A classification of the NORIN 10 and Tom Thumb dwarfing genes in British,Mexican, Indian and other hexaploid bread wheat varieties

Summary The two semi-dwarfing genes Rht1 and Rht2 from Norin 10 have now been incorporated in successful varieties in use in most major wheat growing areas. The more potent dwarfing gene, Rht3, from Tom Thumb has been used in a limited way.These genes may be identified and classified by assessing the associated character of GA-insensitivity in the progeny from test crosses.This paper describes these classifications in the CIMMYT, Mexican, PBI, Cambridge and Indian breeding programmes and for a number of other international varieties.