Studies on the mechanism of variation in Pyricularia oryzae (Magnaporthe grisea) /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The mechanism of variation in Pyricularia oryzae (Magnaporthe grisea) was investigated by comparing stable and unstable isolates. An abnormally high rate of changes in pathotype was found in one of five Texas isolates (T-5). The instability was found in some given isolates and their descendents, but not randomly in the total population. Reversions were common among these unstable progeny. Progeny from different generations had different karyotypes. Chromosomal rearrangement was confirmed in this unstable family by hybridizing Southern blots of their chromosomes with genomic DNA probes. Based on the above observations, it was proposed that a transposable genetic element is present in the genome of unstable isolates and is responsible for the changes from avirulence to virulence by insertional inactivation of the avirulence genes. To test this hypothesis, an attempt was made to clone the prospective transposable element from the T-5 family. A protocol was devised to recover the prospective element from the genome based on differential methylation of stable and unstable isolates. Two clones were obtained that may contain the element. To confirm the hypothesis, tests demonstrating transposition need to be carried out. The observations on the variation in pathotype, karyotype and DNA polymorphism indicated that the instability was associated with developmental stage of this organism. Changes were observed only after conidiation, not after continuous mycelial growth in culture. Heterokaryotic incompatibility within the T-5 family made it impossible to utilize the parasexual cycle for linkage group analysis. However, several genomic DNA clones were identified which will serve as chromosome markers for electrophoretically separated chromosomes. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Plant pathology." |
| Physical Description: | xi, 109 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |