Cat3 is not on chromosome 1L

We reported linkage data in the News Letter last year which were not wholly consistent with the reported localization (D. G. Roupakias, et al., 1980, TAG 58: 211-218) of Cat3 to 1L. Using a TB-1La stock (provided to us by Kathleen Newton) carrying Adh1-2 and Adh1-6 (Adh1-C and Adh1-S in the usual Schwartz notation), exact 'reciprocal crosses were made with a stock homozygous for Adh1-4 (Adh1-F of Schwartz) and for Cat3-14, the most extreme Cat3 variant.

We examined a total of 21 plants. Nine of these were from the cross using the TB-1La stock as female parent. All nine of those plants carried Adh1-4 and either Adh1-2 or Adh1-6 or both. Eight plants were Cat3-12/14. One was Cat3-14/null. An additional five plants were from small kernels from the cross using the TB-1La plant as the male parent. All five carried both Adh1-4 and Adh1-6. At least two of the five, and probably three, carried two doses of Adh1-6. Four were Cat3-12/14; one was Cat3-14/null. Seven plants were from large kernels from the cross with TB-1La as male parent. Each of these carried only the Adh1-4 of the female parent and lacked an Adh1 allele from the male parent. Yet of these seven plants, five were Cat3-12/14, while two were Cat3-14/null. All plants were heterozygous for Acp1, Glu1, and Pgm2, and results for 17 additional loci suggest that contamination was not a factor in these crosses. The seven plants lacking an Adh1 allele from the male parent also appeared to have only one Phi1 allele and one Mdh4 allele. These results demonstrate that Cat3 is not uncovered by TB-1La, but rather suggest that at least some TB-1La stocks carry null alleles or repressors for Cat3. Together with linkage data already available for loci known to be on 1L, these results suggest that Cat3 must reside elsewhere in the genome.

M. M. Goodman and C. W. Stuber


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