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Papers by Robert Stall

Frontiers in Plant Science, May 19, 2023

Phytopathology®, 1998

Until recently, tomato race 1 (T1) of Xanthomonas campestris pv. vesicatoria was the only race ca... more Until recently, tomato race 1 (T1) of Xanthomonas campestris pv. vesicatoria was the only race causing bacterial spot of tomato in Florida. In 1991, tomato race 3 (T3) was first identified in 3 of 13 tomato production fields surveyed. By 1994, T3 was observed in 21 of 28 fields and was the only race identified in 14 fields. In field studies, tomato genotypes with resistance to either T1 or T3 or susceptibility to both were co-inoculated with strains of both races. Lesions on 10 plants in each of three replications for each genotype were sampled three times during the experiment; bacterial isolations were made from each lesion, and tomato race identifications were made for each strain. At the third sampling date, T3 was isolated from 97% of the lesions on the susceptible genotype Walter and the T1-resistant genotype Hawaii 7998, while T3 was isolated from 23% of the lesions and T1 from the remaining 77% on the T3-resistant genotypes PI 128216 and PI 126932. In surface population stud...

EDIS

Bs2 tomatoes are transgenic tomatoes that have been engineered to contain the Bs2 gene from peppe... more Bs2 tomatoes are transgenic tomatoes that have been engineered to contain the Bs2 gene from pepper. As such, they are considered a genetically modified (GM) food, or a genetically modified organism (GMO). Numerous trials conducted by University of Florida researchers have shown the benefits of these cultivars for bacterial spot disease management, and growers and industry members recognize the potential for Bs2 tomatoes to make Florida tomato production more sustainable. This 4-page fact sheet discusses the benefits that might be realized by the adoption of Bs2 tomato varieties, and the challenges standing in the way of their commercial production. Written by S. F. Hutton, J. W. Scott, J. B. Jones, R. E. Stall, G. E. Vallad, B. J. Staskawicz, and D. M. Horvath , and published by the UF Department of Horticultural Sciences, April 2015. HS1259/HS1259: The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes (ufl.edu)

Molecular Plant-Microbe Interactions®, 2012

A novel hypersensitive resistance (HR) in Capsicum baccatum var. pendulum against the bacterial s... more A novel hypersensitive resistance (HR) in Capsicum baccatum var. pendulum against the bacterial spot of pepper pathogen, Xanthomonas gardneri, was introgressed into C. annuum cv. Early Calwonder (ECW) to create the near-isogenic line designated as ECW-70R. A corresponding avirulence gene avrBs7, in X. gardneri elicited a strong HR in ECW-70R. A homolog of avrBs7, avrBs1.1, was found in X. euvesicatoria 85-10, which showed delayed HR on ECW-70R leaves. Genetic analysis confirmed the presence of a single dominant resistance gene, Bs7, corresponding to the two avr genes. Both AvrBs7 and AvrBs1.1 share a consensus protein tyrosine phosphatase (PTP) active site domain and can dephosphorylate para-nitrophenyl phosphate. Mutation of Cys(265) to Ser in the PTP domain and subsequent loss of enzymatic activity and HR activity indicated the importance of the PTP domain in the recognition of the Avr protein by the Bs7 gene transcripts. Superpositioning of AvrBs7 and AvrBs1.1 homology models ind...

Molecular Plant Pathology, Mar 1, 2009

Phytopathology, 1990

... 2, Lane C). ABCD ABCD i M i 1 п <4.9 Fig. ... Although no definite associations were o... more ... 2, Lane C). ABCD ABCD i M i 1 п <4.9 Fig. ... Although no definite associations were observed between streptomycin resistance and host, year of isolation, or plasmid profile among strains from Florida and other ABCDEFG ABCDEFG ■at *ïg.3. Hybridization of the4.9-kb u-oRI ...

Plant Disease, 1996

DISCUSSION Leite et al. (12) used the sequence variation within the hrpB operon among plant-patho... more DISCUSSION Leite et al. (12) used the sequence variation within the hrpB operon among plant-pathogenic xanthomonads to select primers with different specificities, and this approach was successful in our studies to identify primers specific to X. fragariae. The Аф-primers ...

International Journal of Systematic and Evolutionary Microbiology, 2000

Annual Review of Phytopathology, 1998

▪ Xanthomonas campestris pv. vesicatoria, causal agent of bacterial spot of tomato and pepper, ... more ▪ Xanthomonas campestris pv. vesicatoria, causal agent of bacterial spot of tomato and pepper, had been considered for nearly 70 years to be a relatively homogeneous organism. However, in the past decade this bacterium was determined to be composed of two genetically and phenotypically distinct groups. The two groups, designated A and B, were distinguished based on amylolytic activity, expression of unique protein bands, reaction on differential hosts (tomato races T1 and T2), reaction patterns with monoclonal antibodies, DNA restriction profiles, and DNA:DNA hybridization. The A and B groups were placed into X. axonopodis pv. vesicatoria and X. vesicatoria, respectively. A third group, designated C, was pathogenically (race T3) and serologically distinct from A and B strains, and formed unique DNA restriction profiles. DNA:DNA hybridization data suggest that C is distinct but related to A strains and may represent a subspecies of A. A final group, designated D, consisted of X. ga...

