The mutant pb1 is a temperature-sensitive mutant that produces patches of lighter color on its leaves when grown at high temperatures (35 C). The COOP's stocks of pb1 all show complete linkage of pb1 with y1. Because there exist temperature-sensitive alleles at the y1 locus that produce phenotypes similar to that of pb1 (Robertson and Anderson, J. Hered. 52:53-60, 1961), allelism tests were conducted between pb1 and the temperature-sensitive y1 allele y1-wmut (as well as with an unplaced temperature-sensitive piebald mutant, pb*-Burnham). Crosses were made between pb1 and pb*-Burnham as well as between y1-wmut and pb*-Burnham. (No crosses were made directly between pb1 and y1-wmut.) Kernels from these crosses were planted in flats of soil and grown in a 35 C growth chamber. The resulting seedlings all showed the high temperature piebald phenotype. Nonmutant control kernels produced green seedlings under the same conditions. Thus, these three mutants are allelic. We have renamed the pb1 and pb*-Burnham alleles y1-pb1 and y1-pbBurnham, respectively.
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