Abstract
The effects of frequency and density of susceptible plants on barley powdery mildew epidemics were studied in a combined set of addition and replacement series of field trials. In the addition series, plant densities in pure stands of three cultivars, Rambo, Rodos and Grosso (susceptible, moderately resistant and immune, respectively) were varied six‐fold. In the replacement series, the three possible two‐way mixtures were analysed at different frequencies but at a density corresponding to the maximum pure stand density. Disease and yield were assessed on a per‐plant basis. In the pure stands, tillering reduced the range of densities from six‐fold to between three‐ and four‐fold, while in the mixtures, frequencies changed only slightly over time, indicating that competitive interactions among the cultivars were roughly equal. Yield per plant decreased logarithmically with increasing density as expected. However, yield per seed head was not correlated with the final number of heads per plot, indicating low competition among heads even at the highest density. Disease in susceptible pure stands increased strongly with decreasing density in 1994 and to a lesser degree in 1995. These differences could have been caused by differences in plant nutritional status and consequent epidemiological effects. Disease reduction on the susceptible cultivars in mixtures varied between 33% and 71% among years. Depending on the length and strength of the epidemic, the effects of host density and frequency on disease severity varied substantially among years.
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Claims 9
Claim · model-written summary
In pure stands, tillering reduced the range of plant densities from six-fold to three- to four-fold.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaret0 - Outcome
- range of densitiese1
- Direction
- reducede1
- Value
- from six‐fold to between three‐ and four‐folde1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“mixtures of barley cultivars”
e1“In the pure stands, tillering reduced the range of densities from six‐fold to between three‐ and four‐fold”
Claim · model-written summary
In the mixtures, cultivar frequencies changed only slightly over time.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- frequenciese2
- Direction
- changed only slightlye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
e2“in the mixtures, frequencies changed only slightly over time”
Claim · model-written summary
The authors interpret the stable mixture frequencies as showing that competitive interactions among the cultivars were roughly equal.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- competitive interactions among the cultivarse3
- Qualifier
- roughly equale3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
e3“indicating that competitive interactions among the cultivars were roughly equal”
Claim · model-written summary
Yield per plant decreased logarithmically as plant density increased in barley.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- increasing densitye4
- Outcome
- Yield per plante4
- Direction
- decreasede4
- Qualifier
- logarithmicallye4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
e4“Yield per plant decreased logarithmically with increasing density as expected”
Claim · model-written summary
Yield per seed head was not correlated with the final number of heads per plot in barley.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- yield per seed heade5
- Direction
- not correlatede5
- Comparator
- final number of heads per plote5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
e5“yield per seed head was not correlated with the final number of heads per plot”
Claim · model-written summary
The authors interpret the yield results as indicating low competition among heads, even at the highest density.
- Taxon
- barleyHordeum vulgaret0
- Outcome
- competition among headse6
- Qualifier
- even at the highest densitye6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
e6“indicating low competition among heads even at the highest density”
Claim · model-written summary
Disease in susceptible barley pure stands increased strongly with decreasing density in 1994 and less in 1995.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- decreasing densitye7
- Interactor
- powdery mildewt1pathogen
- Outcome
- Diseasee7
- Direction
- increased stronglye7
- Qualifier
- to a lesser degree in 1995e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
t1“powdery mildew”
e7“Disease in susceptible pure stands increased strongly with decreasing density in 1994 and to a lesser degree in 1995”
Claim · model-written summary
Mixtures reduced disease on the susceptible barley cultivars by 33% to 71%, varying among years.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- mixturese2
- Interactor
- powdery mildewt1pathogen
- Outcome
- Diseasee2
- Direction
- reductione2
- Value
- 33% and 71%e2
- Qualifier
- among yearse2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
t1“powdery mildew”
e2“Disease reduction on the susceptible cultivars in mixtures varied between 33% and 71% among years”
Claim · model-written summary
Effects of host density and frequency on barley disease severity varied among years, depending on epidemic length and strength.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- host density and frequencye3
- Interactor
- powdery mildewt1pathogen
- Outcome
- disease severitye3
- Qualifier
- Depending on the length and strength of the epidemice3
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mixtures of barley cultivars”
t1“powdery mildew”
e3“Depending on the length and strength of the epidemic, the effects of host density and frequency on disease severity varied substantially among years”