VIEW ARTICLE

Genetics

DNA Restriction Fragment Length Polymorphisms Among Mycosphaerella graminicola (Anamorph Septoria tritici) Isolates Collected from a Single Wheat Field. B. A. McDonald, Assistant professor, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132; J. P. Martinez, Research technician, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132. Phytopathology 80:1368-1373. Accepted for publication 25 April 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1368.

Restriction fragment length polymorphism (RFLP) markers were used to measure the amount and distribution of genetic variation in a fungal pathogen population on a microgeographical scale. Ninety-three isolates of Septoria tritici sampled from a single wheat field were assayed for RFLP variation using eight probes that hybridized to single RFLP loci and one probe that hybridized to two RFLP loci in nuclear DNA. Single locus and multilocus analysis of RFLP data indicated that a high level of genetic variability was distributed on a fine scale within this population. In eight out of 31 comparisons, different pycnidial isolates collected from the same lesion had different alleles for at least two RFLP loci. Twenty-two different haplotypes were identified among the 93 isolates sampled. Identical haplotypes were clustered in the same location in the field. Data were consistent with the hypothesis that primary inoculum originated from a genetically diverse founding population (probably ascospores of Mycosphaerella graminicola), followed by clonal propagation via asexual pycnidiospores.