Abstract
In July 2013, a melon plant sample (Cucumis melo cv. Saski) with disease symptoms resembling bacterial fruit blotch (BFB), was collected from a 10-acre field located in Yolo County, California, and submitted to the Plant Pest Diagnostics Center of the CDFA. Melon leaves had small (5 to 10 mm in diameter), tan to dark reddish-brown, angular lesions surrounded by yellow halos, and larger V-shaped lesions that extended from the leaf margins to the midrib. Bacterial streaming was observed at 400× magnification. The bacterium isolated from a leaf tissue wet mount formed smooth, round, cream-colored, non-fluorescent colonies on Pseudomonas F agar, was gram-negative, rod-shaped, aerobic, and oxidase-positive. The strain grew at 41°C and produced a strong hypersensitive response on tobacco (Nicotiana tabacum) 24 h after tissue infiltration. Based on a positive immunoassay test for Acidovorax citrulli (Eurofins STA Lab, Inc., Longmont, CO) and positive real-time PCR assays using species-specific primer sets, BX-L1/BX-S-R2 (1) and ZUP2436/2437 (4), the strain was identified as A. citrulli. A 360-bp fragment of the 16S ribosomal RNA gene was amplified using conventional PCR with primers WFB1 and WFB2 (3). The fragment, GenBank Accession No. KJ531595, showed 100% identity with the corresponding regions of A. citrulli (CP000512) strain AAC00-1 by BLAST query. Pathogenicity tests were performed by injecting 0.5 to 1 ml suspensions of the bacteria (10 6 CFU/ml) under the rind of three mature honeydew fruit (Cucumis melo var. indorus), three watermelon fruit (Citrullus lanatus cv. Sugar Baby), and into the cotyledons of ten, 10-day-old watermelon seedlings (cv. Sugar Baby). The fruit and seedlings were incubated in plastic bags at 30°C and similar treatments with sterile water served as negative controls. After 4 days, the seedlings inoculated with the suspect strain exhibited dark brown necrotic lesions with yellow halos that later coalesced, causing the cotyledons to collapse. Seven days after inoculation, the honeydew fruit exhibited dry, rotten gray cavities (4 to 6 cm in diameter) in the pericarp tissue below the rind. In contrast, the watermelon fruit had completely collapsed in a watery rot after 7 days. No symptoms were observed on the negative control fruits and seedlings treated with water. The pathogen was re-isolated from the inoculated fruit and seedlings and confirmed as A. citrulli by species-specific PCR and immunoassay as described above. The melon seed lot used to plant the field in Yolo County, CA, also tested positive for A. citrulli using species-specific real-time PCR assays (1,4). DNA fingerprinting by pulse field gel electrophoresis of Spe I-digested whole cell genomic DNA showed that all of the California A. citrulli strains were members of subgroup II (haplotype C strain) (3). These haplotypes normally occur on watermelon. BFB is a seed-transmitted disease of cucurbits and a major concern for national and global seed trade. First observed in United States commercial watermelon fields in 1989, BFB can cause economic losses up to 90% for commercial watermelon, cantaloupe, and honeydew growers (1,2). While BFB routinely occurs in the southeastern United States, this is the first official record of the disease in California. References: (1) O. Bahar et al. Plant Pathol. 57:754, 2008. (2) R. Walcott et al. J. Phytopathol. 152:277, 2004. (3) R. Walcott et al. Plant Dis. 84:470, 2000. (4) B. Woudt et al. Phytopathology 99:S143, 2009.
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Claims 9
Claim · model-written summary
A California melon sample showed angular and V-shaped leaf lesions.
- Taxon
- Melon
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Cucumis meloe0 - Outcome
- angular lesions surrounded by yellow halos, and larger V-shaped lesionse0
- Setting
- Yolo County, Californiae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Melon leaves had small (5 to 10 mm in diameter), tan to dark reddish-brown, angular lesions surrounded by yellow halos, and larger V-shaped lesions that extended from the leaf margins to the midrib”
e1“Yolo County, California”
Claim · model-written summary
The isolated strain was identified as A. citrulli by immunoassay and PCR.
