--Don Auger and William F. Sheridan

We are modifying a set of forty-five reciprocal translocations and five
pericentric inversion stocks so that they will be useful for transposon
tagging with the *Ac* element. The usefulness of these stocks will
be enhanced by their detailed genetic and cytogenetic characterization.
Presented here are data from nine recombinational mapping experiments to
determine the location of several reciprocal translocation breakpoints.
The first five experiments tested the location of the breakpoint in chromosome
arm 1S and involved the five translocations: T1-3(5597); T1-3(5982); T1-4b;
T1-5(6899); and T1-3k. The other four experiments test the location of
the breakpoint in chromosome arm 3L and involved the four translocations:
T1-3(8995); T1-3k; T1-3(5597); and T1-3(5982).

Plants which are heterozygous for reciprocal translocations show 50% gamete abortion. All plants in this study were scored for semisterile or fully viable pollen. In all mapping experiments the parental translocated chromosome carried dominant alleles at the mapping loci and the parental normal chromosomes carried with them the recessive alleles. Genetic recombination with the breakpoints would bring the recessive traits into coupling with the translocation breakpoint (T). The corresponding locus on the normal chromosome is indicated as N. For these experiments T can be considered as dominant to N. In the tables the loci are shown in the inferred order. The parental (P) class is always presented first. Crossover regions are numbered left to right.

Tables 1 through 5 show the experimental design and the recombination
data for the four translocation breakpoints on chromosome arm 1S. The genetic
mapping markers were *zb4* (*zebra4*) and *P* (*pericarp
color*). Homozygous recessive *zb4* plants have zebra cross banding
on seedling leaves. The *P* locus conditions both pericarp and cob
color and four different alleles were used in these experiments. *P-rr*
produces a red cob and a red pericarp; it is dominant over all other alleles.
*P-vv*
displays a variegated red and white pericarp and cob. *P-wr* conditions
a white (actually clear) pericarp and a red cob. *P-ww* is recessive
to all the other *P* alleles and when homozygous both the pericarp
and the cob are white.

Tables 6 through 9 show the data and experimental design for mapping
the 3L breakpoints. Homozygous recessive *ts4* (*tassel seed4*)
plants have a compact tassel containing both pistillate and staminate florets.
Plants which are homozygous *lg2* (*liguless2*) possess reduced
ligules and auricles. Kernels which are homozygous for recessive *a1*
(*anthocyaninless1*) have colorless aleurones.

Although the order of loci can usually be determined from these data
(there was no recombination between T and *lg2* in T1-3k), the observed
genetic distances between the breakpoints and the adjacent loci are understated.
When translocations are heterozygous with normal chromosomes there is generally
a reduction in crossing over near the breakpoints.

Table 1. Linkage of T1-3(5597) with *zb4* and *P*. The cytological
breakpoints are 1S.77 and 3L.48. The backcross was T *Zb4 P-wr*/N
*zb4
P-ww* x N *zb4 P-ww*/N *zb4 P-ww*.

a) P: | T Zb4 P-wr |
43 | 82 |

N zb4 P-ww |
39 | ||

b) CO1: | T zb4 P-ww |
7 | 22 |

N Zb4 P-wr |
15 | ||

c) CO2: | T Zb4 P-ww |
3 | 4 |

N zb4 P-wr |
1 | ||

d) CO1&2: | T zb4 P-wr |
0 | 0 |

N Zb4 P-ww |
0 | ||

Total=108 |

Conclusion: The breakpoint (T) on 1S is distal to

Table 2. Linkage of T1-3(5982) with *zb4* and *P*. The
cytological breakpoints are 1S.77 and 3L.66. The backcross was *Zb4*
T *P-rr**/*zb4* N *P-ww* x *zb4* N *P-ww*/*zb4*
N *P-ww*.

