v*-424: Allelism tests with v4, w3; linkage to w3

All three loci map to the long arm of chromosome 2 (for v*-424, see Chang, MGNL 56:44, 1982). Allelism tests between v*-424 and w3 or v4 were negative. I employed growth conditions which permitted expression of all three phenotypes and confirmed the parental genotypes for each pair tested. An F2 progeny of the cross: V*-424 v*-424 W3 W3 x V*-424 V*-424 W3 w3 segregated green, albino (w) and virescent (v) seedlings:
  Total Green v w
Number of seedlings 91 39 38  4

Germination was 100 percent. I did not observe any vivipary as is sometimes found for w3. The combined number of v and w individuals is somewhat high, but consistent with the segregation of two independent, recessive loci, if the v-class includes v*-424 v*-424 w3 w3. I will be testing this possibility by backcrosses to material containing only v*-424 or w3. Similar analysis of linkage between v*-424 and v4 is in progress. These two virescent loci can be distinguished by phenotype: v4 requires cold temperatures for expression while v*-424 is expressed at all temperatures tested (up to 95 F).

Mary Polacco

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