—
PNL Volume 19 1987 RESEARCH REPORTS 35
SUPPLEMENTAL LINKAGE DATA FOR CHROMOSOMES 1 AND 7
Marx, G. A. NYS Agricultural Experiment Station
Geneva, NY 14456 USA
Although aeromaculata (aero) was found to be situated in
chromosome 1 in close proximity with I and Af (3), the population
sizes used to make that determination were smaller than desired to
fix the linkage intensity with confidence. Therefore, new crosses
were made to generate segregating populations of larger size.
plants from crosses between af and aero were grown in the
field in 1986 where they produced abundant seed. Nearly 1900
F2 seeds were then planted in flats in the greenhouse. The
resulting seedlings were scored in the 6-8 node stage of develop-
ment, at which time the phenotypes were clearly manifest and re-
liably distinguished. It is evident from the data in Table 1 that
the linkage between af and aero is unusually tight, for not a
single recombinant was recovered.
Table 1. Joint segregation in F2 from crosses: Af aero x af Aero.
Gene Pair XY
Xy xY xy
Tot.
Chi-square Recomb.
S.E.
X Y Linkage fract.
Af-Aero 942
484 465 0
1891
0.138 0.406 211.112** <4.6
(Pops. C286-506-521;675-692;752)
2.3
A, Au, and Af are known to reside in chromosome 1. Un-
fortunately, few favorable markers are located between A, which is
near one end of the chromosome, and the cluster of genes which
includes Af. An analysis of an F2 in which the three genes
segregated simultaneously is given in Table 2. Whereas A and Au
show moderately strong linkage, neither mutant showed linkage with
Af.
Table 2. F2 analysis of a three-point cross:
A au Af x a Au af.
A
Au
Af
No.
Gene Pair
Chi-square
Recomb.
fract. S.E.
+
+
+
115
+
+
-
49
X Y Linkage
+
-
+
2
A-Au
0.37 5.26* 114.80**
8.2 1.9
+
-
-
1
A-Af
0.37 1.89 0.28
- -
-
+
+
17
Au-Af
5.26* 1.89 0.00
- -
-
+
-
5
(Pops. B286-673-676; 680,681,694-696)
-
-
+
28
-
-
-
11
Total
228
36
PNL Volume 19 1987 RESEARCH REPORTS
Table 3A,B,C provides additional data relating to the linkage
of Det and Curl in chromosome 7. These results together with
those presented previously (2) and those reported by other inves-
tigators (1,4,5) establish rather convincingly that Det, Curl, R,
and Tl are all linked on the same chromosome. While the estimates
of linkage intensity for Curl between years and between investi-
gators are rather consistent, the estimates involving Det and R
and Tl are less uniform. The recombinant fraction for Det-Tl in
Table 3A is 27 + 4, which agrees reasonably well with Swiecicki's
data (4), but the estimated distance between Pet and R shown in
Table 3B and C is 1 unit and in 1986 7 units. This tight linkage
is unexpected in light of the fact that Tl and R are so tightly
linked.
The paper by Makasheva and Drozd (page 31, this volume) re-
veals not only that the gene for determinate habit was discovered
in 1975 but also that the symbol det was proposed that year by
Popova. It would appear that the same mutant was induced in exp-
eriments conducted independently in USSR (1) and in Poland (4) and
that the mutant arose spontaneously sometime before that. The
spontaneous mutant is the source of the accession held by the John
Innes Institute.
1. Makasheva, R. Kh. and A. M. Drozd. 1987. PNL 19:31.
2. Marx, G. A. 1986. PNL 18:45-48.
3. Marx, G. A. 1986. PNL 18:42-44.
4. Swiecicki, W. K. 1987. PNL 19:72.
PNL Volume 19 1987 RESEARCH REPORTS
37
Table 3. Linkage analyses of a dihybrid cross (A) and two four-point
crosses (B and C) involving genes on chromosome 7.
A. Joint segregation in F2 of Tl and Det
Gene Pair
XY
Xy
xY
xy Tot.
Chi-square
X Y Linkage
Recomb
fract.
S.E.
Tl-Det
207
112
86
8 413
1.10 3.62 26.69** 26.8
4.5
(Pop. B286-624-641)
B. F2 analysis of cross segregating simultaneously for curl, tl, r,
and bt
Curl
Tl
R
Bt
No.
Gene Pair
Chi-square
Recomb.
fract.
S.E.
+
+
+
+
97
+
+
+
-
30
X Y Linkage
+
+
-
+
0
Curl-Tl
2.82 3.33 18.86**
22.1
6.0
+
+
-
-
0
Curl-R
2.82 2.82 15.38**
25.7
5.8
+
-
+
+
1
Curl-Bt
2.82 2.82 0.94
—
—
+
-
+
-
1
Tl-R
3.33 2.82 300.30**
1.1
0.6
+
-
-
+
57
Tl-Bt
3.33 2.82 0.40
—
—
+
-
-
-
13
R-Bt
2.82 2.82 0.78
-
-
-
+
+
+
40
(Pop. B286-642-651)
-
+
+
-
7
-
+
-
+
1
-
+
-
-
0
-
-
+
+
0
-
-
+
-
0
-
-
-
+
3
-
-
-
-
0
Total 250
C. F2 analysis of cross segregating simultaneously for curl, det,
r, and bt
Curl
Tl
R
Bt
No.
Gene Pair
Chi-square
Recomb.
fract.
S.E
+
+
+
+
96
+
+
+
-
30
X
Y Linkage
+
-
+
1
Curl-Det
7.45**
1.47 15.99**
15.4
6.4
+
+
-
-
0
Curl-R
7.45**
0.82 15.23**
15.7
6.4
+
-
+
+
3
Curl-Bt
7.45**
3.88* 0.11
-
-
+
-
+
-
0
Det-R
1.47
0.82 248.28**
1.4
0.8
+
-
-
+
54
Det-Bt
1.47
3.88* 3.12
-
-
+
-
-
-
8
R-Bt
0.83
3.88* 2.69
-
-
-
+
+
+
32
(Pop. B286-652-660)
-
+
+
-
7
-
+
-
+
0
-
+
-
-
0
-
-
+
+
0
-
-
+
-
0
-
-
-
+
1
-
-
-
—
0
Total 232