AbstractRht12, a dominant dwarfing gene of wheat, was shown to be located distally on the long arm of chromosome 5A. Lack of recombination with the awn inhibitorB1suggested thatRht12is cither tightly linked to this gene or is, in this material, a pleiotropic expression of the gene. Linkage toβ‐Amy‐A1was also very tight, indicating thatRht12is present on the segment of chromosome SAL ancestrally translocated from 4AL. The close linkage toβ‐Amy‐A1also suggests thatRht12is not a homoeoallele of the commercially important GA‐insensitive dwarfing genes.Analysis of near‐isogenic lines in a number of genetic backgrounds showed thatRht12reduces height without altering ear size and significantly increases spikelet fertility. However its successful utilization in breeding programmes will require careful selection since in some backgrounds the gene reduces grain numbers and grain size. In all backgrounds,Rht12delayed ear emergence time by around 6 days. A delay of this magnitude could, in many environments, adversely affect yield if it is not neutralized by altering the balance of other genes determining ear e
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