Figure 2.

Phenotypes of b alleles. A–D and F are photographs of plants carrying exotic or teosinte-derived b alleles, which are the result of at least three backcross generations into our b tester stock. (A) culm (c) and sheath (s) of B-Mag466 showing the “spray” pattern on the sheath. (B) Sheath of B-Mex7a showing nonclonal spots. (C) Tassel branches showing the “glume bar” phenotype from B-M063. (D) B-Gua31 plant. Note the unpigmented node (n). (E) B-Bolivia plant. Note the similarity to B-Gua31, including the unpigmented node (n). (F) auricle (a), ligule (l), and sheath of B-Mex7b. (G) Auricle (a) and sheath of B-I. (H) Sheath and culm of B-Peru. (I) Tassel branches of B-Peru [anther (r) color is caused by an allele of the r gene]. (J) Ear from a B-Peru homozygote. (K) Ear from a B-Bolivia homozygote. (L) Consecutive sheaths of an F₁ plant from the cross between Gua31 and the b tester stock showing the “carbon-copy” response. The plant was numbered when the upper sheath was mostly covered by the lower one, several weeks before this picture was taken. This plant also illustrates the effect of genetic background on expression. Compare F₁ in L to a plant with the same allele after three backcross generations into our b tester stock (D).