10                           PNL Volume 20                       1988 RESEARCH REPORTS
A SCAFFOLD FOR A NEW LINKAGE GROUP (VII)
Folkeson, Donald                                                                                Institute of Genetics
Solvegatan 29, S-223 62 Lund, Sweden
I. Cytological notes for L-lll, L-21, and L-112
In an earlier paper (5), evidence was presented for including the linkage segment r-tl-bt in the linkage segment V (gp), i.e. only six linkage segments for the seven chromosomes of the pea. This leaves a new Linkage group to be found. In previous reports by Folkeson and Lamm the chromosome lacking localized markers was indicated to be a satellite chro­mosome .
A revision in progress of Lamm's tester set using BSG-staining shows that L-lll and L-112 share the same satellite chromosome in their inter­change systems (4). These interchange lines are then suitable for linkage studies to define the missing linkage group. L-lll has, in the latest paper (12), been interpreted as a T(4-5) interchange. The present inves-tigation reveals that the long arm, rather than the short arm, is involved in the satellite chromosome concerned, i.e. T(4L-5L) (Figs. 1, 2).
In a < ross between L-112 and L-21, seven bivalents were found with complete (100%) fertility (Lamm unpub., cf. 10) indicating identical chro­mosome structure (cf. 7). This made it possible to compile the cytologi­cal results of L-112 and L-21.
In a cytological investigation by Blixt (2), L-21 was interpreted as T(1S-4S/7S). However, by plotting analysis, Blixt's cytological measure­ments can also be interpreted as a T(3S-4S/7S). This interpretation has recently been supported by Lamm (10) and Folkeson (4) and is also suppor­ted by unpublished data from work with L-112 in the ongoing revision.
PNL Volume 20                       1988 RESEARCH REPORTS                      11
Fig. 1. (Ml) Arrows I and III indicate the bivalents originating from the split quadrivalent. Two BSG spots in each of the bivalents concerned indicate that the interchange point is in the long arm of the involved SAT-chromosome of L111. Arrow II points to the bivalent of the second SAT-chromosome.
Fig. 2. (A1) Arrow indicates chromosome with unequal chromatids, one with a BSG spot (cf. 18).
II. Ambiguous linkage for wsp and 6pgd-p
The linkage wsp-r previously established (14), which locates these genes in the same linkage group, occurs only in crosses with lines L-21 and L-112 which are of known structure (2,8) and L-25 and 1,-794 of unknown structure. Linkage for wsp-r was, on the other hand, not detectable in crosses no. 429, 607, 999, and 1229 (16, 17). A compilation of H. Lam-precht's results of cross no. 1062 (L-25 x L-998) places the interchange point in the middle of all the combinations with the gene markers wsp, r, and bt (Table 1). This excludes the position of wsp in linkage group V (Table 1).
A persistent, negative interference which occurs in the system of wsp-T-tl/r in crosses with L-25 as well as L-112 (Tables 1, 2), i.e. rec. wsp-T) > rec. (T-tl/r) + rec. (wsp-tl/r), complicates the interpretation, but the result of crosses with L-87 (below) persuaded me to draw the pre­sent conclusion. A similar situation has been analyzed by Sybenga (19).
In a test for linkage of wsp, the following three lines of Lamm's tester set were used:
L-87 T(3-5), ref. 7,8 L-lll T(5-7L), ref. 4,7,above L-112 T(3-7S), ref. 4,7,8. Linkage was expected in two cases of three, but linkage was found only in one case, i.e. with L-112 (Table 2). Linkage with either L-87 or L-lll was also expected to establish whether wsp belongs to Linkage group V or the unassigned new linkage group VII. If wsp is Located in the same linkage group as the tl-r segment, crosses with L-87 or L-112 should show
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PNL Volume 20
1988 RESEARCH REPORTS
Table 1. Segregation data from Lamprecht's cross no. 1062 (L-25 x L-1041) relating to the location of T, wsp, r_, bt_; see
Gene pair
XY
Xy
xY
xy
Total
Chi-square
Recomb. fract.
S.E.
X
Y
Linkage
T-R
182
153
341
10
686
0.37
0.56
166.00
3.1
0.93
T-Wsp
234
101
283
68
686
0.37
0.05
10.64
26.7
3.53
T-Bt
228
107
289
62
686
0.37
0.05
18.67
23.2
2.99
R-Bt
425
98
92
71
686
0.56
0.05
39.53
33.9
2.31
R-Wsp
425
98
92
71
686
0.56
0.05
39.53
33.9
2.31
Bt-Wsp
391
126
125
43
685
0.08
0.04
0.01
49.1
2.84
F2 analysis of segregation data for T, wsp, tl in cross between
1.   L-112 x L-150: T(3-7) , Wsp, Tl x N wsp, tl , D. Folkeson unpub. 1985
2.   L-112 x L-150: T(3-7) , Wsp, Tl_ x N wsp, tl , R. Lamm, unpub.
Gene pair
XY
Xy
xY
xy
Total
Chi-square
Recomb fract.
S.E.