a) P: | Zb4 T P-rr |
143 | 252 |

zb4 N P-ww |
109 | ||

b) CO!: | zb4 T P-ww |
26 | 46 |

Zb4 N P-rr |
20 | ||

c) CO2: | Zb4 T P-ww |
11 | 17 |

zb4 N P-rr |
6 | ||

d) CO1&2: | zb4 T P-rr |
2 | 3 |

Zb4 N P-ww |
1 | ||

Total=318 |

% recombination: T-

Conclusion: The breakpoint (T) on 1S is distal to

Table 3. Linkage of T1-4b with *zb4* and *P*. The cytological
breakpoints are 1S.55 and 4L.83. The backcross was *Zb4 P-vv** T/*zb4
P-ww* N x *zb4 P-ww* N/*zb4 P-ww* N.

a) P: | Zb4 T P-vv |
250 | 453 |

zb4 N P-ww |
203 | ||

b) CO1: | zb4 T P-ww |
2 | 5 |

Zb4 N P-vv |
3 | ||

c) CO2: | zb4 T P-vv |
0 | 5 |

Zb4 N P-ww |
5 | ||

d) CO1&2: | Zb4 T P-ww |
2 | 3 |

zb4 N P-vv |
1 | ||

Total=466 |

% recombination:

Conclusion: The breakpoint (T) on 1S lies between

Table 4. Linkage of T1-5(6899) with *zb4* and *P*. The
cytological breakpoints are 1S.32 and 5S.20. The backcross was *Zb4 P-wr*
T/*zb4 P-ww* N x *zb4 P-ww* N/*zb4 P-ww* N.

a) P: | Zb4 P-wr T |
51 | 83 |

zb4 P-ww N |
32 | ||

b) CO1: | zb4 P-wr T |
3 | 4 |

Zb4 P-ww N |
1 | ||

c) CO2: | zb4 P-ww T |
1 | 3 |

Zb4 P-wr N |
2 | ||

d) CO1&2: | Zb4 P-ww T |
0 | 0 |

zb4 P-wr N |
0 | ||

Total=90 |

Conclusion: The breakpoint (T) on 1S is proximal to

Table 5. Linkage of T1-3k with *zb4* and *P*. The cytological
breakpoints are 1S.17 and 3L.34. The backcross was *Zb4 P-wr* T/*zb4
P-ww* N x *zb4 P-ww* N/*zb4 P-ww* N.

a) P: | Zb4 P-wr T |
127 | 237 |

zb4 P-ww N |
110 | ||

b) CO1: | zb4 P-wr T |
5 | 9 |

Zb4 P-ww N |
4 | ||

c) CO2: | zb4 P-ww T |
11 | 25 |

Zb4 P-wr N |
14 | ||

d) CO1&2: | Zb4 P-ww T |
1 | 2 |

zb4 P-wr N |
1 | ||

Total=273 |

Conclusion: The breakpoint (T) on 1S is proximal to

Table 6. Linkage of T1-3(8995) with *ts4 lg2* and *a1*.
The cytological breakpoints are 1S.49 and 3L.06. The backcross was T *Ts4
Lg2 A1*/N *ts4 lg2 a1* x N *ts4 lg2 a1*/N *ts4 lg2 a1*

a) P: | T Ts4 Lg2 A1 |
49 | 96 |

N ts4 lg2 a1 |
47 | ||

b) CO1: | T ts4 lg2 a1 |
1 | 3 |

N Ts4 Lg2 A1 |
2 | ||

c) CO2: | T Ts4 lg2 a1 |
16 | 39 |

N ts4 Lg2 A1 |
23 | ||

d) CO3: | T Ts4 Lg2 a1 |
25 | 60 |

N ts4 lg2 A1 |
35 | ||

e) CO1&2: | T ts4 Lg2 A1 |
0 | 0 |

N Ts4 lg2 a1 |
0 | ||

f) CO1&3: | T ts4 lg2 A1 |
1 | 3 |

N Ts4 Lg2 a1 |
2 | ||

g) CO2&3: | T Ts4 lg2 A1 |
2 | 4 |

N ts4 Lg2 a1 |
2 | ||

h) CO1,2&3: | T ts4 Lg2 a1 |
0 | 1 |

N Ts4 lg2 A1 |
1 | ||

Total=206 |

Conclusion: The breakpoint (T) on 3L is proximal to

Table 7. Linkage of T1-3k with *ts4 lg2* and *a1*. The
cytological breakpoints are 1S.17 and 3L.34. The backcross was *Ts4*
T *Lg2 A1*/*ts4* N *lg2 a1* x *ts4* N *lg2 a1*/*ts4*
N *lg2 a1*.

