Diversity,spatial variation,and temporal dynamics of virulences in the German leaf rust (<Emphasis Type="Italic">Puccinia recondita</Emphasis> f. sp. <Emphasis Type="Italic">secalis</Emphasis>) population in winter rye |
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Authors: | Thomas Miedaner Bettina Klocke Kerstin Flath Hartwig H Geiger W Eberhard Weber |
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Institution: | 1.State Plant Breeding Institute,Universit?t Hohenheim (720),Stuttgart,Germany;2.Julius-Kühn Institute, Institute of Plant Protection in Field Crops and Grassland,Kleinmachnow,Germany;3.Institute of Plant Breeding, Seed Science, and Population Genetics,Universit?t Hohenheim (350),Stuttgart,Germany;4.Institute of Plant Breeding and Plant Protection,Martin-Luther-University Halle-Wittenberg,Halle/Saale,Germany |
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Abstract: | A large collection of German rye leaf rust isolates was analysed to characterize the diversity, spatial variation and temporal
dynamics of virulences. Virulence-avirulence phenotypes (=pathotypes) were determined on 23 host differentials. We found 93
pathotypes among 177 single-uredinial isolates in 2000, 201 pathotypes among 437 isolates in 2001, and 125 pathotypes among
213 isolates in 2002. In total, the 827 analyzed isolates represented 317 pathotypes. Frequency of virulences on the individual
differentials varied from 2% to 97%. Eight of the differentials showed a high resistance level with virulence frequencies
<10%. Virulence complexity of the isolates ranged from 3 to 21 with a mean of nine. The percentages of highly virulent isolates
(>14 virulences) increased from 4 to 15% during the sampling period. A high level of virulence diversity was observed within
and between individual sampling sites with Simpson indices around 0.9. Evenness indices ranged from 0.88 to 0.92. Four of
the five most frequent pathotypes were found in each year but their frequency never exceeded 10%. Isolates with unusual virulence
combinations could be clearly separated by principal component analysis. Location-specific pathotype frequencies were revealed
in each year, but the frequency patterns varied across years. On four fields a considerable increase of highly virulent pathotypes
occurred within 6 weeks during the epidemic. The high diversity of pathotypes as well as the fast accumulation of highly virulent
pathotypes favour the adaptation of the pathogen to race-specific host resistances. More durable resistance might be achievable
by combining new effective race-specific resistances with adult-plant and/or race-non-specific quantitative resistances. |
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