gay, a new mutant in chromosome 1

Recessive mutations conditioning a germless, anthocyaninless and carotenoidless kernel phenotype have arisen in our colored aleurone stocks three different times since 1974. All three mutations proved to be allelic. Kernels carrying the new mutation, termed gay (g = germless; a = anthocyaninless; y = non-yellow), lack a discernible embryo but possess a variably developed, chalky white endosperm. The endosperm in these kernels does develop sufficiently to allow expression of characters like sh and wx.

The first instance of gay arose in a stock which was segregating coincidentally for variants at the P locus. A very strong linkage between P and gay immediately became evident. Subsequent crosses of gay/+ heterozygotes to TB-1Sb revealed that gay was uncovered by this translocation. Since Neuffer had described (personal communication and MNL 52:87, 89) mutants with similar phenotype mapping to 1S, allelism tests were conducted between gay and Neuffer's mutants E628A, E792, E1348, E1394 and E1401. (Ed. note: The symbol clf was assigned to the 1S factor in Neuffer, 1978, pp. 579-600 in D. B. Walden, ed., Maize Breeding and Genetics.) These tests established allelism between gay and Neuffer's mutants E792, E1348, E1394 and E1401, but not E628A.

Subsequently, the following 3-point cross was performed: (P-WR gay) + / (P-WW +) zb4 x (P-WW +) zb4. Normal (i.e., non-gay) kernels from the above backcross were planted and the resulting plants were scored for zb4 and for gay segregation and P after selfing. The 3-point data and the map constructed from them are given below.
 
P-WR gay + P-WW + zb4 P-WR gay zb4 P-WW + + P-WW gay zb4
51
50
3
5
1

Genetic map: 1 S (centromere) -- gay 0.8 P 7 zb4

The estimated distance between P and zb4 is in excellent agreement with that published in "The Mutants of Maize" (Neuffer, Jones and Zuber). Further 2-point data can be used to obtain a better estimate of the gay-P distance. The following F2 progeny from gay P-WR/+ P-WW plants has been fully classified: 104 P-WW +/ P-WW +; 22 P-WR gay/P-WW + (resolved by F3 testing), and 2 P-WR +/P-WW + (by F3 testing). The fraction of strands recombinant between P and gay is 2/256 or 0.78%. If the backcross and F2 data are pooled this fraction is 3/366 or 0.82%. Therefore, the best estimate of the distance between P and gay is 0.8 map units.

Hugo K. Dooner

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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