http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
RFLP analysis of the population genetics of Mycosphaerella graminicola in a wheat cultivar mixture field experiment
Restriction fragment length polymorphism analysis of Mycosphaerella graminicola in a wheat cultivar mixture field experiment
Restriction fragment length polymorphism (RFLP) analysis was utilized to study the population genetics of Mycosphaerella grarninicola in a wheat cultivar mixture field experiment over a three-year period. Four wheat cultivars that differed in resistance to M. graminicola were planted in pure stands, and in all possible 2-, 3-, and 4-way mixtures in the field. No significant differences in allele frequencies were found for any of the RFLP loci over any of the time periods examined. Genotypic diversity did not change significantly within a year or between years. The population showed a high degree of genetic uniformity over time. A total of 711 M. graminicola isolates were used to test the relative importance of sexual and asexual reproduction on the genetic structure of this fungus. Based on DNA fingerprints, few clones were found in the sample. No particular clone was present at a high frequency. All isolate collections were at a gametic equilibrium for all loci, suggesting that sexual reproduction plays a major role in the genetic structure of M. graminicola populations. Isolate collections sampled from different host treatments were analyzed for the effect of selection driven by the host genotypes on the genetic structure of M. graminicola populations. No correlation was found between the genetic diversity of host treatments and their corresponding pathogen collections. All analyses indicated the genetic structure of these isolate collections were nearly identical. Hierarchical gene diversity analysis showed that most of genetic variation was distributed within the individual plots. Since a high degree of sexual reproduction was present in the M. graminicola population, it was difficult to test the effect of selection in this experiment. However, these data were interpreted as showing little evidence for host-driven selection.
Issued also on microfiche from University Microfilms Inc.