The role of immigration, mating system and selection on the genetic structure of populations of the wheat pathogen Mycosphaerella graminicola /
and DNA fingerprints were used to determine the role of sexual reproduction and selection driven by the host on the genetic structure of Mycosphaerella graminicola populations. Two wheat cultivate differing for resistance to M. graminicola were used in this study. Wheat plots were either artificiall...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=732837711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | and DNA fingerprints were used to determine the role of sexual reproduction and selection driven by the host on the genetic structure of Mycosphaerella graminicola populations. Two wheat cultivate differing for resistance to M. graminicola were used in this study. Wheat plots were either artificially inoculated with known fungal isolates or naturally infected by ascospore showers (control). All isolates in the pathogen population made from the control plots had unique genotypes and RFLP loci were at gametic equilibrium. The genetic structure of this population was similar to populations collected from previous years. Sexual reproduction occurred at a higher frequency on the moderately resistant cultivar than on the susceptible cultivar. Across the three treatments,approximately 66% of the isolates in the population made from the late-season inoculated plots were asexual progeny of the inoculated isolates, 24% were recombinants and 10% were immigrants. The overall frequency of isolates originating from the moderately resistant cultivar was significantly higher than that originating from the susceptible cultivar. Selection driven by the host was evidenced by directional changes in genotypic frequency of the inoculated isolates over the growing season and strong association between the genetic composition of pathogen and host populations. Pathogen populations collected from the moderately resistant cultivar were more stable and had higher genotypic diversity than those collected from the susceptible cultivate and cultivar mixture. The range of selection coefficients was narrower and the values of selection coefficients were smaller on the moderately resistant cultivar than on the susceptible cultivar. The cultivar mixture did not slow down the evolutionary pace of M. graminicola populations. Inoculated isolates varied in degree of host specialization though they as a group were generally more adapted to the cultivate from which they were originally secured. |
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| Item Description: | Vita. "Major Subject: Geneticx". |
| Physical Description: | xii, 124 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references: pages 97-107. |