Abstract
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.
Highlights
Winter rye (Secale cereale L.) contributes to crop diversity primarily in a belt that ranges from Northern Germany through Scandinavia, the Baltic states, Poland, Ukraine, and Belarus, into central and northern Russia
Our genetic analyses confirm previous reports (Korzun et al, 1996; Tenhola-Roininen and Tanhuanpää, 2010) on a monogenic dominant inheritance of Ddw1. Both previous genetic studies were conducted in F2 populations whereas we here analyzed a population of RIL, that originate from an independent F1 plant of the same cross as the F2 population analyzed by Korzun et al (1996)
As phylogenetic relationships can provide information on gene function (Eisen, 1998), the results described for OsGA2ox6 in rice stimulate further research to expand our understanding how ScGA2ox12 operates in rye
Summary
Winter rye (Secale cereale L.) contributes to crop diversity primarily in a belt that ranges from Northern Germany through Scandinavia, the Baltic states, Poland, Ukraine, and Belarus, into central and northern Russia. This multipurpose small grain cereal is highly productive as hybrid variety due to its efficient and sustainable use of nutrients and water. Hybrid breeding resulted in significant breeding progress in rye (Laidig et al, 2017), the genetic gain achieved for lodging tolerance of this cereal crop during the last 26 years has been marginal (Laidig et al, 2018)
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