Abstract: Dwarfing breeding of wheat in the world is confined to the exploitation of recessive dwarfing sources. None of the dominant dwarfing sources discovered in common wheat (Triticum aestivum L.) has found wide exploitation in wheat breeding due to the extreme dwarfness of their plants (20-55 cm). It was found that some stable mutant lines with plant height enhanced to different extents could be obtained in large populations derived from the stock seeds of the dominant dwarfing sources 'Aibian 1' carrying Rht10 on 4DS and being 20-55 cm in height and 'Aisu 3' carrying Rht3 on 4BS and being 55 cm in height, or from their descendants of induced mutation treatments, or from the segregating descendants of their crosses with mid- or tall-statured genotypes. Subsequently, these mutation-derived lines differing in plant height with near isogenic lines were studied and it was observed that the character of their enhanced plant breeds true, each carries a semi-dominant dwarfing gene for a definite height and that as the plant height of the mutation-derived lines rises, the yield-contributing characters of their near isogenic lines are significantly improved. When test crosses with marker genes and physiological and biochemical genetic marker tests were performed to re-localize the semi-dominant dwarfing genes carried by the mutation-derived lines, it was confirmed that they share common loci with Rht10 and Rht3 and that they are all mutation-derived multiple alleles. It is thus speculated that dominant dwarfing genes are of "multiple-allelic polymorphism", in other words, dominant dwarfing genes, which are ultra-dwarfing, are liable to develop by mutation into a group of multiple alleles with plant height enhanced to different extents and some may have a height close to the ideal plant height for wheat breeding.

Key words: Wheat, Dominant dwarfing sources, Mutation, Multiple alleles, Dwarfing breeding