Abstract
Onion (Allium cepa L.) plants growing in a breeding nursery in Canyon County, Idaho were observed with leaf symptoms of powdery mildew in August and September, 1994. The affected leaves showed roughly circular, 10- to 15-mm-diameter, powdery, white-to-grayish white patches with irregular margins. The leaf area under the fungal growth turned chlorotic and later necrotic. Occasionally, lesions coalesced, covering larger areas of the leaf surface. Symptoms were seen on mature and young leaves. Of 620 lines examined, only the 10 lines which had glossy leaves (no or low levels of cuticular wax) displayed symptoms of powdery mildew. Microscopic examination revealed that the white, powdery growth on the lesions consisted entirely of conidiophores and conidia. Conidiophores emerged through stomata, singly or in groups of two or three, were branched, and bore either terminal, pyriform (59 to 68 × 16 to 19 μm), apically pointed (lanceolate) primary conidia or cylindrical (57 to 62 × 18 to 20 μm) secondary conidia. On the basis of the presence of endophytic mycelium, morphological characteristics of the conidiophores, and the dimorphic conidia the fungus was identified as Leveillula taurica (Lev.) G. Arnaud (1) (anamorph = Oidiopsis sicula Scalia). The teleomorph of this fungus was not observed. Greenhouse inoculations were made onto leaves of three 8-week-old plants of a glossy leaf onion genotype (94P240) and three 6-week-old plants of tomato (cv. Payette) grown in pots. Conidia from sporulating lesions on onion leaves were brushed onto the leaves, and the inoculated plants were covered with a plastic bag for 72 h to maintain high humidity. Inoculated leaves on both hosts developed chlorotic lesions with sporulation of L. taurica after 14 days at 25 to 28°C. Noninoculated onion and tomato plants (one of each) did not develop powdery mildew symptoms. This selective susceptibility of onion genotypes with glossy leaves to L. taurica warrants careful consideration by onion breeding programs in utilizing such germ plasm as a potential source for other desirable characters such as nonpreference to thrips. To our knowledge, this is the first report of powdery mildew of onion caused by L. taurica in Idaho. This disease has been reported on onions in California (3) and Washington (2). However, it has not been observed in commercial onion crops in Idaho, even though the cultivars involved apparently vary as to the amount of cuticular wax on their foliage. References: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980. (2) L. J. du Toit et al. Online publication. DOI: 10.1094/PHP-2004-1129-01-HN. Plant Health Progress, 2004. (3) F. F. Laemmlen and R. M. Endo. Plant Dis. 69:451, 1985.
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Claims 8
Claim · model-written summary
Onion nursery plants in Idaho displayed powdery mildew symptoms.
- Taxon
- Onion
Allium cepae0 - Organ / stage
- leafe0
- Interactor
- Leveillula tauricat0pathogen
- Outcome
- leaf symptoms of powdery mildewe0
- Setting
- Canyon County, Idahoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Onion (Allium cepa L.) plants growing in a breeding nursery in Canyon County, Idaho were observed with leaf symptoms of powdery mildew in August and September, 1994.”
t0“Leveillula taurica”
Claim · model-written summary
Only the 10 glossy leaf lines among 620 onion lines displayed powdery mildew symptoms.
- Taxon
- OnionAllium cepat0
- Material
- glossy leavese0
- Outcome
- symptoms of powdery mildewe0
- Value
- 10 linese0
- Qualifier
- 620 lines examinede0
Not reportedInteractorInteractor roleDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Of 620 lines examined, only the 10 lines which had glossy leaves (no or low levels of cuticular wax) displayed symptoms of powdery mildew.”
t0“Glossy Leaf Genotypes of Onion”
Claim · model-written summary
The fungus on onion lesions was identified as Leveillula taurica.
- Taxon
- OnionAllium cepat0
- Interactor
- Leveillula tauricae0pathogen
- Outcome
- fungus was identified as Leveillula tauricae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the fungus was identified as Leveillula taurica (Lev.) G. Arnaud”
t0“Onion”
Claim · model-written summary
The teleomorph was not observed.
- Taxon
- OnionAllium cepat0
- Outcome
- teleomorph of this fungus was not observede0
Not reportedInteractorInteractor role
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The teleomorph of this fungus was not observed.”
t0“Glossy Leaf Genotypes of Onion”
Claim · model-written summary
Inoculated onion leaves developed chlorotic lesions with sporulation after 14 days.
- Taxon
- onionAllium cepae0
- Treatment
- Inoculatede0
- Interactor
- L. tauricae0pathogen
- Outcome
- chlorotic lesions with sporulation of L. tauricae0
- Value
- 14 dayse0
- Comparator
- Noninoculatede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculated leaves on both hosts developed chlorotic lesions with sporulation of L. taurica after 14 days at 25 to 28°C. Noninoculated onion and tomato plants (one of each) did not develop powdery mildew symptoms.”
Claim · model-written summary
Inoculated tomato leaves developed chlorotic lesions with fungal sporulation after 14 days.
- Taxon
- tomato
Solanum lycopersicume0 - Treatment
- Inoculatede0
- Interactor
- L. tauricae0pathogen
- Outcome
- chlorotic lesions with sporulation of L. tauricae0
- Value
- 14 dayse0
- Comparator
- Noninoculatede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculated leaves on both hosts developed chlorotic lesions with sporulation of L. taurica after 14 days at 25 to 28°C. Noninoculated onion and tomato plants (one of each) did not develop powdery mildew symptoms.”
Claim · model-written summary
The authors advise onion breeders to consider the susceptibility of glossy leaf germplasm.
- Taxon
- onionAllium cepae0
- Material
- glossy leavese0
- Interactor
- L. tauricae0pathogen
- Outcome
- careful consideration by onion breeding programse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This selective susceptibility of onion genotypes with glossy leaves to L. taurica warrants careful consideration by onion breeding programs”
Claim · model-written summary
The report identifies onion powdery mildew caused by L. taurica in Idaho as a first report.
- Taxon
- onionAllium cepae0
- Interactor
- L. tauricae0pathogen
- Outcome
- first report of powdery mildewe0
- Setting
- Idahoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this is the first report of powdery mildew of onion caused by L. taurica in Idaho.”
The same questions in other papers
inoculation · disease · Allium cepa (onion)Positive and negative results
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- positive
- positive
- positive
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See all 49 papers →inoculation · disease · Solanum lycopersicum (tomato)Positive and negative results
129 papers in the same direction as this paper · 136 in the opposite direction
- positive
- positive
- positive
262 papers more in this group
See all 266 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.