34                           PNL Volume 20                       1988 RESEARCH REPORTS
SUPPLEMENTAL MAPPING DATA FOR CHROMOSOME 6
Skarzynska, Aldona Garden Plant Breeding Station, Zielonki, Poland
The gene for resistance to Pea Seedborne Mosaic Virus (PSbMV) in pea has been found in two accessions, PI 193586 and PI 193835 (2). Using these lines as sources of resistance, Hagedorn and Gritton developed hor-ticulturally improved lines designated Wisconsin 7105 and Wisconsin 7106, both resistant to SbMV.
Gritton and Hagedorn (1) then reported the linkage of the gene sbm with wlo in chromosome 6 with recombination fraction of ca. 12%. The linkage was confirmed by Hampton and Marx (3) with the suggestion of using wlo as the marker gene in selection for resistance.
We tested this suggestion in our own breeding work. Two sbm lines, Wis 7105 and Wis 7106, were crossed with wlo lines Wt 11340 and 10341 (from the Wiatrowo pea genebank), a repulsion phase cross. The dihybrid segregation in F2 gave little evidence of linkage:
Wlo Sbm
Wlo sbm
wlo Sbm
wlo sbm
Total
233
146
90
41
510
Although those data do not show linkage between sbm and wlo there was an excess of segregants scored as resistant, so there was a possibility that susceptible plants had been misclassified as resistant. Further studies on the localization of sbm therefore were pursued; these studies included other known Loci oi chromosome 6.
In the first step Wt 11778 = PI 193586 (sbm) was crossed with Wt 16140 (wlo art-1 ) . All F1 plants proved susceptible to PSbMV. Monohybrid segregation with no disturbances was observed in F2 (Table 1A). In a population of 906 plants, the dihybrid segregation for sbm-wlo showed deviations from independence and a CrO value = 23.0 (Table IB); for sbm-art-l the calculated CrO value was 41.2.
Wt 12070 == Wis 7106 (sbm) was also crossed with Wt 16141 (art-1 p). Again the F1 plants were susceptible and an undisturbed monohybrid segregation was observed (Table 2A). The dihybrid segregation (about 800 plants) showed a linkage between Sbm and Art-1 with a CrO value of 34.2 +/- 3.1% and between Sbm and P with CrO value of 24.5 +/- 13.3% (Table 2B).
Thus none of the above genes (wlo, art-1, or p) seems to be a closely Linked marker for sbm. On the basis of the gene order presented by Marx (4) and on our own results described above the following situation is pro­posed :
PNL Volume 20
1988 RESEARCH REPORTS
35
Table 1. Phenotypic distribution in an F2 population segregating for genes on chromosome 6 from Wt 11778 (sbm) x Wt 16140 (wlo, art-1) .
A. Monohybrid F2 segregation.
Wlo 672
wlo
238
Total 910
Chi-square (3:1)
0.65
Sbm 690
sbm 216
906
0.65
Art-1 701
art-1 208
909
2.17
B. Joint segregation of sbm with wlo and art-1.
Joint
Chi-
square
Phase
R.F.
S.E.
Wlo Sbm 464
Wlo sbm 204
wlo Sbm 226
wlo sbm 12
Total
906
63.42
R
23.0
3.1
Wlo Art-1 568
Wlo art-1 102
wlo Art-1 132
wlo art-1 106
908
83.53
C
30.5
1.9
Sbm Art-1 516
Sbm art-1
174
sbm Art-1 183
sbm art-1 33
906
8.86
R
41 .2
2.7
Table 2. Phenotypic distribution in an F2 population segregating for genes of chromosome 6 from Wt 12070 (sbm) x Wt 16141 (art-1, p).
A. Monohybrid F? segregation.
Sbm 614
sbm 186
Total
Chi-square (3:1)
800
1.31
Art-1 620
art-1 181
801
2.47
P 611
P 187
798
1.04
B. Joint segregation of sbm with art-1 and p.
Joint
Chi-
square
Phase
R.F.
S.E.
Sbm Art-1 452
Sbm art-1 162
sbm Art-1 167
sbm art-1 19
Total
800
21.19
R
34.2
3.1
Sbm P 435
Sbm p 177
sbm P 176
sbm p 10
798
44.96
R
24.5
3.3
Art-1 P 536
Art-1 p 82
art-1 P 75
art-1 p 105
798
159.02
C
23.1
1.7
36                          PNL Volume 20                      1988 RESEARCH REPORTS
It appears from these data that sbm is located in the Pl end of chromosome 6.
1.   Gritton, E. T. and D. J. Hagedorn. 1975. Crop Sci. 15:447-448.
2.   Hagedorn, D. J. and E. T. Gritton. 1971. PNL 3:16.
3.   Hampton, R. 0. and G. A. Marx. 1981. PNL 13:16.
4.   Marx, G. A. 1982. PNL 14:50-52.
I acknowledge the cooperation of Dr. W. K. Swiecicki and K. Leraczyk, M.Sc, for pea lines from the Wiatrowo genebank and for computer facili­ties to calculate estimates.
*****