X
Y
Linkage
1 T-Tl
61
50
118
4
233
0.52
0.41
54.40
3.5
1 .64
1 T-Wsp
81
30
100
22
233
0.52
0.89
2.65
28.5
6.55
1 Tl-Wsp
156
25
23
29
233
0.41
0.89
35.54
24.5
3.30
2 T-Tl
43
36
92
0
171
0.99
1.42
48.05
Absol.
-
2 T-Wsp
57
22
67
25
171
0.99
0.56
0.002
-
-
2 Tl-Wsp
109
15
26
21
171
1.42
0.56
19.99
27.5
3.25
Table 3. Compiled segregation data for interchange lines L-87 and L-111 Origin of lines cf. ref. 5, 8.
1 L-87
x L-150
T(3-5) Wsp, Tl x N, wsp, tl
Folkeson, unpub. 1987
2 L-87
x L-150
T(3-5) Wsp, Tl x N, wsp,tl
Lamm, Ref. 8
3 L-87
x L-360
T(3-5) Wsp, Tl x N, wsp, tl
Lamm, unpub.
4 L-111
x L-150
T(5-7), Wsp, Tl x N, wsp, tl
Folkeson, Ref. 5
5. L-111
x L-150
T(5-7), Wsp, Tl x N, wsp, tl
Folkeson, unpub.
6. L-111
x L-150
T(5-7), Wsp, Tl x N, wsp, tl
Lamm, unpub.
7 L-lllb
x L-1072
T(5-7), wsp.tl x N, Wsp, Tl,b
Folkeson, unpub.
8 L-111
No. Gene pair
x L-119
XY Xy
T(5-7), B x N, b
Lamm, Ref.
No.
Gene pair
XY
Xy
xY
xy
Total
Chi-square
Recomb. fract. S. E .
X Y Linkage
1-3
Wsp-Tl
456
155
156
49
816
0.01 0.00
0.18
-
4,7
Wsp-Tl
266
73
111
39
489
8.40 1.15
0.96
-
4-7
T-Wsp
226
90
271
115
708
5.79 8.71
0.07
-
7
B-Wsp
97
58
34
15
204
0.10 12.65
1.05
-
7,8
T-B
68
67
141
14
290
1.38 1.33
61.87
8.0 2.3
PNL Volume 20                    1988 RESEARCH REPORTS                    13
the corresponding linkage for wsp-tl/r when the T-tl/r linkage is quite similar (cf. 8, 9; Tables 2, 3). The lack of linkage between wsp-tl/r in crosses with L-87 T(3-5) (Table 3), together with the previous statement, excludes the location of wsp to linkage group V. The lack of significant linkage between_ T-wsp in crosses within L-111 could be explained by the different location of the breakage point in the common SAT-chromosome for L-lll(L) and L-112(S) (cf. above).
The compiled data of crosses no. 7 and 8 (Table 3) for T-b renders b as the closest gene marker (previously T-st) to the interchange point of L-111. An additional linkage test for wsp in crosses with L-111 requires a marker gene that is linked closer to the interchange point than b.
The linkage of 6pgd-p has previously been assigned to a segment of unknown chromosome location (20), which makes it a candidate for the mis­sing linkage group. A linkage test for 6pgd-p to the interchange point of L-111 has been performed, but no linkage was determined in 201 indivuais scored.
SUMMARY. The most probable location of wsp would be in the short arm of one of the satellite chromosomes 4 or 7 outside the interchange point of L-112/L-21.
1.  Allard, R. W. 1956. Hilgardia 2:235-279.
2.  Blixt, S. 1959. Agri Hort. Genet. 17:47-75.
3.  Blixt, S. 1972. Agri Hort. Genet. 30:1-293.
4.  Folkeson, D. 1984. Hereditas 101:119-121.
5.  Folkeson, D. 1984. Hereditas 101:227-233.
6.  Folkeson, D. 1985. PNL 17:15-16.
7.  Kasha, K. J. and C. R. Burnham. 1965. Canad. J. Genet. Cyt. 7:620-632.
8.  Lamm, R. and R. J. Miravalle. 1959. Hereditas 15:417-440.
9.  Lamm, R. 1960. Hereditas 46:737-744.
10.  Lamm, R. 1974. PNL 6:29.
11.  Lamm, R. 1986. PNL 18:34-36.
12.  Lamm, R. 1987. PNL 19:20-23.
13.  Lamm, R. Unpublished.
14.  Lamprecht, H. 1954. Agri Hort. Genet. 12:115-120 (L-794).
15.  Lamprecht, H. 1955. Agri Hort. Genet. 13:173-182 (L-21).
16.  Lamprecht, H. 1955. Agri Hort. Genet. 13:214-229 (cf. 222)
17.  Lamprecht, H. 1959. Agri Hort. Genet. 17:15-25.
18.  Sybenga, J. 1975. Meiotic Configuration. Spring-Verlag, Berlin, Heidelberg, New York. p. 109-110.
19.  Sybenga, J. 1980. Heredity 44:83-92.
20.  Weeden, N. F. 1984. The Pea Crop. Hebblethwaite, et al., eds. Butterworths, London, p. 55-66.