between some symptoms and CTV genotypes and reaction to the selective monoclonal antibody MCA13 were observed, absolute correlations were not established.

HortScience, 2011

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a key pes... more The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a key pest in most citrus-growing regions worldwide. Adult citrus leafminers oviposit primarily on young elongating flush of Citrus as well as other Rutaceae and some ornamental plants. Larvae feed on the epidermal cell layer of developing leaves and injury to leaves provides a pathway for infection by the bacterium Xanthomonas citri subsp. citri (Hasse), the causal agent of Asiatic citrus canker. In this study, we quantified abundance of citrus leafminer larvae on progeny of 87 seed parent genotypes of Citrus and Citrus relatives (family Rutaceae) in the field in East–central Florida to identify those that have low abundance of leafminers. Progeny from the 87 parent genotypes varied in abundance of the leafminer. Progeny of 15 parent genotypes had a high mean abundance of more than six leafminers per flush shoot. All but one of these genotypes were in the Citrus genus. Progeny of 16 parent genot...