Nrs1, a Repetitive Element Linkedto Pisatin Demethylase Genes on a DispensableChromosome of Nectria haematococc . Hong Gi Kim . Department of Agricultural Biology, Chungnam National University, Taejon 305-764, Korea. Lyndel W. Meinhardt, Ulla Benny and H. Corby Kistler. Plant Molecular and Cellular Biology Program, Plant Pathology Department, P.O. Box 110680, University of Florida, Gainesville, Fla. 32611-0680, U.S.A. MPMI 8:524-531. Accepted for publication 14 April 1995. Copyright 1995 The American Phytopathological Society.

We have identified a repetitive DNA element in Nectria haematococca mating population VI, isolate T-2. This repetitive sequence has been called Nrsl. DNA hybridization analysis indicates the sequence is found in several isolates of the fungus pathogenic to Pisum sativum. A 2,027-bp clone containing the Nrsl-2 allele contains a long polyA sequence, imperfect RNA polymerase III promoter sequences, multiple inverted repeats, and the potential for extensive secondary structure similar to known RNA polymerase III transcripts and related retroelements. Ten of the 11 Hindlll restriction fragments from isolate T-2 DNA that hybridize to Nrsl-2 segregate in a manner consistent with a 1:1 ratio for random ascospore progeny. The 10 restriction fragment length polymorphism (RFLP) loci define three linkage groups and correspond to three chromosome-sized DNAs from T-2 separated by pulsed field gel electrophoresis. Three RFLP loci defined by hybridization to the gene for pisatin demethylase and localized on the 1.6 million base pair (Mb) chromosome were genetically linked to each other and to several Nrsl loci. These sequences recombined despite the fact that no obvious homolog exists for the 1.6-Mb chromosome in one parent strain. Allelic RFLPs corresponding to the gene sequence of cutinase were unlinked to Nrsl loci