Abstract
In March 1998, a leaf blight of onion (Allium cepa L. ‘1015’) was found on many plants in a plot on the Texas A&M Agricultural Experiment Station in Weslaco. The symptoms were longitudinal chlorotic areas on one side of the leaf, containing sunken, elliptical necrotic lesions. Affected leaves ultimately died. Chlorotic lesions were swabbed with 70% ethanol, and tissue from beneath the epidermis was placed in a drop sterile water for 20 min. Drops were streaked on nutrient agar and incubated at 30°C. Isolations yielded gram-negative, rod-shaped bacteria that formed dark yellow, gummy colonies on yeast dextrose carbonate agar medium, hydrolyzed starch, and had a single, polar flagellum. Analysis of fatty acid methyl ester (FAME) profiles, using the Microbial Identification System (MIS, version 4.15; Microbial Identification, Newark, DE), done at the Texas Plant Disease Diagnostic Laboratory, College Station, identified nine isolates as Xanthomonas campestris (similarity indices of 0.31 to 0.54). Tests at the University of Florida supported this identification: FAME profiles using MIS version 3.9 gave similarity indices of 0.89 to 0.95, and profiles using Biolog GN Microplates, MicroLog database release 3.50 (Biolog, Hayward, CA), gave similarity indices of 0.03 to 0.76. Leaves (15 to 20 cm long) of potted onions (cv. 1015 at the five- to six-leaf stage) were infiltrated with a suspension of bacteria (10 7 CFU per ml), using a needle and syringe. Plants were maintained in mist chamber in a greenhouse at 24°C. Water-soaking and development of pale green color of the inoculated leaf occurred after 2 days, followed by death after 4 days. There were no symptoms on leaves inoculated with sterile water. Pathogenicity tests on four isolates were repeated once. Bacteria were reisolated on nutrient agar from symptomatic tissue but not from controls. In the field plot, disease severity did not increase as season progressed nor were there any symptoms on bulbs. Symptoms were not observed on onion during the 1999 season. X. campestris was first reported on onion from Hawaii (1). This is the first report of this pathogen on onion in the continental United States. Reference: (1) A. M. Alvarez et al. Phytopathology 68:1132, 1978.
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Claims 8
Claim · model-written summary
Onion plants in a Weslaco plot had leaf blight with chlorotic and necrotic lesions, and affected leaves died.
Not reportedInteractorInteractor role
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a leaf blight of onion (Allium cepa L. ‘1015’) was found on many plants in a plot on the Texas A&M Agricultural Experiment Station in Weslaco”
e1“The symptoms were longitudinal chlorotic areas on one side of the leaf, containing sunken, elliptical necrotic lesions. Affected leaves ultimately died.”
Claim · model-written summary
Nine bacterial isolates from onion lesions were identified as Xanthomonas campestris.
- Interactor
- Xanthomonas campestris
_(25868012152).jpg?width=60)
Xanthomonas campestrise0pathogen - Outcome
- nine isolatese0
- Value
- nine isolatese0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_(25868012152).jpg?width=500)
Verbatim
e0“identified nine isolates as Xanthomonas campestris (similarity indices of 0.31 to 0.54)”
Claim · model-written summary
Bacterial infiltration produced water soaking and pale green color in onion leaves after two days, followed by death after four days.
- Taxon
- onions
Allium cepae0 - Material
- 1015e0
- Treatment
- infiltrated with a suspension of bacteriae0
- Outcome
- Water-soaking and development of pale green colore1
- Direction
- occurrede1
- Qualifier
- after 2 dayse1
- Comparator
- sterile watere1
Not reportedInteractorInteractor role
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaves (15 to 20 cm long) of potted onions (cv. 1015 at the five- to six-leaf stage) were infiltrated with a suspension of bacteria (10 7 CFU per ml)”
e1“Water-soaking and development of pale green color of the inoculated leaf occurred after 2 days, followed by death after 4 days. There were no symptoms on leaves inoculated with sterile water.”
Claim · model-written summary
Bacteria were reisolated from symptomatic onion tissue but not controls.
Not reportedTaxon
Verbatim
e0“Bacteria were reisolated on nutrient agar from symptomatic tissue but not from controls.”
Claim · model-written summary
Field disease severity did not increase as the season progressed.
Not reportedTaxon
Verbatim
e0“In the field plot, disease severity did not increase as season progressed”
Claim · model-written summary
No onion bulb symptoms occurred in the field plot.
Not reportedTaxon
Verbatim
e0“nor were there any symptoms on bulbs”
Claim · model-written summary
Onion symptoms were not observed in the 1999 season.
- Taxon
- onionAllium cepae0
- Outcome
- Symptomse0
- Direction
- not observede0
- Qualifier
- 1999 seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Symptoms were not observed on onion during the 1999 season.”
Claim · model-written summary
This was the first report of X. campestris on onion in the continental United States.
- Taxon
- onionAllium cepae0
- Interactor
- Xanthomonas campestrisXanthomonas campestrist0pathogen
- Outcome
- first reporte0
- Setting
- continental United Statese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is the first report of this pathogen on onion in the continental United States.”
t0“First Report of Leaf Blight of Onion Caused by Xanthomonas campestris in the Continental United States”
The same questions in other papers
inoculation · quality: postharvest · Allium cepa (onion)Positive and negative results
4 papers in the same direction as this paper · 7 in the opposite direction
- positive
- positive
- positive
8 papers more in this group
See all 12 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.