Abstract
In 2014, a leaf blight of cilantro was observed in two commercial fields in Ventura Co., CA. Symptoms included water-soaked lesions 5 to 10 mm dia that became necrotic and coalesced with age to consume entire leaves. The following year, six nearby fields were affected. Damage in these fields was estimated at 15 to 50% incidence making symptomatic cilantro unmarketable. In 2017, the disease was observed in 2 fields in Monterey Co., CA. Concurrent reports of Alternaria dauci on cilantro in Florida with similar symptoms (Poudel & Zhang 2018) suggested a similar etiology. However, continued occurrence from 2017 to 2024 revealed characteristics distinct from A. dauci, so further studies were conducted. Fungi were recovered from original diseased cilantro on potato dextrose agar (PDA) using standard mycological techniques. Ten single-spored isolates were incubated on potato carrot agar (PCA) for production of spores used for morphometrics and for pathogenicity testing. Also cultured were the representative strain of A. poonensis, EGS 47-138 (Simmons 2007), first reported as causal agent of cilantro leaf blight in India (Raghunath 1963), and 5 strains of A. dauci isolated from carrot in Monterey Co. On PDA, all cilantro isolates produced light gray colonies and a diffusible maroon pigment in the medium. All A. dauci isolates produced light gray colonies and a diffusible violet pigment. On PCA, spore dimensions were obtained from 20 mature conidia per isolate. Mean spore dimensions (length X width) for the CA cilantro isolates, A. poonensis, and A. dauci isolates were 57.5 X 20.3, 56.0 X 19.6, and 88.4 X 21.8, um, respectively. Mean beak lengths were 158, 152, and 170 um, respectively. To assess pathogenicity, isolates were tested on cilantro (cv Slow Bolt) and carrot (cv Short N Sweet). Seeds were sown in potting soil in a greenhouse and thinned to 5 plants per 10 cm pot. Spore solutions were prepared by flooding PCA plates with sterile H2O, then adjusting the spore solution to 4 x 104 conidia/ml. At 5 to 6 leaf stage, plants were sprayed with solutions until runoff, enclosed in plastic bags for 24 hr, then misted intermittently for 10 d. After 10 d, the foliar area diseased (FAD) on cilantro ranged from 30 to 70% for cilantro isolates and 0 to 3% for A. dauci isolates. In contrast, the FAD on carrot ranged from 0 to 3% for cilantro isolates and 60 to 80% for A. dauci isolates. Control plants sprayed with water remained healthy. The fungus was re-isolated from inoculated cilantro to fulfill Koch´s postulates. Disease symptoms, culture characteristics, and pathogenicity were similar to A. poonensis (Raghunath 1963, 1969). DNA was extracted from each isolate and the allergen Alt a1 and calmodulin genes were sequenced using established procedures (Lawrence et al. 2013). Representative sequences were deposited in GenBank. For Alt a1, cilantro isolates had 100% identity (435/435 bp) and differed by 1 bp from A. dauci isolates, which had 100% identity (accessions OR763779 and OR763781, respectively). For calmodulin, cilantro isolates had 100% identity (593/593 bp) and differed by 3 bp from A. dauci isolates, which had 100% sequence identity (accessions OR763786 and OR763788, respectively). This is the first report of A. poonensis on cilantro in the United States. Because of high quality standards, this disease limits production. Alternaria leaf spot also creates diagnostic challenges because symptoms are similar to common bacterial leaf spot caused by Pseudomonas syringae (Cooksey et al. 1991).
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Claims 19
Claim · model-written summary
Leaf blight occurred in two Ventura County commercial cilantro fields in 2014.
- Taxon
- cilantro
Coriandrum sativumt0 - Outcome
- leaf blight of cilantroe0
- Setting
- Ventura Co., CAe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 2014, a leaf blight of cilantro was observed in two commercial fields in Ventura Co., CA”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Symptoms developed from water soaked lesions into necrosis across entire leaves.
- Taxon
- cilantroCoriandrum sativumt0
- Organ / stage
- leavese0
- Outcome
- water-soaked lesionse0
- Value
- 5 to 10 mme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Symptoms included water-soaked lesions 5 to 10 mm dia that became necrotic and coalesced with age to consume entire leaves”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Six nearby fields were affected the next year.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- fields were affectede0
- Value
- sixe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The following year, six nearby fields were affected”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Disease incidence was estimated at 15 to 50%, making symptomatic cilantro unmarketable.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- incidencee0
- Value
- 15 to 50%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Damage in these fields was estimated at 15 to 50% incidence making symptomatic cilantro unmarketable”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
The disease was observed in two Monterey County fields in 2017.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- diseasee0
- Value
- 2 fieldse0
- Setting
- Monterey Co., CAe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 2017, the disease was observed in 2 fields in Monterey Co., CA”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Cilantro isolates made light gray colonies and maroon pigment on PDA.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- light gray colonies and a diffusible maroon pigmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On PDA, all cilantro isolates produced light gray colonies and a diffusible maroon pigment in the medium”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
