Results of additional allele tests of mutants from the Mu line

The results of a number of allele tests of phenotypically similar mutants that arose in the same family from the mutator line were presented last year (MGCNL 50: 68-70, 1976). Several ambiguities were noted. In family 72-3120, 4 luteus mutants arose. All seemed to be allelic by process of elimination. Mutants 6 x 18 and 6 x 20 gave positive tests but crosses of 18 x 20 gave negative results. Also, tests in family 72-3125, in which 5 luteus mutants arose, were incomplete. Crosses of mutants 18 x 29 were not done, making uncertain the results of crosses 18 x 20, which gave one positive test, and 20 x 29, which gave three positive tests. The following table presents results of allele tests made this summer that clarify these inconsistencies.
Family number Mutant numbers Number of crosses Number of positive tests Probability of allelism
72-3120 18 x 20 15 8 1
72-3125 18 x 20 17 0 < .01
  18 x 29 9 0 < .01
  20 x 29 6 1

Thus in family 72-3120 the four mutants are allelic while in family 72-3125, of five mutants tested, only mutants 20 and 29 are allelic.

These results, and results of additional allele tests done this summer do not alter last year's conclusion that most mutations occur very late in development or during meiosis.

Peter Mascia and D. S. Robertson

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

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