Applied and Environmental Microbiology, 1994

The hrp gene cluster of strains of Xanthomonas campestris that cause diseases of citrus was exami... more The hrp gene cluster of strains of Xanthomonas campestris that cause diseases of citrus was examined by Southern hybridization of genomic DNA and by restriction endonuclease analysis of enzymatically amplified DNA fragments of the hrp gene cluster. The hrp genes were present in all strains of the pathovars of X. campestris tested in this study, including strains of the three aggressiveness groups of the citrus bacterial spot pathogen, X. campestris pv. citrumelo. X. campestris pv. citri strains in groups A, B, and C, which cause citrus canker A, B, and C, respectively, each produced characteristic restriction banding patterns of amplified hrp fragments. The restriction banding patterns of all strains within each group were identical. In contrast, restriction fragment length polymorphism was evident among strains of the moderately and weakly aggressive groups of X. campestris pv. citrumelo. X. campestris pv. citrumelo strains in the highly aggressive group had a homogeneous restricti...

HortScience, 1995

Tomato (Lycopersicon esculentum Mill.) accessions were tested for hypersensitivity and rated for ... more Tomato (Lycopersicon esculentum Mill.) accessions were tested for hypersensitivity and rated for resistance following field inoculation with tomato race 3 (T3) of the bacterial spot pathogen Xanthomonas campestris pv. vesicatoria (Doidge) Dye (Xcv) in 1992 and 1993. Hawaii 7981, PI 126932, PI 128216, and selections of the latter two expressed hypersensitivity. Hawaii 7981, only tested in the field in 1993, was nearly symptomless and developed significantly less disease than any other accession. PI 128216 had a level of disease similar to susceptible `Solar Set' when tested in 1993. However, a selection from it (PI 126218-S) was significantly more resistant than `Solar Set' in both years. Although PI 126932 had a level of disease similar to `Solar Set' in both years, a selection from it (PI 126932-1-2) was significantly more resistant than `Solar Set' in 1993. Other accessions without hypersensitive responses but more resistant than `Solar Set' for two seasons wer...

Bacterial spot caused by Xanthomonas euvesicatoria is a major disease of pepper (Capsicum annuum ... more Bacterial spot caused by Xanthomonas euvesicatoria is a major disease of pepper (Capsicum annuum L.) in warm and humid production environments. Use of genetically resistant cultivars is an effective approach to manage bacterial spot. Two recessive resistance genes, bs5 and bs6, confer non-race-specific resistance against bacterial spot. The objective of our study was to map these two loci in the pepper genome. We used a genotyping-by-sequencing approach to initially map the position of the two resistances. Segregant populations for bs5 and bs6 were developed by crossing susceptible Early CalWonder (ECW) with near-isogenic lines ECW50R (bs5 introgression) or ECW60R (bs6 introgression). Following fine-mapping, bs5 was delimited to a ~535 Kbp interval on chromosome 3, and bs6 to a ~666 Kbp interval in chromosome 6 of pepper. We also identified 14 and 8 candidate resistance genes for bs5 and bs6, respectively, based on predicted protein coding polymorphisms between ECW and the correspon...

HortScience

Bell pepper (Capsicum anuum L.) leaves inoculated with Race 1 of Xanthomonas campestris pv. vesic... more Bell pepper (Capsicum anuum L.) leaves inoculated with Race 1 of Xanthomonas campestris pv. vesicatoria (XCV) produced more ethylene and methanol than water-infiltrated controls in studies with leaves attached or detached during inoculation and dissipation of water-soaking. `Early Calwonder 20R'. a pepper genotype resistant to Race 1 of XCV, evolved more ethylene and methanol than `Early Calwonder 10R' (susceptible) following syringe inoculation of detached leaves with ≈ 7 × 107 cells/ml. A light intensity of ≈ 500 μmol· m-2·s-1 during dissipation of water-soaking of attached leaves triggered more ethylene and methanol than covering inoculated leaves with aluminum foil. Volatile hydrocarbon production from leaves infiltrated with distilled water was not significantly affected by light intensity during dissipation of water-soaking. The lipid peroxidation products, ethane and pentane, were not detected by headspace sampling following bacterial inoculation.

Phytopathology, Jan 20, 2018

Field trials were conducted at two locations in Florida to evaluate transgenic tomatoes expressin... more Field trials were conducted at two locations in Florida to evaluate transgenic tomatoes expressing the EFR gene from Arabidopsis thaliana, the Bs2 gene from pepper, or both Bs2/EFR for managing bacterial wilt caused by Ralstonia solanacearum and bacterial spot caused by Xanthomonas perforans. Expression of EFR or Bs2/EFR, in the susceptible genotype, Fla. 8000, significantly reduced bacterial wilt incidence (50-100%) and increased total yield (57-114%) relative to lines expressing only Bs2 or non-transformed Fla. 8000 control, although the marketable yield was not significantly affected. Following harvest, surviving symptomatic and non-symptomatic plants were assessed for colonization by R. solanacearum. There were no significant differences in the population at the lower stem. Interestingly, in the middle stem, no bacteria could be recovered from EFR or Bs2/EFR lines, but viable bacterial populations were recovered from Bs2 and non-transformed control lines at 10-10 colony forming ...

International Journal of Systematic Bacteriology