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RESISTANCE AND VIRULENCE STRUCTURE IN TWO LINUM MARGINALE-MELAMPSORA LINI HOST-PATHOGEN METAPOPULATIONS WITH
J J Burdon1, P H Thrall1, A H D Brown1
1Centre for Plant Biodiversity Research, CSIRO-Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia.
Abstract:
Different patterns of resistance to six pathotypes of Melampsora lini were detected in 11 populations of Linum marginale distributed across two metapopulations. The two metapopulations (mountains and plains of New South Wales, Australia) differed in the annual cycle of disease development, which barely overlapped, and in the growth cycle and mating system of the host. Host populations in the mountains metapopulation were highly inbred, whereas those on the plains showed appreciable levels of outcrossing. Within each metapopulation there was significant variation among component populations in (1) levels of host resistance to individual pathogen isolates; (2) mean levels of resistance to all six isolates; (3) the number of resistance phenotypes present and the evenness of their distribution within the population; and (4) the average number of pathogen lines to which individual hosts were resistant. A more limited comparison of pathogen populations from the two metapopulations (two from each) found greater similarities in the structure of populations and particular virulence frequencies within, rather than among, the two metapopulations. Differences in host outcrossing rates between the two metapopulations are reflected in marked differences in the overall level of resistance, its partitioning within and among populations, the number and distribution of resistance phenotypes in the two areas, and the level of polymorphism for specific virulence factors in the pathogen, with the plains metapopulation showing consistently higher values. However, these differences were not significant. In general, variation for all parameters was just as great among populations within a metapopulation as between the two metapopulations.
Insights
Host plant resistance to flax rust (Melampsora lini) varied significantly across populations of Linum marginale in Australia. Mating system differences between mountain and plains populations influenced resistance patterns and pathogen virulence.
Area of Science:
- * Plant pathology
- * Evolutionary biology
- * Population genetics
Background:
- * Plant-pathogen interactions are shaped by host genetic diversity and mating systems.
- * Melampsora lini (flax rust) and Linum marginale (wild flax) provide a model system to study coevolutionary dynamics.
- * Metapopulations in distinct environments (mountains vs. plains) offer insights into local adaptation.
Purpose of the Study:
- * To investigate resistance patterns to six Melampsora lini pathotypes in 11 Linum marginale populations.
- * To compare host resistance and pathogen virulence across two metapopulations with differing host mating systems.
- * To understand the influence of host mating systems on genetic variation in resistance and virulence.
Main Methods:
- * Field surveys of 11 Linum marginale populations across two metapopulations (mountains and plains).
- * Assessment of host resistance patterns to six Melampsora lini pathotypes.
- * Analysis of host mating systems (inbreeding vs. outcrossing).
- * Comparison of pathogen virulence frequencies between metapopulations.
Main Results:
- * Significant variation in host resistance to Melampsora lini was observed among populations within each metapopulation.
- * Plains metapopulation (higher outcrossing) showed higher overall resistance, greater resistance diversity, and higher pathogen virulence polymorphism compared to the inbred mountain metapopulation.
- * Variation within metapopulations was often as substantial as variation between them.
- * Pathogen populations showed greater similarity within metapopulations than between them.
Conclusions:
- * Host mating systems significantly influence the structure of genetic variation for resistance and pathogen virulence.
- * Environmental factors and host population structure interact to shape plant-pathogen coevolutionary dynamics.
- * Despite observed differences, substantial genetic variation exists both within and between metapopulations, highlighting complex evolutionary processes.
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