Identification and differentiation of host - specialized isolates of Sporisorium reilianum using molecular markers /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1992.
|
| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Texas populations of Sporisorium reilianum, the causal agent of head smut in maize and sorghum, exhibit two levels of host specificity. Certain isolates are restricted to the maize host, while other isolates infect sorghum predominantly. The latter type can be further divided into four races based on its reactions on a series of sorghum differentials. Head smut of both maize and sorghum is a disease of worldwide importance and is controlled by host resistance. Markers associated with pathogen variability will be extremely valuable in the disease management program. An examination of morphological and physiological traits, including a previous study employing isozymes failed to provide markers to distinguish the host specialized isolates. The objective of this study was to find unique molecular markers which would clearly differentiate between the host specialized isolates of S. reilianum. Polymorphisms were sought by using an arbitrary primer-PCR based assay and pulse field gel electrophoresis. Karyotype analysis of the haploid sporidia revealed a polymorphism that seems to be associated with the host specificity. The maize pathotype of S. reilianum possesses 15 chromosomes, while only 13/14 bands were separated from the sorghum. This difference of 750 kb in the sorghum pathotype was common in all 15 isolates examined. The additional chromosome was unique to all maize pathotypes examined. No other size or length polymorphism was observed among the samples examined. The genome size was estimated to be 11 Mb using Saccharomyces cerevisiae as a standard size marker. No length heterogeneity was observed in the ITS region of the rDNA of the different pathotypes when the genes were amplified by PCR. PCR with single ten nucleotide long arbitrary primers resulted in DNA polymorphisms between the isolates of a pathotype and among the pathotypes. Amplifications at lower annealing temperatures were more successful and reproducible. Almost all of the 40 primers assayed resulted in polymorphisms. DNA fragments that were polymorphic between the pathotypes should be useful in pathotype differentiation and need to be tested on a larger number of isolates. This assay has provided markers which can be used in future genetic and population studies of the head smut organism. |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Plant Pathology." |
| Physical Description: | xi, 100 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |