A previous report (Modena and Coe, MNL 55:115) eliminated ten chromosomal arm segments by TB tests. During the summer of 1981 I have excluded 5S by TB uncovering, the centromeric region of 4 by a linkage test with su, and 6S and the centromeric region by a linkage test with y.
The TB observations of last year were conducted in an isolated open pollinated block. The ears on hypoploid plants were recovered. Following the suggestion of Beckett (J. Hered. 69:27-36, 1978), families from these ears, of size sufficient to distinguish a 3:1 vs. 1:1 ratio at the 5% level, were grown as two replicates. No linkages to the TB breakpoints were discerned, thereby excluding these segments: 1S proximal and centromeric; 3 centromeric; 4 centromeric; 5 centromeric; 6S proximal and centromeric; and 9 centromeric.
Tests are advancing for the remainder of the genome (1S, 2, 4L, 7S, 8S and centromeric, 10).
Stephen A. Modena
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