A map of rye chromosome 4R with cytological and isozyme markers.

The progeny of two crosses between a structural heterozygote for a reciprocal translocation (4RL/5RL) and a homozygote for the standard chromosome arrangement and of four crosses between standard chromosome homozygotes were analysed in rye (Secale cereale L. cv 'Ailés') for the electrophoretic patterns of five different leaf and endosperm isozymes (LAP, PGM, NDH, ADH and EPER). The presence or absence of the quadrivalents at metaphase I (MI) was also tested. Loci Adh-1, Pgm-1 and Ndh-1 were located on chromosome arm 4RS, and locus Eper-1 on chromosome arm 4RL. Locus Lap-2 was located on the 4RS chromosome arm. The estimated distances among the different linked loci support the following gene order: Eper1¨ (breakpoint-centromere)¨Lap-2¨ ¨Adh-1 ¨Pgm-1¨Ndh-1. These results provide evidence for the chromosomal location of Lap-2 locus on chromosome arm 4RS in cv 'Ailés'. A high negative interference was detected between the zones delimited by centromere and Lap-2, and Lap-2 and Pgm-1 in plants with the 4RL/5RL translocation.