Maize
Genetics Cooperation Newsletter 80. 2006.
In MNL 78:63-64 (2004), we reported the placement of Fcu to the long arm of chromosome 2 using wx1 marked reciprocal translocations. In order to further refine the position of Fcu on 2L, we conducted a five-point linkage test of Fcu with the chromosome 2 markers fl1, v4, w3, and Ch1. The linkage test cross and the results are presented in Table 1. A line homozygous for Fcu was crossed by a line homozygous for fl1, v4, and Ch1, and segregating for w3. Kernels from the resulting cross were planted, and the resulting plants self-pollinated and outcrossed to the Fcu responsive r1 haplotype R1‑r(Venezuela559‑PI302355). Only those outcrosses of plants carrying the factor w3 were advanced to the next generation. Kernels from outcross ears were separated into spotted (Fcu) and nonspotted (fcu) classes, planted in our 2004 Puerto Rico winter and 2005 summer nurseries, and the resulting plants self-pollinated. The resulting ears were scored for the presence of fl1, w3, and Ch1, and scoring was confirmed for Fcu. Kernel samples from each ear were planted in sand benches and scored for the presence of v4. The results were tabulated, and linkage values were calculated (see Table 1). The linkage order and distances were established as:
fl1 – 13.8 – v4 – 15.9 – fcu – 6.6 – w3 – 43.9 – ch1
The linkage values for fl1,
v4, w3, and ch1
are close to those previously reported on the 1993 genetic map of chromosome 2
(Neuffer et al., Mutants of Maize, Cold Spring Harbor Laboratory Press, 1997), fl1 – 15 – v4 – 28 – w3 – 44 – ch1, there being a slight discrepancy in the v4 – w3 distance (22.5 cM, our data, vs. 28 cM, genetic map). However, individually reported linkage
data from Robertson et al. (Genetics 46:649-662,
1961; 22.7 cM, n = 304; and 23.9, n = 376) and Patterson et al. (MNL 42:44-48, 1968; 24 cM, n = 71) are in close agreement with
our data.
Table 1. Five point
linkage data for fl1 v4 fcu w3 ch1.
Testcross: R1‑r(Venezuela559‑PI302355) X [Fl1 V4 Fcu W3 ch1 X fl1 v4 fcu w3 Ch1]
|
Region |
Phenotype |
No. |
Totals |
|
0 |
fl1 v4 fcu w3 Ch1 |
48 |
|
|
|
Fl1 V4 Fcu W3 ch1 |
57 |
105 |
|
1 |
fl1 V4 Fcu W3 ch1 |
9 |
|
|
|
Fl1 v4 fcu w3 Ch1 |
7 |
16 |
|
2 |
fl1 v4 Fcu W3 ch1 |
10 |
|
|
|
Fl1 V4 fcu w3 Ch1 |
10 |
20 |
|
3 |
fl1 v4 fcu W3 ch1 |
6 |
|
|
|
Fl1 V4 Fcu w3 Ch1 |
7 |
13 |
|
4 |
fl1 v4 fcu w3 ch1 |
42 |
|
|
|
F11 V4 Fcu W3 Ch1 |
45 |
87 |
|
1 + 2 |
fl1 V4 fcu w3 Ch1 |
2 |
|
|
|
Fl1 v4 Fcu W3 ch1 |
3 |
5 |
|
1 + 3 |
fl1 V4 Fcu w3 Ch1 |
1 |
|
|
|
Fl1 v4 fcu W3 ch1 |
1 |
2 |
|
1 + 4 |
fl1 V4 Fcu W3 Ch1 |
11 |
|
|
|
Fl1 v4 fcu w3 ch1 |
6 |
17 |
|
2 + 3 |
fl1 v4 Fcu w3 Ch1 |
0 |
|
|
|
Fl1 V4 fcu W3 ch1 |
1 |
1 |
|
2 + 4 |
fl1 v4 Fcu W3 Ch1 |
7 |
|
|
|
Fl1 V4 fcu w3 ch1 |
13 |
20 |
|
3 + 4 |
fl1 v4 fcu W3 Ch1 |
2 |
|
|
|
Fl1 V4 Fcu w3 ch1 |
1 |
3 |
|
|
|
|
|
|
Total (n) |
|
|
289 |
|
|
|
|
|
|
No triple or quadruple crossovers |
|
|
|
Map distance fl1 - v4 =
13.8 � 2.0 cM
Map distance v4 - fcu =
15.9 � 2.2 cM
Map distance fcu - w3 = 6.6
� 1.5 cM
Map distance w3 - ch1 =
43.9 � 3.0 cM
_________________________________________________
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note:
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with consent of the authors.
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