Abstract
Although widely adopted by growers worldwide, hydroponic cultivation of lettuce is relatively new in Cyprus. Currently, ∼32 ha of lettuce are cultivated in the region, with only a few commercial trials using hydroponics. During March and April 2016, ∼23% of lettuce plants cv. Verde Degli Ortolani grown hydroponically (deep flow technique) in Polemidia, Limassol, showed severe stunting and poor growth. Older leaves wilted during the warmer period of the day and over the next 2 weeks the outer leaves became chlorotic and yellow. Small feeder roots had brown lesions, and subsequently the entire root system became necrotic. Diseased roots of 10 plants were excised, surface-disinfested, and plated on PARP-V8 medium selective for oomycetes (Jeffers and Martin 1986). Root isolations consistently yielded pure cultures of Pythium species. After 48 h incubation at 25°C, isolates produced white, circular, flat colonies with little aerial mycelia. Sections from the margin of colonies were transferred to 9 cm dia. plates containing 15 ml sterile water, which was incubated for at least 24 h at 25°C. Microscopic examination revealed filamentous and slightly inflated sporangia forming dendroid structures. Zoospores formed in vesicles and were up to 8 μm in diameter. The isolates failed to produce sexual structures during 30 days of incubation. Based on these morphological characteristics, the isolates could not be identified to the species level. Therefore, genomic DNA was extracted from six isolates, and the internal transcribed spacer (ITS) region of rDNA was partially amplified and sequenced using universal primers ITS4 and ITS5. A representative sequence was deposited in GenBank (accession no. KX518318). BLAST analysis revealed a 99% similarity to a P. dissotocum strain CBS 166.68 sequence (AY598634). This species belongs to the Pythium cluster B2a species complex including P. coloratum, P. diclinum, P. dissotocum, and P. lutarium (Robideau et al. 2011), which are indistinguishable based on ITS and cytochrome c oxidase subunit I (COI) sequences. To confirm pathogenicity under hydroponic conditions, six different Pythium isolates, of which the sequences were similar than accession AY598634, were used in pathogenicity experiments. Two-week-old lettuce plants cv. Nogal, started in a nursery in peat pellets, were placed in 14-liter plastic containers containing a full-based nutrient solution (Christoulaki et al. 2014) in growth chambers at 25 ± 1°C and 16-h photoperiod. Three containers were used per isolate, each containing four plants. Five days after transplanting, one intact 48-h old Pythium culture growing on a V-8 agar plate (9 cm dia.) was added to each container and removed 48 h later. Control plants were inoculated with sterile V-8 agar plates. After 3 weeks, older leaves of inoculated plants exhibited chlorosis, and feeder roots and taproots showed discrete brownish lesions. Control plants did not show any symptoms. Pythium was consistently reisolated from symptomatic roots but not from the control plants, fulfilling Koch’s postulates. The pathogenicity experiments were repeated once. P. dissotocum, which belongs to Pythium cluster B2a, has long been reported to infect lettuce plants in hydroponic culture (Stanghellini and Kronland 1986). To our knowledge, this is the first report of root rot of lettuce caused by a Pythium spp. belonging to Pythium cluster B2a species complex in Cyprus.
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Claims 9
Claim · model-written summary
About 23% of hydroponic Verde Degli Ortolani lettuce plants showed severe stunting and poor growth.
- Taxon
- lettuce
Lactuca sativae0 - Material
- Verde Degli Ortolanie0
- Outcome
- severe stunting and poor growthe0
- Value
- ∼23%e0
- Setting
- Polemidia, Limassole0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“∼23% of lettuce plants cv. Verde Degli Ortolani grown hydroponically (deep flow technique) in Polemidia, Limassol, showed severe stunting and poor growth.”
Claim · model-written summary
Affected lettuce developed wilt and then chlorotic yellow outer leaves.
- Taxon
- lettuceLactuca sativat0
- Organ / stage
- Older leavese0
- Outcome
- Older leaves wiltede0
- Qualifier
- warmer period of the daye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Older leaves wilted during the warmer period of the day and over the next 2 weeks the outer leaves became chlorotic and yellow.”
t0“lettuce”
Claim · model-written summary
Affected lettuce feeder roots developed brown lesions and the whole root system became necrotic.
- Taxon
- lettuceLactuca sativat0
- Organ / stage
- Small feeder rootse0
- Outcome
- brown lesionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Small feeder roots had brown lesions, and subsequently the entire root system became necrotic.”
t0“lettuce”
Claim · model-written summary
Diseased lettuce roots consistently yielded Pythium cultures.
- Taxon
- lettuceLactuca sativat0
- Outcome
- Root isolations consistently yielded pure cultures of Pythium speciese0
.jpg?width=60){kind=small}
PythiumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Root isolations consistently yielded pure cultures of Pythium species.”
t0“lettuce”
Claim · model-written summary
The representative isolate sequence had 99% similarity to P. dissotocum strain CBS 166.68.
- Taxon
- lettuceLactuca sativat0
- Interactor
- P. dissotocumPythium dissotocume0pathogen
- Outcome
- 99% similaritye0
- Value
- 99%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“BLAST analysis revealed a 99% similarity to a P. dissotocum strain CBS 166.68 sequence (AY598634).”
t0“lettuce”
Claim · model-written summary
Inoculated lettuce developed leaf chlorosis and brown root lesions after three weeks.
- Taxon
- lettuceLactuca sativat0
- Treatment
- inoculated plantse0
- Outcome
- chlorosise0
- Qualifier
- After 3 weekse0
- Comparator
- Control plantse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 3 weeks, older leaves of inoculated plants exhibited chlorosis, and feeder roots and taproots showed discrete brownish lesions. Control plants did not show any symptoms.”
t0“lettuce”
Claim · model-written summary
Inoculated lettuce developed root lesions while controls had no symptoms.
- Taxon
- lettuceLactuca sativat0
- Organ / stage
- feeder roots and taprootse0
- Treatment
- inoculated plantse0
- Outcome
- discrete brownish lesionse0
- Comparator
- Control plantse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 3 weeks, older leaves of inoculated plants exhibited chlorosis, and feeder roots and taproots showed discrete brownish lesions. Control plants did not show any symptoms.”
t0“lettuce”
Claim · model-written summary
Pythium was reisolated from symptomatic lettuce roots but not controls.
- Taxon
- lettuceLactuca sativat0
- Outcome
- Pythium was consistently reisolatede0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pythium was consistently reisolated from symptomatic roots but not from the control plants, fulfilling Koch’s postulates.”
t0“lettuce”
Claim · model-written summary
The authors reported the first Cyprus case of lettuce root rot caused by a Pythium cluster B2a species.
- Taxon
- lettuceLactuca sativae0
- Outcome
- root rot of lettucee0
- Setting
- Cypruse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this is the first report of root rot of lettuce caused by a Pythium spp. belonging to Pythium cluster B2a species complex in Cyprus.”
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See all 29 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.