Abstract
ABSTRACT The selective effect of quantitative host resistance on pathogen aggressiveness is poorly understood. Because two previous experiments with a small number of bread wheat cultivars and isolates of Mycosphaerella graminicola had indicated that more susceptible hosts selected for more aggressive isolates, we conducted a larger experiment to test that hypothesis. In each of 2 years, six cultivars differing in their levels of partial resistance were planted in field plots, and isolates were collected from each cultivar early and late in the growing season. The isolates were inoculated as populations bulked by cultivar of origin, field replicate, and collection date on seedlings of the same six cultivars in the greenhouse. The selective impact of a cultivar on aggressiveness was measured as the difference in aggressiveness between early and late isolates from that cultivar. Regression of those differences on disease severity in the field yielded significance values of 0.0531 and 0.0037 for the 2 years, with moderately resistant cultivars selecting for more aggressive isolates. In a related experiment, the protectant fungicide chlorothalonil was applied to plots of two susceptible cultivars to retard epidemic development. When tested in the greenhouse, isolates of M. graminicola from those plots were significantly more aggressive than isolates from the same cultivars unprotected by fungicide.
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Claims 2
Claim · model-written summary
Moderately resistant wheat cultivars selected for more aggressive M. graminicola isolates over the season.
- Taxon
- Wheat
Triticum aestivumt0 - Material
- moderately resistant cultivarse0
- Interactor
- Mycosphaerella graminicola
Zymoseptoria triticit1pathogen - Outcome
- aggressive isolatese0
- Direction
- more aggressivee0
- Value
- 0.0531 and 0.0037e0
- Setting
- fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Regression of those differences on disease severity in the field yielded significance values of 0.0531 and 0.0037 for the 2 years, with moderately resistant cultivars selecting for more aggressive isolates.”
t0“Wheat Cultivars”
t1“Mycosphaerella graminicola”
Claim · model-written summary
Isolates from chlorothalonil-treated plots were significantly more aggressive than isolates from untreated plots of the same susceptible cultivars.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- chlorothalonile0
- Interactor
- M. graminicolaZymoseptoria triticie0pathogen
- Outcome
- isolates of M. graminicolae0
- Direction
- more aggressivee0
- Comparator
- same cultivars unprotected by fungicidee0
- Setting
- greenhousee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the protectant fungicide chlorothalonil was applied to plots of two susceptible cultivars to retard epidemic development. When tested in the greenhouse, isolates of M. graminicola from those plots were significantly more aggressive than isolates from the same cultivars unprotected by fungicide.”
t0“Wheat Cultivars”