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The gibberellin (GA)-sensitive dwarfing gene Ddw1 provides an opportunity to genetically reduce plant height in rye. Genetic analysis in a population of recombinant inbred lines confirmed a monogenetic dominant inheritance of Ddw1 . Significant phenotypic differences in PH between homo- and heterozygotic genotypes indicate an incomplete dominance of Ddw1 . De novo transcriptome sequencing of Ddw1 mutant as well as tall genotypes resulted in 113,547 contigs with an average length of 318 bp covering 36.18 Mbp rye DNA. A hierarchical cluster analysis based on individual groups of rye homologs of functionally characterized rice genes controlling morphological or physiological traits including plant height, flowering time, and source activity identified the gene expression profile of stems at the begin of heading to most comprehensively mirror effects of Ddw1 . Genome-wide expression profiling identified 186 transcripts differentially expressed between semi-dwarf and tall genotypes in stems. In total, 29 novel markers have been established and mapped to a 27.2 cM segment in the distal part of the long arm of chromosome 5R. Ddw1 could be mapped within a 0.4 cM interval co-segregating with a marker representing the C20-GA2-oxidase gene ScGA2ox12 , that is up-regulated in stems of Ddw1 genotypes. The increased expression of ScGA2ox12 observed in semi-dwarf rye as well as structural alterations in transcript sequences associated with the ScGA2ox12 gene implicate, that Ddw1 is a dominant gain-of-function mutant. Integration of the target interval in the wheat reference genome sequence indicated perfect micro-colinearity between the Ddw1 locus and a 831 kb segment on chromosome 5A, which resides inside of a 11.21 Mb interval carrying the GA-sensitive dwarfing gene Rht12 in wheat. The potential of Ddw1 as a breeder’s option to improve lodging tolerance in rye is discussed.

The genetics and relationships between the genes in rye located in the nucleus and cytoplasm of the male sterility of the G-type were investigated. A factor inducing male sterility was found in the cytoplasms or rye cv Schlägler alt and rye cv Norddeutscher Champagner. Monogenic inheritance was observed in linkage tests. Using primary trisomies of rye cv Esto, the nuclear gene ms1 was found to be located on chromosome 4R. Modifying genes, probably masked in normal cytoplasm but expressed in male-sterility-inducing cytoplasm together with gene ms1, were located on chromosomes 3R (ms2) and 6R (ms3). Mono-, di-, and trigenic inheritance types were found in backcross progenies of trisomies.

An F2 population was established for mapping the two dominant genes for dwarfness (Ddw1) and hairy peduncle (Hp) on chromosome 5R. The location of both genes was shown to be on the segment of chromosome 5RL which was ancestrally translocated and is homoeologous to Triticeae 4L. Hp cosegregated with the wheat gDNA probe WG199, localised in wheat on chromosomes 5AL, 4BL and 4DL. No segregation was observed between the traits hairy peduncle and hairy leaf sheath. The locus for Ddw1 was found to map distally to Hp/Xwg199 but proximal to the isozyme marker β-amy-R1. The genetical distances were 5.6 cM between Hp/Xwg199 and Ddw1 and ll.ScM between Ddw1 and β-amy-R1, respectively. The map position of Ddw1 suggests that it is homoeologous to the wheat dominant dwarfing gene Rht12, present on chromosome 5AL and linked to β-amy-A1.

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