Frego bract, a genetic marker in upland cotton.

The search for sufficient genetic markers to map the 26 chromosomes of upland cotton (Gossypium hirsutum L.) is continuing. This report describes a useful marker. Seed of a mutant type of upland cotton designated as ‘frago’ was sent to the U.S. Cotton Field Station at Stoneville, Mississippi, in 1945 by Mr. Keith J. Bilbrey of Blytheville, Arkansas. The bractlets of this cotton are abnormally long and slender and they curl back away from the open boll when dry. The long narrow shape is characteristic throughout the period of blooming and boll development. Frego plants can be identified by their leaf growth before squares are formed. The veins from unusually acute angles and the lamina forms longitudinal folds. The frago type is inherited as a simple recessive. The homozygous dominant and heterozygote cannot be distinguished and a phenotypic ratio approaching a 3:1 was observed in the F2 generation. In frego x Deltatype Webber the ratio in the F2 was 784 normal:263 frego, a very close fit to a 3:1 retio (χ2=0.008, P=.90-.95).