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GrainGenes Gene Class Report: Tipped awns

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Gene Class
Tipped awns
Reference
ReferenceSikka SM et al. (1959) Monosomic analysis in bread wheats. II. Identification of chromosomes carrying genes for awning and glume beak shape Indian Journal of Genetics and Plant Breeding 19:56-63.
ReferenceWatkins AE and Ellerton S (1940) Variation and genetics of the awn in Triticum. Journal of Genetics 40:243-270.
Abbreviation
B
See Also
Tipped 1
Hooded
Awnless
Tipped 2
Character affected
Awns
Comment
Dominant inhibitor.
Bearded (fully-awned) genotype is homozygous hd, b1, b2
Genotypes Hd B2 (e.g., Chinese Spring) and B1 B2 (e.g., Federation) are awnless. Presumably Hd B1 is awnless. Watkins and Ellerton (1137) noted the probability of a third allele 'b1a' leading to a half-awned condition, and in discussion they consider the possibility of a similar third allele at the B2 locus. In view of more recent cytogenic analyses, it seems that the half- awned condition could result from epistatic interactions between the alleles B1 and/or B2 and various promoter genes.
Although hooded, half-awned, tip-awned and awnless variants occur among tetraploid wheats, these are relatively infrequent. It has not been established with certainty that the above inhibitors are involved.
The inhibitor alleles have a pleiotropic effect on glume-beak shape (966). Acuminate beak is associated with full beardedness and occurs only in b1 b2 types. B2 reduces beak length producing an acute beak shape. B1 reduces beak length producing an obtuse beak shape. In this effect, B1 is epistatic to B2.

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