bt

 

Bt - Blunt pod (acutilegumen)

The gene with primary control of the shape of the pod apex in peas is Bt. The dominant allele (Bt) confers a rather squared-off, or blunt shape to the pod apex, while the recessive allele (bt) results in a pod apex that has a distinctly acute angle, or point, when homozygous. This gene can only be properly scored in pods where the terminal seed has developed, as a Bt pod with an aborted terminal seed will appear rather pointed. Blunt pods are more common in the species than are pointed pods, accounting for about 75% of the accessions in the USDA PI collection. It should be mentioned, however, that not all examples of the distinction between blunt and pointed pods are as clear as the example shown above, and we often puzzle a bit in the field when deciding whether a pod is pointed or blunt. Because of this, I would place a rather large error interval on that 75% figure. In the Genetic Stocks collection, however, Dr. Marx worked with material that was genetically defined, and in this collection, 318 of the 400 accessions for which the allele at the Bt locus is specified are blunt (Bt).

The locus for Bt maps at the very end of linkage group V. If you would like to query for this gene, click here.