Abstract
The three genomes of cucumber show different modes of transmission, nuclear DNA bi-parentally, plastid DNA maternally, and mitochondrial DNA paternally. The mosaic (MSC) phenotype of cucumber is associated with mitochondrial DNA rearrangements and is a valuable tool for studying mitochondrial transmission. A nuclear locus (
Psm
) has been identified in cucumber that controls sorting of paternally transmitted mitochondrial DNA. Comparative sequencing and mapping of cucumber and melon revealed extensive synteny on the recombinational and sequence levels near
Psm
and placed this locus on linkage group R of cucumber and G10 of melon. However, the cucumber genomic region near
Psm
was surprisingly monomorphic with an average of one SNP every 25 kb, requiring that a family from a more diverse cross is produced for fine mapping and eventual cloning of
Psm
. The cucumber ortholog of
Arabidopsis
mismatch repair (MSH1) was cloned and it segregated independently of
Psm
, revealing that this candidate gene is not
Psm
.