- Taxon
- melonCucumis meloe2
- Interactor
- Acidovorax citrulliParacidovorax citrullie0pathogen
- Outcome
- strain was identified as A. citrullie1
- Value
- positivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“positive immunoassay test for Acidovorax citrulli”
e1“positive real-time PCR assays using species-specific primer sets, BX-L1/BX-S-R2 (1) and ZUP2436/2437 (4), the strain was identified as A. citrulli”
e2“melon plant sample”
Claim · model-written summary
The 16S fragment matched an A. citrulli reference at 100% identity.
- Taxon
- melonCucumis meloe1
- Interactor
- A. citrulliParacidovorax citrullie0pathogen
- Outcome
- identity with the corresponding regions of A. citrullie0
- Value
- 100%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“showed 100% identity with the corresponding regions of A. citrulli (CP000512) strain AAC00-1”
e1“melon plant sample”
Claim · model-written summary
Inoculated watermelon seedlings developed necrotic lesions and collapsed cotyledons.
- Taxon
- watermelon
Citrullus lanatuse1 - Material
- cv. Sugar Babye1
- Treatment
- inoculated with the suspect straine0
- Interactor
- A. citrulliParacidovorax citrullie3pathogen
- Outcome
- dark brown necrotic lesions with yellow halose0
- Comparator
- negative controlse2
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seedlings inoculated with the suspect strain exhibited dark brown necrotic lesions with yellow halos that later coalesced, causing the cotyledons to collapse”
e1“watermelon seedlings (cv. Sugar Baby)”
e2“negative controls”
e3“confirmed as A. citrulli by species-specific PCR”
Claim · model-written summary
Inoculated honeydew fruit developed dry rotten cavities.
- Taxon
- honeydew
Cucumis melo var. inodoruse0 - Treatment
- inoculatione2
- Interactor
- A. citrulliParacidovorax citrullie3pathogen
- Outcome
- dry, rotten gray cavitiese0
- Value
- 4 to 6 cme0
- Comparator
- negative control fruitse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“honeydew fruit exhibited dry, rotten gray cavities (4 to 6 cm in diameter) in the pericarp tissue below the rind”
e1“negative control fruits”
e2“inoculation”
e3“confirmed as A. citrulli by species-specific PCR”
Claim · model-written summary
Inoculated watermelon fruit collapsed in watery rot.
- Taxon
- watermelonCitrullus lanatuse0
- Treatment
- inoculatione2
- Interactor
- A. citrulliParacidovorax citrullie3pathogen
- Outcome
- completely collapsed in a watery rote0
- Comparator
- negative control fruitse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“watermelon fruit had completely collapsed in a watery rot after 7 days”
e1“negative control fruits”
e2“inoculation”
e3“confirmed as A. citrulli by species-specific PCR”
Claim · model-written summary
The melon seed lot tested positive for A. citrulli.
- Taxon
- melonCucumis meloe0
- Interactor
- A. citrulliParacidovorax citrullie1pathogen
- Outcome
- tested positive for A. citrullie0
- Setting
- Yolo County, CAe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“melon seed lot used to plant the field in Yolo County, CA, also tested positive for A. citrulli”
e1“positive for A. citrulli using species-specific real-time PCR assays”
Claim · model-written summary
California A. citrulli strains were subgroup II haplotype C.
- Taxon
- melonCucumis meloe1
- Interactor
- A. citrulliParacidovorax citrullie0pathogen
- Outcome
- subgroup II (haplotype C strain)e0
- Setting
- Californiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“all of the California A. citrulli strains were members of subgroup II (haplotype C strain)”
e1“melon seed lot”
Claim · model-written summary
The authors report the first official record of bacterial fruit blotch in California.
- Taxon
- melonCucumis meloe2
- Outcome
- first official record of the diseasee0
- Setting
- Californiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this is the first official record of the disease in California”
e1“BFB is a seed-transmitted disease of cucurbits”
e2“melon plant sample”
The same questions in other papers
inoculation · Paracidovorax citrulli · Citrullus lanatus (watermelon)Positive and negative results
4 papers in the same direction as this paper · 2 in the opposite direction
- positive
- positive
- negative
3 papers more in this group
See all 7 papers →inoculation · Paracidovorax citrulli · Cucumis melo (muskmelon)Results agree
1 paper in the same direction as this paper
- no effect
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.