The sudden appearance of white pollen in progenies with c2 and pedigrees tracing to K55 inbred line (Coe, McCormick and Modena, J. Hered. 72:318, 1981) raises the question of the source of the whp factor. Among the likely possibilities would be that whp is present in the K55 inbred itself; the factor might occur in other inbred lines as well.

To test for whp constitution, K55 (supplied by M. S. Zuber) and several other inbreds were crossed onto white-pollen plants, then backcrossed to white pollen. Colorless (c2 c2) seeds from the backcross were planted for observation of pollen color. Each of 5 tested plants from K55 was homozygous for whp. Tests on one plant of each of 3 other white-endosperm inbreds (Ky21, Mo20W, Ky27) and 2 yellow inbreds (L289 and Mo17) identified each to be dominant (Whp).

K55 is clearly carrying whp, either homozygous or in a high frequency in the inbred. There is no evidence from tests of the other inbreds that whp is present in them. The presence of whp in K55 as a cryptic recessive, not recognized until the duplicate locus, C2, was recessive, exemplifies the difficulty of recognizing mutants at loci whose functions are duplicated elsewhere in the genome.

E. H. Coe, Jr.

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