Deletion mapping of a nematode resistance gene on rye chromosome 6R in wheat

Four deletion mutants of rye chromosome 6R were identified in progeny of wheat (Triticum aestivum L.) lines of ph1bph1b genotype and monosomic for chromosome 6R. The rye chromosome carried a resistance gene against the cereal cyst nematode (CCN) (Heterodera avenae Woll.) and this chromosome originated in triticale line T-701 (X Triticosecale Witt.). The deletion mutants were selected on the basis of dissociation of three isozyme loci on the long arm of the rye (Secale cereale L.) chromosome. Three plants and their progeny showed expression of the rye genes alpha-Arny-R1 and Got-R2 but lacked the gene PgdR2. The other plant and its progeny showed expression of the alpha-Amy-R1 gene while the genes Got-R2 and PgdR2 were absent. The four deletion chromosomes displayed long-arm terminal deficiencies of different sizes which enabled mapping of the rye isozyme genes and the CCN resistance gene. The distal to proximal order of the 6R isozyme loci was found to be: PgdR2, Got-R2, and then alpha-Amy-R1. Bioassay tests demonstrated that the CCN resistance gene (CreR) was located on an interstitial section of the long arm of 6R adjacent to Got-R2.