A. dauci isolates made light gray colonies and violet pigment.
- Taxon
- cilantroCoriandrum sativumt0
- Interactor
- A. dauciAlternaria daucie0pathogen
- Outcome
- A. dauci isolates produced light gray colonies and a diffusible violet pigmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All A. dauci isolates produced light gray colonies and a diffusible violet pigment”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Cilantro isolates had mean conidial dimensions of 57.5 X 20.3 um.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- spore dimensionse0
- Value
- 57.5 X 20.3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mean spore dimensions (length X width) for the CA cilantro isolates, A. poonensis, and A. dauci isolates were 57.5 X 20.3, 56.0 X 19.6, and 88.4 X 21.8, um, respectively”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Cilantro isolate beaks averaged 158 um.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- beak lengthse0
- Value
- 158e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mean beak lengths were 158, 152, and 170 um, respectively”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Cilantro isolates produced 30 to 70% diseased leaf area on cilantro.
- Taxon
- cilantroCoriandrum sativumt0
- Treatment
- cilantro isolatese0
- Outcome
- foliar area diseased (FAD) on cilantroe0
- Value
- 30 to 70%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the foliar area diseased (FAD) on cilantro ranged from 30 to 70% for cilantro isolates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Cilantro isolates produced 0 to 3% diseased leaf area on carrot.
- Taxon
- cilantroCoriandrum sativumt0
- Treatment
- cilantro isolatese0
- Outcome
- FAD on carrote0
- Value
- 0 to 3%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the FAD on carrot ranged from 0 to 3% for cilantro isolates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
A. dauci isolates produced 60 to 80% diseased leaf area on carrot.
- Taxon
- cilantroCoriandrum sativumt0
- Treatment
- A. dauci isolatese0
- Interactor
- A. dauciAlternaria daucie0pathogen
- Outcome
- FAD on carrote0
- Value
- 60 to 80%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the FAD on carrot ranged from 0 to 3% for cilantro isolates and 60 to 80% for A. dauci isolates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Water sprayed controls remained healthy.
- Taxon
- cilantroCoriandrum sativumt0
- Treatment
- watere0
- Outcome
- remained healthye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Control plants sprayed with water remained healthy”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
The fungus was reisolated from inoculated cilantro.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- fungus was re-isolatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The fungus was re-isolated from inoculated cilantro to fulfill Koch´s postulates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Alt a1 sequences of cilantro isolates had 100% identity and differed by one base pair from A. dauci.
- Taxon
- cilantroCoriandrum sativumt0
- Interactor
- A. dauciAlternaria daucie0pathogen
- Outcome
- Alt a1, cilantro isolates had 100% identitye0
- Value
- 100%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For Alt a1, cilantro isolates had 100% identity (435/435 bp) and differed by 1 bp from A. dauci isolates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Calmodulin sequences of cilantro isolates had 100% identity and differed by three base pairs from A. dauci.
- Taxon
- cilantroCoriandrum sativumt0
- Interactor
- A. dauciAlternaria daucie0pathogen
- Outcome
- calmodulin, cilantro isolates had 100% identitye0
- Value
- 100%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For calmodulin, cilantro isolates had 100% identity (593/593 bp) and differed by 3 bp from A. dauci isolates”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
This is the first US report of A. poonensis on cilantro.
- Taxon
- cilantroCoriandrum sativumt0
- Interactor
- A. poonensisAlternaria poonensise0pathogen
- Outcome
- first report of A. poonensis on cilantroe0
- Setting
- United Statese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is the first report of A. poonensis on cilantro in the United States”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
The disease limits cilantro production.
- Taxon
- cilantroCoriandrum sativumt0
- Outcome
- disease limits productione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Because of high quality standards, this disease limits production”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”
Claim · model-written summary
Alternaria leaf spot resembles bacterial leaf spot and challenges diagnosis.
- Taxon
- cilantroCoriandrum sativumt0
- Interactor
- Pseudomonas syringae
Pseudomonas syringaee0pathogen - Outcome
- diagnostic challengese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Alternaria leaf spot also creates diagnostic challenges because symptoms are similar to common bacterial leaf spot caused by Pseudomonas syringae”
t0“First Report of Leaf Blight of Cilantro, Coriandrum sativum, Caused by Alternaria poonensis in the United States”