a) P: | Ts4 T Lg2 A1 |
71 | 148 |

ts4 N lg2 a1 |
77 | ||

b) CO1: | ts4 T Lg2 A1 |
11 | 30 |

Ts4 N lg2 a1 |
19 | ||

c) CO2: | Ts4 T lg2 a1 |
0 | 0 |

ts4 N Lg2 A1 |
0 | ||

d) CO3: | Ts4 T Lg2 a1 |
29 | 46 |

ts4 N lg2 A1 |
17 | ||

e) CO1&2: | ts4 T lg2 a1 |
0 | 0 |

Ts4 N Lg2 A1 |
0 | ||

f) CO1&3: | ts4 T Lg2 a1 |
6 | 13 |

Ts4 N lg2 A1 |
7 | ||

g) CO2&3: | Ts4 T lg2 A1 |
0 | 0 |

ts4 N Lg2 a1 |
0 | ||

h) CO1,2&3: | ts4 T lg2 A1 |
0 | 0 |

Ts4 N Lg2 a1 |
0 | ||

Total=237 |

Conclusion: The breakpoint (T) on 3L lies between

Table 8. Linkage of T1-3(5597) with *ts4 lg2* and *a1*.
The cytological breakpoints are 1S.77 and 3L.48. The backcross was *Ts4
Lg2* T *A1*/*ts4 lg2* N *a1* x *ts4 lg2* N *a1*/*ts4
lg2* N *a1*.

a) P: | Ts4 Lg2 T A1 |
59 | 124 |

ts4 lg2 N a1 |
65 | ||

b) CO1: | ts4 Lg2 T A1 |
14 | 25 |

Ts4 lg2 N a1 |
11 | ||

c) CO2: | ts4 lg2 T A1 |
0 | 0 |

Ts4 Lg2 N a1 |
0 | ||

d) CO3: | Ts4 Lg2 T a1 |
25 | 42 |

ts4 lg2 N A1 |
17 | ||

e) CO1&2: | Ts4 lg2 T A1 |
1 | 2 |

ts4 Lg2 N a1 |
1 | ||

f) CO1&3: | ts4 Lg2 T a1 |
4 | 6 |

Ts4 lg2 N A1 |
2 | ||

g) CO2&3: | ts4 lg2 T a1 |
0 | 1 |

Ts4 Lg2 N A1 |
1 | ||

h) CO1,2&3: | Ts4 lg2 T a1 |
0 | 0 |

ts4 Lg2 N A1 |
0 | ||

Total=200 |

Conclusion: The breakpoint (T) on 3L lies between

Table 9. Linkage of T1-3(5982) with *ts4*, *lg2* and
*a1*.
The cytological breakpoints are 1S.77 and 3L.66. The backcross was *Ts4
Lg2* T *A1*/*ts4 lg2* N *a1* x *ts4 lg2* N *a1*/*ts4
lg2* N *a1*.

a) P: | Ts4 Lg2 T A1 |
47 | 97 |

ts4 lg2 N a1 |
50 | ||

b) CO1: | ts4 Lg2 T A1 |
19 | 49 |

Ts4 lg2 N a1 |
30 | ||

c) CO2: | ts4 lg2 T A1 |
5 | 11 |

Ts4 Lg2 N a1 |
6 | ||

d) CO3: | Ts4 Lg2 T a1 |
5 | 11 |

ts4 lg2 N A1 |
6 | ||

e) CO1&2: | Ts4 lg2 T A1 |
1 | 1 |

ts4 Lg2 N a1 |
0 | ||

f) CO1&3: | ts4 Lg2 T a1 |
5 | 5 |

Ts4 lg2 N A1 |
0 | ||

g) CO2&3: | ts4 lg2 T a1 |
1 | 3 |

Ts4 Lg2 N A1 |
2 | ||

h) CO1,2&3: | Ts4 lg2 T a1 |
0 | 0 |

ts4 Lg2 N A1 |
0 | ||

Total=177 |

Conclusion: The breakpoint (T) on 3L lies between

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