a2-m668144 - a2-rcy responds to Cy

--Peter A. Peterson

This a2-m allele arose in a 1965 isolation plot. It was originally cited in the 1975 Urbana Maize Symposium (Walden, ed. 1978). The early segregation pattern showed colorless segregants and the nature of the mutation pattern suggested segregation rather than mutation-induced loss of mutability events. Early observations eliminated En as the active element though many En were present in the genome.

With the availability of the bz-rcy reporter allele, tests were made to test the involvement of Cy in a2-m668144 mutability. From a segregating progeny, from the cross a2 bt x a2-m/A2, Bz/bz-rcy, Cy, the following phenotypes were selected and intercrossed:
 
  colored round A2 Bt/a2 bt + Cy '88 2359-2360
  colorless round a2(?), Bt/a2 bt '88 2357-2358

The cross:
 
    round bt
    Cl sp cl Cl sp cl
  2360-10 x 2358-2 207 96 119 9 1 110
  2359 x 2357-1 215 47 108 7 0 115

This is a reconstitution test and confirms that the colorless segregants are a2-rcy (responsive allele) and they respond to the presence of Cy. The role of Cy in the mutability of these crosses had previously been established as well as the lack of involvement of En. This is the second a2-m allele to be established as a Cy-related allele from that TEL population in the 1965 series.


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