The a2 gene is in linkage group III
Gorel, F.L., Rozov, S.M. Institute
of Cytology and Genetics
and Berdnikov, V.A. 630090
Novosibirsk, Russia
A mutant SGR-a with white flowers and complete absence of anthocyanin in all plant organs was induced in the SG line by treatment with 7 krad of gamma rays. SGR-a was crossed with line Sprint-1. These lines possess contrasting allelic variants of the His(2-6) locus, the complex of histone H1 genes, known to be linked with the anthocyanin gene a (2). Although the SGR-a mutant phenotype is identical to the phenotype caused by the a mutation (anthocyanin inhibition), we failed to find any linkage of this mutant trait with locus His(2-6). F1 plants from the cross SGR-a ¥ WL-102 (a) had red flowers. These experiments indicated that the SGR-a mutation involves a locus other than a.
Earlier a new locus a2 controlling anthocyanin production was described by Marx et al. (1). The F1 plants from the cross of line SGR-a with Marx’ a2 line had white flowers. Thus our newly obtained anthocyanin mutant is allelic with a2.
After treatment of line SG with 0.15% EMS, another mutant SGE-0845 completely lacking anthocyanin was obtained. SGE-0845 also proved to be allelic with a2.
To locate the a2 gene, we crossed line SGR-a (A, a2, St) with tester line WL-1393 (A, A2, st). The F2 data (Table 1), analysed using S.M. Rozov’s program (CROS), indicate that the a2 locus is linked to gene st in linkage group III.
Table 1. Joint segregation data for a2 and st in the F2 of the cross SGR-a (a2, St) ¥ WL-1393 (A2, st).
| Genes |
Phenotype |
Joint | Prob | RCV | SE | |||
| A/B | A/b | a/B | a/b | Chi-sq | ||||
| a2 st | 128 | 51 | 61 | 4 | 13.6 | < 0.0005 | 26.2 | 5.9 |
We crossed one plant with phenotype a2, st from the above mentioned F2 population with line SGE-0656 (A2, St, uni). (This mutant line was obtained after EMS-treatment of line SG. It has the same phenotype as unitac and proved to be allelic to this group III marker). In addition, line SGE-0845 (a2, Uni) was crossed with line SGE-0656 (A2, uni). The results from these two crosses (Table 2) provide additional evidence that gene a2 is located in pea linkage group III.
Table 2. Joint segregation data for genes a2, st and uni.
| Genes |
Phenotype |
Joint |
Prob |
RCV |
SE |
||||
|
A/B |
A/b |
a/B |
a/b |
Chi-sq |
|||||
| Cross (a2, st, Uni) ¥ SGE-0656 (A2, St, uni) | |||||||||
| a2 st |
65 |
7 |
23 |
20 |
20.28 |
< 0.0001 |
27.3 |
5.0 |
|
| a2 uni |
53 |
19 |
42 |
1 |
10.85 |
< 0.001 |
16.5 |
9.0 |
|
| st uni |
71 |
19 |
26 |
1 |
4.44 |
< 0.05 |
26.6 |
8.5 |
|
| Cross SGE-0845 (a2, Uni) ¥ SGE-0656 (A2, uni) | |||||||||
| a2 uni |
62 |
25 |
19 |
0 |
7.14 |
< 0.01 |
< 24 |
9.0 |
|
| Combined | |||||||||
| a2 uni |
115 |
44 |
61 |
1 |
18.68 |
< 0.0001 |
14.1 |
6.6 |
|
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1. Marx, G.A, Weeden, N.F. and Muehlbauer, F.J. 1989. Pisum Newsletter 21:35-36.
2. Smirnova, O.G., Rozov, S.M. and Berdnikov, V.A. 1989. Pisum Newsletter 21:63-65.
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