Abstract
ABSTRACT Experiments to identify the factors affecting survival of Bremia lactucae sporangia after deposition on lettuce leaves were conducted in growth chambers and outdoors under ambient conditions. Lettuce seedlings at the four-leaf stage were inoculated with B. lactucae sporangia under dry conditions. Sporangia deposited on lettuce seedlings were incubated at different temperature and relative humidity (RH) combinations, exposed to 100, 50, 25, and 0% sunlight in the second experiment, and exposed to different artificial lights in wavelength ranges of UVA (315 to 400 nm), UVB (280 to 315 nm), or fluorescent light in the third experiment. After exposure for 0 to 48 h in the first experiment and 0 to 12 h in the second and third experiments, seedlings in two pots were sampled for each treatment, and sporangia were washed from 15 leaves excised from the sampled seedlings. Germination of sporangia was determined in water after incubation in the dark at 15 degrees C for 24 h. The sampled seedlings with remaining leaves were first transferred to optimal conditions for infection (24 h), for the development of downy mildew, and then assessed for disease after 9 days. Sporangia survived much longer at 23 degrees C (>12 h) than at 31 degrees C (2 to 5 h), regardless of RH (33 to 76%). Germination percentage was significantly reduced after exposure to 50 and 100% sunlight. UVB significantly reduced sporangium viability, while fluorescent light and UVA had no effect relative to incubation in the dark. Infection of seedlings followed a pattern similar to germination of sporangia. Solar radiation is the dominant factor determining survival of B. lactucae sporangia, while temperature and RH have small, insignificant effects in coastal areas of California. This suggests that infections by sporangia that survived a day are probable only on cloudy days or on leaves that are highly shaded.
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Claims 9
Claim · model-written summary
Bremia sporangia survived longer at 23 than 31 degrees C regardless of humidity.
- Taxon
- lettuce
Lactuca sativat0 - Outcome
- Sporangia survivede0
- Direction
- much longere0
- Value
- >12 he0
- Qualifier
- regardless of RH (33 to 76%)e0
- Comparator
- 31 degrees Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sporangia survived much longer at 23 degrees C (>12 h) than at 31 degrees C (2 to 5 h), regardless of RH (33 to 76%).”
t0“lettuce”
Claim · model-written summary
Exposure to 50 and 100% sunlight significantly reduced sporangial germination.
- Taxon
- lettuceLactuca sativat0
- Treatment
- 50 and 100% sunlighte0
- Outcome
- Germination percentagee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Germination percentage was significantly reduced after exposure to 50 and 100% sunlight.”
t0“lettuce”
Claim · model-written summary
UVB significantly reduced sporangium viability.
- Taxon
- lettuceLactuca sativat0
- Treatment
- UVBe0
- Outcome
- sporangium viabilitye0
- Direction
- reducede0
- Comparator
- incubation in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UVB significantly reduced sporangium viability, while fluorescent light and UVA had no effect relative to incubation in the dark.”
t0“lettuce”
Claim · model-written summary
Fluorescent light had no effect on sporangium viability relative to dark incubation.
- Taxon
- lettuceLactuca sativat0
- Treatment
- fluorescent lighte0
- Outcome
- sporangium viabilitye0
- Direction
- no effecte0
- Comparator
- incubation in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UVB significantly reduced sporangium viability, while fluorescent light and UVA had no effect relative to incubation in the dark.”
t0“lettuce”
Claim · model-written summary
UVA had no effect on sporangium viability relative to dark incubation.
- Taxon
- lettuceLactuca sativat0
- Treatment
- UVAe0
- Outcome
- sporangium viabilitye0
- Direction
- no effecte0
- Comparator
- incubation in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“UVB significantly reduced sporangium viability, while fluorescent light and UVA had no effect relative to incubation in the dark.”
t0“lettuce”
Claim · model-written summary
Lettuce seedling infection followed a pattern similar to sporangial germination.
- Taxon
- lettuceLactuca sativat0
- Outcome
- Infection of seedlingse0
- Direction
- similare0
- Comparator
- germination of sporangiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Infection of seedlings followed a pattern similar to germination of sporangia.”
t0“lettuce”
Claim · model-written summary
Solar radiation was considered the dominant factor in sporangial survival in coastal California.
- Taxon
- lettuceLactuca sativat0
- Outcome
- survival of B. lactucae sporangiae0
- Qualifier
- Solar radiatione0
- Setting
- coastal areas of Californiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Solar radiation is the dominant factor determining survival of B. lactucae sporangia, while temperature and RH have small, insignificant effects in coastal areas of California.”
t0“lettuce”
Claim · model-written summary
Temperature and relative humidity had small, insignificant effects on sporangial survival in coastal California.
- Taxon
- lettuceLactuca sativat0
- Outcome
- effectse0
- Direction
- smalle0
- Setting
- coastal areas of Californiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“temperature and RH have small, insignificant effects in coastal areas of California”
t0“lettuce”
Claim · model-written summary
Infection by sporangia surviving one day was considered probable only on cloudy days or highly shaded leaves.
- Taxon
- lettuceLactuca sativat0
- Outcome
- infections by sporangiae0
- Qualifier
- only on cloudy days or on leaves that are highly shadede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“infections by sporangia that survived a day are probable only on cloudy days or on leaves that are highly shaded.”
t0“lettuce”
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See all 300 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.